Motor proficiency and physical fitness in adolescent males with and without autism spectrum disorders

Abstract

This study compared components of motor proficiency and physical fitness in adolescents with and without autism spectrum disorders, and assessed the associations between the two measures within each group. A total of 62 adolescent males with (n = 31) and without (n = 31) autism spectrum disorders aged 10–17 years completed the Bruininks–Oseretsky Test of Motor Proficiency (2nd ed.), the BROCKPORT Physical Fitness Test, and the bioelectrical impedance analysis. The main findings are as follows: (1) adolescents with autism spectrum disorders had significantly lower scores on all motor proficiency and fitness measures, except body composition, than adolescents without autism spectrum disorders and that (2) the types of associations between the two measures differed significantly across the groups. Specific interventions to maximize motor proficiency and physical fitness in adolescents with autism spectrum disorders are urgently needed.

Keywords

adolescents autism motor proficiency physical fitness

Introduction

Autism spectrum disorder (ASD) is a developmental disorder characterized by impaired social interaction, communication, and behavioral development (American Psychiatric Association, 1994). Clinicians now recognize that youths with ASD also experience delayed or impaired motor development (Green et al., 2009; Pan et al., 2009; Staples and Reid, 2010). Such motor difficulties and social and behavioral deficits may limit opportunities for individuals with ASD to successfully participate in physical activities, thus placing them at risk for being physically inactive and unfit. Although such research is scant, studies have reported that youths with ASD (Pan and Frey, 2006) were less active than their peers without disabilities (Trost et al., 2002), and the level of physical activity of the ASD youths declined with age (Pan et al., 2011b; Pan and Frey, 2006). Recent research with adolescents with Asperger’s syndrome, a higher end disorder within the ASD continuum, indicated that they were less physically active and scored lower on all physical fitness subtests, compared with adolescents without Asperger’s syndrome (Borremans et al., 2010). These studies have collectively established that lower levels of physical activity and fitness are widespread in youths with ASD, compared with their typically developing peers.

Because maintaining appropriate levels of physical activity and health-related physical fitness are critical for developing healthy lifestyles, identifying the potential underlying factors that may contribute to the adoption of physically inactive lifestyles is important for developing strategies to improve the health of youths with and without disabilities. One possible determinant of adolescent physical activity and fitness is motor-skill proficiency. The existing data for the general population seem to provide a compelling argument that motor-skill competence is related to physical activity and fitness. Whereas studies of the general population indicated that children with good motor skills are more likely to become fit adolescents (Barnett et al., 2008b) and maintain adequate fitness levels into adulthood (Stodden et al., 2009), others reported that the statistical relationship between these variables was typically small (Jaakkola et al., 2009), or non-existent (Jaakkola et al., 2009; McKenzie et al., 2002), or were initially reciprocal (Barnett et al., 2011) and then ever changing based on subsequent evaluations of demographic characteristics and skills-related measures, such as process- versus product-oriented motor-skill assessments. McKenzie et al. (2002) assessed the relationships between a select number of movement skills and physical activity in adolescents, and observed that the development of fundamental skills was low, and that it was not related to subsequent physical activity behaviors. However, they speculated that the process-oriented assessments may have been inappropriate and that the range of the components for the movement skills may have been restrictive. Jaakkola et al. (2009) evaluated the association between adolescents’ movement skills and certain physical activities, including sports club usage and leisure activities, and found small correlations between fundamental movement skills and physical activity in sports clubs, but no correlation with leisure-time physical activity was observed. They suggested that typical light to moderate intensity of leisure-time physical activities may not lead to the development of movement skills to the same extent as vigorous physical activities that are typically performed in sports clubs. Barnett et al. (2011) explored the directional relationships between adolescent’s motor-skill proficiency and moderate-to-vigorous physical activity (MVPA), and concluded that the relationship between motor-skill proficiency and MVPA is reciprocal for object-control skill but not for locomotor skill. Despite these inconsistencies, motor-skill proficiency is clearly important for achieving sufficient physical activity levels and maintaining aspects of health-related physical fitness.

Reports of the associations between motor-skill proficiency and physical fitness levels of youths have also been inconsistent. A recent study (Emck et al., 2010) reported association between specific combinations of impaired motor skills and physical fitness levels in youths with psychiatric disorders aged 9–11 years, including youths with ASD. ASD is also referred to as a pervasive developmental disorder (PDD). Emck et al. (2010) compared evaluations of gross motor performance and physical fitness in three psychiatric subgroups: children with emotional disorders, behavioral disorders, or PDD. Gross motor performance and physical fitness were measured according to the Test of Gross Motor Development (2nd ed.; TGMD-2) and the Motor Performance Test (MOPER), respectively. The authors observed poor gross motor performance and neuromotor fitness in all three groups of children. The PDD group showed the most severe gross motor impairment among all the groups, but no significant differences in neuromotor fitness were observed among the groups. Furthermore, a significant relationship between locomotion performance and the overall neuromotor fitness (r = 0.47) was observed in the PDD group, and the overall gross motor performance was significantly correlated with the overall strength (r = 0.52) in these children as well. Because the relationship between motor-skill proficiency and physical fitness may differ between childhood and adolescence, research across age groups using more skill-related tests is warranted to evaluate the relationship between motor-skills performance and physical fitness in young people with ASD.

To date, information on fitness levels in youths with ASD is scarce, and no published study has examined whether there is an association between fitness levels and motor-skills performance in sedentary school-aged adolescents with ASD. In addition, evaluations of the associations between these two variables in typically developing youths are inconsistent. Improving the physical fitness of adolescents with ASD through teaching motor skills, while simultaneously increasing their physical activity levels, should be a public health priority. Other research indicated that physical activity interventions improved both motor skills and fitness levels in children with and without ASD (Pan, 2011). This suggests that children with ASD can learn motor skills and increase fitness levels through increased participation in physical activities, thus narrowing the skill gap and leading to more active lifestyles and better physical fitness. Such long-term improvements may result in greater participation in competitive sports with peers without disabilities or later participation at recreation centers as adults.

The purposes of the present study were to compare components of motor proficiency and physical fitness in adolescents with and without ASD, and to assess the associations between these variables within each participant group. Based on previous theoretical considerations, it was hypothesized that (1) adolescents with ASD would demonstrate lower levels of motor proficiency in all subtests and a lower total motor composite as assessed with the Bruininks–Oseretsky Test of Motor Proficiency (2nd ed.; BOT-2; Bruininks and Bruininks, 2005), compared with adolescents without ASD; (2) adolescents with ASD would exhibit lower levels of physical fitness profiles as measured using the BROCKPORT Physical Fitness Test (BPFT; Winnick and Short, 1999), compared with adolescents without ASD; and (c) group-dependent relationships would exist between motor proficiency scores and physical fitness profiles.

Method

Participants

Participants with and without ASD were recruited from a single large urban city (N = 2,773,483) of high social and economic deprivation through a university-based physical activity program for youths with ASD, local autism support groups, and available media, including direct contact, e-mail announcements, and autism LISTSERVs. All of the ASD adolescents who were selected for our study met the diagnostic criteria for ASD as presented in the American Psychiatric Association’s (1994) Diagnostic and Statistical Manual of Mental Disorders. Adolescents with ASD had been previously diagnosed through medical and psychological assessments administered by experienced physicians in the public hospitals (Taiwan Executive Yuan Department of Health, 2010a).

A total of 62 adolescent males with (n = 31) and without (n = 31) ASD aged 10–17 years from 41 secondary schools participated in the study. The mean age was 14.58 ± 1.55 and 14.70 ± 1.63 years, the mean height was 167.05 ± 7.23 and 167.01 ± 9.35 cm, and the mean body mass was 61.34 ± 12.93 and 60.04 ± 14.32 kg for adolescents with and without ASD, respectively. A total of 7 children with Asperger’s syndrome and 24 children with mild autistic disorders (high-functioning autism) were included in our study (Taiwan Executive Yuan Department of Health, 2010b). The intelligence of the children with mild autistic disorders were within normal ranges, but social-adaptive skills and language comprehension and expression were slightly impaired (Taiwan Executive Yuan Department of Health, 2010b). The control group consisted of 31 age- and gender-matched adolescents. According to their parents’ reports, the participants in the control group had no physical or mental disabilities. This study was approved by the Ethics Committee for Human Experimentation at the National Kaohsiung Normal University, and written informed consent was obtained from all participants and their parents.

Measures

Although selecting an appropriate assessment instrument to evaluate youths with ASD can be difficult, there were several benefits of using the BOT-2 (Bruininks and Bruininks, 2005) and the BPFT (Winnick and Short, 1999) within this population. First, the BOT-2 is an individually administered test that uses goal-directed activities to measure a wide array of motor skills in individuals aged 4–21 years. Second, the BOT-2 is designed to provide practitioners, such as occupational therapists, physical therapists, adapted physical education teachers, and researchers, with a reliable and efficient measure of fine and gross motor control skills. Third, the BPFT field tests do not require laboratory conditions, and therefore provide valuable information on the physical fitness of participants. Fourth, the BPFT addresses significant health indicators, such as detection of risk factors associated with cardiovascular disease, as predictors for lifelong physical activity engagement. Fifth, different or modified test items or standards are presented in the BPFT for most youths with disabilities and unique physical fitness needs.

Motor proficiency

Motor proficiency was assessed with the BOT-2, a standardized evaluation of gross and fine motor skills (Bruininks and Bruininks, 2005). The BOT-2 consists of four motor-area composites, and each motor-area composite consists of two subtests that assess related aspects of motor function. The four motor-area composites of the BOT-2 are fine motor control, manual coordination, body coordination, and strength and agility. The fine manual control composite consists of evaluations of fine motor precision (seven items, score range = 0–41) and fine motor integration (eight items, score range = 0–40). The manual coordination composite consists of evaluations of manual dexterity (five items, score range = 0–45) and upper-limb coordination (seven items, score range = 0–39). The body coordination composite consists of evaluations of bilateral coordination (seven items, score range = 0–24) and balance (nine items, score range = 0–37). The strength and agility composite consists of evaluations of running speed and agility (five items, score range = 0–52) and strength (five items, score range = 0–42). The four composite scores were combined to generate a total motor composite score. The average age-adjusted scale score for the subtests was 15 ± 5, whereas composites that were derived by summing the subtest scale scores and converting them to a quotient had a mean of 100 ± 15. The test items are presented in Table 1.

Table 1.

BOT-2 contents.

Composite	Subtest	Item
Fine manual control	Fine motor precision	Filling in shapes—circle, filling in shapes—star; drawing lines through paths—crooked, drawing lines through paths—curved, connecting dots; folding paper; cutting out a circle
	Fine motor integration	Copying a circle, copying a square, copying overlapping circles, copying a wavy line, copying a triangle, copying a diamond, copying a star, copying overlapping pencils
Manual coordination	Manual dexterity	Making dots in circles, transferring pennies, placing pegs into a pegboard, sorting cards, stringing blocks
	Upper-limb coordination	Dropping and catching a ball—both hands, catching a tossed ball—both hands, dropping and catching a ball—one hand, catching a tossed ball—one hand, dribbling a ball—one hand, dribbling a ball—alternating hands, throwing a ball at a target
Body coordination	Bilateral coordination	Touching nose with index fingers—eye closed, jumping jacks, jumping in place—same sides synchronized, jumping in place—opposite sides synchronized, pivoting thumbs and index fingers, tapping feet and fingers—same sides synchronized, tapping feet and fingers—opposite sides synchronized
	Balance	Standing with feet apart on a line—eyes open, walking forward on a line, standing on one leg on a line—eyes open, standing with feet apart on a line—eyes closed, walking forward heel-to-toe on a line, standing on one leg on a line—eyes closed, standing on one leg on a balance beam—eyes open, standing heel-to-toe on a balance beam, standing on one leg on a balance beam—eyes closed
Strength and agility	Running speed and agility	Shuttle run, stepping sideways over a balance beam, one-legged stationary hop, one-legged side hop, two-legged side hop
	Strength	Standing long jump, knee push-ups, sit-ups, wall sit, V-up

This table is adapted from Bruininks and Bruininks (2005).

The BOT-2 has demonstrated validity and reliability for the evaluation of children, adolescents, and young adults with development coordination disorders and intellectual disabilities (Bruininks and Bruininks, 2005). Interrater reliability, test–retest reliability, and internal consistency were moderate to strong (>0.80). Content validity, internal structure, and relationships with other measures of motor performance were strong (r = 0.80; Bruininks and Bruininks, 2005).

All evaluations in our study were administered by the researcher and two trained graduate students using the standardized procedures that are specified in the test manuals (Bruininks and Bruininks, 2005). Before the data collection, all assessors were formally trained and were given written instructions on the application and scoring of the tests. To monitor the reliability of the BOT-2 evaluations, all of the assessors were tested using a criterion-test videotape.

Physical fitness

The BPFT (Winnick and Short, 1999) and bioelectrical impedance analysis (BIA) (MF-BIA8, InBody 720, Biospace) were used to assess fitness components and body composition, respectively. Developed through a research project funded by the US Department of Education in 1993, the BPFT is a health-related, criterion-referenced physical fitness test for youths aged 10–17 years, and the BPFT manual includes separate instructions for youths with and without disabilities. Each component of physical-fitness functioning can be evaluated using gender- and age-specific minimal or preferred general standards. For example, for a male aged 17 years, the minimal and preferred standards for the 20-m progressive aerobic cardiovascular endurance run (PACER) are 57 and 94 laps, respectively. Individuals should score at minimum levels of each component of physical fitness for independent living and participation in physical activities. Raw scores were used for the data analysis in the current study. The validity of the BPFT has been determined using concurrent, construct, and content validity on each item for each disability involved (Winnick and Short, 1999). For this study, the following physiological assessments in the BPFT were performed on all the participants: (a) The isometric push-up test, for assessment of upper-body muscular strength and endurance; (b) the curl-up test, for assessment of abdominal muscular strength and endurance; (c) the back-saver sit-and-reach test, for assessment of lower-body flexibility; and (d) the 20-m PACER, for assessment of aerobic functioning.

In the isometric push-up test, participants attempted to sustain a raised push-up position for 40 s. The participants assumed a front-leaning rest position with the hands directly below the shoulders, arms extended, the whole body in a straight line, and toes touching the floor. Scoring was terminated at 40 s, or when the correct front-leaning rest position was no longer held.

In the curl-up test, the participants completed as many curl-ups as possible at a rate of one curl every 3 s. The participants lied on a mat in a supine position. Their knees were bent at approximately 140° with their feet placed flat on the floor and their legs held slightly apart. Their outstretched arms were held parallel to their trunk, with their palms facing downward, and their fingers outstretched. The tips of the participants’ outstretched fingers rested on the leading edge of the 11.4-cm measuring strip. As participants curled up, their hands were moved across the measuring strip. When their fingertips reached the opposing edge of the measuring strip, they returned to the starting, supine position. Scoring was terminated at 75 curl-ups, or when additional repetitions could no longer be performed.

In the back-saver sit-and-reach test, the participants sat with one leg straight and the other leg bent. The foot of the bent leg was placed flat on the floor beside the knee of the straight leg. The sit-and-reach box was approximately 30 cm high and 30 cm wide. The participants’ arms were extended forward over the measuring scale with their palms facing downward, one on top of the other. The participants reached directly forward with both hands along the scale toward the sit-and-reach box. Participants performed four reaching repetitions, holding the final reach position for at least 1 s. Following the initial set of sit-and-reach measurements, the participants switched leg positions, and a second set of sit-and-reach measurements were collected.

For the PACER test, a 20 m distance was measured and marked with tape at each end. The participants ran back and forth across the 20 m distance as long as possible at a specified pace that was progressively increased each minute during the performance. The test was terminated when the children could no longer maintain the pace for two laps. The participants’ scores were recorded as the number of repetitions that were completed. The PACER test has shown acceptable concurrent validity and criterion-referenced validity for measured maximum oxygen uptake (VO₂max) and estimated VO₂max (Mao and Lin, 2006).

The body composition of participants was measured using BIA (MF-BIA8, InBody 720, Biospace). The BIA analyzer uses an alternating current of 250 mA at multiple frequencies, including 1, 5, 50, 250, 500, and 1000 kHz to measure segmental impedances at both arms, both legs, and the trunk for all frequencies. Participants stood with bare feet on the footplate, holding one electrode in each hand because measurements were acquired for 2 min. Fat-free mass (FFM), fat mass (FM), and percentage of body fat (%BF) were displayed by the instrument. FFM was estimated from total body water, using a prediction equation developed for Asians. The FM was calculated in kilogram units as FM = weight − FFM, and %BF was calculated as %BF = FM/weight × 100%. The precision error of the FFM, FM, and %BF measurements using the BIA instrument is less than 2% (Lim et al., 2009). Only body mass index (BMI) and %BF were used for the data analysis in the current study.

Procedure

During testing, all test equipment not in use was stored elsewhere to ensure the participants’ safety and full attention. Participants were not allowed to play with the equipment. All participants were tested in an isolated gymnasium because the individual data collection procedures were recommended for the unique behavioral problems and learning styles of individuals with ASD that may have otherwise affected optimal movement performance. There were no modifications to test items and/or instructions, and all test instructions were followed precisely. However, both tests permitted the administrator to give verbal directions and physical demonstrations to ensure the correct performance of the task. For example, participants with ASD were allowed to run with a tester during the PACER test, but the assistants did not pull or push participants or give them any other physical advantage. To ensure maximum effort for the motor proficiency and the fitness tests, parents were permitted to observe the testing, and each participant was motivated during testing with verbal praise and guidance. The durations of the BOT-2 and the BPFT were approximately 40–60 min per participant for each test.

Statistical analysis

The means and standard deviations are provided for all variables. Independent group t-tests were used to compare the physical fitness components between adolescents with and without ASD. One-way multivariate analysis of variance (MANOVA) was performed to evaluate the statistical significance of differences between the groups for the BOT-2 results. If significance was observed using MANOVA, a one-way analysis of variance (ANOVA) was performed on each subcomponent of the BOT-2 as a follow-up test to MANOVA. The effect size was computed and reported as ES (Cohen’s d = M₁ − M₂/σ_pooled) and partial η² for the independent t-test and the MANOVA/follow-up ANOVA evaluations, respectively.

For each group, Pearson’s partial correlations, controlled for age, were computed to assess the relationship between the BOT-2 scores and the fitness measures. The correlation was graded on the following scale according to a previously described method as follows (Domholdt, 2000): (1) 0–0.25 = little, (2) 0.26–0.49 = low, (3) 0.50–0.69 = moderate, (4) 0.70–0.89 = high, and (5) 0.90–1 = very high. All statistical analyses were performed using SPSS software (version 13.0), and the probability level was set at p < 0.05.

Results

Preliminary data analyses were conducted to determine the possibility of stimulant medication effects on motor-skill performance and the physical fitness of participants with ASD. No significant differences were found between adolescents with ASD who were receiving stimulant medication and those not receiving such medication across all dependent measures (fine manual control, t = −0.52, p = 0.61; manual coordination, t = 0.63, p = 0.54; body coordination, t = −0.04, p = 0.97; strength and agility, t = −1.01, p = 0.32; total motor composite, t = 0.16, p = 0.88; BMI, t = −1.54, p = 0.13; %BF, t = −0.96, p = 0.35; 20-m PACER, t = 1.46, p = 0.16; isometric push-up, t = 0.36, p = 0.73; curl-up, t = 0.75, p = 0.46; sit-and-reach right leg, t = −0.57, p = 0.57; sit-and-reach left leg, t = −0.67, p = 0.51). In addition, there were no significant differences between adolescents with and without ASD for age (t = −0.30, p = 0.76), height (t = 0.02, p = 0.99), and weight (t = 0.38, p = 0.71).

Motor proficiency and physical fitness in adolescents with and without ASD

The age- and gender-specific scores were used to determine the raw scores for each subtest using the BOT-2 manual. The raw scores were converted to composite scores and Z-scores by using the test manual. Adolescents with ASD had statistically significant lower scores than control adolescents for all BOT-2 subtests, composites, and total motor composite (Table 2). The manual coordination mean composite Z-score was the lowest (−14.48), followed by strength and agility mean composite Z-score (−12.55).

Table 2.

Motor proficiency and physical fitness measures of participants.

	ASD (n = 31)	Non-ASD (n = 31)	F or t	p values	Partial η² or ES
Motor proficiency
Composite^a
Fine manual control	37.87 ± 8.44	51.10 ± 7.21	16.80	0.00	0.22
Manual coordination	42.10 ± 7.56	50.39 ± 8.35	37.30	0.00	0.38
Body coordination	38.71 ± 8.13	53.19 ± 10.40	6.46	0.01	0.10
Strength and agility	40.84 ± 11.76	47.26 ± 7.71	40.38	0.00	0.40
Total	39.48 ± 9.50	52.03 ± 5.53	43.99	0.00	0.42
Subtests^b
Fine motor precision	10.68 ± 4.22	14.68 ± 4.13	14.21	0.00	0.19
Fine motor integration	13.35 ± 4.76	16.39 ± 4.36	6.84	0.01	0.10
Manual dexterity	12.26 ± 6.13	18.00 ± 4.29	18.25	0.00	0.23
Upper-limb coordination	8.87 ± 3.04	14.90 ± 4.02	44.40	0.00	0.43
Bilateral coordination	11.19 ± 5.46	13.87 ± 3.54	5.25	0.03	0.08
Balance	11.52 ± 6.80	14.42 ± 3.22	4.62	0.04	0.07
Running speed and agility	11.00 ± 5.66	16.65 ± 2.79	24.80	0.00	0.29
Strength	9.32 ± 5.15	15.81 ± 3.05	36.49	0.00	0.38
Physical fitness
BMI (kg/m²)	21.94 ± 4.60	21.43 ± 4.27	0.45	0.66	0.11
Percent body fat	21.43 ± 8.98	18.51 ± 8.11	1.34	0.18	0.34
20-m PACER	17.77 ± 13.00	42.65 ± 16.58	−6.57	0.00	−1.67
Isometric push-up (s)	31.32 ± 14.58	39.94 ± 0.36	−3.29	0.00	−0.84
Curl-up	15.84 ± 25.12	23.23 ± 25.14	−1.16	0.25	−0.29
Sit-and-reach (cm)
Right leg	21.65 ± 11.47	29.89 ± 8.66	−3.19	0.00	−0.81
Left leg	21.13 ± 10.92	29.65 ± 8.66	−3.40	0.00	−0.86

ASD = autism spectrum disorders; ES = effect size; BMI: body mass index; PACER: progressive aerobic cardiovascular endurance run; MANOVA: multivariate analysis of variance.

MANOVA (Wilks’s Lambda Criterion), for group, F_{(1, 60)} = 10.38, p < 0.01, Partial η² = 0.48.

MANOVA (Wilks’s Lambda Criterion), for group, F_{(1, 60)} = 7.42, p < 0.01, Partial η² = 0.53.

For the BPFT, significant differences between the two groups were observed in the results for the PACER, the isometric push-up, and the sit-and-reach tests (Table 2), indicating that adolescents with ASD had lower levels of cardiovascular endurance, upper-body muscular strength and endurance, and lower-body flexibility, compared with adolescents without ASD. No significant differences were observed between the groups for body composition and abdominal muscular strength and endurance.

The relationships between motor proficiency and physical fitness in adolescents with and without ASD

Partial correlations, controlled for age, between parameters of the BOT-2 and the BPFT scores in adolescents with ASD are shown in Table 3. Low to moderate correlations were found between total motor composite and all fitness measures, except body composition. For each motor composite, fine manual control was the only composite that was not significantly correlated with any fitness measure. Low to moderate correlations were found between lower-body flexibility, body coordination with aerobic functioning, and upper-body and abdominal muscular strength and endurance. Moderate to high correlations were found between strength and agility and all fitness measures, except body composition. Low to moderate correlations were found among manual coordination, the PACER, the isometric push-up, and the sit-and-reach test results.

Table 3.

Partial correlation coefficients between motor proficiency and physical fitness measures in adolescents with autism spectrum disorders.

	BMI	Percent body fat	20-m PACER	Curl-up	Isometric push-up	Sit-and-reach (left leg)	Sit-and-reach (right leg)
Subtests
Fine motor precision	0.02	−0.10	0.20	0.30	0.35	0.10	0.11
Fine motor integration	0.16	0.11	0.22	0.11	0.20	0.38*	0.36
Manual dexterity	−0.08	−0.13	0.49**	0.28	0.25	0.45*	0.40*
Upper-limb coordination	−0.09	−0.24	0.39*	0.29	0.40*	0.17	0.12
Bilateral coordination	0.02	−0.03	0.44*	0.33	0.30	0.46*	0.40*
Balance	−0.03	−0.14	0.39*	0.28	0.55**	0.22	0.24
Running speed and agility	0.03	−0.13	0.81**	0.56**	0.41*	0.46*	0.42*
Strength	0.04	−0.17	0.76**	0.67**	0.56**	0.67**	0.68**
Composites
Fine manual control	0.09	−0.00	0.25	0.19	0.36	0.29	0.27
Manual coordination	−0.12	−0.23	0.54**	0.30	0.38*	0.41*	0.35
Body coordination	0.00	−0.12	0.49**	0.38*	0.54**	0.41*	0.39*
Strength and agility	−0.05	−0.19	0.81**	0.63**	0.55**	0.60**	0.60**
Total motor composite	−0.01	−0.14	0.69**	0.44*	0.53**	0.47**	0.43*

BMI: body mass index; PACER: progressive aerobic cardiovascular endurance run.

The correlation is graded as follows: (a) 0–0.25 = little; (b) 0.26–0.49 = low; (c) 0.50–0.69 = moderate; (d) 0.70–0.89 = high; and (e) 0.90–1.00 = very high (Domholdt, 2000); level of significance *p < 0.05, **p < 0.01.

Table 4 shows the partial correlations, controlled for age, between parameters of the BPFT and the BOT-2 scores in adolescents without ASD. As shown in Table 4, the total motor composite was not significantly correlated with any fitness measure. For each motor composite, strength and agility was the only composite that was significantly correlated with fitness measures. Moderate correlations were found between the results of the PACER and the curl-up tests. A low correlation was observed between %BF and the scores for strength and agility.

Table 4.

Partial correlation coefficients between motor proficiency and physical fitness measures in adolescents without autism spectrum disorders.

	BMI	Percent body fat	20-m PACER	Curl-up	Isometric push-up	Sit-and-reach (left leg)	Sit-and-reach (right leg)
Subtests
Fine motor precision	−0.14	−0.03	−0.07	−0.10	0.30	−0.30	−0.19
Fine motor integration	0.19	0.15	−0.10	−0.15	−0.03	0.01	0.09
Manual dexterity	0.03	−0.18	0.31	0.30	−0.13	−0.02	0.01
Upper-limb coordination	−0.02	−0.13	0.05	0.26	−0.30	0.13	0.08
Bilateral coordination	−0.29	−0.26	0.16	−0.03	−0.22	−0.09	−0.09
Balance	−0.23	−0.14	0.07	0.03	0.14	0.19	0.17
Running speed and agility	−0.12	−0.37*	0.56**	0.52**	0.31	−0.18	−0.22
Strength	−0.04	−0.33	0.53**	0.37*	−0.08	0.42*	0.36*
Composites
Fine manual control	0.05	0.08	−0.12	−0.17	0.17	−0.16	−0.04
Manual coordination	0.02	−0.17	0.20	0.33	−0.27	0.03	0.01
Body coordination	−0.30	−0.19	0.10	−0.01	−0.04	0.07	0.08
Strength and agility	−0.08	−0.43*	0.62**	0.53**	0.11	0.14	0.09
Total motor composite	−0.14	−0.30	0.28	0.28	−0.05	0.07	0.07

BMI: body mass index; PACER: progressive aerobic cardiovascular endurance run.

The correlation is graded as: (a) 0–0.25 = little; (b) 0.26–0.49 = low; (c) 0.50–0.69 = moderate; (d) 0.70–0.89 = high; and (e) 0.90–1.00 = very high (Domholdt, 2000); level of significance *p < 0.05, **p < 0.01.

Discussion

This study examined the motor proficiency and the fitness levels in adolescents with and without ASD, and the possible associations between the two variables within each group. Findings indicated that adolescents with ASD performed significantly poorer on all motor proficiency measures, compared with adolescents without ASD. The results also indicated that adolescents with ASD demonstrated lower cardiovascular endurance, upper-body muscular strength and endurance, and lower-body flexibility than adolescents without ASD. For adolescents with ASD, significantly positive associations were found between total motor composite and all physical fitness components, except body composition. Body coordination and the strength and agility composites primarily contributed to these findings. For adolescents without ASD, total motor composite was not significantly related to any fitness measure, and the strength and agility composite was the only BOT-2 variable that was related to physical fitness in adolescents without ASD, including cardiovascular endurance, upper-body muscular strength and endurance, and %BF.

Adolescents with ASD demonstrated less-proficient motor skills than adolescents without ASD, and our findings are consistent with those of previous studies (Berkeley et al., 2001; Green et al., 2009; Staples and Reid, 2010), which reported that youths with ASD displayed poorer motor skills than typically developing youths. This may be attributable to the poorer social skills (American Psychiatric Association, 1994) or the lack of physical skills and motivation in adolescents with ASD (Pan et al., 2011a) because these variables may play a role in the practice and refinement of motor skills. Physical activity interventions should target motor learning with ambulant support, such as explicit instruction, prompting, and consistent reinforcement, to encourage lifestyle physical activity and to maintain motor abilities in daily life. Furthermore, in adolescents with ASD, low motor competence may also reflect an underlying delay or impairment in the development of motor skills. Poor levels of motor proficiency in adolescents with ASD may represent an additional aspect of ASD symptomatology. Findings support the notion that an assessment of the motor skills of people with ASD is required, in addition to the other developmental skill areas that are outlined in the diagnostic manuals (Berkeley et al., 2001; Emck et al., 2010). People with ASD have heterogeneous motor-skill profiles. A standard motor-skill assessment is therefore recommended for individuals with ASD, to provide interventions tailored to the specific symptoms of each person.

The significant differences that existed between fitness levels of adolescents with and without ASD are not surprising. Several fitness indices indicated that adolescents with ASD had lower fitness levels in cardiovascular endurance, lower-body flexibility, and upper-body muscular strength and endurance. These results are consistent with previous research indicating that adolescents with Asperger’s syndrome, a higher end disorder within the ASD continuum, had lower fitness levels in cardiorespiratory endurance, flexibility, and muscular strength, compared with typically developing adolescents (Borremans et al., 2010). Motivating adolescents with ASD and featuring individualized training adapted for adolescents with ASD may improve their overall fitness. This can be achieved by including typically developing adolescents as participants in activities, resulting in both groups of youths feeling closer and more connected to one another. This can also be achieved by establishing a noncompetitive, stimulating environment using certain basic teaching strategies for people with ASD, such as organizing and structuring events into routines, using visual schedules and work systems to facilitate learning, establishing clear boundary markings, and focusing on individual strengths of ASD youths to create a respectful and long-lasting working relationship.

The finding that adolescents with ASD had body compositions that were similar to adolescents without ASD is, however, inconsistent with previous research (Cantell et al., 2008; Foley et al., 2008) indicating that the low motor competence group had significantly higher BMIs or %BF measurements. Because adolescents with ASD demonstrated lower motor-skill performance than their counterparts without ASD, a negative relationship between motor skill and body composition, such as BMI and %BF, is indicated in this population. However, our study did not support the current body of knowledge on the relationship between decreased motor skills and increased BMI or %BF in adolescents with ASD. However, %BF was minimally associated with strength and agility in adolescents without ASD, perhaps because the BMI values of the participants in our study were within the reference ranges for Taiwanese adolescents of similar age (Taiwan Ministry of Education, 2010). The inverse relationship between motor skills and BMI may be more obvious in obese youths, compared with overweight and normal weight youths (D’Hondt et al., 2009). Another possibility may be that measurements, such as BMI and %BF, are nonmotor in nature. Motor skills have direct effects on health-related physical fitness and indirect effects on body fat composition (Foley et al., 2008). Factors such as eating habits, nutrition, physical activity, and sedentary behavior may possibly help adolescents with ASD avoid becoming overweight or obese. Nonetheless, the underlying factors remain unknown, and this relationship in adolescents with ASD should be investigated further.

One of the main goals of this study was to determine whether motor proficiency was related to physical fitness in adolescents with ASD. The finding that overall motor proficiency was related to poor aerobic functioning, muscular strength and endurance, and flexibility in adolescents with ASD is partly in line with the results obtained in an earlier study (Emck et al., 2010), indicating that the overall gross motor performance was significantly correlated to the overall strength. Adolescents with ASD with low motor proficiency completed fewer laps, push-ups, and sit-and-reaches than their age-matched peers without ASD, contributing to the compromised fitness results in endurance, strength, and flexibility. Other disability studies have indicated positive relationships between motor skills and fitness levels in youths with cerebral palsy (Verschuren et al., 2009), visual impairment (Houwen et al., 2010), intellectual disability (Foley et al., 2008), and developmental coordination disorders (Cantell et al., 2008), suggesting the importance of motor-skill acquisitions and fitness levels in youths with disabilities. To continue participating in sports and recreational activities as children grow older, it is important that the developmental needs of children with ASD be addressed as early as possible. Traditional school physical education and sports programs may not sufficiently address the needs of adolescents with ASD. Therefore, improving sports-related motor skills, such as dribbling, throwing, dropping, catching, and jumping, of adolescents with ASD should be a priority because many lack proficiency in these skills (Green et al., 2009; Staples and Reid, 2010).

Another goal of this study was to determine whether motor proficiency of typically developing adolescents was related to physical fitness. Our results showed that, for a number of variables, this was not the case. There were few relevant positive relationships that were observed in typically developing adolescents that were inconsistent with the previous research in young adults (Stodden et al., 2009), which showed that motor skills, such as throwing, kicking, and jumping, are highly related to physical fitness parameters, such as body composition, muscle strength, and cardiovascular endurance. The nonsignificant relationship of overall motor proficiency to fitness for adolescents without ASD suggests that the level of fitness was related to other factors. These relationships may be influenced by contextual factors, including environment, peer-related influences, or socioeconomic status, which affect a person’s opportunity to be active. The type and level of physical activity (Stodden et al., 2008) or the perceived sports competence (Barnett et al., 2008a) may also be mediating factors in the relationship between motor proficiency and physical fitness, thus accounting for the different correlations we observed for the two groups in our study. Therefore, based on the literature, we cannot rule out the possibility that other variables differentially mediated the relationship between motor-skill proficiency and physical fitness in typically developing adolescents. Such observations merit further investigation.

The strength and agility variable was found to be associated with the cardiovascular endurance and upper-body muscular strength and endurance variables in both groups of adolescents. However, whether these relationships between motor skills and physical fitness variables were task specific is unclear. To some extent, our results are consistent with the previous research (Barnett et al., 2008a, 2008b) in which certain motor skills were observed to be associated with aerobic performance, as measured by the 20-m PACER. Barnett et al. (2008b) found that object-control proficiency, such as kicking, catching, and overhand throwing, which is demonstrated during elementary school, was a predictor of subsequent cardiorespiratory fitness levels in adolescence. Barnett et al. (2008a) indicated that childhood object skill proficiency predicted adolescent physical activity and fitness (cardiorespiratory endurance), and that the variance explained for fitness was higher than for physical activity because many organized sporting activities require a certain level of object skill proficiency for participation. In our study, the strength and agility composite included two subtests: (1) running speed and agility, which included the shuttle run, stepping sideways over a balance beam, one-legged stationary hop, and one- and two-legged side hop measurements; and (2) strength, as represented by standing long jump, push-ups, sit-ups, wall sit, and V-up performances. These types of skills are generally associated with cardiorespiratory development activity. Our results may be more in line with the findings reported by Kemper et al. (2001), who concluded that the relationships between physical activity (>4 metabolic equivalent of task (METs)) and physical fitness are only meaningful for maximum aerobic power, especially for typically developing adolescents. Nevertheless, differences in the selected motor skills and tests between previous studies are clear. Therefore, future investigations on whether object-control skills are predictors of these aspects of motor-skill fitness are warranted.

The lower level of motor proficiency and physical fitness in adolescents with ASD requires increased attention and immediate intervention. Physical education teachers can increase enjoyment and active participation of all students by using typically developing peers as intervention agents, such as in-peer tutoring and peer-assisted learning, to teach students with ASD motor skills (Ward and Ayvazo, 2006). Physical education teachers can also encourage all students to participate in fun physical activities together to help students with ASD fulfill their need to be an integral part of the class as a whole (Pan et al., 2011a). These studies were performed in inclusive settings providing empirical support for peer-mediated intervention (Ward and Ayvazo, 2006) and self-determined motivation (Pan et al., 2011a) as successful strategies for increasing motor skills and physical fitness levels for youths with ASD. Furthermore, group activities involving both students and their families, such as swimming, biking, and walking, are strongly recommended because of the limited duration of physical education in schools and the lack of active recess times in secondary schools.

This study has several limitations. First, generalization of the results is limited because of the small sample size and the cross-sectional design of the study. Second, the use of the BOT-2 and BPFT permitted limited assessment of other motor and fitness functions. Regarding the tests used in our study, the full range of adolescents’ motor skills and fitness levels were not assessed or controlled. Several different versions of motor skills and fitness tests should be considered for overall motor and fitness assessments in the future. Third, 22% of the adolescents with ASD were on medication. We did not control for the time of day at which the BOT-2 and the BPFT assessments were performed in relation to the effects of medication levels in participants. However, preliminary analyses indicated that motor-skill performance and physical fitness levels did not differ significantly between adolescents with ASD who were receiving stimulant medication and those who were not receiving such medication, suggesting no medication effects on the dependent variables. Fourth, although ASD is more frequently observed in males than in females, adolescent females with ASD should not be overlooked.

In conclusion, motor skills play a significant role in fitness levels of adolescents with ASD. Continued development of motor skills and physical fitness in adolescents with ASD is important. These preliminary findings indicate the need for further investigations of more diverse samples, as well as longitudinal and experimental studies to examine the causal relations between motor proficiency and physical fitness. Clinicians diagnosing and treating youths with ASD should also assess whether motor problems are present, and offer those with ASD and motor comorbidities evidence-based interventions to narrow the motor skills and physical-fitness gaps between youths with and without ASD.

Footnotes

Acknowledgements

The author would like to express her gratitude to all the adolescents who participated in this study, parents of adolescents for their support, and research assistants who helped with the data collection and other contributions.

Funding

This research was supported by NSC 99-2410-H-017-036-MY2.

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