The pressure for children to excel and succeed in sport continues to mount. Although resistance training for youth was in disfavor by many organizations even into the early 21st century, children’s training programs are more closely resembling the volume and intensity of adult programs. The physiological maturation of adolescent youth may impact their response to advanced training programs. Furthermore, the pressure to specialize in specific sports rather than engage in a variety of sporting activities may affect not only training responses but also injury incidence. The highlighted articles first illustrate the training-specific responses of prepeak and postpeak height velocity stage youth with more specific training stimuli needed for the postpeak height velocity stage youth. Second, individual sports tend to promote earlier and greater specialization compared with team sports, which tend to result in a higher proportion of overuse injuries. Based on the findings of these 2 studies, the planning and implementation of high-intensity training for youth, such as plyometrics, should take into consideration the physical maturation of the child and that the prevention of overuse injuries would benefit from a more varied participation in sports and activities.
Nicole A. Dinn and David G. Behm
Studies have both supported and refuted the concept that it is the intent to perform ballistic contractions that determines velocity-specific gains in resistance training. The purpose of this investigation was to determine whether ballistic intent is as effective as ballistic movement in improving muscle activation, force, movement time, and reaction time.
Subjects completed 8 wk of punch training. A dynamic (DYN) group trained with elastic resistance bands, and the isometric (ISO) group trained with an unyielding strap. A control (CTRL) group was also tested. Pretesting and posttesting measures included isometric force; electromyography (EMG) of triceps, biceps, pectoralis major, and latissimus dorsi; movement and reaction time of both arms; and a quick-hands test of coordination.
Triceps iEMG increased by 63% in the ISO group (P = .03). Pectoralis major iEMG increased by 65% in the DYN group (P = .007). Movement time decreased 17.6% in the DYN training group (P = .001). Isometric force did not improve in either training group or in the CTRL group.
Because of its specificity of movement, dynamic training might be a more appropriate method to improve punching speed for martial artists and boxers. The intent to contract explosively over a short duration does not appear to be beneficial in increasing force production or speed of movement in punching.
Eric J. Drinkwater, Erica J. Pritchett and David G. Behm
Resistance training while using an instability-training device is known to increase activation of stabilizing muscle groups while decreasing the force generated by the prime movers during isometric contractions.
To investigate differences in squat kinetics during dynamic resistance training in an increasingly unstable training environment.
Fourteen active men participated in this study. In each testing session, each participant performed 3 repetitions of squats with a 10-repetition maximum (10-RM) resistance, 40% of their 10-RM resistance, and 20.45 kg. The 3 testing session consisted of standing on a stable foor, foam pads, or BOSU balls. All repetitions were recorded with an optical encoder to record barbell kinetics.
The transition from stable (floor) to very unstable (BOSU) resulted in high likelihoods (>75%) of clinically meaningful differences ranging from small to large (effect size [ES] 0.31–1.73) in factors relating to concentric kinetics, eccentric power, and squat depth, regardless of the resistance used for training. There were also likely differences at the heaviest resistance in peak concentric power (stable to foam: ES 2.06; foam to BOSU: ES 0.38), eccentric power (stable to foam: ES 1.88; foam to BOSU: ES 0.74), and squat depth (stable to foam: ES 0.50; foam to BOSU: ES 0.67).
Resistance training in an unstable environment at an intensity sufficient to elicit strength gains of the prime movers results in deleterious effects in concentric squat kinetics and squat technique. Such observations are particularly evident on very unstable platforms.
Meaghan E. Maddigan, David G. Behm and Glen R. Belfry
High intensity interval training (HIIT) has been shown to improve muscle power and endurance, as well as aerobic power.
To assess the effects of HIIT that utilizes resistive elastic bands to improve overhand throwing velocity.
Healthy female volunteers (n = 13) ranging in age from 18–29 years.
Participants were randomly assigned to either a control group or an experimental group that exercised 3 days per week for 3 weeks. Each training session involved performance of 5 sets of 20 throwing motions against elastic band resistance, which was performed by both extremities.
Main Outcome Measures:
Maximal oxygen consumption was measured during performance of a graded exercise test that utilized an upper extremity cycle ergometer. A radar gun was used to assess peak throwing velocity and the extent to which throwing velocity was sustained during performance of a 20-throw endurance test.
After completing the training, the experimental group exhibited faster peak throwing velocity (61.6 ± 6.6 km/hr to 63.2 ± 8.6 km/hr) and a reduced fatigue index (1.18 ± 0.16 to 1.01 ± 0.02). Training also resulted in a 14% improvement in maximum oxygen consumption (1.40 ± 0.46 L/min to 1.60 ± 0.49 L/ min) and longer time to fatigue (9.99 ± 1.84 min to 11.43 ± 2.29 min).
The high-intensity interval training program was effective for improvement of overhand throwing performance.
Anis Chaouachi, Monoem Haddad, Carlo Castagna, Del P. Wong, Fathi Kaouech, Karim Chamari and David G. Behm
The objective of this study was to examine the response and recovery to a single set of maximal, low and high angular velocity isokinetic leg extension-flexion contractions with boys. Sixteen boys (11–14 yrs) performed 10 isokinetic contractions at 60°.s−1 (Isok60) and 300°.s−1 (Isok300). Three contractions at both velocities, blood lactate and ratings of perceived exertion were monitored pretest and at 2, 3, 4, and 5 min of recovery (RI). Participants were tested in a random counterbalanced order for each velocity and recovery period. Only a single contraction velocity (300°.s−1 or 60°.s−1) was tested during recovery at each session to remove confounding influences between the recovery intervals. Recovery results showed no change in quadriceps’ power at 300°.s−1, quadriceps’ power, work and torque at 60°.s−1 and hamstrings’ power and work with 60°.s−1. There was an increase during the 2 min RI in hamstrings’ power, work and torque and quadriceps’
Monoem Haddad, Anis Chaouachi, Carlo Castagna, Del P. Wong, David G. Behm and Karim Chamari
The session rating of perceived exertion (RPE) is a practical and non-invasive method that allows a quantification of the internal training load (TL) in individual and team sports, but no study has investigated its construct validity in martial arts. Therefore, the purpose of this study was to examine the convergent validity between the session-RPE method and two objective HR-based methods for quantifying the similar TL during a high-TL camp in young Taekwondo (TKD) athletes.
Ten young TKD athletes (mean ± SD: age, 13.1 ± 2.4 y; body mass, 46.1 ± 12.7 kg; height, 1.53 ± 0.15 m; maximum heart rate (HRmax), 201.0 ± 8.2 bpm) participated in this study. During the training period, subjects performed 35 TKD training sessions, including two formal competitions during which RPE and HR were recorded and analyzed (308 individual training sessions). Correlation analysis was used to evaluate the convergent validity between session-RPE method and the two commonly used HR-based methods for assessing TL in a variety of training modes.
Significant relationships were found between individual session-RPE and all the HR-based TLs (r values from 0.55 to 0.90; P < .001). Significant correlations were observed in all mode of exercises practiced in TKD.
This study shows that session-RPE can be considered as a valid method to assess TL in TKD.
Olaf Prieske, Helmi Chaabene, Christian Puta, David G. Behm, Dirk Büsch and Urs Granacher
Purpose: To examine the effects of drop height on drop-jump (DJ) performance and on associations between DJ and horizontal-jump/sprint performances in adolescent athletes. Methods: Male (n = 119, 2.5 [0.6] y post-peak-height velocity) and female (n = 120, 2.5 [0.5] y post-peak-height velocity) adolescent handball players (national level) performed DJs in randomized order using 3 drop heights (20, 35, and 50 cm). DJ performance (jump height, reactive strength index [RSI]) was analyzed using the Optojump Next system. In addition, correlations were computed between DJ height and RSI with standing-long-jump and 20-m linear-sprint performances. Results: Statistical analyses revealed medium-size main effects of drop height for DJ height and RSI (P < .001, 0.63 ≤ d ≤ 0.71). Post hoc tests indicated larger DJ heights from 20 to 35 and 35 to 50 cm (P ≤ .031, 0.33 ≤ d ≤ 0.71) and better RSI from 20- to 35-cm drop height (P < .001, d = 0.77). No significant difference was found for RSI between 35- and 50-cm drop height. Irrespective of drop height, associations of DJ height and RSI were small with 5-m-split time (−.27 ≤ r ≤ .05), medium with 10-m-split time (−.44 ≤ r ≤ .14), and medium to large with 20-m sprint time and standing-long-jump distance (−.57 ≤ r ≤ .22). Conclusions: The present findings indicate that, irrespective of sex, 35-cm drop heights are best suited to induce rapid and powerful DJ performance (ie, RSI) during reactive strength training in elite adolescent handball players. Moreover, training-related gains in DJ performance may at least partly translate to gains in horizontal jump and longer sprint distances (ie, ≥20-m) and/or vice versa in male and female elite adolescent athletes, irrespective of drop height.
Jonathan C. Reid, Rebecca M. Greene, Nehara Herat, Daniel D. Hodgson, Israel Halperin and David G. Behm
Contrary to adult force reserve strategies, it is not known whether adolescent females with less experience performing maximal voluntary contractions (MVC) have specific responses to a known or unknown fatigue endpoint.
Using a counterbalanced random crossover design, fourteen inexperienced female adolescents completed three elbow flexor (EF) fatiguing protocols. Participants were randomly assigned to a control (informed they would perform 12 MVCs), unknown (not informed of the number of MVCs to be completed, but stopped after 12) or deception condition (instructed to complete 6 MVCs, however, after the sixth repetition performed another 6 MVCs). Before and during the interventions, EF impulse, force, and biceps brachii (BB) and triceps brachii (TB) electromyography (EMG) activity were recorded. Results: Participants exhibited decreases in impulse (10.9%; p < .05), force (7.5%; p = .001), BB (16.2%; p < .05) and TB (12.9%; p < .05) EMG activity between the pretest and the first repetition of all protocols. Knowledge of endpoint, or lack of it, did not change measures with the repeated MVCs. When informed about the final repetition, force remained depressed suggesting no physiological reserve.
Adolescent females exhibited an anticipatory response to the task of performing repeated MVCs. A lack of change with knowledge of endpoint indicates that those lacking in MVC experience do not employ the same pacing strategies as in previous studies of participants with MVC experience.
Raouf Hammami, Anis Chaouachi, Issam Makhlouf, Urs Granacher and David G. Behm
Balance, strength and power relationships may contain important information at various maturational stages to determine training priorities.
The objective was to examine maturity-specific relationships of static/dynamic balance with strength and power measures in young male athletes.
Soccer players (N = 130) aged 10–16 were assessed with the Stork and Y balance (YBT) tests. Strength/power measures included back extensor muscle strength, standing long jump (SLJ), countermovement jump (CMJ), and 3-hop jump tests. Associations between balance with strength/power variables were calculated according to peak-height-velocity (PHV).
There were significant medium-large sized correlations between all balance measures with back extensor strength (r = .486–.791) and large associations with power (r = .511–.827). These correlation coefficients were significantly different between pre-PHV and circa PHV as well as pre-PHV and post-PHV with larger associations in the more mature groups. Irrespective of maturity-status, SLJ was the best strength/power predictor with the highest proportion of variance (12–47%) for balance (i.e., Stork eyes opened) and the YBT was the best balance predictor with the highest proportion of variance (43–78%) for all strength/power variables.
The associations between balance and muscle strength/power measures in youth athletes that increase with maturity may imply transfer effects from balance to strength/power training and vice versa in youth athletes.
Wissem Dhahbi, Anis Chaouachi, Johnny Padulo, David G. Behm and Karim Chamari
To examine the concurrent validity and absolute and relative reliabilities of a commando-specific power test.
21 antiterrorism commandos.
All participants were assessed on a 5-m rope-climbing test (RCT) and the following tests: pull-ups, push-ups, estimated-1-repetition-maximum (est-1RM), medicine-ball put, and handgrip-strength test. The stopwatch method related to the execution time (ET) was validated by comparison with video motion analysis. The best individual attempt of 3 trials was kept for analysis, and the performance was expressed in absolute power output (APO) and body-mass relative power output (RPO).
Stopwatch assessment had an excellent criterion validity (r = .99, P < .001), intraclass correlation coefficient (ICC3,1) of .98, standard errors of measurement (SEM%) of 1.19%, bias ± the 95% limits of agreement of 0.03 ± 0.26 s, and minimal detectable change (MDC95) of 0.51 s. The ET, APO, and RPO were significantly correlated (P < .05) with all cited tests (absolute-value r range .55−.98), while est-1RM was not significantly correlated with the other tests. Test-retest reliability coefficients were excellent for ET, APO, and RPO (ICC3,1 > .90). The SEM% values for the ET, APO, and RPO were all under 5% (range 3.73−4.52%), all being smaller than the corresponding smallest worthwhile change. The coefficients of variation for the ET, APO, and RPO were all under 10%. %MDC95 ranged from 10.37% to 12.53%.
Considering the strong concurrent validity and excellent test–retest reliability, the RCT is simple to administer, has ecological validity, and is a valid specific field test of upper-body power for commandos and, in addition, can be accurately assessed with a stopwatch.