Exercise Interventions in Children and Adolescents With ADHD: A Systematic Review

Abstract

Objective: Exercise has attracted attention as a potential helpful intervention in children with ADHD. Effects are emphasized on cognition, social-emotional, and motor development. Method: A systematic literature search was conducted using the electronic databases Web of Science, PubMed, Scopus, and ERIC to analyze the efficacy of different types of exercise interventions in children and adolescents with ADHD. Seven studies examining the acute and 14 studies examining the long-term effects were included. Results: The largest effects were reported for mixed exercise programs on ADHD symptomatology and fine motor precision. However, because of the large differences in the study designs, the comparability is limited. Conclusion: At this time, no evidence-based recommendation can be formulated regarding frequency, intensity, or duration of exercise. Nevertheless, some first trends regarding the effects of certain types of exercise can be identified. When focusing on long-term health benefits in children and adolescents with ADHD, qualitative exercise characteristics might play an important role.

Keywords

ADHD exercise physical activity children adolescents

ADHD is a common neurodevelopmental disorder in children and adolescents with a worldwide prevalence of around 5% (Polanczyk, Silva de Lima, Lessa Horta, Biederman, & Rohde, 2007). The main symptoms of ADHD are inattention, hyperactivity, and impulsivity, which are present in multiple settings and affect social, educational, and work performance. Based on the specific symptoms, the American Psychiatric Association distinguishes between three different presentations of ADHD: the predominantly inattentive presentation (ADHD-I), the predominantly hyperactive/impulsive presentation (ADHD-H/I), and the combined presentation (ADHD-C; American Psychiatric Association, 2013).

Self-regulatory deficits are discussed in a comprehensive model explaining the etiology of ADHD (Barkley, 1997; Sonuga-Barke, 2002) because of the wide range of symptoms and associated social-emotional problems. The core deficits and comorbid symptoms can be classified into mental, behavioral, physical, and social aspects of health. Mental aspects include the main symptoms such as inattention and deficits in inhibitory control (American Psychiatric Association, 2013) as well as comorbidities such as depression (Daviss, 2008) or anxiety (Schatz & Rostain, 2006). Behavioral problems, rated by parents or teachers, are often described as academic difficulties resulting from cognitive and motivational deficits (Gawrilow, Schmitt, & Rauch, 2011). Difficulties with peers (Barbosa Goulardins, Fernandes Bilhar Marques, & Barbante Casella, 2011; Holtmann et al., 2011), and fine and gross motor deficits (Kaiser, Schoemaker, Albaret, & Geuze, 2014) are examples for physical and social health problems.

Further approaches exist, explaining the etiology of ADHD on neurobiological level. Structural brain abnormalities were found in frontostriatal areas, the tempoparietal lobes, the basalganglia, the thalamus, the corpus callosum, the cerebellum, and the amygdala (Cortese, 2012; Mahone, 2011). In addition, neurotransmitter dysfunctions were described as neurobiological pathology (Levy, 1991). Abnormalities in dopamine and norepinephrine levels in prefrontal cortex have been suggested to account for ADHD symptoms such as deficits in inhibitory control and the executive control of attention (Sharma & Couture, 2014).

Therefore, treatment of ADHD commonly includes sympathomimetic drugs, such as methylphenidate, amphetamines, or atomoxetine, which enhance the level of dopamine and norepinephrine in the prefrontal cortex (Sharma & Couture, 2014; Zuvekas, Vitiello, & Norquist, 2006). Pharmacological treatment is confirmed to improve ADHD symptomatology as well as comorbid symptoms such as motor deficits (Kaiser et al., 2014; Mahone, 2011).

In addition to medication management, the proposed concept of multimodal treatment of ADHD includes psychosocial and behavioral interventions. Results of the Multimodal Treatment Study of Children with ADHD (MTA), a randomized clinical trial in which the effects of intensive behavioral treatment, medication, and a combined treatment were compared, reveal positive results (Arnold et al., 1997). Well-monitored medication seems to be most successful for short-term symptomatic improvement, whereas a superiority of combination treatment could be shown for composite outcomes and domains of functional impairment such as academic achievement. However, evidence for long-term effectiveness remains elusive up to now (Hinshaw & Arnold, 2015). Therefore, and because of the negative side-effects of pharmacological treatment (Clavenna & Bonati, 2014; Vitiello, 2001), research on the treatment of ADHD in recent years has also focused on further non-pharmacological interventions.

Exercise is hypothesized to be an effective additional therapeutic option because of its positive effects on cognition in general (Loprinzia, Herodb, Cardinalc, & Noakes, 2013) and, in particular, on the neurobiological pathologies associated with ADHD (Berwid & Halperin, 2012; Gapin, Labban, & Etnier, 2011). A range of types of exercise interventions has shown positive effects on cognition, especially on executive function in healthy children and in the elderly (Fedewa & Ahn, 2011; Kubesch & Walk, 2009; Lees & Hopkins, 2013). Acute and chronic effects on brain structure and activity, neurotransmitter and neurotrophin levels, neuroendocrinology, angiogenesis, and cerebral blood flow are possible neurobiological mediators of health effects of exercise (Hillman, Erickson, & Kramer, 2008). In the case of ADHD, increasing levels of serotonin, dopamine, and norepinephrine within the frontostriatal lobes of the brain were highlighted when discussing the effects on this neurodevelopmental disorder (e.g., Wigal et al., 2003). In addition, the level of the brain-derived neurotrophic factor (BDNF), which is involved in the differentiation and survival of dopaminergic neurons and discussed to play a role in the etiology of ADHD, is shown to increase following physical activity in rodents (Berwid & Halperin, 2012; Gapin et al., 2011). To date, especially studies in animal models of ADHD exist, which emphasize these potential neurochemical effects. The review article of Wigal, Emmerson, Gehricke, and Galassetti (2013) provides an overview of the current state of research concerning the hypothesis that exercise training alters the underlying physiology present in ADHD.

However, research in individuals with ADHD symptoms primarily examines the impact of physical activity and exercise on behavioral aspects and cognitive performance (Gapin et al., 2011). For example, Gapin and Etnier (2010) examined the extent to which physical activity is associated with executive functions in children with ADHD. The results suggest that higher daily moderate to vigorous physical activity, measured with an accelerometer, is associated with better cognitive performance in ADHD children. In addition, results of the nationally representative U.K. Millennium Cohort Study reveal that 5-year-old children, who regularly participated in sports, had fewer symptoms of inattention/hyperactivity measured with the Strength and Difficulties Questionnaire (SDQ; Griffiths, Dowda, Dezateux, & Pate, 2010).

Most studies examining the neurobiological, cognitive, or behavioral effects of exercise focused on improving physical fitness by aerobic exercises characterized by “ATP generating reactions that require oxygen” (Howley, 2012, p. 84) and achieved through running or cycling. These exercises are characterized by the quantity duration, frequency, intensity, and the metabolic responses (Pesce, 2012). In contrast, developmental-psychological and neurocognitive approaches focus on neural stimulation by complex movement tasks with high cognitive and motor demands leading to experience-dependent benefits for neuronal growth and maturation, synaptogenesis, and neural connectivity in brain regions associated with executive functioning (Best, 2010; Debarnot, Sperduti, Di Rienzo, & Guillot, 2014). These exercises are characterized by nonphysical or qualitative exercise characteristics (Pesce, 2009). To date, only few authors have regarded physical exercise as an effective ADHD treatment option from a developmental-psychological or social cognitive point of view (Halperin & Healey, 2011; Lehnert, 2014). For instance, Halperin and Healey (2011) suggested that physical activity and directed play may promote neural growth and development in children with ADHD; however, they mainly emphasized the effects on behavioral and cognitive functions as well as motor development based on research in rodents or human adults.

Thus, compared with the many theoretical approaches that promote the efficacy of exercise on cognition in children with ADHD (Archer & Kostrzewa, 2012; Berwid & Halperin, 2012; Gapin et al., 2011; Halperin & Healey, 2011; Lehnert, 2014; Wigal et al., 2013), few studies have directly investigated the efficacy of exercise interventions in these children. In addition, the potential effects of physical activity and exercise on comorbid symptoms, such as social/emotional problems or motor deficits, have only rarely been taken into account when promoting exercise as an additional treatment option.

To date, interventional approaches in the field of physical activity and exercise in children and adolescents with ADHD have not been systematically reviewed. Rommel, Halperin, Mill, Asherson, and Kuntsi (2013) summarized the current state of research on the effects of solely aerobic exercise on cognition and behavior in humans and animal models of ADHD. A recent German-language review studied the sole effects of exercise on cognitive functions in children and adolescents with ADHD (Lehnert, 2014) and emphasized the importance of considering qualitative exercise characteristics for evaluating the efficacy of exercise in the treatment of ADHD. A recent systematic review included five studies (four interventional) assessing the effects of different types of exercise programs with a minimum duration of 6 days on outcome measures including ADHD symptoms, social behavior, motor performance, and cognition (Kamp, Sperlich, & Holmberg, 2014), which was insufficient for formulating evidence-based conclusions about the relation between exercise characteristics and intervention effects. However, specific recommendations for exercise interventions in children and adolescents with ADHD are needed.

Therefore, the purpose of this article was to systematically review published studies examining the acute or long-term effects of all types of exercise interventions in children and adolescents with ADHD on all aspects of health including physical, mental, and social well-being in accordance with the definition of the World Health Organization 1948 (Grad, 2002).

Methods

Prospective interventional studies and trials examining the acute and long-term health effects of exercise in children and adolescents with ADHD were included. Neither the types of exercise nor the outcome measures were constricted to investigate possible benefits of exercise on all aspects of health. In addition, differences in intervention programs regarding quantitative and qualitative exercise characteristics were analyzed. In contrast, studies only were included if participants had received an ADHD diagnosis according to the Diagnostic and Statistical Manual of Mental Disorders (3rd or 4th ed.; DSM-III or DSM-IV; American Psychiatric Association, 1987 or 1994) or the International Statistical Classification of Diseases and Related Health Problems–10th Revision (ICD-10) criteria by a pediatrician, psychiatrist, physician, or psychologist.

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Statement was used as guideline for reporting the systematic review (Moher, Liberati, Tetzlaff, & Altman, 2009). All eligibility criteria presented in Table 1 had to be met. Animal studies, studies with a single-case or observational design, and studies without a within-subjects factor as an independent variable were excluded.

Table 1.

Inclusion Criteria.

Participant	Study design	Target group	Language
Effects of different types of exercise or physical activity on cognition, neurophysiology, physical fitness, and social behavior in patients with ADHD	Acute and long-term intervention studies (randomized and non-randomized) with repeated-measures-type methodology; (IG) > 5	Children and adolescents ≤ 18 years with ADHD as primary diagnosis independent of the ADHD subtype	English (or German with English abstract)

Note. IG = intervention group.

The literature search was conducted by the lead author (C.N.) on September 4, 2014. The following electronic databases were searched for peer-reviewed journal articles: in all fields in PubMed, ERIC and Scopus, and in topic in Web of Science. Relevant journal articles were identified using the following query: ADHD AND (“physical activity” OR exercise OR “sensorimotor training*” OR sport*) NOT/AND NOT (rat* OR animal*). In the first step, all articles were screened based on titles and, if necessary, on abstracts to identify studies meeting the inclusion criteria. In the second step, full-text articles were assessed for eligibility. Furthermore, cited references were manually searched for additional literature. Figure 1 illustrates the search process in a flow diagram. The lead author extracted the following study characteristics from the articles: sample characteristics, description of the intervention program including type, duration, frequency, and intensity of exercise, measures, and the main results. Effect sizes were reported if stated or if Cohen’s d could be calculated from the available data. According to the classification by Cohen (1992), effects were interpreted as small (d < 0.5), medium (d < 0.8), and large (d ≥ 0.8). Results with p < .05 were considered as statistically significant. A meta-analysis was not performed because of the heterogeneity in study designs and the lack of available data.

Figure 1.

Process of literature search and selection referring to the work of Moher, Liberati, Tetzlaff, and Altman (2009).

Results

In total, 439 records were found by database and reference search. After removing studies not meeting the eligibility criteria, finally 21 studies remained and were included in this review. Seven experimental studies examined the acute and 14 studies examined the long-term effects of exercise on health in children and adolescents with ADHD aged between 7 and 18 years using repeated-measures designs. Tables 2 and 3 summarize the study characteristics of studies examining the acute or long-term effects of exercise in children/adolescents with ADHD, respectively. The sample sizes of the intervention groups ranged from n = 10 (Wigal et al., 2003) to n = 25 (Medina et al., 2010) in studies examining the acute effects, and from n = 11 (Jensen & Kenny, 2004) to n = 47 (Park et al., 2013) in studies examining the long-term effects. All studies included mostly male participants, and eight studies included only boys.

Table 2.

Studies Examining the Acute Effect of Exercise in Children/Adolescents With ADHD.

	Sample n (male/female)
Reference	Age range or M ± SD	Intervention	Outcome	Outcome measures	Results
Chang, Liu, Yu, and Lee (2012)	IG: 20 (19/1) ADHD 10.5 ± 1.0 years CG: 20 (18/2) ADHD 10.4 ± 0.9 years	IG: treadmill run with moderate intensity (50%-70% HRR) for 30 min CG: watching video	Executive functions	Stroop test; WCST	IG and CG improved sign. in the Stroop color-word condition (d = −1.26 and −0.58); IG also showed sign. changes in single parameters of WCST (d = −0.74 and 0.52)
Flohr, Saunders, Evans, and Raggi (2004)	IG: 17 (17/1) ADHD 7-11 years	IG₁: board games for 25 min IG₂: cycle ergometer at 40%-50% of VO_2max for 25 min IG₃: cycle ergometer at 65%-75% of VO_2max for 25 min	AP ADHD symptoms	Math and reading tasks Conners’ Rating Scale (IOWA)	No sign. changes in AP; IG₂ and IG₃ showed sign. reduced disruptive behavior (IOWA) following exercise
Medina et al. (2010)	IG: 25 (25/0) ADHD 7-15 years	High-intensity treadmill run (1): 10 × 2 min loads of effort (work rate of 50% of the difference between anaerobic threshold and VO_2max) with 10 resting intervals (1 min); stretching (2)	Attention	Conners’ Continuous Performance Test–II	Sign. improvements in the index of confidence (d = 0.55), vigilance (d = 0.37-0.54), and impulsivity measure (d = 0.67) after (1) compared with (2)
Pontifex, Saliba, Raine, Picchietti, and Hillman (2013)	IG: 20 (14/6) ADHD 8-10 years CG: 20 (14/6) healthy 9.8 ± 0.1 years	Treadmill run with moderate intensity (65%-75% HR_max) (1) and reading for 20 min (2) (Both groups)	Executive functions Academic achievement	Eriksen FT + ERP; WRAT3	IG and CG showed sign. greater response accuracy in FT (d = 0.94) attended by larger P3 amplitudes (d = 0.80) and enhanced reading and arithmetic achievements (d = 1.25-1.58) after (1)
Tantillo, Kesick, Hynd, and Dishman (2002)	IG: 18 (10/8) ADHD 10.0 ± 1.7 years CG: 25 (11/14) healthy 10.0 ± 1.6 years	VO_2peak exercise test (1) and a submaximal exercise test (65%-75% VO_2peak) (2) for 5-25 min on a treadmill (both groups)	Brain activity Motor skills	Spontaneous eye blinks, ASER, MIB	Sign. increased blink rate (d = 0.86), decreased ASER_latency (d = −1.14), and improved MIB (d = 1.70) after (1) in IG boys; sign. increase in ASER_amplitude (d = 0.60) and decrease in ASER_latency (d = −1.23) after (2) in IG girls
Taylor & Kuo (2009)	IG: 17 (15/2) ADHD 7-12 years	Individually guided 20-min walks in a park (1), in a downtown area (2), and in a residential area (3)	Attention	DSB	Concentration after the walk in the park (1) was sign. better than after the downtown (2) and the neighborhood walk (3)
Wigal et al. (2003)	IG: 10 (10/0) ADHD 8.4 ± 0.4 years CG: 8 (8/0) healthy 8.6 ± 0.5 years	Cycling on an ergometer: 10 × 2 min loads of effort (work rate of 50% of the difference between anaerobic threshold and VO_2peak) with 10 resting intervals (1 min; both groups)	Physiological response	Blood sampling: epinephrine, norepinephrine, and dopamine	Mean plasma levels of nor-/epinephrine rose in both groups with a greater increase in CG; dopamine levels did not change in IG compared with a sign. increase in CG

Note. IG = intervention group; HRR = heart rate reserve; CG = control group; IOWA = Inattention Overactivity With Aggression; WCST = Wisconsin Card Sorting Test; sign. = significant/-ly; VO_2max = maximal oxygen consumption; AP = academic performance; HR_{max =} maximum heart rate; FT = Flanker task; ERP = event-related brain potentials; WRAT = Wide Range Achievement Test; ASER = acoustic startle eye blink response; MIB = motor impersistence battery; DSB = Digit Span backward; VO_2peak = peak oxygen uptake.

Table 3.

Studies Examining the Long-Term Effects of Exercise Interventions in Children/Adolescents With ADHD.

Reference	Sample n (male/female) age range or M ± SD	Intervention/program	Outcomes	Outcome measures	Results
Ahmed and Mohamed (2011)	IG: 42 (27/15) ADHD 13.9 ± 1.6 years CG: 42 (27/15) ADHD 13.8 ± 1.7 years	IG: 10-week aerobic exercise program(3 × 40-50 min/week) CG: no program	ADHD symptoms	Modified CTRS	IG showed sign. improvement in attention (d = 1.32), motor skills (d = 0.77), and academic/ classroom behavior (d = 1.34); no sign. changes in CG
Banaschewski, Besmens, Zieger, and Rothenberger (2001)	IG: 12 (10/2) ADHD 7-10 years	20 sessions (2 × 50 min/week) within 4 months of both ST and CT in a within-subject crossover design	Motor skills Impulse control ADHD symptoms Emotional and behavioral problems	Sensory Integration and Practice Test; Body Coordination Test for Children MFFT Conners’ ASQ CBCL	Sign. improvement in sensory integration and coordination only after ST (d = 0.55-0.72) and of impulse control only after CT (d = 0.98); Behavioral problem scores decreased sign. after ST (ASQ: d = 0.85; CBCL: d = 0.54-1.38)
Chang, Hung, Huang, Hatfield, and Hung (2014)	IG: 14 (10/4) ADHD 8.2 ± 0.5 years CG: 13 (13/0) ADHD 8.8 ± 0.5 years	8-week moderate-intensity aquatic exercise program (2 × 90 min/week)CG: no program	Motor skills Executive functions	BMAT: hand–eye coordination Go/No-go Task	IG sign. improved in response inhibition (No-go condition; d = 0.9) and in the motor tasks; no sign. changes in CG
Choi, Han, Kang, Jung, and Renshaw (2014)	IG: 13 (13/0) ADHD 15.8 ± 1.7 years CG: 17 (17/0) ADHD 16.0 ± 1.2 years	IG: methylphenidate + aerobic exercise at 60% HR_max for 6 weeks (3 × 90 min/ week) CG: methylphenidate + 12 educational sessions for behavior (50 min/day)	ADHD symptoms Brain activity + executive functions	K-ARS Functional magnetic resonance imaging in response to WCST	K-ARS total score and perseverative errors decreased sign. in IG (d = −2.39 and −0.84) compared with those in CG (d = −1.95 and −0.34); sign. changes in the brain activity of IG compared with lower or no changes in CG
Haffner, Roos, Goldstein, Parzer, and Resch (2006)	IG: 19 (12/9) ADHD 8-11 years	Yoga training (1) and a conventional motor training (2) both for 8 weeks (2 × 60 min/ week) in a within-subject crossover design	ADHD symptoms Attention	FBB-HKS DAT	Sign. improved attention (d = 1.37) and reductions in ADHD symptoms (d = −0.88) after (1) and (2) with larger effects for yoga training (DAT: d = 2.66; FBB: d = 0.60-0.97)
Hernandez-Reif, Field, and Thimas (2001)	IG: 13 (11/2) ADHD 13-16 years	Tai Chi classes for 5 weeks (2 × 30 min/week)	ADHD symptoms	CTRS	Sign. positive changes in total CTRS score (d = −1.52) and nearly all subscores (d = −0.71 to −1.58), which persisted over a 2-week follow-up
Jensen and Kenny (2004)	IG: 11 (11/0) ADHD 10.6 ± 1.8 years CG: 8 (8/0) ADHD 9.4 ± 1.7 years	IG: 20 sessions of Yoga training (60 min/week) CG: 5 sessions of cooperative activities	ADHD symptoms Attention	CTRS/CPRS-R: L TOVA	Sign. improvements on 8 subscales of the CPRS for IG (d = 0.29-0.79) and on 6 subscales for CG (d = 0.39-0.85); no sign. changes in CTRS scores and attention for both groups
Kang, Choi, Kang, and Han (2011)	IG: 15 (15/0) ADHD 8.4 ± 0.9 years CG: 13 (13/0) ADHD 8.6 ± 1.2 years	IG: methylphenidate + aerobic exercise at 60% HR_max for 6 weeks (3 × 90 min/week) CG: methylphenidate + 12 educational sessions for behavior (50 min/day)	ADHD symptoms Executive functions Social behavior	K-ARS DST TMT B SSRS	IG showed sign. larger improvements in K-ARS (total score and inattention), in cognitive functionning (DST, TMT), and in cooperativeness (SSRS) compared with those of CG
Lufi and Parish-Plass (2011)	IG: 15 (15/0) ADHD 11.1 ± 1.5 years CG: 17 (17/0) other behavioral problems 10.7 ± 1.4 years	20-week sport-based group therapy (individual sport activity and team games + behavioral interventions) in groups of 6-10 (90 min/week; both groups)	Emotional and behavioral problems ADHD symptoms	YSR CBCL Conners’ ASQ-P	Sign. improvement in all measures in both groups (ASQ-P: d = 0.26; YSR: d = 0.26-0.50; CBCL: d = 0.32-0.38); no sign. differences between IG and CG
McKune, Pautz, and Lombard (2003)	IG: 13 (10/3) ADHD 10.8 ± 1.9 years CG: 6 (3/3) ADHD 11.2 ± 1.5 years	IG: 5-week mixed exercise program at 50%-75% HR_max (5 × 60 min/week) CG: no program	ADHD symptoms	Modified CPRS	Sign. improvements in CPRS scores (total behavior, attention, emotional, and motor skills); no sign. differences between IG and CG
Pan et al. (2017)	IG: 12 (12/0) ADHD 9.6 ± 2.5 years CG₁:12 (12/0) ADHD 9.4 ± 2.7 years CG₂:24 (24/0) healthy 9.6 ± 2.5 years	IG: 12-week SDHRP + fitness training (90 min/week) in groups of 6 children CG_1&2: no program	Physical fitness	BOT BPFT	Sign. overall improvement in IG (d = 0.31-2.82); sign. improvement in several BOT measures of CG₁ (d = 0.21-1.56) and in several BOT and fitness measures of CG₂ (d = 0.20-0.75)
Park et al. (2013)	IG: 47 (47/0) ADHD 8.9 ± 1.4 years	Visual and auditory stimuli program (Neurosync) for more than 12 weeks (2-3 × 60 min/week)	Executive functions Intelligence	Stroop color-word test TONI	Sign. increase in Stroop scores (d = 0.37-0.66); no sign. changes in TONI scores; sign. improved performance in Neurosync tasks (d = 0.51 −1.72)
Verret, Guay, Berthiaume, Gardiner, and Béliveau (2012)	IG: 10 (9/1) ADHD CG: 11 (10/1) ADHD overall: 9.1 ± 1.1 years	10-week mixed-moderate– to high-intensity physical activity program (77% HR_max; 3 × 45 min/week) CG: no program	Physical fitness Emotional and behavioral problems Attention	TGMD-2; Bruce maximal progressive treadmill test CBCL Test of Everyday Attention	IG showed sign. improved motor performance (push-up, locomotion score, raw motor skills), improved information processing, and CBCL scores
Zivkovic, Zivanovic, Zivkovic, Milojkovic, and Djordjevic (2012)	IG: 26 (19/7) ADHD 7-10 years CG: 10 ADHD 7-10 years	12-week exercise program including warm-up and attention training (3 × 30 min/week) CG: no program	ADHD symptoms	Modified Conners’ Behavior Rating Scale (IOWA)	Sign. improvement in all measures; no sign. changes in CG

Note. IG = intervention group; CG = control group; sign. = significant/-ly; ST = sensorimotor training; CT = cognitive training; IOWA = Inattention Overactivity With Aggression; MFFT = Matching Familiar Figures Test; K-ARS = DuPaul’s ADHD Rating Scale–Korean version; ASQ = Abbreviated Symptom Questionnaire; ASQ-P = ASQ–Parent version; CBCL = Child Behavior Checklist; BMAT = Basic Motor Ability Test; HR_max = maximum heart rate; WCST = Wisconsin Card Sorting Test; DAT = Dortmund Attention Test; CTRS = Conners’ Teacher Rating Scale; CPRS = Conners’ Parent Rating Scale; CPRS-R: L = CPRS Revised–Long Form; FBB-HKS = Fremdbeurteilungsbogen für hyperkinetische Störungen [Assessment for parents, teachers, and educators]; TOVA = Test of Variables of Attention; DST = Digit Symbol Test; TMT B = Trail Making Test part B; SSRS = Social Skills Rating System; YSR = Youth Self-Report; SDHRP = Simulated Developmental Horse-Riding Program; BPFT = Brockport Physical Fitness Test; TONI = Test of Nonverbal Intelligence; TGMD-2 = Test of Gross Motor Development–2; BOT = Bruininks–Oseretsky Test of Motor Proficiency; (x) = condition.

There were major differences in the description of how the selection of ADHD participants was made. Only eight studies reported detailed information on ADHD subtype, medication status, and comorbidities (Banaschewski, Besmens, Zieger, & Rothenberger, 2001; Chang, Liu, Yu, & Lee, 2012; Choi, Han, Kang, Jung, & Renshaw, 2014; Haffner, Roos, Goldstein, Parzer, & Resch, 2006; Medina et al., 2010; Pan, Chang, Tsai, Chu, Cheng, & Sung, 2014; Verret, Guay, Berthiaume, Gardiner, & Béliveau, 2012; Wigal et al., 2003). Some studies restricted inclusion/exclusion criteria to a specific subtype of ADHD (Banaschewski et al., 2001; Kang, Choi, Kang, & Han, 2011; Verret et al., 2012; Wigal et al., 2003). Moreover, 13 studies reported individually defined comorbidities as exclusion criteria. One study included diagnosed and, in addition, suspected ADHD cases in their sample (Pontifex, Saliba, Raine, Picchietti, & Hillman, 2013). Nevertheless, this study was reviewed because of the verification of clinical status through a semistructured diagnostic interview using DSM-IV (American Psychiatric Association, 1994) criteria (Pontifex et al., 2013). Only one study (Medina et al., 2010) considered medication status of the participants in their evaluation and examined the efficacy of physical activity in dependence of the use of methylphenidate.

Fourteen studies included a control group in their study design, which received either no intervention (Ahmed & Mohamed, 2011; Chang, Hung, Huang, Hatfield, & Hung, 2014; McKune, Pautz, & Lombard, 2003; Pan et al., 2017; Verret et al., 2012; Zivkovic, Zivanovic, Zivkovic, Milojkovic, & Djordjevic, 2012) or a non-exercise treatment (Chang et al., 2012; Choi et al., 2014; Jensen & Kenny, 2004; Kang et al., 2011), or comprised age- and gender-matched controls without developmental or behavioral problems undergoing the same exercise program (Pontifex et al., 2013; Tantillo, Kesick, Hynd, & Dishman, 2002; Wigal et al., 2003). Two studies used a within-subject crossover design to compare the effects of two different interventions in the same sample (Banaschewski et al., 2001; Haffner et al., 2006). The long-term intervention programs consisted of 10 (Hernandez-Reif, Field, & Thimas, 2001) to 36 sessions (Zivkovic et al., 2012). The duration of a single exercise session ranged from 20 min (Pontifex et al., 2013; Taylor & Kuo, 2009) to 90 min (Chang et al., 2014; Choi et al., 2014; Kang et al., 2011; Lufi & Parish-Plass, 2011; Pan et al., 2017).

The effects of the exercise interventions on ADHD symptomatology, (neuro)physiology, cognition, physical fitness, emotional problems, and (social) behavior were evaluated, and hence there were major differences in the measures used in different studies (see Tables 2 and 3). Fourteen studies evaluated the effect of exercise on aspects of cognitive performance or brain activity, and 12 studies investigated the efficacy of exercise programs on social behavior and ADHD symptomatology. Only five studies used fitness tests or assessed motor development to investigate effects on the physical level.

The intervention programs considered in this review can be classified into four groups: acute running or cycling exercises, mixed long-term exercise programs, specific exercise programs, and sensori- or perceptual-motor training. Mixed long-term exercise programs aimed at improving physical fitness of the participants and therefore included different activities (e.g., running, jumping, coordination tasks, exercise stations, or ball games) to improve different motor abilities (e.g., endurance, strength, balance). In contrast, specific training programs were characterized by one specific type of exercise or sport, which is trained every session. However, the programs did not only aim at improving specific motor skills but also at improving different motor abilities. Sensori- or perceptual-motor training could, in general, be seen as a form of specific exercise program, but it differs by only focusing on training of sensorimotor control. According to this classification, the studies and results are presented in detail in the following sections.

Acute Effects of Running and Cycling Exercises in Children and Adolescents With ADHD

Six studies investigated the acute effects of treadmill running and ergometer cycling on cognition and behavior in laboratory settings. Most studies implemented a moderate-intensity exercise program and examined its efficacy on attention or response inhibition. For instance, Chang et al. (2012) evaluated the effect of a 30-min treadmill running exercise at 50% to 70% of heart rate reserve (HRR) on executive functioning in 19 boys and 1 girl with ADHD. A control group of 20 children and adolescents with ADHD watched a running video for 30 min (control intervention). Both groups included children with all subtypes of ADHD and without comorbidities, half of them treated with medication. Although the response inhibition was significantly greater after the intervention in both groups, the effect was larger in the exercise group (d = −1.26 vs. −0.58). Similarly, Pontifex et al. (2013) observed a greater response accuracy in a modified Eriksen Flanker task after a 20-min treadmill running exercise at moderate intensity (65%-75% of maximum heart rate [HR_max]) than after completing a reading task (control intervention) in 20 children with and without ADHD (d = 0.94). Individuals with ADHD mainly presented the inattentive subtype and were free of any comorbid conditions. The improvements were attended by significantly larger P3 amplitudes (d = 0.80) and shorter P3 latencies (d = 0.99) in neuroelectric measures of event-related brain potentials (ERPs), reflecting enhanced allocation of attentional resources toward stimulus engagement as well as stimulus classification and processing speed (Pontifex et al., 2013). In addition, both groups showed significantly enhanced reading and arithmetic achievements with effect sizes between d = 1.25 and d = 1.58 after the exercise session.

In contrast, Flohr, Saunders, Evans, and Raggi (2004) did not confirm this improvement in academic performance following low or moderate exercise in children with ADHD. The authors compared the effects of 25-min ergometer cycling exercise at 40% to 50% and at 65% to 75% of maximum oxygen consumption (VO_2max) compared with playing board games for 25 min (control intervention) on math and reading performance and ADHD symptomatology in 19 boys. Combining the data of both exercise conditions, the children showed a significant decrease in ADHD symptoms after exercise compared with the control intervention but the academic performance did not differ between interventions. Moreover, because of the similar results for the low- and moderate-intensity interventions, the authors suggested that exercise intensity does not significantly influence the positive behavioral change. Unfortunately, no information on ADHD subtype or comorbidities of the participants was given, which might explain the different study results.

Tantillo et al. (2002) compared the effects of exercise programs with moderate and high intensities in 10 boys and 8 girls with ADHD, currently taking methylphenidate, and included 25 healthy children in the same age as control group. Both groups completed a VO_2peak treadmill running exercise test and a submaximal treadmill running exercise test (65%-75% VO_2peak) lasting between 5 and 25 min. Spontaneous eye blinks and acoustic startle eye blink response (ASER) were measured by electromyography (EMG) as indicators for brain dopaminergic activity, and motor impersistence was assessed. The authors observed gender-related differences in the exercise response: Boys showed significantly higher blink rate (d = 0.86), lower ASER_latency (d = −1.14), and greater motor impersistence (d = 1.70) after maximal exercise compared with submaximal exercise, whereas girls performed significantly better after submaximal than after maximal exercise indicated by a higher ASER_amplitude (d = 0.60) and a lower ASER_latency (d = −1.23). However, it has to be taken into account that the methods, which were used to reflect brain dopaminergic activity, do not permit the conclusion that exercise had a dopaminergic effect (Tantillo et al., 2002).

Medina et al. (2010) assessed the impact of high-intensity treadmill running (consisting of ten 2-min exercise bouts interspersed with 1-min resting intervals) and stretching (control intervention) on attention in 25 boys diagnosed with ADHD and without psychiatric comorbidity. Nine of them were treated non-pharmacologically. The authors observed significant differences in confidence, vigilance, and impulsivity between the exercise and control interventions. Compared with the other studies, the effect sizes were smaller (d = 0.37-0.67), and the intake of methylphenidate did not affect these effects. Results reported by Taylor and Kuo (2009) confirmed these positive effects of exercise on attention in 17 children with ADHD-C/ADHD-I provided that the physical activity takes place in a natural environment.

Wigal et al. (2003) determined the physiological response of the ergometer cycling protocol previously used by Medina et al. (2010) in 10 boys with ADHD-C, free of psychiatric and neurological comorbidities and naïve with respect to the use of stimulant medications. The catecholamine response was measured before and after cycling using blood sampling. The mean dopamine levels of the ADHD group did not significantly increase after exercise and the increase in nor-/epinephrine levels was smaller than that in an age- and gender-matched healthy control group.

Overall, the studies investigating the acute effects of exercise in children and adolescents with ADHD reveal that there might be positive effects, especially on cognitive functioning. Two studies reported medium to large effects of exercise on aspects of executive function (Chang et al., 2012; Pontifex et al., 2013), and one study reported small to medium effects of exercise on several aspects of attention (Medina et al., 2010). These cognitive improvements came along with significant changes in neuroelectric measures, showing medium to large effects (Pontifex et al., 2013; Tantillo et al., 2002), which might indicate exercise-related changes in brain activity. However, the strength of the acute influence of exercise on academic performance in children with ADHD is still unclear. Large effects as well as no effects were reported regarding the math and reading performance in two different samples of the same age (Flohr et al., 2004; Pontifex et al., 2013). Finally, to date only one study investigated the acute effects of exercise on behavioral problems associated with ADHD reporting a significant reduction in disruptive behavior following exercise (Flohr et al., 2004).

Chronic Effects of Exercise in Children and Adolescents With ADHD

In contrast to the acute efficacy of running or cycling exercises, identifying the long-term effects of aerobic exercise and endurance training programs in children and adolescents with ADHD is difficult mainly because interventions did not only include an isolated aerobic exercise training focused on maintaining a target heart rate while exercising, but also include other aspects of physical activity such as motor skill training or team sports. In the following section, the effects of such mixed exercise programs are summarized.

Mixed exercise programs

Studies with different running activities as major part of treatment reported positive effects on different aspects of behavior and cognitive functioning. For instance, McKune et al. (2003) and Ahmed and Mohamed (2011) evaluated moderate-intensity exercise programs that included running through obstacle courses or over a longer distance and aerobic exercises for the upper and lower limbs, trunk, and neck (e.g., tuck jumps). Target exercise intensity was defined as 50% to 75% of HR_max. McKune et al. (2003) included a group of 10 boys and 3 girls diagnosed with ADHD according to the Diagnostic and Statistical Manual of Mental Disorders (3rd ed., rev.; DSM-III-R; American Psychiatric Association, 1987) guidelines and currently taking methylphenidate who completed a 1-hr exercise program five times per week for 5 weeks. The control group comprised six children (three boys and three girls) also diagnosed with ADHD and taking medication who did not receive any intervention. After the intervention period, both groups showed significant improvements in several scores of the modified Conners’ Parent Rating Scale (total behavior, attention, emotional, and motor skills) without significant differences between the intervention and control groups. The authors discussed the effect of greater attention paid by the parents to their children during the intervention period and the impact of increased social interaction among participants of both groups, who all attended the same school, as possible reasons for these results. Ahmed and Mohamed (2011) applied the same exercise program (40-50 min) three times per week for 10 weeks in a larger cohort and reported positive effects in teacher ratings of ADHD symptoms in the intervention compared with a non-exercising control group. After the intervention period, the intervention group had significantly improved attention (d = 1.32), motor skills (d = 0.77), and academic classroom behavior (d = 1.34) on Conners’ Teacher Rating Scale, which is comparable with the results reported by McKune et al. (2003). In contrast, the 42 control participants with ADHD and comparable general characteristics showed no significant changes in their behavior during the same period. Unfortunately, no further information on ADHD diagnosis criteria or medication status of the participants was given, which complicates a comparison of the study results.

Another exercise program with a focus on aerobic exercise was evaluated two times with positive results. Kang et al. (2011) examined the efficacy of a 6-week aerobic exercise training (three sessions per week at 60% HR_max). The 90-min training session comprised a brief introduction, a 200-m shuttle run and a 200-m zigzag run (15 min), goal-directed exercise such as throwing balls (20 min), rope-jumping (20 min), two 10-min breaks between the different tasks, and a feedback phase. The intervention group consisted of 15 boys with ADHD-C and was compared to a control group consisting of 13 boys with ADHD-C who received 12 educational sessions. In the post-test, the exercise group showed significantly greater positive changes in the DuPaul’s ADHD scores (total score and inattention score), cooperativeness, and executive functioning than the control group. In addition, the improvements in attention, cognition, and social skills were cross-correlated. Choi et al. (2014) evaluated the effects of the same exercise program with an additional focus on changes in brain activity measured by functional magnetic resonance imaging (fMRI) in adolescents with ADHD. The intervention group consisted of 13 boys and was compared with a control group consisting of 17 boys with ADHD who received educational sessions. Participants of both groups were drug naïve or drug free during the prior 6 months and without other psychiatric and neurological disorders. In addition to a larger decrease in behavioral problems measured by DuPaul’s ADHD Rating Scale (d = −2.39) than the control group (d = −1.95), the intervention group showed significant changes in brain activity while performing the Wisconsin Card Sorting Test. These changes were described as an increase in the mean β value of right frontal lobe and a decrease in the mean β value of the right temporal lobe. The latter has been associated with an improvement in speed of attention processing in the temporal lobe in response to working memory by the authors (Choi et al., 2014). In addition, a significant negative correlation was found between the change in activity within the right prefrontal cortex and the change in behavior (r = −0.57) and the change in perseverative errors in the Card Sorting Test (r = −0.53).

The potential of mixed exercise interventions for affecting behavior in children and adolescents with ADHD was confirmed by studies of Lufi and Parish-Plass (2011) and Zivkovic et al. (2012). Lufi and Parish-Plass (2011) evaluated the effects of a 20-week sport-based group therapy consisting of individual sport activities as team games combined with behavioral training (90 min per week). Fifteen boys with diagnosed ADHD based on the Diagnostic and Statistical Manual of Mental Disorders (4th ed., text rev.; DSM-IV-TR; American Psychiatric Association, 2000) criteria and 17 boys with other behavioral or social disorders diagnosed according to the DSM-IV-TR criteria completed this intervention. Both groups were tested before the intervention, immediately following the intervention, and 1 year after completing the intervention, and showed similar significant improvements in social behavior (d = 0.26-0.50) and ADHD-specific problems (d = 0.26) over time. The largest effect was found for internalizing problems with an effect size of d = 0.50. Both parents and participants reported significant improvements in anxiety and this effect was not only maintained but also increased 1 year later.

Zivkovic et al. (2012) integrated specific attention training exercises in their physical activity program for children with diagnosed ADHD lasting for at least 2 years and without defined comorbidities. After a 12-week program of three 30-min training sessions per week, a group of 19 boys and seven girls showed significant improvements in all measures of the IOWA Conners’ Behavior Rating Scale. A control group of 10 age-matched children with ADHD did not show significant changes over time.

To date, only three studies have investigated the effects of mixed exercise programs on different aspects of physical fitness in children or adolescents with ADHD. Verret et al. (2012) evaluated a 10-week physical activity program (three 45-min sessions per week) with moderate- to high-intensity exercises including progressive aerobic, muscular, and motor skill exercises combined with team games such as basketball or soccer in 10 children with ADHD including one girl. An age and gender matched control group was included. Both groups consisted of children with ADHD-C or ADHD-H/I diagnosis according to the DSM-IV criteria, and without further defined psychiatric and neurological disorders, but individuals of the control group were all taking medication in contrast to 30% in the intervention group. After the intervention, the intervention group showed significantly improved motor performance (push-ups, locomotion score, and raw motor skills) compared with the control group. Moreover, the intervention group showed significant improvements in information processing indicated by a faster visual research in the Sky Search test, a part of the Test of Everyday Attention, and significant reductions in behavioral and emotional problems. The latter differed significantly between parent and teacher ratings: Parents reported significant changes in total, social, thought, and attention problems, whereas teachers noted significant improvements in anxiety, depression, and social problems in the intervention group.

Pan et al. (2017) combined a simulated horse-riding program with fitness training including continuous jogging/running for 5 min, muscular training for 15 min (such as push-ups, sit-ups, ball games, or exercise stations), and flexibility exercises for 10 min. Twelve boys participated in this 12-week program for 90 min per week. Twelve boys with ADHD and 24 healthy boys in the same age did not receive any treatment and formed the control groups. All ADHD subtypes according to the DSM-IV-TR criteria were included, whereas children with ADHD-C made up the majority, and some comorbidities were defined as exclusion criteria. The results showed a significant overall improvement in motor fitness measured by the Bruininks–Oseretsky Test of Motor Proficiency (2nd ed.) and the Brockport Physical Fitness Test. The effect sizes ranged from d = 0.31 to d = 2.82, with the largest effect for fine motor precision. In the post-tests, the control groups performed significantly better only in several motor tasks and fitness measures with smaller effect sizes than the intervention group.

One study systematically evaluated the efficacy of an aquatic exercise program in children with ADHD using a repeated-measures design (Chang et al., 2014). The exercise intervention consisted of 16 sessions involving moderate-intensity water aerobic exercises and perceptual-motor training for 90 min per day at a local swimming pool. Thirty children diagnosed with all subtypes of ADHD based on the DSM-IV-TR criteria and without further neurological disorders were assigned to either the intervention group (10 boys and 4 girls) or a waitlist control group (13 boys). Motor performance (specifically hand–eye coordination and dexterity) and response inhibition were measured. After the intervention, the exercise group showed significantly improved cognitive and motor functioning whereas the control group did not show any significant changes.

Specific exercise programs

Only three studies evaluating different specific training programs were found. These studies investigated the effects of Yoga and Tai Chi on behavioral problems and attention in children and adolescents with ADHD. For instance, Hernandez-Reif et al. (2001) reported positive effects of ten 30-min Tai Chi sessions over 5 weeks on ADHD symptoms, especially on hyperactivity, in 13 adolescents diagnosed with ADHD according to the DSM-IV criteria. After the intervention, ADHD symptoms were significantly reduced according to teacher ratings with the largest effects on hyperactivity (d = −1.58). These results showed that effects are apparent after as few as 10 sessions of structured training. The effect sizes were comparable with or even larger than those attained by longer intervention programs also using Conners’ rating scales for evaluating ADHD symptom reduction (Ahmed & Mohamed, 2011; Banaschewski et al., 2001; Jensen & Kenny, 2004; Lufi & Parish-Plass, 2011).

Haffner et al. (2006) and Jensen and Kenny (2004) evaluated the efficacy of Yoga training in children with ADHD. The results of these studies were inconsistent with respect to the effects on attention. Haffner et al. (2006) compared Yoga training with conventional motor training (60-min sessions two times per week for 8 weeks) using a within-subject crossover study design in 12 boys and 9 girls with ADHD. Both interventions significantly improved attention and reduced ADHD symptoms, but the effects of the Yoga intervention were greater than those of the conventional motor training. In contrast, Jensen and Kenny (2004) did not find significant changes in attention after 20 sessions of Yoga training in 11 boys with ADHD. Compared with a control group of 8 boys who received five sessions of cooperative activities, the Yoga group showed only small benefits in the parent rating of ADHD symptoms after the treatment. The scores on the teacher rating scale did not change significantly after the interventions in both groups. The discrepancies between these results may be caused by the high influence of the investigator on the results as stated by Haffner et al. (2006). However, differences in sample characteristics have to be taken into account when interpreting the study results. Haffner et al. (2006) included children with ADHD diagnosis following ICD-10 (F90.0, F90.1 & F90.9), partly receiving pharmacological treatment. In contrast, participants in the study from Jensen and Kenny (2004) partly were medicated, but diagnosis was based on the DSM-IV criteria and some comorbidities, such as anxiety disorder and learning disability, were not excluded.

Sensori- or perceptual-motor training

Some single-case reports and pilot studies documented the effects of exclusive psychomotor treatments or movement therapies focusing on perception and motor control in children with ADHD (Cuypers, De Ridder, & Strandheim, 2011; Grönlund, Renck, & Weibull, 2005; Majorek, Tüchelmann, & Heusser, 2004). Only few studies examined the effects of such treatments in sufficiently large samples and under controlled conditions. For instance, Banaschewski et al. (2001) and Park et al. (2013) evaluated the efficacy of sensorimotor training in children with ADHD and observed significant improvements in sensory and motor function and in impulse control, and significant reductions in behavioral problems. The sensorimotor program used by Banaschewski et al. (2001) consisted of motor activities stimulating the vestibular system, training self-control and motor control and perception with and without visual feedback, and participation in different sports. Twelve children (five receiving medication of methylphenidate) with a diagnosis of hyperkinetic disorder (ICD-10 F90.0), also fulfilling DSM IV criteria for ADHD-C, and without other medical disorders, completed 20 exercise sessions and cognitive training each over a period of 4 months in a within-subject crossover design. The results indicated that sensorimotor training was associated with significant improvements in sensory integration and body coordination, and with significant reductions in behavioral and emotional problems. The largest effects were reported for the reduction in aggressive behavior (d = 1.38) and the ADHD symptom score (d = 0.85). In contrast, only cognitive training significantly affected objective measured impulse control (d = 0.98).

In comparison, the results of Park et al. (2013) suggested that sensorimotor training can also positively affect cognitive development. A visual and auditory stimuli program called Neurosync was evaluated in 47 boys, clinically diagnosed with ADHD and without mental and neurological comorbidities, and significantly positively influenced aspects of executive function. The program included exercise-related games to strengthen sensory integration and information processing, motor planning and execution, balance, and rhythm, and consisted of four different parts: core muscle training, targeting ball exercises, ocular motor exercises, and visual auditory motor integration. After the 12-week treatment (60 min per day two to three times a week), the participants showed significantly improved executive functions indicated by significantly increased Stroop color, word, and color-word scores (d = 0.37-0.66). There were no significant changes in nonverbal intelligence.

Summary

Referring to the interventional studies reviewed here, long-term effects of exercise in children and adolescents with ADHD have been mainly described as a decrease in emotional and behavioral problems. Mixed and specific exercise programs as well as sensorimotor trainings resulted in small to large effects on ADHD symptoms (Ahmed & Mohamed, 2011; Banaschewski et al., 2001; Choi et al., 2014; Haffner et al., 2006; Hernandez-Reif et al., 2001; Jensen & Kenny, 2004; Kang et al., 2011; Lufi & Parish-Plass, 2011; McKune et al., 2003; Zivkovic et al., 2012). The effect sizes for the improvement in the total parent or teacher rating scores ranged from d = 0.26 (Lufi & Parish-Plass, 2011) to d = 2.39 (Choi et al., 2014). Results of six studies including objective tests measuring cognitive function confirmed that exercise programs can have medium to large effects (d = 0.37-1.37) on attention and inhibition in children and adolescents with ADHD (Chang et al., 2014; Choi et al., 2014; Haffner et al., 2006; Kang et al., 2011; Park et al., 2013; Verret et al., 2012). Two studies did not find an effect of Yoga or sensorimotor training on attention and impulse control especially in boys with ADHD (Banaschewski et al., 2001; Jensen & Kenny, 2004).

Teacher and parent ratings (Ahmed & Mohamed, 2011; McKune et al., 2003) and results of objective motor performance tests (Banaschewski et al., 2001; Chang et al., 2014; Pan et al., 2017; Verret et al., 2012) revealed that exercise interventions can also have positive effects on motor skill development and physical fitness in children and adolescents with ADHD. The effect sizes ranged from d = 0.31 for strength-related tasks such as curl-ups to d = 2.82 for fine motor control (Pan et al., 2017).

Discussion

The present systematic review suggests the possibility of both acute and long-term effects of exercise on health in children and adolescents with ADHD. The effects have been mainly described on the cognitive, behavioral, and physical level with the largest effects reported for mixed exercise programs on ADHD symptomatology (Choi et al., 2014) and fine motor precision (Pan et al., 2017) in samples of male participants. The latter is particularly important due to the fact that a majority of children with ADHD have poorer fine motor skills than their peers (Barbosa Goulardins et al., 2011; Fliers et al., 2010; Kaiser et al., 2014; Martin, Piek, & Hay, 2006; Meyer & Sagvolden, 2006). In contrast to previous findings and theoretical approaches suggesting a higher efficacy of interventions earlier in development (Halperin, Bédard, & Curchack-Lichtin, 2012; Rommel et al., 2013), large effects have also been reported for intervention programs in adolescents with ADHD (Ahmed & Mohamed, 2011; Choi et al., 2014; Hernandez-Reif et al., 2001). However, effect sizes were not available for all studies and there were large differences between individual study designs. For instance, the intervention programs differed in duration and frequency, and many different tests and instruments were used for measuring similar outcomes. In addition, the samples varied widely not only in age but also in gender, ADHD subtype, medication status, and adherence, and other individual characteristics such as physical fitness or sport-specific motor and cognitive skills were not specified, which may have also moderated the efficacy of an intervention (Pesce, 2012). Another very important aspect, which has to be taken into consideration when evaluating an intervention in children with ADHD, is the presence of comorbidities. A number of studies did not report detailed information on exclusion criteria and those that excluded children with further medical disorders differed widely regarding their formulated diagnoses of exclusion. Similarly, socioeconomic status of parents has not been considered in the majority of interventional approaches. However, considering the effects of all these factors would require much larger sample sizes.

Nonetheless, all studies investigating the long-term effects of exercise on motor development and ADHD symptomatology rated by parents or teachers reported significant positive effects. In contrast, the results regarding long-term effects on objectively measured cognitive functioning are not evident to date. Studies evaluating mixed exercise programs showed significant medium to large effects on several aspects of executive function and attention in children and in adolescents with ADHD. However, Banaschewski et al. (2001) and Jensen and Kenny (2004) did not report a significant improvement in impulse control or attention following 20 sessions of sensorimotor or Yoga training. The duration and frequency of the intervention did not vary largely from those of other programs. The major differences between studies are the type of exercise and the tests used to measure cognitive function as well as ADHD diagnosis criteria and included comorbidities. Nonetheless, there is not sufficient evidence that sensorimotor or Yoga trainings do not have positive effects on cognition in children and adolescents with ADHD because of the positive findings in similar studies by Haffner et al. (2006) and Park et al. (2013). Further research is needed to elucidate the effects of such specific interventions in sufficiently large samples and with standardized measures to verify their efficacy. Gender differences between cohorts included in studies investigating the efficacy of Yoga suggest the possibility that Yoga has stronger effects on girls than on boys with ADHD. However, Haffner et al. (2006) did not report their results by gender, and hence further research is necessary to test this assumption. It is important to note that in all studies participants were predominantly male and eight studies included only boys. These aspects and the specific interests and inclinations of the target group must be taken into account when planning and implementing a motivating exercise program for children with ADHD. Creating exercise programs, which capture children with attentional and frequently motor deficits, and keep them involved, provides a future research challenge. To date, only few studies have investigated sport participation and exercise patterns in children and adolescents with ADHD (e.g., Harvey, Reid, Bloom, & Staples, 2009; Johnson & Rosén, 2000; Lee, Causgrove Dunn, & Holt, 2014).

In addition, understanding the physiological mechanisms underlying exercise-related acute and chronic effects in children and adolescents with ADHD is necessary to explain the outcomes of different exercise programs on functional parameters such as cognition. In contrast to the extensive neuroimaging research in normally developing children (e.g., Chaddock et al., 2010; Chaddock et al., 2012; Hillman, Kamijo, & Scudder, 2011), to the best of our knowledge only one study has investigated the effects of exercise on brain activity in adolescents with ADHD using fMRI (Choi et al., 2014). Moreover, only Wigal et al. (2003) examined the physiological response to exercise on catecholamine levels in children with ADHD. The results of that study raise the question if acute improvements of cognitive functions are independent of changes in catecholamine levels. Only Medina et al. (2010) evaluated the acute efficacy of exercise dependent on the use of methylphenidate and reported that methylphenidate treatment did not affect these effects. In comparison, Haffner et al. (2006) showed that a long-term Yoga intervention was particularly effective in children undergoing pharmacotherapy with methylphenidate. Despite these results, the physiological mechanisms underlying the acute and long-term effects of exercise on cognition and behavior in children with ADHD and the specific role of catecholamine are still unclear.

Moreover, the optimal range of exercise intensity for maximum effects is still unknown. The results reported by Tantillo et al. (2002) indicate that high-intensity exercise is required to achieve significant changes in brain dopaminergic activity in boys with ADHD whereas girls performed significantly better after submaximal exercises. The significantly greater prevalence of ADHD in boys than girls (Faraone, Sergeant, Gillberg, & Biederman, 2003) questions the focus on moderate, aerobic exercise in most exercise programs. As stated previously by Rommel et al. (2013), aerobic exercise in humans and animal models of ADHD has positive effects but to date there has not been sufficient evidence that proves that the efficacy of this type of exercise is superior to that of other types of exercise. In addition, further research is needed to elucidate the acute effects of exercises of different intensities in larger samples and in field settings. However, attributing particular long-term effects of exercise interventions to specific activities or exercise intensities, especially if the program also includes behavioral or cognitive trainings, is difficult (Lufi & Parish-Plass, 2011; Zivkovic et al., 2012). For instance, the exercise program used by Pan et al. (2017) is an intervention that did not only include aerobic exercises but also focused on different aspects such as improving physical fitness, motor proficiency, team building, and social interaction. Unfortunately, only few articles provide detailed descriptions of the exercise program and its contents. The simple assumption that multiple bouts of acute aerobic exercise have an additive effect responsible for the long-term effects of a training program (Wigal et al., 2013) appears questionable. Moreover, exercise interventions including high-intensity training regimen are needed to elucidate the long-term effects of exercise programs of different intensities.

Similarly, to date recommendation regarding the optimal frequency or duration of exercise for achieving best possible results cannot be specified. Clearly, a minimum amount of exercise is needed to attain significant effects and additional (home) practice may also have a positive impact. For instance, Jensen and Kenny (2004) showed that the children who attended the maximum Yoga sessions showed the greatest reductions in ADHD symptoms. The authors concluded that children need to exercise regularly and frequently over a longer period to show large effects. However, the evidence presented in the studies included in this review is insufficient to conclude that exercise programs with the longest intervention period are the most effective.

The discussion of the efficacy of aerobic exercise in children with ADHD is closely linked to the fundamental question if quantitative or qualitative characteristics of physical activity are responsible for the success of an exercise program. Pesce (2012) and Lehnert (2014) suggested that the complexity and cognitive demands of a movement task play an important role in obtaining long-term cognitive benefits of exercise. Similarly, Best (2010) formulated three general mechanisms of how exercise may facilitate executive functioning in children. In addition to the physical changes that depend on quantitative exercise characteristics, the cognitive demands of the exercise task and the movement complexity have been described as important pathways (Best, 2010). Children with ADHD do not only have difficulties in cognition but also show general deficits in self-regulation affecting social interaction, emotion regulation, and motor control. These observations suggest that the type and demands (social, cognitive, and coordinative) of exercise play an even larger role. The concept of self-regulation defined as a “volitional cognitive and behavioural process through which an individual maintains levels of emotional, motivational, and cognitive arousal” (Blair & Diamond, 2008, p. 900) is closely linked to the neuropsychological concept of executive function (Posner, Rothbart, Sheese, & Tang, 2007; Rizzo, Steinhausen, & Drechsler, 2010). Several aspects of executive function might be trained by complex motor planning, problem solving, and goal-setting tasks and by cooperative activities in exercise programs (Goudas, Dermitzaki, Leondari, & Danish, 2006; Pesce, 2012). Intervention studies in children and adolescents with ADHD focusing more on qualitative than on quantitative exercise characteristics revealed that different types of exercise can have many positive effects (Banaschewski et al., 2001; Haffner et al., 2006; Lufi & Parish-Plass, 2011; Pan et al., 2017; Park et al., 2013). These effects have been mainly described as behavioral changes rated by parents or teachers and as enhanced motor performance. In contrast, the effects of exercise on cognitive functions are rarely investigated and remain unclear. To date, the acute effects of exercises have only been studied for running or cycling, and hence a comparison between different types of exercise is currently not possible. The positive results of Budde, Voelcker-Rehage, Pietraßyk-Kendziorra, Ribeiroc, and Tidowa (2008), who investigated the effects of acute bilateral coordinative exercises on attention in comparison with an exercise program without specific coordinative demands in healthy adolescents, suggest a pre-activation of brain structures that are also responsible for mediating attention by complex motor tasks.

The aim of an exercise program to improve behavioral self-regulation is closely linked to the aspect of enhancing social behavior. For both, training in a group is an important exercise characteristic. Social interaction with peers who experience similar problems has also been discussed as an independent factor decreasing the severity of ADHD symptoms in children (McKune et al., 2003). Most intervention programs have been applied in groups of 10 to 15 participants according to the sample size of the intervention group. Whereas some articles did not specify the size of the exercise groups (Ahmed & Mohamed, 2011; Park et al., 2013; Zivkovic et al., 2012), other studies divided the participants into smaller training groups of less than 10 participants (Banaschewski et al., 2001; Lufi & Parish-Plass, 2011; Pan et al., 2017). Latter studies focused on improving sensory integration, motor coordination, or behavior and social skills rather than cognitive performance. Smaller group sizes facilitate individual supervision and adaption of the exercise program. Further interventional studies should include such intervention characteristics and investigate differences in long-term effects between individual exercise sessions and group exercise sessions.

In addition to exercise characteristics such as type, physical, cognitive and social demands, supervision, and support, the environment may play an important role (Halperin & Healey, 2011; Taylor & Kuo, 2009). For instance, brain development is highly responsive to environmental enrichment (Halperin & Healey, 2011). However, the moderating influence of the (natural) environment on the efficacy of acute and chronic exercise interventions is still largely unknown. Results of Taylor and Kuo (2009) indicate that exercising in a natural environment might have larger effects than exercising in an urban area. Future research should address the question if exercising outdoors has superior effects than standard indoor exercise programs in gyms or laboratory settings.

Taken together, based on the current state of research, and the limitations of the presented studies, a general statement on the effectiveness of different types of exercise interventions cannot be made at this time. The studies are lacking with regard to the small sample sizes and heterogeneous sample characteristics, the incomplete presentation as well as documentation of the implemented exercise program, the investigation of physiological changes only on rare occasions, the lack of consideration of important factors (e.g., medication, ADHD subtypes, comorbidities, and socioeconomic status) and randomized controlled trials, and the choice of control groups. Although some of the present studies included control groups, there were no other homogeneous intervention groups consisting of children with a diagnosis other than ADHD (e.g., depression). Only one study included children with other behavioral disorders as the comparison group, but the diagnoses were heterogeneous and the effects did not differ significantly between intervention and control groups (Lufi & Parish-Plass, 2011). Therefore, the question arises if the reported results are specific to ADHD or apply to any child or adolescent with some psychiatric disorder. The final point that has to be taken into account is the lack of blinding in many of the studies. Teacher and parent ratings are commonly used measures to evaluate behavioral changes in children and adolescents with ADHD (e.g., McKune et al., 2003). However, the results of a meta-analysis on non-pharmacological interventions in ADHD treatment show that the effect sizes dramatically lower when only probably blinded ratings are considered (Sonuga-Barke et al., 2013).

Based on these limitations, challenges for future research include (a) examining the physiological mechanisms underlying the positive effects of different types of exercise on ADHD symptomatology; (b) examining the moderating effects of individual characteristics such as age, gender, socioeconomic status, ADHD subtypes and diagnosis criteria, comorbidities, medical status, physical fitness, and so on; (c) replicating and blinding studies to validate the reported effects; (d) answering the question how exercise programs have to be designed to best capture and sustain children’s engagement despite their cognitive and motor deficits; and (e) the development of strategies to understand the additional benefits of exercise over common treatment components such as medication or parent management.

Strength and Limitations

The strengths of this review are the systematic literature search and analysis of literature providing an overview of the efficacy of different types of exercise interventions in children and adolescents with ADHD. This review presents all approaches and outcomes of exercise published to date. One limitation of this study is that because of the lack of available data the study results could not be analyzed quantitatively. In addition, the quality of the included studies was not assessed using a study quality assessment tool, and articles with abstracts not written in English were excluded. Therefore, some relevant studies may have been omitted.

Conclusions

The results presented in the literature suggest that multifaceted exercise programs seem to be the most effective in enhancing all facets of health including physical, mental, and social well-being (following the definition of the WHO 1948; Grad, 2002) in children and adolescents with ADHD. To date, there is no evidence for the importance of controlling for intensity and duration of exercise for the efficacy of exercise programs in children and adolescents with ADHD. However, neural development requires being physically active for extended periods of time (Halperin & Healey, 2011). Hence, not only the quantitative exercise characteristics but also the qualitative, educational, and developmental aspects of sports and exercise are important. Team activities, and coordinative and body perception exercises should be tailored to the individual’s needs to achieve improvements in social behavior, self-regulation skills, and motor performance. Moreover, exercise programs provide a good opportunity to integrate cognitive trainings and behavioral education (Lufi & Parish-Plass, 2011; O’Connor et al., 2014; Zivkovic et al., 2012). For instance, exercise games and tasks can be designed to include “if-then plans,” which have been evaluated as an effective behavioral treatment option (Gawrilow et al., 2011).

Because positive, especially acute, effects of aerobic running or cycling exercises on cognition in children with ADHD have been reported by several studies, endurance training should be part of exercise programs. In addition to the direct effects on executive function and attention, improvements in aerobic fitness lead to further physiologic health benefits, which are particularly important because obesity is a common problem in children with ADHD (Cortese et al., 2008). Compared with simple running or cycling exercises, sport-specific training (for instance, ball games) offers the opportunity of improving physical fitness in combination with social behavior and sports skills. Another positive effect of the latter might be the facilitated integration of children and adolescents with ADHD into physical education and sport clubs in non-therapeutic settings. Moreover, improvements in the sports context, such as rule adherence and cooperation, may positively influence behavior in daily life (O’Connor et al., 2014).

Clearly, controlled studies with larger sample sizes are needed to verify these findings and to formulate specific evidence-based recommendations for intervention planning. At that time, the results reported in the literature only allow identifying some first trends and illustrate the complexity of studying the effects of exercise in children and adolescents with ADHD.

Footnotes

Acknowledgements

We would like to express our appreciation to PD Dr. Annegret Mündermann (University of Konstanz) for their writing assistance.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work is part of the Motorik Modul Longitudinal Study, which is funded by a project grant from the German Ministry of Education and Research (Bundesministerium für Bildung und Forschung). The content of this article reflects only the authors’ views and the funders are not liable for the content of this manuscript.

Author Biographies

Christina Neudecker, MSc, is a research assistant at the Department of Sports and Sports Sciences at the Karlsruhe Institute of Technology. Her research interests include exercise patterns and effects of physical activity and exercise in children with developmental disorders.

Nadine Mewes is a research associate at the Department of Sports and Sports Sciences at the Karlsruhe Institute of Technology. She received her PhD in sports sciences from the University of Bochum, Germany. The focus of her research is the interrelationship between physical activity and mental health of children and adolescents.

Anne K. Reimers is a postdoctoral fellow at the Department of Sports Science at the University of Konstanz and at the Department of Sports and Sports Science at the Karlsruhe Institute of Technology, Germany. She received her PhD in social sciences from the University of Konstanz, Germany. Her primary interests are preventive and therapeutic effects of physical activity and exercise, and health promotion and determinants of physical activity in children and adolescents.

Alexander Woll is a full professor and head of the Department of Sports and Sports Science at the Karlsruhe Institute of Technology. Before, he was head of the Department of Sports Science at the University of Konstanz, Germany (2004-2012). His research interests are the relationships between physical activity, fitness, and health in the life course. He is the chairman of the commission “Health” of the German Union of Sport Science.

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