Effects of complex strength training with elastic band program on repeated change of direction in young female handball players: Randomized control trial

Abstract

This study examined the effect of 10-week complex strength training with elastic band program on fitness components in young female handball players. Thirty-eight handball players aged 15.8 ± 0.2 years were randomly assigned to an experimental group or control group. The experimental group performed complex strength training with elastic band twice a week over 10 weeks, which included 8 workshops of progressing set length (number of sets) and band resistance for each specific exercise. Sessions were lasted approximately 35 min. The control group maintained regular in-season training. Tests included handgrip; back extensor; medicine ball throw; 30 m sprint times; Modified Illinois change-of-direction (Illinois-MT); four jump tests (squat jump, countermovement jump, countermovement jump with arms and five jump test; static (stork test) and dynamic (Y balance test) balance; and repeated sprint T-test. The experimental group enhanced all strength performance (handgrip right (p < 0.001), handgrip left (p < 0.001), back extensor strength (p < 0.001) and medicine ball throw (p < 0.001) compared to the controls); sprint performance (5 m (p<0.001), 10 m (p < 0.001), 20 m (p < 0.001), and 30 m (p < 0.001)); the change of direction (Illinois-MT (p < 0.001)); jump performance (squat jump (p < 0.001), countermovement jump (p < 0.001), countermovement jump with arms (p < 0.001), and five jump test (p < 0.01)); and the repeated sprint T-test scores (p<0.001in all scores). In contrast, no significant difference in both static and dynamic balance performance between experimental group and control group. Ten weeks of complex strength training with elastic band improve fitness components measures in young female handball players then habitual training.

Keywords

Balance change-of-direction speed countermovement jump handgrip repeated sprints youth sport

Introduction

Female handball is considered a complex, multifactorial, highly demanding intermittent sport that requires high level of specific technical and tactical skills, good team coordination, and fitness to support frequent body contact and perform multiple high-intensity actions^1–4. During game, handball players perform running, jumping, pushing, and change of direction.^1,3,5 High levels of physical fitness are required throughout a match during defense, counterattack, and positional attack situations.^1,3,5 To develop effective training programs for female team handball players ranging from amateur to elite, physical trainers, coaches, athletic trainers, and sport physicians can effectively use the relevant information to develop more effective strength and conditioning programs for female team handball players to increase strength/power.

Although handball matches are interspersed with low lower intensity periods of works, it has been observed that a decline in performance occurs, independent of player of position,^4,6 which may influence the outcome of a given match. In addition to handball-specific training, resistance are often integrated into training programs. Several studies have shown that resistance training done either with heavy loads (traditional strength training) or utilize lighter/optimal loads, plyometric training and ballistic exercises have led to improvement in fitness and performance measures in handball.^7,8 Several studies have investigated the effects of resistance training of the performance measures in team handball players^4,6,9–11. Although, these studies reported significant improvements in physical performance measures in throwing velocity, strength output, vertical jump height and sprint velocity, however the majority utilized free weights as part of their training programs.^9,12 More importantly, access to training facilities, fitness centers and free weights are costly and prohibitive, even more so during the COVID-19 pandemic.¹³

As such, training using an elastic band has been used in a variety of settings¹⁴ and has emerged as a cost-effective alternative to expensive traditional strength training equipment.^6,10,14,15 Elastic resistance bands are inexpensive, easy to use, portable, and easier to implement in regular handball training sessions than conventional resistance training equipment.^6,10,16 The effects of elastic band training have been supported by most scientifically controlled studies evaluating its chronic development effects on strength/power, sprint, and sports performance.^6,10,14 Recently, two randomized control trials^10,15 investigated the potential effect of elastic band training on youth, amateur, female handball players. Both studies implemented a 6-week intervention aimed at strengthening shoulder rotators using elastic bands. Although both studies reported no significant improvement in in throwing velocity between the intervention group and control group (CG), increased power output¹⁰ and increased isokinetic strength¹⁰ were observed in the intervention group.

Although the literature has previously investigated either the effects of resistance training or plyometric training on handball performance measures, there is limited evidence on the effects of complex training on these same measures. Only a handful of studies have investigated the effect of complex training on physical performance in adults and young athletes, and demonstrated increases in fitness measures such as sprint, jump, and CoD.^7,17,18 The concept of complex training is derived from the combination of resistance training and plyometric training in an attempt to meet the physiological demands of games and improve performance.¹⁹ The specific aim of complex training is to develop strength and neuromuscular power by combining resistance with plyometric or power exercises, set for set, in the same workout^19–22. However, no previous studies have examined the effects of combination elastic band training and plyometric training on athletic performance in young female handball players. Therefore, this study aimed to investigate the effect of complex strength training with an elastic band (CSTEB) (i.e. elastic band exercise (resistance training) followed by jump exercise (plyometric training)) on sprint, jump, CoD, strength, balance, and repeated CoD in young female handball players.

Therefore, the aim of the present investigation was to evaluate the effects upon performance-related abilities of young female handball players when a part of their normal in-season regimen was replaced by CSTEB. The abilities measured included the sprint times, CoD, jump height, balance, and repeated change-of-direction performance. The hypothesis tested was that replacing a part of regular in-season training with a 10-week program of biweekly CSTEB would enhance sprint times, CoD, jump height, balance, and repeated change-of-direction performance relative to control players who maintained their standard in-season regimen.

Methods

Participants

Thirty-eight (n = 38) female handball players from two clubs participated in this study. The players reported a mean of 8 years of handball experience. All the players had some experience with resistance training but not performed weekly. A team physician examined all players for possible conditions that may preclude elastic band training, and all the players were found to be in good health at the time of the study (Table 1).

Table 1.

Demographic characteristic of participants.

	Experimental group (n = 19)	Control group (n = 19)	Independent t-test (F; P)
Age (years)	15.8 ± 0.2	15.8 ± 0.2	F = 0.230; P = 0.634
Body Mass (kg)	63.1 ± 5.0	62.8 ± 3.7	F = 2.336; P = 0.133
Height (cm)	167.7 ± 3.7	166.7 ± 3.3	F = 0.421; P = 0.521
Body fat (%)	26.2 ± 3.5	26.1 ± 3.1	F = 0.193; P = 0.663
Maturity offset (years)	3.0 ± 0.4	3.0 ± 0.4	F = 0.029; P = 0.865

Ethical considerations

All procedures were approved by the Institute's Committee on Research for the Medical Sciences (Manouba University Ethics Committee: UR17JS01). The study was conducted in accordance with the latest version of the Declaration of Helsinki. Written informed parental consent (for those < 18 years), and participants’ assent were obtained prior to the start of the study. All participants and their parents/legal representatives were fully informed about the experimental protocol and its potential risks and benefits.

Pre-season conditioning and training

Prior to the 10-week intervention, all the participants underwent six weeks of pre-intervention training at the beginning of the competitive season (6 training sessions per week for six weeks). During the first three weeks of this phase, a resistance training program aimed at improving muscle endurance by light loads (30–50% 1-repetition maximum (RM)). The second 3 weeks were devoted to improving muscular power with light loads (40–70% 1RM), supplemented by participation in friendly matches each weekend. All participants were involved in five to six training sessions per week (90-to-120 min each session (i.e. physical training, mainly technical-tactical drills, small-sided and simulated games, and injury prevention drills)).

Complex strength training program

The training intervention consisted of a progressive 10-week CSTEB program. The CSTEB program was completed during the mid-portion of the competitive season 2018/2019 (from January to March). The design of the CSTEB intervention was based on the players’ previous training records and research results^6,10,16 (Table 2). Biweekly CSTEB sessions (Tuesdays and Thursdays) included eight workshops: –

Workshop 1: Six flies then six push up.

–

Workshop 2: Six knee extension then six hopping on one foot (three on the right and three on the left side) at 30 cm.

–

Workshop 3: Six rows with a high elbow then six push up.

–

Workshop 4: Six knee flexion then six hurdle jumps at 35 cm.

–

Workshop 5: Six trunk rotations then six push up.

–

Workshop 6: Six half squats then Six hurdle jumps (30 cm height) with extended legs.

–

Workshop 7: Six standing press then Six push up.

–

Workshop 8: Six hip adductions (three at the right limb and three at the left limb) then six horizontal jumps.

Table 2.

Complex strength training program.

Workshop	Week 1	Week 2	Week 3	Week 4	Week 5	Week 6	Week 7	Week 8	Week 9	Week 10
Upper limb	Red elastic band at 250% elongation (3.2 kg)	Green elastic band at 250% elongation (4.4 kg)			Blue elastic band at 250% elongation (6 kg)			Black elastic band at 250% elongation (8 kg)
	Sets	Sets	Sets	Sets	Sets	Sets	Sets	Sets	Sets	Sets
Workshop 1	3	3	4	5	3	4	5	3	4	5
Workshop 3	3	3	4	5	3	4	5	3	4	5
Workshop 5	3	3	4	5	3	4	5	3	4	5
Workshop 7	3	3	4	5	3	4	5	3	4	5
Lower limb	Red elastic band “Folding” at 250% elongation (6.4 kg)	Green elastic band “Folding” at 250% elongation (8.8 kg)			Blue elastic band “Folding” at 250% elongation (12 kg)			Black elastic band “ Folding” at 250% elongation (16 kg)
	Sets	Sets	Sets	Sets	Sets	Sets	Sets	Sets	Sets	Sets
Workshop 2	3	3	4	5	3	4	5	3	4	5
Workshop 4	3	3	4	5	3	4	5	3	4	5
Workshop 6	3	3	4	5	3	4	5	3	4	5
Workshop 8	3	3	4	5	3	4	5	3	4	5

The number of sets is described in Table 2. The workshops were alternated (upper limb exercise and lower limb exercise). Four different bands were used, red (week1), green (week 2, week3, and week 4), blue (week 5, week 6 and week 7), and black (week 8, week 9, and week 10). The elastic band was folded to double its resistance to extension in the lower limb exercise, but not double for the upper limb exercise. The necessary amplitudes of movement during each exercise were calculated individually, thus determining appropriate attachments of the bands to the wall and the player's body. Recovery between sets was 30 s. All exercises were performed with maximal effort. The initial length of the elastic band was 120 cm for all exercises. Players stood at a distance from the wall attachment equal to the needed elongation of the elastic band (100% or 250% elongation) minus the amplitude of motion. The CSTEB was not added to the regular handball training but was immediately performed after the warm-up program⁶ replacing some low-intensity technical-tactical handball drills. The CSTEB replacement activity accounted for <10% of the total handball-training load (competitive and friendly matches not accounted for). The CG followed their regular handball training (i.e. mainly technical-tactical drills, small-sided and simulated games, and injury prevention drills). The overall handball training load was comparable between both groups. This is because they were following similar handball training routines consisting of 6 sessions per week with 90-to-120 min each.

Those who enrolled into the CG maintained their standard in-season regimen

Randomization

Following the pre-season conditioning period, players were divided by playing position, and players from each position were then randomly assigned between experimental group (EG) and the CG. Participants were blinded to their specific group allocation. Further, the researchers who analyzed the data are not the same researchers who collected the data to reduce bias.

Intervention

Thereafter, for ten weeks, each Tuesday and Thursday, the EG replaced a part of their standard regimen with the elastic band training program. The EG performed the CSTEB program to replace some handball-specific drills so that overall training time was similar between groups. Athletes who missed more than 10% of the total training sessions and/or more than two consecutive sessions were excluded from the study.

The training intervention was conducted during the in-season period of the year 2018–2019. In the week before the intervention, two 80 to 90 min sessions familiarized players with all test procedures. Initial and final test measurements were made at the same time of day (17:00– 19:00 PM), under approximately the same environmental conditions (temperature: 16–198 C), at least 3 days after the most recent competition, and 5–9 days after the last CSTEB session. Measurements were made in a fixed order over four days, immediately before and four days after the last strength training session. Participants did not participate in any exhausting exercise for 24 h before testing, and no food or caffeine-containing drinks were taken for 2 h before testing. A standardized warm-up (10–20 min of low- to moderate-intensity aerobic exercise and dynamic stretching) preceded all the tests.

Testing design

Measurements were made in a fixed order over four days, immediately before and four days after the last strength training session. Participants did not participate in any exhausting exercise 24 h before testing, and no food or caffeine-containing drinks were taken for 2 h before testing. A standardized warm-up (10–20 min of low- to moderate-intensity aerobic exercise and dynamic stretching) preceded all the tests.

On the first test day, the assessment a 30 m sprint followed by the modified Illinois change-of-direction test;²³ 3 trials were allowed for each test (separated by 6–8 min of recovery), and the best times performances were noted using paired photocells (Microgate, Bolzano, Italy). The second day was devoted to jumping (squat jump (SJ), countermovement jump (CMJ), CMJ with arms (CMJA), and horizontal 5-jump tests) followed by dominant and nondominant handgrip strength assessments. On the third day, anthropometric measurements were followed by determinations of back extensor strength (3trials separated by at least 2 min of recovery) and medicine ball throw tests (2 trials separated by 5 min of recovery), with the best attempts used for further analyses. On the fourth day, the stork test, Y balance test, and repeated sprint T-test were completed.

Testing procedures

30 m sprint performance

Players started from a standing position, with the front foot 0.2 m from the first photocell (Microgate, Bolzano, Italy) beam and then they ran 30 m, with times recorded over 5, 10, 20, and 30 m distances.¹⁸

Modified Illinois change-of-direction test (Illinois-MT)

Four cones formed the change-of-direction area for the modified Illinois test. On command, players sprinted 5 m, turned and ran back to the starting line, then swerving in and out of the four markers, completed two 5-m sprints.²⁴ No advice was given as to the most effective technique, but players were instructed to complete the test as quickly as possible without cutting over markers. If they did so, the trial was repeated after an appropriate recovery period.

Vertical jump

Jump height was assessed using an infrared photocell mat connected to a digital computer (Optojump System; Microgate SARL) that measured contact and flight times and the height of jump with a precision of 1/1000 s.²⁵ Participants began the SJ at a knee angle of ∼90° (self-controlled, using a mirror), avoiding any downward movement, and pushed upward, keeping their legs straight throughout. The CMJ began from an upright position; a rapid downward movement to a knee angle of ∼90° (again self-controlled, using a mirror) accompanied the beginning of the push-off. During the CMJA, the hands were used freely while jumping. One minute of rest was allowed between three trials of each test, and the highest jump of each type was used in subsequent analyses.

Five jump test (5JT)

The test was performed as previously described.²⁵ From an upright standing position with both feet flat on the ground, participants tried to cover as much distance as possible with five forward jumps, alternating left- and right-leg ground contacts. Participants were allowed three maximal trials, with 3 min of rest between efforts, and the best performance was used for analyses.

Handgrip strength test

The hand dynamometer (Takei, Tokyo, Japan) was held with the arm at right angles and the elbows at the side of the body.²⁶ The instrument was adjusted so that its base rested on the first metacarpal, and the handle rested on the middle four fingers. A maximal isometric effort was maintained for 5 s, without ancillary body movements. Two trials were made with each hand, with 1 min of rest between trials, and the highest readings were used in subsequent analyses.

Anthropometry

Anthropometric measurements included height and sitting height (accuracy of 0.1 cm; HoltainQ 3, United Kingdom) and body mass (0.1 kg; Tanita BF683 W scales, Munich, Germany). The overall percentage of body fat was estimated from the triceps and subscapular skinfolds, using the equations of Durnin and Womersly²⁷ for children and youth females: % Body fat = (495/D) − 450, where D = 1.1369–0.0598 (Log sum of four skinfolds). Maturity status was calculated using the equation of Mirwald et al.,²⁸ an approved noninvasive method to predict years from peak height velocity:

Maturity offset = − 9.38 + (0.000188 × leg length × sitting height) + (0.0022 × age × leg length) + (0.00584 × age × sitting height) + (0.0769 × weight/height ratio).

Back extensor strength

Maximal isometric back extensor strength was measured using a back extensor dynamometer (Takei).²⁹ Participants stood on the dynamometer, with their feet shoulder-width apart and gripped the handlebar positioned across the patellae. The chain length was adjusted so that initially, the legs were held straight, and the back was flexed to 30°, as guided by wall markings. Participants then stood upright without bending their knees, pulling upward as firmly as possible.

Medicine ball throw

The test was performed using a 21.5 cm diameter, 1 and 3 kg rubber medicine balls (Tigar, Pirot, Serbia) powdered with magnesium carbonate. A familiarization session included a brief description of the optimal technique.³⁰ The seated player grasped the medicine ball with both hands, and on signal forcefully pushed the ball from the chest. The score was measured from the front of the sitting line to the powder-marked spot where the ball landed.

Stork balance test

Subjects stood on their dominant leg with their opposite foot resting against the inside of the supporting knee and both hands on their hips.³¹ On signal, they raised their heel; the test was terminated when the heel touched the ground, or the foot moved away from the patella.

Dynamic balance test

Dynamic balance was assessed on the dominant leg, using the Y-balance test.³¹ Supine leg lengths were first determined from the anterior superior iliac spine to the most distal aspect of the medial malleolus. Subjects then stood barefoot and single-legged, with the tip of their great toe at the center of the grid, and reached in anterior, postero-medial, and postero-lateral directions, marked on the floor by tape. The posterior lines extended at an angle of 135° from the anterior line. Trials were repeated if the participant (1) did not touch the required line with the reaching foot while maintaining weight-bearing on the stance leg, (2) lifted the stance foot from the center of the grid, (3) lost balance, (4) did not maintain start and return positions for one full second, or (5) touched the reaching foot to gain support. The maximal reach was measured in each direction, and a composite score was calculated as ([maximum anterior + maximum postero-medial + maximum postero-lateral reach distance]/[leg length × 3] × 100).³¹ Three trials were conducted in each direction, with two-minute rest intervals.

Repeated sprint T-test (RSTT)

This test offers a reliable and valid measurement³² of the ability to change directions rapidly, four simulating a game with short, intense efforts, recovery periods, and multi-directional displacements. Seven executions of the agility T-test were made, with subjects walking back slowly to the next start point during 25 s recovery intervals. Measures included best time, mean time, total time, and a fatigue index calculated as³³:

FI = ((Total time/(Best time × 7)) × 100) − 100.

Statistics analyses

Statistical analyses were carried out using the SPSS 23 program for Windows (SPSS, Inc, Chicago, IL). Normality of all variables were tested using the Kolmogorov–Smirnov test procedure. Data are presented as mean (SD), and as median values for skewed variables. Independent sample t-tests were performed separately to determine changes pre-intervention and post-intervention for the experimental and CGs, with the magnitude of the changes determined via Cohen d effect sizes.³⁴ Training-related effects were assessed by two-way analyses of variance (group × time). The criterion for statistical significance was set at p < 0.05, whether a positive or a negative difference was seen (i.e. a two-tailed test was adopted). The reliabilities of all dependent variables were assessed by calculating intraclass correlation coefficients (two-way mixed).³⁵ Effect sizes were determined by converting partial eta-squared to Cohen's d³⁴ values were classified as small (0.00≤d ≤ 0.49), medium (0.50≤d ≤ 0.79), and large (d≥0.80).

Results

Reliability of the tests

Test–retest reliability was above the established threshold and ranged from 0.71 to 0.95 according to the intra-class correlation coefficient and ranged from 1.9 to 49 according to the coefficient of variation (Table 3).

Table 3.

Reliability and variability of performance tests.

	ICC	95%CI	CV
5m	0.921	0.848–0.959	4.1
10m	0.888	0.784–0.942	2.7
20m	0.846	0.704–0.920	2.2
30m	0.850	0.712–0.922	1.9
Illinois-MT	0.959	0.920–0.978	2.5
SJ	0.963	0.928–0.981	8.8
CMJ	0.879	0.768–0.937	7.8
CMJA	0.831	0.674–0.912	7.7
5JT	0.959	0.922–0.979	8.5
Handgrip right	0.891	0.791–0.944	8.4
Handgrip left	0.927	0.859–0.962	10.2
Back extensor	0.873	0.756–0.934	9.6
Medicine ball throw	0.945	0.895–0.972	17.4
Stork right	0.710	0.441–0.849	45.1
Stork left	0.716	0.453–0.852	49
RL/R	0.871	0.751–0.933	10.7
RL/L	0.842	0.695–0.918	9.5
RL/F	0.928	0.861–0.962	18
LL/L	0.894	0.795–0.945	10.2
LL/R	0.884	0.776–0.940	8
LL/F	0.935	0.875–0.966	18.8

CI: confidence intervals; CV: coefficient of variation; CMJ: counter-movement jump; CMJA: counter-movement jump; ICC: intraclass correlation coefficient; Illinois-MT: Illinois modified test; SJ: squat jump; F: forward; L: left; R: right; LL: left leg; RL: right leg.

Between-group differences at baseline

Initial values showed no significant intergroup differences for any of the dependent variables (Tables 1 and 4).

Table 4.

Comparison of performance tests between experimental and control groups before 10-week intervention.

	Experimental group (n = 17) pre-test	Control group (n = 17) pre-test	Independent t-test (F; P)
5 m (s)	1.27 ± 0.05	1.29 ± 0.05	F = 0.185; P = 0.669
10 m (s)	2.19 ± 0.05	2.25 ± 0.05	F = 0.168; P = 0.685
20 m (s)	3.83 ± 0.09	3.75 ± 0.05	F = 1.83; P = 0.190
30 m (s)	5.47 ± 0.12	5.55 ± 0.05	F = 2.552; P = 0.119
Illinois-MT (s)	13.11 ± 0.27	13.14 ± 0.39	F = 0.197; P = 0.300
SJ (cm)	22.6 ± 1.9	23.0 ± 2.1	F = 0.005; P = 0.942
CMJ (cm)	24.0 ± 1.7	24.2 ± 2.1	F = 0.181; P = 0.673
CMJA (cm)	25.3 ± 1.7	25.5 ± 2.2	F = 0.359; P = 0.553
5JT (m)	8.0 ± 0.4	8.3 ± 1.4	F = 0.272; P = 0.437
Handgrip right (N)	233.5 ± 19.5	232.3 ± 20.3	F = 0.006; P = 0.939
Handgrip left (N)	225.8 ± 30.0	226.6 ± 13.8	F = 0.197; P = 00.579
Back extensor (N)	784.0 ± 93.8	791.5 ± 53.3	F = 0.186; P = 0.637
Medicine ball throw (m)	3.1 ± 0.4	3.3 ± 0.7	F = 0.157; P = 0.773
Stork right (s)	2.56 ± 1.09	2.69 ± 1.30	F = 1.114; P = 0.298
Stork left (s)	2.83 ± 1.09	2.52 ± 1.52	F = 0.494; P = 0.487
RL/R (cm)	77.0 ± 6.9	73.6 ± 8.9	F = 0.541; P = 0.467
RL/L (cm)	91.7 ± 7.8	87.6 ± 8.9	F = 0.072; P = 0.790
RL/F (cm)	46.4 ± 8.6	48.7 ± 8.6	F = 0.001; P = 0.977
LL/L (cm)	80.6 ± 7.8	78.7 ± 8.6	F = 0.058; P = 0.811
LL/R (cm)	95.3 ± 8.0	95.9 ± 7.5	F = 0.580; P = 0.451
LL/F (cm)	48.5 ± 10.2	45.7 ± 7.2	F = 1.624; P = 0.211
RSTT-BT (s)	12.63 ± 0.17	12.62 ± 0.18	F = 0.001; P = 0.975
RSTT-MT (s)	12.90 ± 0.17	12.91 ± 0.18	F = 0.001; P = 0.975
RSTT-TT (s)	90.30 ± 1.22	90.37 ± 1.29	F = 0.001; P = 0.975
RSTT-FI (%)	2.14 ± 0.03	2.30 ± 0.03	F = 0.000; P = 0.984

CMJ: counter-movement jump; CMJA: counter-movement jump; ICC: intraclass correlation coefficient; Illinois-MT: Illinois modified test; SJ: squat jump; F: forward; L: left; R: right; LL: left leg; RL: right leg; RSTT: repeated sprint T-test; BT: best time; MT: mean time; TT: total time; FI: fatigue index.

Training-related effects

All data for both groups were significantly increased after the 10-week intervention with the exception of the Stork balance test (left leg), which remained unchanged for the CG (Tables 5 and 6). With a group × time interaction, the EG enhanced all strength performance over handgrip right (p < 0.001, d = 1.70 (large)), handgrip left (p < 0.001, d = 1.15 (large)), back extensor strength (p < 0.001, d = 1.53 (large)), and medicine ball throw (p < 0.001, d = 1.20 (large)) compared to the controls (Table 5). The EG enhanced their sprint performance over 5 m (Δ = 11.6%, p < 0.001, d = 1.01 (large)), 10 m (Δ = 7.7%, p < 0.001, d = 1.18 (large)), 20 m (Δ = 14.2%, p < 0.001, d = 2.90 (large)), and 30 m (Δ = 10.9%, p < 0.001, d = 2.53 (large)) (Table 5). The EG also improved performance in the Illinois-MT (Δ = 8.7%, p < 0.001, d = 1.57 (large)).

Table 5.

Upper-limb performance in experimental and control groups before and after the 10-week intervention.

	Experimental group (n = 17)					Control group (n = 17)					ANOVA group × time interaction
	Pre	Post	%Δ change	Paired t-test		Pre	Post	%Δ change	Paired t test		p	Cohen d
	Pre	Post	%Δ change	p	D (Cohen)	Pre	Post	%Δ change	p	d (Cohen)
Handgrip right (N)	233.5 ± 19.5	309.1 ± 21.1	32.5 ± 4.6	p < 0.001	−3.82	232.3 ± 20.3	241.5 ± 19.2	4.0 ± 1.7	p < 0.001	−0.48	p < 0.001	1.70
Handgrip left (N)	225.8 ± 30.0	295.8 ± 36.4	31.3 ± 5.7	p < 0.001	−2.16	226.6 ± 13.8	239.6 ± 13.1	5.8 ± 2.5	p < 0.001	−0.99	p < 0.001	1.15
Back extensor (N)	784.0 ± 93.8	1098.6 ± 91.5	40.7 ± 5.5	p < 0.001	−3.49	791.5 ± 53.3	867.9 ± 72.7	9.7 ± 7.3	p < 0.001	−1.23	p < 0.001	1.53
Medicine ball throw (m)	3.1 ± 0.4	4.7 ± 0.4	50.7 ± 10.8	p < 0.001	−4.11	3.3 ± 0.7	3.5 ± 0.7	7.7 ± 7.5	p < 0.001	−0.29	p < 0.001	1.20

Table 6.

Lower-limb performance in experimental and control groups before and after the 10-week intervention.

	Experimental group (n = 17)					Control group (n = 17)					ANOVA group × time interaction
	Pre	Post	%Δ change	Paired t-test		Pre	Post	%Δ change	Paired t test		p	Cohen d
	Pre	Post	%Δ change	p	d (Cohen)	Pre	Post	%Δ change	p	d (Cohen)
Sprint
5 m (s)	1.27 ± 0.05	1.13 ± 0.05	11.6 ± 1.9	p < 0.001	2.88	1.29 ± 0.05	1.24 ± 0.05	3.5 ± 1.7	p < 0.001	1.03	p < 0.001	1.01
10 m (s)	2.19 ± 0.05	2.02 ± 0.04	7.7 ± 0.6	p < 0.001	3.86	2.25 ± 0.05	2.20 ± 0.07	1.9 ± 2.0	p = 0.001	0.84	p < 0.001	1.18
20 m (s)	3.83 ± 0.09	3.29 ± 0.10	14.2 ± 0.6	p < 0.001	5.83	3.75 ± 0.05	3.68 ± 0.08	2.0 ± 1.3	p < 0.001	1.08	p < 0.001	2.90
30 m (s)	5.47 ± 0.12	4.88 ± 0.13	10.9 ± 1.1	p < 0.001	4.85	5.55 ± 0.05	5.48 ± 0.07	1.1 ± 0.7	p < 0.001	1.18	p < 0.001	2.73
Change of direction
Illinois-MT	13.11 ± 0.27	11.97 ± 0.28	8.7 ± 0.3	p < 0.001	4.26	13.14 ± 0.39	13.03 ± 0.38	0.8 ± 0.2	p < 0.001	0.29	p < 0.001	1.57
Jump
SJ (cm)	22.6 ± 1.9	27.5 ± 2.6	21.5 ± 3.2	p < 0.001	−2.21	23.0 ± 2.1	23.9 ± 1.7	4.2 ± 4.1	p < 0.001	−0.48	p < 0.001	0.96
CMJ (cm)	24.0 ± 1.7	30.0 ± 1.9	24.8 ± 1.9	p < 0.001	−3.42	24.2 ± 2.1	25.2 ± 1.9	4.2 ± 3.3	p < 0.001	−0.51	p < 0.001	1.32
CMJA (cm)	25.3 ± 1.7	31.6 ± 2.1	24.7 ± 2.3	p < 0.001	−3.39	25.5 ± 2.2	26.1 ± 2.2	2.3 ± 1.0	p < 0.001	−0.28	p < 0.001	1.41
5JT (m)	8.0 ± 0.4	9.3 ± 0.6	15.8 ± 2.1	p < 0.001	−2.62	8.3 ± 1.4	8.6 ± 1.4	4.2 ± 3.2	p < 0.001	−0.22	p = 0.003	0.71
RSTT
RSTT-BT (s)	12.63 ± 0.17	11.26 ± 0.20	10.9 ± 0.5	p < 0.001	7.58	12.62 ± 0.18	12.49 ± 0.22	1.0 ± 0.6	p < 0.001	0.66	p < 0.001	3.26
RSTT-MT (s)	12.90 ± 0.17	11.55 ± 0.20	10.5 ± 0.5	p < 0.001	7.47	12.91 ± 0.18	12.78 ± 0.22	1.0 ± 0.6	p < 0.001	0.66	p < 0.001	3.21
RSTT-TT (s)	90.30 ± 1.22	80.84 ± 1.39	10.5 ± 0.5	p < 0.001	7.43	90.37 ± 1.29	89.49 ± 1.56	1.0 ± 0.6	p < 0.001	0.63	p < 0.001	3.21
RSTT-FI (%)	2.14 ± 0.03	2.58 ± 0.05	20.5 ± 0.6	p < 0.001	−10.96	2.30 ± 0.03	2.32 ± 0.04	1.0 ± 0.6	p < 0.001	−0.58	p < 0.001	5.63
Y Balance test
Right support leg
RL/R (cm)	77.0 ± 6.9	84.3 ± 8.4	9.5 ± 3.9	p < 0.001	−0.98	73.6 ± 8.9	79.9 ± 8.6	9.0 ± 6.4	p < 0.001	−0.74	p = 0.802	0.06
RL/L (cm)	91.7 ± 7.8	97.8 ± 8.8	6.7 ± 1.7	p < 0.001	−0.75	87.6 ± 8.9	92.4 ± 9.9	5.5 ± 3.6	p < 0.001	−0.52	p = 0.747	0.06
RL/F (cm)	46.4 ± 8.6	53.7 ± 10.7	16.2 ± 10.7	p < 0.001	−0.77	48.7 ± 8.6	54.7 ± 6.6	14.3 ± 18.1	p < 0.001	−0.80	p = 0.734	0.08
Left support leg
LL/L (cm)	80.6 ± 7.8	85.7 ± 8.0	6.4 ± 1.5	p < 0.001	−0.66	78.7 ± 8.6	84.7 ± 6.6	8.3 ± 9.4	p < 0.001	−0.80	p = 0.803	0.01
LL/R (cm)	95.3 ± 8.0	101.8 ± 8.9	6.8 ± 1.8	p < 0.001	−0.79	95.9 ± 7.5	99.4 ± 6.6	3.7 ± 2.7	p < 0.001	−0.51	p = 0.404	0.10
LL/F (cm)	48.5 ± 10.2	53.3 ± 10.0	10.4 ± 6.5	p < 0.001	−0.49	45.7 ± 7.2	49.6 ± 7.0	9.1 ± 7.3	p < 0.001	−0.56	p = 0.835	0.06
Stork balance test
RL (s)	2.56 ± 1.09	3.50 ± 1.26	42.4 ± 32.5	p < 0.001	−0.82	2.69 ± 1.30	3.90 ± 1.86	54.5 ± 51.4	p = 0.002	−0.77	p = 0.673	0.08
LL (s)	2.83 ± 1.09	3.71 ± 1.40	39.1 ± 49.4	p = 0.009	−0.72	2.52 ± 1.52	3.28 ± 1.70	50.5 ± 74.2	p = 0.127	−0.48	p = 0.856	0.00

Illinois-MT: Illinois modified test; SJ: squat jump; CMJ: countermovement jump; CMJA: countermovement jump with arms; 5JT: 5 jump test; RSTT: repeated sprint T-test; BT: best time; MT: mean time; TT: total time; FI: fatigue index; RL: right leg; L: left; R: right; F: forward; LL: left leg.

All jump performance improved significantly in the EG, with gains in the SJ (Δ = 21.5%, p < 0.001, d = 0.96 (large)), CMJ (Δ = 24.8%, p < 0.001 d = 1.32 (large)), CMJA (Δ = 24.7%, p < 0.001, d = 1.41 (large)), and 5JT (Δ = 15.8%, p = 0.003, d = 0.71 (medium)) (Table 6). All the repeated sprint T-test scores increased significantly in the EG relative to the CG, with group × time interactions at p < 0.001, d = 3.26 (large); p < 0.001, d = 3.21 (large); p < 0.001, d = 3.21 (large); and p < 0.001, d = 5.63 (large), in RSTT-BT, RSTT-MT, RSTT-TT, and RSTT-FI, respectively (Table 4). In contrast, group × time interactions showed no significant difference in both static and dynamic balance performance between EG and CG (Table 6).

Discussion

This study aimed to assess the effectiveness of a 10-week CSTEB on sprint times, CoD, jump height, balance and repeated change-of-direction performance in young female handball players. With the exception of balance, fitness and performance measures (i.e. sprint, CoD, jump, and repeated CoD, Tables 5 and Table 6) were significantly improved not only between the groups but also significantly pre- and post CSTEB intervention. The improvement across several fitness and performance-related variables suggests that a CSTEB program is one potential option to optimize explosive actions in young female handball players. Therefore, the null hypothesis that there would be no difference between final measures contributing to athletic performance between the two groups is rejected. Moreover, the observed gains would make a significant contribution to competitive performance. These results are consistent with several studies investigating similar interventions within similar populations^6,7,16–18.

The goal of athletic training is to create meaningful improvements in performance. Our results showed increases in Illinois-MT in EG compared to CG. The magnitude of the improvement was in line with that in previous studies, which have shown that the increase in CoD was accompanied by augmentation of neuromuscular adaptations after complex training. For example, Hammami et al.¹⁸ demonstrated that CoD performance (T-half test (p < 0.05) and the modified Illinois-test (p < 0.05)) in junior female handball players improved simultaneously after performing 8 weeks of complex training. Likewise, Ali et al.³⁶ found increases in the CoD performance (agility T-test (p < 0.01)) after six complex training in male soccer players. In contrast, Anderson et al.⁶ found no significant change in agility performance after 6-week strength training with elastic band in young female handball players. The discrepant findings from studies could be explained by the test procedures and interventions (frequency, duration, and progression of training relative to the playing season). The improvements in linear sprinting and sprinting with COD performance following complex training may be related to adaptative mechanisms similar to those induced by RT and PT alone, including maximal strength, hormonal milieu, structural, and neuromechanical adaptations, which may be potentiated through a cumulative post-activation performance enhancement effect induced with complex training.^17,19,22

High levels of upper limb power (i.e. passing and throwing the ball) are important physical fitness attributes in female handball.⁵ Finding of the present study showed increases in handgrip, back extensor strength and medicine ball throw performance in the EG compared to the CG. To the best of the authors’ knowledge, no study has previously addressed the effects of CSTEB training on upper limb strength performance in young female athletes. Anderson et al.⁶ found increases in throwing velocity ball and bench press performance after 6-week strength training with elastic band in young female handball players. Moreover, using similar a similar CSTEB training program in female athletes, Hammami et al.²⁵ found increases in upper limb strength (i.e. back extensor strength) after 8-week complex strength training in junior female handball players. Similarly, Elbadry et al.³⁷ found improvement in seated medicine ball throw after 8-week French contrast strength training (a combination of complex and contrast methods) in female college athletes. Although the training methods used by Hammami et al.¹⁸ and Elbadry et al.³⁷ used different methodologies, they employed a similar program (i.e. complex training (strength with external load exercise followed by plyometric exercise immediately), in addition to the population being young female athletes.

Despite the different methods of assessing power and strength (handgrip test, 1-RM bench press, ball throwing speed, medicine ball throw, and isokinetic test) in the upper limb after co-program, the majority of studies showed increases in power upper limb performance.^8,10,25,26 These changes are potentially related to adaptations induced by complex strength training. The unique combination of complex exercises (elastic band exercise combined with plyometric exercise) stimulates the post-activation potentiation (PAP) of performance, a phenomenon,³⁸ that stimulates motor unit recruitment, thus increasing the force-producing potential of the utilized musculature within a given movement.^19–22.

In terms of sprint running measures, findings of the present study showed that the CSTEB training intervention induced a large performance benefit in all sprint performance. Similarly, Hammami et al.¹⁸ found increases in sprint performance (10,20, and 30 m) after nine weeks of complex training in junior female handball players. The meta-analyses of Freitas et al.¹⁹ revealed that this type of training (i.e. complex training) led to positive medium effects on sprint performance over distances between 15 and 30 m. Recently, Abade et al.¹⁷ found improvement in 10 m (10.7%) and 20 m (6%) sprint performance after 12 weeks of complex training in male handball players. Increases in sprint performance are explained by the fact that strength provided by the band's elasticity resulted in a significant increase in knee extensor and flexor power production, which was transferred effectively to running at maximal speed.^39–41. The mechanism responsible for this effect has been attributed mainly to neural adaptations because less muscle hypertrophy occurs after training with elastic bands than after typical heavy strength training.⁴²

The meta-analyses of Pagaduan et al.²¹ demonstrated increases in vertical jump performance after complex training. Our results showed increases in all jump performance. Hammami et al.¹⁸ found increases in jump performance (SJ (p = 0.001), CMJ (p = 0.004), and CMJA (p = 0.001)) after eight weeks complex strength training in junior female handball players. Similarly, Abade et al.¹⁷ found large increases in vertical jump performance after 12 weeks of complex training in male handball players. The authors demonstrated improvement in jump performance after complex training in male soccer players.⁴³ In contrast, Aloui et al.¹⁶ noted no significant change in jump performance (SJ and CMJ) after 8 weeks of an elastic band training program in junior male handball players. An examination of the included studies shows discrepancies regarding jump adaptations to complex training. Therefore, due to such inconsistencies found in literature, the subgroup analysis focused on identifying potential moderating factors explaining the different adaptations following complex training. Enhancement in vertical jump performance with CSTEB compared to controls may be related to the added stimulus in CSTEB that facilitated PAP.^38,44 PAP refers to the enhancement of performance from myosin phosphorylation and h-reflex excitation. In relation to this, vertical jump gains from CSTEB may be related to cellular and hormonal adaptations favourable to power enhancement.⁴⁵ For example, Beaven et al.⁴⁵ presented increased testosterone in addition to enhancement in VJ performance after CT. It may also be possible that greater preservation of IIX muscle fibers is achieved with complex training than the controls (i.e. CG).⁴⁶ Greater selective recruitment of FTx muscle fibers in complex training compared to the controls (i.e. CG) may have also occurred.^38,44

All the repeated sprint T-test scores increased significantly in the EG relative to the CG. One possible explanation for the lack of significant change in RSTT-FI in these studies could be the poor reproducibility of this particular measure.⁴⁷ Likewise, Aloui et al.¹⁶ found increases in repeated CoD (best time; mean time; and total time) performance after eight weeks of elastic band training in junior male handball players. In contrast, Hammami et al.¹⁸ found no change in repeated CoD parameters (men time, total time, and fatigue index) after 8-week complex strength training in junior female handball players. The capacity to repeat high-intensity runs is on both neuromuscular (e.g. neural drive and motor-unit activation) and metabolic factors (e.g. oxidative capacity, PCr recovery, and H + buffering).⁴⁸ The mechanism responsible for this improvement has been attributed mainly to neural adaptations.^22,38

This is the first investigation to have studied the effects of complex strength with elastic band training on the balance performance in handball players. Group × time interaction showed no significant difference between groups in both right and left leg in static (Stork test) balance performance. This may be due to poor reproducibility. Indeed, the intra-class correlation coefficients are 0.73 and 0.72 for the right leg and the leg, respectively. Despite that, there was a significant change in dynamic balance for each group (Using T student test), group × time interaction showed no significant change between groups. Similarly, no significant change in any dynamic balance scores. The small improvement in both groups can explain this. The magnitude of the unchanged performance after complex training was in line with, Hammami et al.;¹⁸ however, they found no significant change in both static and dynamic balance performance after eight weeks of complex strength training in junior female handball players.

This study has some limitations that need to be acknowledged. First, no direct physiological (e.g. electromyography; isokinetic strength test) or biomechanical (e.g. vertical ground reaction force) measures were conducted. This has to be considered in future research. Second, we cannot consider the results of the relevant stork balance test simply because this test is not reliable for our study population (ICC = 0.71 and ICC = 0.71 for the right and the left leg, respectively).

Markers of handball-related performance measures are enhanced by introducing 10 weeks of biweekly upper- and lower-body CSTEB into the regular handball training schedule of young female handball players. Coaches should thus consider incorporating elements of complex strength training with elastic band into conventional in-season handball training for young female players. It seems that significant gains of performance-related attributes can be realized safely without the need of demanding additional training time.

Limitations

Several limitations were noted in the current study and must be considered when interpreting the results. The main limitation was that of the investigated population, in particular the small sample size and that of pubescent female athletes. However, through the use of a randomized control, statistical power was improved. Moreover, to keep motivation of the players similar in all measures, the participants were blinded to their results until the end of the study. Finally, as this study was conducted in a small and rather specialized group, the results may not necessarily be generalizable to other populations.

Conclusions

The findings of this study demonstrated that the use of the CSTEB (two sessions per week) during the in-season training routine of young female handball players could substantially improve a wide variety of physical performance measures (i.e. strength, speed, jumping, CoD, and RSTT). Of note, the CSTEB intervention lasted approximately 35 min, making it a time-efficient training method that can be routinely carried out in a sporting environment with few resources required. Further research is needed that examines the effects of CSTEB on muscle morphology and neural adaptations, with maturation status considered as a potential moderator variable.

Footnotes

Declaration of conflicting interests

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

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

ORCID iDs

Mohamed Souhaiel Chelly

Beat Knechtle

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