Canadian Society for Exercise Physiology position paper: resistance training in children and adolescents

A comprehensive study of the academic benefits and practical recommendations to include resistance training programs in institutional education

The connection between physical activity and cognitive function has become a focus of attention in educational research in recent years. Regular exercise has been shown to have significant positive effects on physical health, but it also appears to have a significant impact on cognitive function and academic performance. Of all the exercise modalities, resistance training has drawn interest for its ability to improve cerebral abilities in addition to physical well-being. However, there is limited available knowledge exploring the relationship between resistance training regimens and academic performance. This narrative review aims to investigate the underlying mechanisms linking resistance training to academic performance. Firstly, we will examine the biological mechanisms and psychosocial links that potentially connect resistance training to academic performance to find and describe the different mechanisms by which resistance training improves academic performance. In the next part of the work, we delve into the existing observational and intervention studies that have explored the relationship between resistance training and academic performance. Lastly, we provide practical recommendations for including resistance training in institutional education settings, emphasizing the need of dispelling myths and addressing barriers to increase participation as well as the relevance of considering key training variables and adaptation of protocols to developmental stages, always guided by a properly trained professional. Overall, the available evidence supports that resistance training provides potential benefits to the academic performance of youth students with many biological and psychosocial factors that explain this relationship. However, most of the studies are observational, and broader interventional studies are needed to understand and maximize the benefits of this type of physical exercise.

Vertical Strength Transfer Phenomenon Between Upper Body and Lower Body Exercise: Systematic Scoping Review

BACKGROUND

There are a myriad of exercise variations in which upper body (UB) and lower body (LB) exercises have been intermittently used. However, it is still unclear how training of one body region (e.g. LB) affects adaptations in distant body areas (e.g. UB), and how different UB and LB exercise configurations could help facilitate physiological adaptations of either region; both referred to in this review as vertical strength transfer.

OBJECTIVE

We aimed to investigate the existence of the vertical strength transfer phenomenon as a response to various UB and LB exercise configurations and to identify potential mechanisms underpinning its occurrence.

METHODS

A systematic search using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) for Scoping Reviews protocol was conducted in February 2024 using four databases (Web of Science, MEDLINE, Scopus and CINAHL) to identify peer-reviewed articles that investigated the vertical strength transfer phenomenon.

RESULTS

Of the 5242 identified articles, 24 studies met the inclusion criteria. Findings suggest that the addition of UB strength training to LB endurance exercise may help preserve power-generating capacity for the leg muscle fibres. Furthermore, systemic endocrine responses to high-volume resistance exercise may beneficially modulate adaptations in precedingly or subsequently trained muscles from a different body region, augmenting their strength gains. Last, strength training for LB could result in improved strength of untrained UB, likely due to the increased central neural drive.

CONCLUSIONS

Vertical strength transfer existence is enabled by neurophysiological mechanisms. Future research should involve athletic populations, examining the potential of vertical strength transfer to facilitate athletic performance and preserve strength in injured extremities.

Effect of leg dominance on ipsilateral and contralateral limb training adaptation in middle-aged women after unilateral sensorimotor and resistance exercise training

The aim was to examine the directionality of global training effects in middle-aged women after unilateral training.

Thirty-nine middle-aged female volunteers (59.4 ± 5.4 years) were randomly assigned to one of three groups: 1. Unilateral Dominant Lower Limb Training (UDLT); 2. Unilateral Non-Dominant Lower Limb Training (UNDLT) or 3. Control group. Outcome measures assessing isometric strength, static and dynamic balance were recorded at baseline, and 1 week after 12 weeks (post-test) of training or no-intervention.

The net cross education adaptation changes of the contralateral quadriceps isometric maximum voluntary (MVC) force (F2,34 = 4.33; p = 0.022), Stork balance score (F2,34 = 4.26; p = 0.023) and the Star Excursion Balance test score (F2,34 = 11.80; p = 0.001) were asymmetrical in the UNDLT group and on average, exceeded the UDLT group.

The results demonstrated asymmetrical cross education training adaptations with unilateral training of non-dominant leg (UNDLT) to contralateral homologous and heterologous muscles, with the exception of knee flexor MVC. The results of this study provide a novel exercise or rehabilitation strategy that can be employed when one of the limbs is affected.

Relative Cross-Education Training Effects of Male Youth Exceed Male Adults

ABSTRACT

Ben Othman, A, Anvar, SH, Aragão-Santos, JC, Behm, DG, and Chaouachi, A. Relative cross-education training effects of male youth exceed male adults. J Strength Cond Res 38(5): 881-890, 2024-Cross-education has been studied extensively with adults, examining the training effects on contralateral homologous muscles. There is less information on the cross-education effects on contralateral heterologous muscles and scant information comparing these responses between adults and youth. The objective was to compare cross-education training effects in male youth and adults to contralateral homologous and heterologous muscles. Forty-two male children (10-13-years) and 42 adults (18-21-years) were tested before and following an 8-week unilateral, dominant or nondominant arm, chest press (CP) training program or control group (14 subjects each). Unilateral testing assessed dominant and nondominant limb strength with leg press and CP 1 repetition maximum (1RM), knee extensors, elbow extensors (EE), elbow flexors, and handgrip maximum voluntary isometric contraction (MVIC) strength and shot put distance and countermovement jump height. Upper-body tests demonstrated large magnitude increases, with children overall exceeding adults ( p = 0.05- p < 0.0001, η2 : 0.51, 10.4 ± 11.1%). The dominant trained limb showed significantly higher training adaptations than the nondominant limb for the adults with CP 1RM ( p = 0.03, η2 : 0.26, 6.7 ± 11.5%) and EE ( p = 0.008, η2 : 0.27, 8.8 ± 10.3%) MVIC force. Unilateral CP training induced significantly greater training adaptations with the ipsilateral vs. contralateral limb ( p = 0.008, η2 : 0.93, 27.8 ± 12.7%). In conclusion, children demonstrated greater training adaptations than adults, upper-body strength increased with no significant lower-body improvements, and ipsilateral training effects were greater than contralateral training in adults.

Motor unit firing rates increase in prepubescent youth following linear periodization resistance exercise training

PURPOSE

The purpose was to examine the effects of 8-weeks (3 days/week) of linear periodization resistance exercise training (RET) on neuromuscular function in prepubescent youth.

METHODS

Twenty-five healthy prepubescent youth (11 males, 14 females, age = 9.1 ± 0.8 years) completed the RET (n = 17) or served as controls (CON, n = 8). Isometric maximal voluntary contractions (MVCs) and trapezoidal submaximal contractions at 35 and 60% MVC of the right leg extensors were performed with surface electromyography (EMG) recorded from the leg extensors [vastus lateralis (VL), rectus femoris, and vastus medialis] and flexors (biceps femoris and semitendinosus). EMG amplitude of the leg extensors and flexors were calculated during the MVCs. Motor unit (MU) action potential trains were decomposed from the surface EMG of the VL for the 35 and 60% MVCs. MU firing rates and action potential amplitudes were regressed against recruitment threshold with the y-intercepts and slopes calculated for each contraction. Total leg extensor muscle cross-sectional area (CSA) was collected using ultrasound images. ANOVA models were used to examine potential differences.

RESULTS

Isometric strength increased post-RET (P = 0.006) with no changes in leg extensor and flexor EMG amplitude. Furthermore, there were no changes in total CSA or the MU action potential amplitude vs. recruitment threshold relationships. However, there were increases in the firing rates of the higher-threshold MUs post-RET as indicated with greater y-intercepts (P = 0.003) from the 60% MVC and less negative slope (P = 0.004) of the firing rates vs. recruitment threshold relationships at 35% MVC.

CONCLUSIONS

MU adaptations contribute to strength increases following RET in prepubescent youth.

Strength Training Frequency and Athletic Performance in High School Girls Basketball Players

This study investigated the effects of a six-week strength training intervention on the physical fitness of female high school athletes, with a focus on training frequency. Twenty-three female high school basketball athletes were recruited and split into two groups: one group participated in strength training once per week (S1), while the other participated in two training sessions per week (S2). The groups were not random as training sessions were voluntary, and some participants were only able to train once per week. Participants were tested before and after the intervention, and the data included: age, body height, body mass, body fat percentage, grip strength, leg/back dynamometer (LBD) strength, a seated medicine ball throw (MBT), a vertical jump (VJ), 505 tests from each foot, 0-5, 0-10, and 0-20 sprint times, and multistage fitness test shuttles. Data were analyzed by a two (time) x two (group) repeated measures analysis of variance (ANOVA; p < 0.05). When significant F ratios were detected in any ANOVA calculations, post hoc pairwise comparisons were conducted using the Bonferroni adjustment procedure. There were significant main effects for time that indicated the following: increased body height, body mass, grip strength, LBD strength, MBT distance, and VJ height, faster 505 times, and slower 0-5 and 0-10 m sprint times (p ≤ 0.021). There were no significant time by group ANOVAs or between-group main effects. These performance changes occurred irrespective of training frequency. High school girls who participate in at least one strength training session per week can improve their strength (grip, LBD), power (MBT, VJ), and change-of-direction speed (505).

Effects of plyometric jump training on measures of physical fitness and lower-limb asymmetries in prepubertal male soccer players: a randomized controlled trial

BACKGROUND

High level of physical fitness is a paramount soccer performance factor. As such, developing key components of physical fitness such as sprinting, jumping, and change of direction (CoD) at an early age empowers both short- and long-term performance success. Although previous research in prepubertal male soccer players has reported physical fitness performance enhancements following plyometric jump training (PJT), the effects on inter-limb asymmetries remain unclear.

OBJECTIVE

To assess the effects of PJT on measures of physical fitness and inter-limb asymmetries in prepubertal male soccer players.

METHODS

A total of 27 participants were recruited, and randomly assigned to either a PJT group (n = 13; age = 12.7 ± 0.2 years; maturity offset = -1.6 ± 0.7) or an active control group (CG) (n = 14; age = 11.8 ± 0.4 years; maturity offset = -2.51 ± 0.61). The training intervention lasted eight-week and was conducted during the in-season period, with twice-weekly sessions. Physical fitness tests were conducted before and after the intervention, including the 505 change-of-direction (CoD; [505 CoD test]), countermovement-jump (CMJ) height, standing-long-jump (SLJ) distance, and single-leg hop test for distance with dominant (SHTD-D) and non-dominant legs (SHTD-ND). A jump-based asymmetry score was calculated as the difference between HTD and HTND.

RESULTS

ANCOVA analysis revealed significant between-group differences in all physical fitness measures at post-test. Specifically, the PJT group showed significant large improvements in CMJ height, SLJ distance, HTD and HTND, and CoD speed (d = 0.84 to 2.00; ∆1.05% to 16.85%). Moreover, the PJT group showed a significant, small reduction in the inter-limb asymmetry score (d = 0.43; ∆-45.21%). In contrast, no significant changes were reported in the CG between pre-and post-tests (d = 0.07 to 0.24; ∆0.21% to 0.98%).

CONCLUSIONS

The incorporation of PJT into the training schedules of prepubertal male soccer players resulted in positive effects on various measures of physical fitness. Furthermore, our findings suggest that PJT can reduce lower-limb asymmetry, which could potentially decrease the risk of lower limb injuries.

TRIAL REGISTRATION

This study does not report results related to healthcare interventions using human participants and therefore it was not prospectively registered.

Minimalist Training: Is Lower Dosage or Intensity Resistance Training Effective to Improve Physical Fitness? A Narrative Review

BACKGROUND

Findings from original research, systematic reviews, and meta-analyses have demonstrated the effectiveness of resistance training (RT) on markers of performance and health. However, the literature is inconsistent with regards to the dosage effects (frequency, intensity, time, type) of RT to maximize training-induced improvements. This is most likely due to moderating factors such as age, sex, and training status. Moreover, individuals with limited time to exercise or who lack motivation to perform RT are interested in the least amount of RT to improve physical fitness.

OBJECTIVES

The objective of this review was to investigate and identify lower than typically recommended RT dosages (i.e., shorter durations, lower volumes, and intensity activities) that can improve fitness components such as muscle strength and endurance for sedentary individuals or beginners not meeting the minimal recommendation of exercise.

METHODS

Due to the broad research question involving different RT types, cohorts, and outcome measures (i.e., high heterogeneity), a narrative review was selected instead of a systematic meta-analysis approach.

RESULTS

It seems that one weekly RT session is sufficient to induce strength gains in RT beginners with < 3 sets and loads below 50% of one-repetition maximum (1RM). With regards to the number of repetitions, the literature is controversial and some authors report that repetition to failure is key to achieve optimal adaptations, while other authors report similar adaptations with fewer repetitions. Additionally, higher intensity or heavier loads tend to provide superior results. With regards to the RT type, multi-joint exercises induce similar or even larger effects than single-joint exercises.

CONCLUSION

The least amount of RT that can be performed to improve physical fitness for beginners for at least the first 12 weeks is one weekly session at intensities below 50% 1RM, with < 3 sets per multi-joint exercise.

The effect of core stability training on the balance ability of young male basketball players

Introduction: This study aimed to investigate the impact of a 10-week Core Stability Training (CST) compared to Traditional Strength Training (TST) on the balance abilities of adolescent male basketball players. Methods: Subjects (age: 15.70 ± 0.75, height: 178.4 ± 8.31, weight: 66.55 ± 8.34) were randomly assigned to either the Core Stability Training group or the Traditional Strength Training group. Three selected balance assessment indicators included the Single-leg Standing with Eyes Closed Test, Star Excursion Balance Test, and Core Four-Direction Endurance Test. Results: 1) The scores were significantly different in both groups before and after the Single-leg Standing with Eyes Closed Test; (p < 0.01, d = 1.692, d = 1.837); 2) In the Star Excursion Balance Test, the scores of the experimental group showed significant difference (p < 0.05) or highly significant difference (p < 0.01) with an average effect size of (d = 1.727) when the left or right foot supported in the other directions before and after the training. However, there was no significant difference in scores in the c direction when the left foot supported (p > 0.05, d = 0.954); 3) In the Core Four-Direction Endurance Test, there were no significant differences in scores for the control group before and after training (p > 0.05, d = 0.567), while the experimental group showed significant differences in scores before and after training (p < 0.05, d = 1.889). Discussion: Both CST and TST were effective in enhancing the balance abilities of adolescent basketball players. CST, in particular, demonstrated improvements in dynamic balance and agility across multiple planes. Basketball coaches are encouraged to consider incorporating CST training programs into their overall training plans for optimal balance enhancement.

Data Informing Governing Body Resistance-Training Guidelines Exhibit Sex Bias: An Audit-Based Review

The objective of this review was to examine the ratio of female and male participants utilised in data informing consensus statements and position stands in the field of resistance training (RT). In order to achieve this objective, we conducted an 'audit' style review. We accessed three databases: SPORTDiscus, MEDLINE and Google Scholar utilising the following search terms: resistance or strength training AND consensus statements or position statements/stands. Eligibility criteria included consensus statements and position stands for RT in youth, adults and older adults. In this paper we have used the term 'female' to describe biological sex. Gender is a social construct and often describes roles and behaviours that society assigns to men or women. In this paper we have used the term 'women' to describe gender. Reference lists from each guideline were screened with the number of male and female participants extracted from each study. We also extracted data on the gender of the authors of the statements. We located 11 guidelines encompassing a total of 104,251,363 participants. Youth guidelines were comprised of 69% male participants. There were 287 studies that included both sexes, 205 male-only and 92 female-only studies. Adult guidelines were comprised of 70% male participants. There were 104 studies that included both sexes, 240 male-only and 44 female-only studies. Older adult guidelines were comprised of 54% female participants. There were 395 studies that included both sexes, 112 male-only and 83 female-only studies. Women authors comprised 13% of all authors of position stands and consensus statements. These results demonstrate an under-representation of females and women as both participants and as authors. It is imperative to ensure that data informing governing body guidelines and consensus statements are representative of the population they aim to inform. If this is not possible, guidelines should clearly state when their data and recommendations are based primarily upon one sex.

Reporting of Adverse Events in Muscle Strengthening Interventions in Youth: A Systematic Review

Clear definition, identification, and reporting of adverse event (AE) monitoring during training interventions are essential for decision making regarding the safety of training and testing in youths.

PURPOSE

To document the extent to which AEs, resulting from intervention studies targeting muscle strengthening training (MST) in youth, are reported by researchers.

METHODS

Electronic databases (CINAHL, PubMed, SPORTDiscus, and Web of Science) were searched for English peer-reviewed articles published before April 2018. Inclusion criteria were: (1) average age <16 years, (2) use of MST, (3) statement(s) linked to the presence/absence of AEs, and (4) randomized controlled trials or quasi-experimental designs. Risk of reporting bias for AEs followed recommendations by the Cochrane Collaboration group.

RESULTS

One hundred and ninety-one full-text articles were screened. One hundred and thirty met all MST criteria, out of which only 44 (33.8%; n = 1278, age = 12.1 [1.1] y) included a statement as to the presence/absence of adverse events. The 86 other studies (66.2%) included no such statement. Of the reporting 44 studies, 18 (40.1%) indicated one or more adverse events. Of the 93 reported adverse events, 55 (59.1%) were linked to training or testing.

CONCLUSIONS

Most MST studies in youth do not report presence/absence of adverse events, and when reported, adverse events are not well defined.

School-Based Circuit Training Intervention Improves Local Muscular Endurance in Primary School Students: A Randomized Controlled Trial

BACKGROUND

This study aimed to explore the effectiveness of a 12-week circuit training program in improving local muscular endurance in normal-weighted primary school students.

METHODS

The study involved a parallel-group randomized trial with 606 primary school boys assigned to an experimental or a control group. The participants underwent a 12-week circuit training program that involved multi-joint, total-body workouts using body weight, resistance bands, and medicine ball exercises. The study measured the participants' local muscular endurance during sit-ups, dynamic trunk extensions on a Roman bench (DTE), and push-ups.

RESULTS

After adjusting for the baseline, the treatment-grade interaction was significant for sit-ups (F = 7.74, p < 0.001, η_p² = 0.04), DTE (F = 6.49, p < 0.001, η_p² = 0.03), and push-ups (F = 9.22, p < 0.001, η_p² = 0.05), where the experimental treatment was more beneficial than the control. The treatment effect seemed to vary depending on the individual's baseline local muscle endurance capacity. As the baseline local muscular endurance values increased, the treatment and grade effects became less beneficial.

CONCLUSION

A 12-week circuit training program involving body weight, resistance bands, and medicine ball exercises suits school-based programs and can improve local muscular endurance in normal-weighted primary school boys. The experimental treatment was more effective than the control, and the individual baseline muscular endurance should be considered when designing training programs.

Exploring of two different equated instability resistance training programs on measure of physical fitness and lower limb asymmetry in pre-pubertal weightlifters

BACKGROUND

Although previous research in pediatric populations has reported performance enhancements following instability resistance training, the effects of different volumes on measures of balance, strength and power and lower limb asymmetry remain unclear.

OBJECTIVE

To compare the effect of two 8-week instability resistance training programs (IRT1: 2 sets x 8 repetitions, 20% one-repetition maximum (1RM); IRT2: 2 sets x 4 repetitions, 40% 1RM) in balance (center of pressure displacements), 1RM, single-leg jumps, and inter-limb asymmetry of prepubescent weightlifters.

METHODS

Thirty-two male athletes (10.94 ± 0.47 yrs, 17.05 ± 0.14 kg/m², and 6.44 ± 0.93% bodyfat) voluntarily participated and combined IRT (front and back squat, lunge, and deadlift) with their usual weightlifting training. Nonparametric tests evaluated the differences between pre- and post-intervention.

RESULTS

Significant improvements were encountered in all the variables for both groups (effect sizes [ES] from 0.46 to 2.60), except the inter-limb asymmetry and the velocity of displacement of the center of pressure, which did not improve in IRT2. It is also worth highlighting that in the single-leg jumps and center of pressure displacements, whereas no significant differences were observed between IRT1 and IRT2 in the baseline, significant differences appeared in the follow-up measurements.

CONCLUSION

IRT combined with weight-lifting training improves prepubescent weightlifters' performance; therefore, strength and conditioning coaches may consider including unstable devices with low loads into an overall conditioning program and warm-ups for prepuberal male weightlifters to promote their physical fitness and potentially decrease inter-limb asymmetry.

TRIAL REGISTRATION

This study does not report results related to healthcare interventions using human participants; therefore, it was not prospectively registered.

National Strength and Conditioning Association Position Statement on Weightlifting for Sports Performance

ABSTRACT

Comfort, P, Haff, GG, Suchomel, TJ, Soriano, MA, Pierce, KC, Hornsby, WG, Haff, EE, Sommerfield, LM, Chavda, S, Morris, SJ, Fry, AC, and Stone, MH. National Strength and Conditioning Association position statement on weightlifting for sports performance. J Strength Cond Res XX(X): 000-000, 2022-The origins of weightlifting and feats of strength span back to ancient Egypt, China, and Greece, with the introduction of weightlifting into the Olympic Games in 1896. However, it was not until the 1950s that training based on weightlifting was adopted by strength coaches working with team sports and athletics, with weightlifting research in peer-reviewed journals becoming prominent since the 1970s. Over the past few decades, researchers have focused on the use of weightlifting-based training to enhance performance in nonweightlifters because of the biomechanical similarities (e.g., rapid forceful extension of the hips, knees, and ankles) associated with the second pull phase of the clean and snatch, the drive/thrust phase of the jerk and athletic tasks such as jumping and sprinting. The highest force, rate of force development, and power outputs have been reported during such movements, highlighting the potential for such tasks to enhance these key physical qualities in athletes. In addition, the ability to manipulate barbell load across the extensive range of weightlifting exercises and their derivatives permits the strength and conditioning coach the opportunity to emphasize the development of strength-speed and speed-strength, as required for the individual athlete. As such, the results of numerous longitudinal studies and subsequent meta-analyses demonstrate the inclusion of weightlifting exercises into strength and conditioning programs results in greater improvements in force-production characteristics and performance in athletic tasks than general resistance training or plyometric training alone. However, it is essential that such exercises are appropriately programmed adopting a sequential approach across training blocks (including exercise variation, loads, and volumes) to ensure the desired adaptations, whereas strength and conditioning coaches emphasize appropriate technique and skill development of athletes performing such exercises.

Effects of running-based versus body-weight-based high-intensity interval training on physical fitness in healthy adolescents

Objectives: High-intensity interval training improves aerobic endurance, but the effectiveness of different training protocols is unclear. This study compared the effects of running-based high-intensity interval training (R-HIIT) and body weight-based high-intensity interval training (B-HIIT) on physical fitness in adolescents.

Methods: This was a pre-and post-test quasi-experimental design in which a seventh-grade natural class was randomly selected from three homogeneous middle schools, and then the three natural classes were randomly divided into three groups: the R-HIIT group (n = 54), the B-HIIT group (n = 55), and the control group (Con, n = 57). Both intervention groups exercised twice a week for 12 weeks with a 2:1 (1 min:30 s) load-interval ratio and exercise intensity controlled at 70%–85% maximum heart rate. R-HIIT was in the form of running, and B-HIIT was in the form of resistance exercises using the participants’ body weight. The control group was instructed to continue their normal behavior. cardiorespiratory fitness, muscle strength and endurance, and speed were measured before and after the intervention. Statistical differences between and within groups were determined using repeated measures analysis of variance.

Results: Compared to the baseline, both the R-HIIT and B-HIIT intervention groups significantly improved CRF, muscle strength, and speed (p &lt; 0.05). The B-HIIT group was significantly better than R-HIIT in improving CRF (4.48 mL/kg/min vs 3.34 mL/kg/min, p &lt; 0.05), and only the B-HIIT improved sit-up muscle endurance (ηp2 = 0.30, p &lt; 0.05).

Conclusion: The B-HIIT protocol was significantly more effective than the R-HIIT protocol in developing CRF and improving muscle health indicators.

Influence of Strength Training Variables on Neuromuscular and Morphological Adaptations in Prepubertal Children: A Systematic Review

Strength training in prepubertal children is one of the topics that has aroused the most interest and controversy among training professionals in recent years. Therefore, the aim of the present study was to analyze the available scientific evidence on the influence of strength training variables on morphological and/or neuromuscular adaptations in healthy prepubertal populations with no previous experience in this type of training according to the descriptive sample characteristics. According to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis, 22 studies were selected after a systematic search and selection process using four electronic databases: Google Scholar, PubMed, Scopus, and SPORT Discus. Furthermore, the internal validity of the studies included was assessed using the modified PEDro scale. The sample consisted of 604 prepubertal children (age, 10.02 ± 0.75 years), of whom 473 were boys and 131 were girls, with 104 strength training programs recorded. Strength training resulted in a significant increase in jumping (n = 29) and sprinting (n = 13) abilities. Moreover, muscle strength was increased in 100% of the cases. Morphologically, strength training resulted in a decrease in body fat percentage (n = 19) and an increase in lean body mass (n = 17). With regard to gender, increases in general sport skills and basic physical abilities were significant in males but not in females. Thus, the results are more heterogeneous in girls due to the small number of studies carried out. Therefore, this research provides practical applications for coaches to design and implement more effective training programs to maximize adaptations, enhance physical performance, and reduce injury risk.

Relevance and Effectiveness of Combined Resistance and Balance Training to Improve Balance and Muscular Fitness in Healthy Youth and Youth Athletes: A Scoping Review

BACKGROUND

Balance and resistance training applied as single-mode interventions have proven to enhance measures of balance and/or muscular fitness in youth and youth athletes. Less is known on the effectiveness of combined or sequenced balance and resistance training in youth and youth athletes.

OBJECTIVE

The objective of this scoping review was to describe the effects of concurrently performed balance and resistance training (i.e., metastable resistance training) and different sequencing schemes of balance and resistance training on measures of balance and/or muscular fitness in healthy youth and youth athletes. We additionally aimed to identify knowledge gaps in the literature.

METHODS

According to the principles of a scoping review, we followed a broad research question, identified gaps in the literature, and reported findings on the level of single studies but did not aggregate and meta-analyze outcomes across studies. For this purpose, systematic literature searches were conducted in the electronic databases PubMed (including MEDLINE), Web of Science, and SPORTDiscus from inception until August 2022. We included metastable resistance training and sequenced balance and resistance training studies in healthy youth and youth athletes aged 6-18 years that investigated the training-induced effects on measures of balance (e.g., stork balance test) and muscular fitness (e.g., countermovement jump test) in contrast to active/passive controls. The Physiotherapy Evidence Database (PEDro) scale was used to assess the risk of bias. The Strength of Recommendation Taxonomy (SORT) was applied for the whole scoping review on levels A (high strength of recommendation) to C (low strength of recommendation) and for individual studies on levels 1 (high-quality evidence) to 3 (low-quality evidence).

RESULTS

The strength of recommendation for the scoping review was level B based on inconsistent or limited-quality evidence. Eleven randomized controlled trials were eligible to be included in this scoping review and each study was rated as 'limited-quality evidence'. A median PEDro score of 6 was computed across the included studies. Four studies examined the effects of metastable resistance training (e.g., plyometric training on unstable surfaces) on measures of balance and/or muscle fitness in youth athletes. The remaining seven studies investigated the impact of sequenced balance and resistance training (e.g., blocked balance training followed by blocked resistance training) on measures of balance and/or muscle fitness in youth and youth athletes. The duration of the intervention programs ranged from 6 to 10 weeks with 2-weekly to 3-weekly exercise sessions. Participants' age range was 10-18 years (mean 15 years). Ten studies examined young male and female athletes from different sports (i.e., basketball, handball, soccer) and one study physical education students. Metastable resistance training compared with plyometric training performed on stable surfaces showed no extra effect on measures of balance and muscular fitness. Stable plyometric training appears to be even more effective to improve jump performance. Sequenced balance and resistance training in the form of a mesocycle of balance followed by plyometric training seems to be particularly effective to improve measures of balance and muscular fitness in young athletes. This scoping review identified knowledge gaps that may indicate future research avenues: (i) comparative studies should be designed to examine how sex, age, maturity status, and expertise level impact on the adaptive potential following metastable resistance training or sequenced balance and resistance training in youth and youth athletes, (ii) at least one established measure of balance and muscular fitness should always be included in study designs to allow future comparison between studies and to aggregate (meta-analyze) findings across studies and (iii) studies are needed that examine neuromuscular and tendomuscular adaptations following these exercise types as well as dosage effects.

CONCLUSIONS

According to the results of this scoping review, balance training should be an essential training component for youth that is incorporated with the resistance training exercises or introduced at least a month before resistance and plyometric training within a periodized training program. More research is needed to examine the moderating roles of age, maturity status, and sex.

Regulatory Mechanisms of Muscle Mass: The Critical Role of Resistance Training in Children and Adolescent

Muscle mass and strength are subjected to several regulations. We found endocrine signals such as growth hormone, insulin-like growth factor 1, testosterone, thyroid hormones, and glucocorticoids among them. Neural inputs also influence muscle development, modulating mass and strength. Among the external stimuli that modulate these muscular features is physical training such as resistance and endurance training. Specifically, resistance training can mediate an increase in muscle mass by hypertrophy in adults, but the effects in children and adolescents are full of myths for most of the population. However, the evidence shows that the impact of resistance training on children and adolescents is clear and provides a wide range of benefits. However, qualified professionals must be available since exercise prescription and subsequent supervision must follow this population's abilities, needs, and interests.

Associations of muscle-strengthening exercise with overweight, obesity, and depressive symptoms in adolescents: Findings from 2019 Youth Risk Behavior Surveillance system

Background

Previous studies have focused on the opposite relation between muscle strength, obesity, and depression in adults. Moreover, the evidence has indicated that obesity and depression in adults might be significantly decreased with Muscle Strength Exercise (MSE) albeit it might be insufficient. Therefore, the current study aimed to investigate the association between MSE, adiposity, and depression among United States adolescents.

Materials and methods

This cross-sectional study used the Youth Risk Behavioral Survey (YRBS) data. In YRBS, a cluster sample was used, and the investigation was divided into three stages. The study surveyed 13,677 high school students and conducted self-reported questionnaires on sex, grade, race/ethnicity, MSE days, overweight, obesity, and depressive symptoms. The study got the nationally representative population of American students in Grade 9 to 12 (around 12–18 years).

Results

A total of 13,677 participants (female = 6,885, male = 6641) were included in the final analysis. The participants meeting the guidelines’ requirements seemed more likely to be obese than those not meeting (OR = 1.28, 95% CI = 1.06–1.55). There was no statistical significance in the relations between the MSE guidelines and overweight and depression (OR = 0.86, 95% CI = 0.73–1.01: OR = 0.94, 95% CI = 0.83–1.06). For all the participants, the prevalence of those conforming to MSE was 30.1%. One-fifth of the participants reported no MSE per week, 7.8% reported 3 days of MSE per week, and 7.7% reported 7 days.

Conclusion

The main finding of this study indicated a positive relationship between the normative MSE required in guidelines and low-level obesity. Beyond that, the evidence was insufficient to confirm the positive links between MSE and depression among American adolescents. Our study could offer evidence for future MSE interventions in adolescents.

Effects of COVID-19 Lockdown on Physical Performance, Sleep Quality, and Health-Related Quality of Life in Professional Youth Soccer Players

Background

In March 2020, the COVID-19 outbreak led to the declaration of a pandemic. The accompanying restrictions on public life caused a change in the training routines of athletes worldwide. The present study aimed to investigate the effects of a 13-week supervised home training program on physical performance, sleep quality, and health-related quality of life in professional youth soccer players during the first COVID-19 lockdown in Germany.

Methods

Eight professional soccer players (age range 16–19; height: 1.81 ± 0.07 m; body weight: 72.05 ± 6.96 kg) from a Bundesliga team in Germany participated in this study. During the lockdown, they trained 5–6 days per week with home-based training plans and were monitored via tracking apps and video training. To determine the effects of home training, measurements were taken before (March 2020) and after (June 2020) the home training period. Bioelectrical impedance analysis was used to determine body composition, and an isokinetic strength test and a treadmill step test, including lactate measurements, were used to measure physical performance. Two questionnaires were responded to in order to assess health-related quality of life [Short-Form 36 Health Survey (SF-36)] and sleep quality (Pittsburgh Sleep Quality Index).

Results

When comparing measurements before and after the home training period, we observed significant increases in the following variables: body weight (72.05 ± 6.96 kg vs. 73.50 ± 6.68 kg, p = 0.034), fat mass (11.99 ± 3.13 % vs. 13.98 ± 3.92 %, p = 0.030), body mass index (22.04 ± 0.85 kg/m2 vs. 22.49 ± 0.92 kg/m2, p = 0.049), and mental health component summary score (MCS) of the questionnaire SF-36 (53.95 ± 3.47 vs. 58.33 ± 4.50, p = 0.044). Scores on the general health (77.88 ± 14.56 vs. 89.75 ± 13.76, p = 0.025) and mental health (81.50 ± 9.30 vs. 90.00 ± 11.71, p = 0.018) subscales of the SF-36 also increased significantly.

Conclusion

The COVID-19 lockdown led to an increase in body composition parameters and showed an improvement in the MCS and scores on the general and mental health subscales of the SF-36. Physical performance and sleep quality could be maintained during the home training period. These observations may help trainers for future training planning during longer interruptions in soccer training.

Recommendations for Resuming PA after Prolonged Rest in Children and Adolescents: A Systematic Integrative Review of Relevance for Immunity

This systematic integrative review aims to summarize the protective effect of PA on children and adolescents, with special reference to the immune system. Periods of prolonged inactivity in children and adolescents are rare and due to exceptional events, such as illness or environmental circumstances, e.g., natural disasters, wars, or epidemics. The recent COVID-19 pandemic forced billions of children in developmental ages into inactivity. This exceptional event was the reason for studying the compensational behavioral strategies adopted by children and adolescents to counteract physical inactivity. Several studies showed the rise of spontaneous physical activity (PA) among children and adolescents to compensate for sedentarism. However, for some children, sedentarism could in turn foster other sedentarism. With the restart of "normal daily life" worldwide, a question is posed on both how to resume PA without causing damage and how to improve the immune response. Some key points emerged from the literature. Children must resume PA gradually using different methods, considering age, sex, health status, and the presence of overweight conditions. Immunity can be stimulated with PA by aerobic exercise, resistance training, flexibility exercise, relaxation, and coordinative exercises.

Effects of 8-Week In-Season Contrast Strength Training Program on Measures of Athletic Performance and Lower-Limb Asymmetry in Male Youth Volleyball Players

Strength training using high and lower load such as contrast training (CST) seems to be beneficial as it addresses larger adaptive reserves in youth athletes. Therefore, the aim of this study was to investigate the effects of CST on dynamic balance (composite score during dynamic balance test (CS-YBT)), one repetition maximum lower-limb back squat (1RM), jumping performance (single-leg hop (SLH) or countermovement jump height (CMJ)), lower-limb asymmetry (predicted from the single-leg jump performance between two legs [ILA]) in elite youth male volleyball players. Thirty-one male youth volleyball players aged 14 years were randomly assigned to a CST group (n = 16) or a control group (n = 15). The tests were performed before and after 8 weeks of training. Significant group × time interactions was observed for CS-YBT [p < 0.001, ηp2 = 0.70], 1RM [p < 0.001, ηp2 = 0.95], SLH with right and left leg [p < 0.001, ηp2 = 0.69 and 0.51], CMJ [p < 0.001, ηp2 = 0.47]), whilst it was not notable in ILA [p < 0.294]. Post hoc tests showed that CST group demonstrated greater improvement in all of the dependent variables from medium to large effect size (for all p < 0.001). As a result, 8 weeks of CST twice a week can be an effective and efficient training along with volleyball training to improve skill-related fitness measures, except for lower-limb asymmetry in young volleyball players.

Consensus statement on Singapore integrated 24-hour activity guide for children and adolescents

INTRODUCTION

Lifestyle activities, such as regular physical activity, are important for good metabolic health and the prevention of non-communicable diseases. Epidemiological studies highlight an increase in the proportion of overweight children in Singapore. A workgroup was formed to develop recommendations to encourage children and adolescents (aged 7-17 years) to adopt a holistic approach towards integrating beneficial activities within a daily 24-hour period for good metabolic and general health.

METHODS

The Grading of Recommendations Assessment, Development and Evaluation (GRADE) Evidence to Decision framework was employed to formulate the public health question, assess the evidence and draw conclusions for the guide. The evidence for international 24-hour movement guidelines, and guidelines for physical activity, sedentary behaviour, and sleep and eating habits were reviewed. An update of the literature review from August 2018 to end of September 2020 was conducted through an electronic search of Medline and Cumulative Index to Nursing and Allied Health Literature (CINAHL) databases.

RESULTS

Ten consensus statements were developed. The statements focused on the overall aim of achieving good metabolic health through integration of these activities and initiatives: light and moderate- to vigorous-intensity physical activity on a regular basis; muscle- and bone-strengthening activities; limiting sedentary behaviour; regular and adequate sleep; good eating habits and choosing nutritionally balanced foods and drinks; practise safety in exercise; and aiming to achieve more or all aforementioned recommendations for the best results.

CONCLUSION

This set of recommendations provides guidance to encourage Singapore children and adolescents to adopt health-beneficial activities within a 24-hour period.

Block-sequence of plyometric and balance training is superior to the alternating-sequence for enhancing motor function in children with hemiplegic cerebral palsy: A comparative randomized clinical trial

BACKGROUND: Postural control deficits are prevalent in children with hemiplegic cerebral palsy (CwHCP). Therefore, the best rehabilitative strategies for remediating these deficits are warranted, which could then enhance function. OBJECTIVE: To examine effects of a block versus an alternating sequence of balance training (BT) and plyometric training (PT) on postural control in CwHCP. METHODS: Forty-eight CwHCP (812 years) were randomized to a block or an alternating BT/PT training. The block BT/PT group (n= 24) received a sixweek BT followed by a sixweek PT, twice/week over 12 consecutive weeks. The alternating BT/PT group (n= 24) received an interchanging sequence of BT and PT changed every two weeks for 12 weeks. Postural control [center-of-pressure reaction time (RT), movement velocity (MV), maximum excursion (ME), end-point excursion (EE), and directional control (DC)], functional balance (indicated by pediatric balance scale; PBS), and balance/risk-of-falls during walking (denoted by dynamic gait index; DGI) were assessed before and after training. RESULTS: The block BT/PT group showed greater enhancements in postural control variables [RT (P= 0.004), MV (P= 0.028), ME (P= 0.002), EE (P= 0.003), and DC (P= 0.012)] and functional balance (P= 0.006), and lesser risk-of-falls during walking (P= 0.018) when compared to the alternating BT/PT group. CONCLUSION: The block BT/PT sequence is more effective to enhance postural control than the alternating sequence in CwHCP.

Plyometric training effects on physical fitness and muscle damage in high school baseball players

[Purpose]

The objective of this study was to investigate the effects of plyometric training on physical fitness and muscle damage in high school baseball players.

[Methods]

The participants in the study included 21 high school baseball players who are healthy and well-training. The participants were randomly allocated to the plyometric training (n=11) and control (n=10) groups. The plyometric training was applied 3 times a week for a total of 8 weeks and the control group took part in only regular baseball skills training without plyometric training. For physical fitness, measures included maximal strength (left and right hand-grip strength), muscle endurance (sit-up), agility (side-step), power (standing long jump), and balance (left and right Rhomberg test). For muscle damage, creatine kinase (CK) and lactate dehydrogenase (LDH) levels were measured.

[Results]

The results showed a significant interaction effect between time and groups in left hand-grip strength (P = 0.022), side-step (P = 0.004), and standing long jump (P < 0.001) after the 8-week plyometric training, with greater improvement in the plyometric training group than the control group. On the other hand, there was no significant interaction effect between time and groups in right hand-grip strength, situp, left and right Rhomberg test, CK level, and LDH level (P > 0.05).

[Conclusion]

In conclusion, 8-week plyometric training had a positive effect on improving physical fitness, such as maximal strength, agility, and power, in high school baseball players without causing additional muscle damage.

The Efficacy of Upper-Extremity Elastic Resistance Training on Shoulder Strength and Performance: A Systematic Review

Elastic resistance exercise is a popular mode of strength training that has demonstrated positive effects on whole-body strength and performance. The purpose of this work was to identify the efficacy of elastic resistance training on improving upper limb strength and performance measures for the shoulder. Seven online databases were searched with a focus on longitudinal studies assessing shoulder elastic training strength interventions. In total, 1367 studies were initially screened for relevancy; 24 full-text articles were included for review. Exercise interventions ranged from 4-12 weeks, assessing pre-/post-strength and performance measures inclusive of isometric and isokinetic strength, 1RM strength, force-velocity tests, and throwing-velocity tests. Significant increases in various isometric strength measures (IR:11–13%, ER:11–42%, FL: 14–36%, EXT: 4–17%, ABD: 8–16%), 1RM strength (~24% in bench press), force-velocities, throwing- and serve-velocities (12%) were all observed. Elastic resistance training elicited positive effects for both strength and performance parameters regardless of intervention duration. Similar significant increases were observed in isometric strength and 1RM strength across durations. Isokinetic strength increases were variable and dependent on the joint velocity conditions. Quantifying the dosage of appropriate exercise prescription for optimal strength and performance gains is inconclusive with this study due to the heterogeneity of the intervention protocols.

Resistance Training Recommendations for Children and Adolescents With Cystic Fibrosis-Related Diabetes

Cystic fibrosis (CF) is the most prevalent hereditary life-threatening disease in the Caucasian population. With the improvement in clinical care, individuals with CF are living longer, and CF-related diabetes (CFRD) has emerged as a major complication. The diagnosis of CFRD is associated with shortening survival, increasing morbidity, worsening physical capacity, and body composition. Engagement in exercise training has become a prominent nonpharmacologic intervention that aims to improve fitness and clinical outcomes in individuals with CF and CFRD. This column will specifically focus on the potential benefits of resistance training and provide recommendations for children and adolescents with CF and CFRD.

Effects of plyometric jump training versus power training using free weights on measures of physical fitness in youth male soccer players

This study aimed to contrast the effects of power training (PT) and plyometric-jump-training (PJT) programmes on measures of physical fitness in prepubertal male soccer players. Thirty-three participants were randomly allocated to PT group (n = 11), PJT group (n = 11), and an active control group (CG; n = 11). Before and after 12 weeks of training, tests were performed for the assessment of sprint-speed , change-of-direction (CoD) speed, muscular strength , and aerobic-endurance (AE). Findings indicated significant group×time interaction effects for all sprint-speed intervals, CoD speed, AE, and strength (d = 0.20-0.32). Post-hoc analyses revealed significant, moderate-to-large improvements in all sprint-speed intervals, CoD speed, AE, and muscle strength following PT (ES = 0.71 to 1.38). The PJT induced significant, moderate-to-large enhancements in 10 m, 20 m, and 30 m sprint, CoD speed, and AE (ES = 0.51 to 0.96) with no significant changes for 5 m sprint-speed and muscle strength (ES = 0.71 and 0.16, respectively). No significant pre-post changes were observed for the CG . Overall, PT and PJT are effective means to improve various measures of physical fitness in prepubertal male soccer players. Notably, to additionally improve acceleration and muscle strength, PT has an advantage over PJT.

Asia-Pacific Consensus Statement on integrated 24-hour activity guidelines for children and adolescents

Non-communicable diseases (NCDs) constitute a significant public health challenge and pose a great burden on health and social systems throughout the world. The Asia-Pacific region is in a vulnerable position as the prevalence of NCDs will inevitably increase with rapid socioeconomic transitions; yet it is ill prepared for this public health challenge as Asian children are among the most physically inactive in the world. Aligned with the WHO's global strategy to control NCDs via preventive measures and health promotion policies, representatives from the Asia-Pacific region came together to develop consensus statement on integrated 24-hour activity guidelines for children and adolescents. These guidelines apply to children and adolescents, aged 5-18 years, in the Asia-Pacific region, regardless of gender, cultural background or socioeconomic status. These guidelines aim to provide the latest evidence-based recommendations, taking a holistic approach to lifestyle activities and adopting a practical perspective by framing these activities within a 24-hour period. Eating and dietary elements were incorporated as they closely influence the energy balance of the movement behaviours and vice versa. By investing in the younger generations through advocacy for healthier lifestyles, we aim to reduce the burden of NCDs in the Asia-Pacific region.

An 8-Week Program of Plyometrics and Sprints with Changes of Direction Improved Anaerobic Fitness in Young Male Soccer Players

This study examined the effects of 8 weeks of twice-weekly combined plyometric and sprint with change-of-direction (CPSCoD) training into habitual training regimes of young male soccer players. Participants were randomly allocated to an experimental group (n = 17, age: 14.6 ± 0.44 years, body mass: 61.2 ± 7.34 kg, height: 1.67 ± 0.09 m, body fat: 11.2 ± 1.56%) and a control group (n = 16, age: 14.6 ± 0.39 years, body mass: 61.1 ± 3.96 kg, height: 1.67 ± 0.05 m, body fat: 11.8 ± 1.47%). Measures obtained pre- and post intervention included vertical and horizontal jump performance (i.e., squat jump (SJ), countermovement jump (CMJ), and standing long jump (SLJ)), and sprint performance (i.e., 5 m and 20 m sprint). In addition, Measures obtained pre- and post-intervention included change-of-direction ability (4 × 5 m sprint test (S 4 × 5 m) and sprint 9-3-6-3-9 m with backward and forward running (SBF)), repeated change of direction (RCoD), and static balance performance (stork balance test). The training group experienced superior jump (all p < 0.05; d ≥ 0.61), sprint (all p < 0.05; d ≥ 0.58), change-of-direction (CoD) ability (all p < 0.05; d ≥ 0.58), RCoD (all parameters except the fatigue index p < 0.01; effect size (d) ≥ 0.71), and static balance (all p < 0.05; d ≥ 0.66) improvement. Adding twice-weekly CPSCoD training to standard training improves the anaerobic performance of U15 male soccer players.

Home-Based Exercise Training in Childhood-Onset Takayasu Arteritis: A Multicenter, Randomized, Controlled Trial

Introduction

Childhood-onset Takayasu Arteritis (c-TA) is a rare, large-vessel vasculitis seen in children that could predisposing patients to a high risk of mortality. Exercise has the potential to improve overall health in several diseases, but evidence remains scant in c-TA. The main objective of this study was to investigate the safety and potential therapeutic effects of exercise in c-TA.

Methods

This was a 12-week, multicenter, randomized, controlled trial, to test the effects of a home-based, exercise intervention vs. standard of care in c-TA patients in remission. The primary outcomes were arterial inflammation, assessed by [¹⁸F] FDG- PET/MRI and systemic inflammatory markers. Secondary outcomes included, physical activity levels, functionality, body composition, disease-related parameters, and quality of life.

Results

Thirty-seven patients were assessed for eligibility, which represents the total number of c-TA patients being followed by the three specialized medical ambulatory services in Sao Paulo. After exclusions, fourteen c-TA patients (71.4% females) aged 12-25 years were randomly allocated into exercised (n=5) and non-exercised groups (n=9). Exercise did not exacerbate arterial inflammation. In fact, exercised patients had a reduction in the frequency of vessel segments with severe inflammation, whereas the non-exercised patients had an opposite response (P=0.007). Greater improvements in visceral fat, steps per day, functionality and physical component SF-36 were observed in the exercised patients (P ≤ 0.05).

Conclusions

Exercise is safe and may improve visceral fat, physical activity levels, functionality, and physical component SF-36 in c-TA patients. Thus, exercise arises as a novel, evidence-based intervention to improve general health in c-TA.

Clinical Trial Registration

https://www.clinicaltrials.gov/ct2/show/NCT03494062?term=NCT03494062&draw=2&rank=1, identifier NCT03494062.

Strength Training Intensity and Volume Affect Performance of Young Kayakers/Canoeists

Purpose

The aim of this study was to compare the effects of moderate intensity, low volume (MILV) vs. low intensity, high volume (LIHV) strength training on sport-specific performance, measures of muscular fitness, and skeletal muscle mass in young kayakers and canoeists.

Methods

Semi-elite young kayakers and canoeists (N = 40, 13 ± 0.8 years, 11 girls) performed either MILV (70–80% 1-RM, 6–12 repetitions per set) or LIHV (30–40% 1-RM, 60–120 repetitions per set) strength training for one season. Linear mixed-effects models were used to compare effects of training condition on changes over time in 250 and 2,000 m time trials, handgrip strength, underhand shot throw, average bench pull power over 2 min, and skeletal muscle mass. Both between- and within-subject designs were used for analysis. An alpha of 0.05 was used to determine statistical significance.

Results

Between- and within-subject analyses showed that monthly changes were greater in LIHV vs. MILV for the 2,000 m time trial (between: 9.16 s, SE = 2.70, p < 0.01; within: 2,000 m: 13.90 s, SE = 5.02, p = 0.01) and bench pull average power (between: 0.021 W⋅kg^–1, SE = 0.008, p = 0.02; within: 0.010 W⋅kg^–1, SE = 0.009, p > 0.05). Training conditions did not affect other outcomes.

Conclusion

Young sprint kayakers and canoeists benefit from LIHV more than MILV strength training in terms of 2,000 m performance and muscular endurance (i.e., 2 min bench pull power).

Effects of Plyometric and Short Sprint with Change-of-Direction Training in Male U17 Soccer Players

This project investigated the effect of adding 8 weeks of bi-weekly plyometric and short sprint with change-of-direction (PSSCoD) training into standard training for elite youth soccer players from Tunisia. A training group (n = 18; age: 16.6 ± 0.5 years; body mass: 63.2 ± 4.8 kg; stature: 1.73 ± 0.07 m; body fat: 11.2 ± 1.7%), and control group (n = 16; age: 16.6 ± 0.5 years; body mass: 63.6 ± 4.3 kg; height: 1.73 ± 0.06 m; body fat: 11.6 ± 1.5%) participated. The pre- and post-intervention measures were squat-jump (SJ), countermovement jump (CMJ), standing long jump (SLJ), 5 m and 20 m sprint, change-of-direction ability (4 × 5 m sprint test (S 4 × 5 m)), repeated sprint ability (RSA), and static balance (stork balance test). The training group displayed superior jump (all p < 0.05; d > 0.49), sprint (p < 0.05; d > 0.52), change-of-direction ability (p < 0.01; d = 0.78), RSA (p < 0.01; d > 0.70), and static balance (p < 0.05; d > 0.49) improvements. Adding bi-weekly PSSCoD improves the athletic performance of young soccer players.

The Influence of Growth, Maturation and Resistance Training on Muscle-Tendon and Neuromuscular Adaptations: A Narrative Review

The purpose of this article is to provide an overview of the growth, maturation and resistance training-related changes in muscle-tendon and neuromuscular mechanisms in youth, and the subsequent effect on performance. Sprinting, jumping, kicking, and throwing are common movements in sport that have been shown to develop naturally with age, with improvements in performance being attributed to growth and maturity-related changes in neuromuscular mechanisms. These changes include moderate to very large increases in muscle physiological cross-sectional area (CSA), muscle volume and thickness, tendon CSA and stiffness, fascicle length, muscle activation, pre-activation, stretch reflex control accompanied by large reductions in electro-mechanical delay and co-contraction. Furthermore, a limited number of training studies examining neuromuscular changes following four to 20 weeks of resistance training have reported trivial to moderate differences in tendon stiffness, muscle CSA, muscle thickness, and motor unit activation accompanied by reductions in electromechanical delay (EMD) in pre-pubertal children. However, the interaction of maturity- and training-related neuromuscular adaptions remains unclear. An understanding of how different neuromuscular mechanisms adapt in response to growth, maturation and training is important in order to optimise training responsiveness in youth populations. Additionally, the impact that these muscle-tendon and neuromuscular changes have on force producing capabilities underpinning performance is unclear.

Effects of Resistance Training on Physical Fitness in Healthy Children and Adolescents: An Umbrella Review

Background

Over the past decades, an exponential growth has occurred with regards to the number of scientific publications including meta-analyses on youth resistance training (RT). Accordingly, it is timely to summarize findings from meta-analyses in the form of an umbrella review.

Objectives

To systematically review and summarise the findings of published meta-analyses that investigated the effects of RT on physical fitness in children and adolescents.

Design

Systematic umbrella review of meta-analyses.

Data Sources

Meta-analyses were identified using systematic literature searches in the databases PubMed, Web of Science, and Cochrane Library.

Eligibility Criteria for Selecting Meta-analyses

Meta-analyses that examined the effects of RT on physical fitness (e.g., muscle strength, muscle power) in healthy youth (≤ 18 years).

Results

Fourteen meta-analyses were included in this umbrella review. Eleven of these meta-analyses reported between-subject effect sizes which are important to eliminate bias due to growth and maturation. RT produced medium-to-large effects on muscle strength, small-to-large effects on muscle power, small-to-medium effects on linear sprint, a medium effect on agility/change-of-direction speed, small-to-large effects on throwing performance, and a medium effect on sport-specific enhancement. There were few consistent moderating effects of maturation, age, sex, expertise level, or RT type on muscle strength and muscle power across the included meta-analyses. The analysed meta-analyses showed low-to-moderate methodological quality (AMSTAR2) as well as presented evidence of low-to-very low quality (GRADE).

Conclusion

This umbrella review proved the effectiveness of RT in youth on a high evidence level. The magnitude of effects varies according to the respective outcome measure and it appears to follow the principle of training specificity. Larger effect sizes were found for strength-related outcome measures. Future studies should consistently report data on participants’ maturational status. More research is needed with prepubertal children and girls, irrespective of their maturational status.

Electronic supplementary material

The online version of this article (10.1007/s40279-020-01327-3) contains supplementary material, which is available to authorized users.

Acute effects of different balance exercise types on selected measures of physical fitness in youth female volleyball players

BACKGROUND

Earlier studies have shown that balance training (BT) has the potential to induce performance enhancements in selected components of physical fitness (i.e., balance, muscle strength, power, speed). While there is ample evidence on the long-term effects of BT on components of physical fitness in youth, less is known on the short-term or acute effects of single BT sessions on selected measures of physical fitness.

OBJECTIVE

To examine the acute effects of different balance exercise types on balance, change-of-direction (CoD) speed, and jump performance in youth female volleyball players.

METHODS

Eleven female players aged 14 years participated in this study. Three types of balance exercises (i.e., anterior, posterolateral, rotational type) were conducted in randomized order. For each exercise, 3 sets including 5 repetitions were performed. Before and after the performance of the balance exercises, participants were tested for their static balance (center of pressure surface area [CoP SA] and velocity [CoP V]) on foam and firm surfaces, CoD speed (T-Half test), and vertical jump height (countermovement jump [CMJ] height). A 3 (condition: anterior, mediolateral, rotational balance exercise type) × 2 (time: pre, post) analysis of variance was computed with repeated measures on time.

RESULTS

Findings showed no significant condition × time interactions for all outcome measures (p > 0.05). However, there were small main effects of time for CoP SA on firm and foam surfaces (both d = 0.38; all p < 0.05) with no effect for CoP V on both surface conditions (p > 0.05). For CoD speed, findings showed a large main effect of time (d = 0.91; p < 0.001). However, for CMJ height, no main effect of time was observed (p > 0.05).

CONCLUSIONS

Overall, our results indicated small-to-large changes in balance and CoD speed performances but not in CMJ height in youth female volleyball players, regardless of the balance exercise type. Accordingly, it is recommended to regularly integrate balance exercises before the performance of sport-specific training to optimize performance development in youth female volleyball players.

TRIAL REGISTRATION

This study does not report results related to health care interventions using human participants and therefore it was not prospectively registered.

Effects of neuromuscular training on psychomotor development and active joint position sense in school children

As psychomotor development occurs in a specific social context, the environment in which a child is reared is important. The randomized study involved forty-five school children between 8 and 10 years. They were assigned to a control group (n = 23) and a neuromuscular training group (n = 22). A neuromuscular intervention for six weeks, on two nonconsecutive days, and in a circuit with 30-second stations was performed. The psychomotor development was evaluated through a psychomotor battery and the active joint position sense through the positional error. In the control group, the positional error decreased significantly in the shoulder (p < 0.001) and hip (p < 0.001), while the scores of motor function increased significantly which included balance (p < 0.001), spatio-temporal structuring (p = 0.022), global praxia (p = 0.002), and fine praxia (p = 0.003). In the neuromuscular training group, the positional error decreased significantly in the shoulder (p = 0.015), elbow (p = 0.015), wrist (p < 0.001), hip (p < 0.001), knee (p < 0.001), and ankle (p < 0.001), while the motor function scores increased significantly which included tonicity (p < 0.001), balance (p < 0.001), notion of the body (p < 0.001), spatio-temporal structuring (p < 0.001), global praxia (p < 0.001), and fine praxia (p < 0.001). A six-week neuromuscular training improved active joint position sense and psychomotor development in children.

Greater Power but Not Strength Gains Using Flywheel Versus Equivolumed Traditional Strength Training in Junior Basketball Players

The main aim of the present study was to compare the effects of flywheel strength training and traditional strength training on fitness attributes. Thirty-six well trained junior basketball players (n = 36; 17.58 ± 0.50 years) were recruited and randomly allocated into: Flywheel group (FST; n = 12), traditional strength training group (TST; n = 12) and control group (CON; n = 12). All groups attended 5 basketball practices and one official match a week during the study period. Experimental groups additionally participated in the eight-week, 1–2 d/w equivolume intervention conducted using a flywheel device (inertia = 0.075 kg·m⁻²) for FST or free weights (80%1 RM) for TST. Pre-to post changes in lower limb isometric strength (ISOMET), 5 and 20 m sprint time (SPR5m and SPR20m), countermovement jump height (CMJ) and change of direction ability (t-test) were assessed with analyses of variance (3 × 2 ANOVA). Significant group-by-time interaction was found for ISOMET (F = 6.40; p = 0.000), CMJ (F = 7.45; p = 0.001), SPR5m (F = 7.45; p = 0.010) and T test (F = 10.46; p = 0.000). The results showed a significantly higher improvement in CMJ (p = 0.006; 11.7% vs. 6.8%), SPR5m (p = 0.001; 10.3% vs. 5.9%) and t-test (p = 0.045; 2.4% vs. 1.5%) for FST compared to the TST group. Simultaneously, th FST group had higher improvement in ISOMET (p = 0.014; 18.7% vs. 2.9%), CMJ (p = 0.000; 11.7% vs. 0.3%), SPR5m (p = 0.000; 10.3% vs. 3.4%) and t-test (p = 0.000; 2.4% vs. 0.6%) compared to the CON group. Players from the TST group showed better results in CMJ (p = 0.006; 6.8% vs. 0.3%) and t-test (p = 0.018; 1.5% vs. 0.6%) compared to players from the CON group. No significant group-by-time interaction was found for sprint 20 m (F = 2.52; p = 0.088). Eight weeks of flywheel training (1–2 sessions per week) performed at maximum concentric intensity induces superior improvements in CMJ, 5 m sprint time and change of direction ability than equivolumed traditional weight training in well trained junior basketball players. Accordingly, coaches and trainers could be advised to use flywheel training for developing power related performance attributes in young basketball players.

Recovery of the lumbar multifidus muscle size in chronic low back pain patients by strengthening hip abductors: A randomized clinical trial

INTRODUCTION

Decrease in cross-sectional thickness of lumbar multifidus (MF) muscles during prolonged low back pain episodes commonly occurs. Restoration of the MF muscle size can be an effective way of treating chronic low back pain (CLBP) patients. Traditionally, clinicians apply muscle stabilization exercises for these patients. Recent studies support the need for active strengthening exercises for treatment of the CLBP patients.

OBJECTIVE

The MF muscles provide lumbar stability, and therefore we hypothesized that strengthening of these muscles can be more effective than the MF muscle stabilization exercises in restoration of the muscle size.

DESIGN

Study design was a randomized allocation control trial with two groups of adult female CLBP patients (n = 12 each; age range of 20-45). Patients in the control group underwent stabilization exercises and the patients in the intervention group underwent the hip abductor strengthening exercises.

SETTING

For all subjects of each group, the trials continued in 24 sessions distributed over 8 weeks and the MF muscles were measured in the beginning of the first session and one week after completion of the last session.

MAIN OUTCOME MEASURES

Statistical significance (p-value) of the change in the average MF muscle thickness, pain, and disability scores along with for each group were estimated.

RESULTS

Both regimens of exercises can significantly decrease the pain and disability: average pain and disability reductions of 46% (p-value of 0.001) and 33% (p-value of 0.02) via stabilization versus average pain and disability reductions of 65% (p-value of 0.001) and 59% (p-value of 0.001) via hip abductor strengthening. However, the hip abductor strengthening is the sole statistically significant exercise regimen (p-value of 0.014 vs 0.94) for increasing the MF muscle size.

CONCLUSION

Replacement of the traditional stabilization exercises with the hip abductor strengthening exercises for effective treatment of female adults with CLBP is recommended.

Functional relevance of resistance training-induced neuroplasticity in health and disease

Repetitive, monotonic, and effortful voluntary muscle contractions performed for just a few weeks, i.e., resistance training, can substantially increase maximal voluntary force in the practiced task and can also increase gross motor performance. The increase in motor performance is often accompanied by neuroplastic adaptations in the central nervous system. While historical data assigned functional relevance to such adaptations induced by resistance training, this claim has not yet been systematically and critically examined in the context of motor performance across the lifespan in health and disease. A review of muscle activation, brain and peripheral nerve stimulation, and imaging data revealed that increases in motor performance and neuroplasticity tend to be uncoupled, making a mechanistic link between neuroplasticity and motor performance inconclusive. We recommend new approaches, including causal mediation analytical and hypothesis-driven models to substantiate the functional relevance of resistance training-induced neuroplasticity in the improvements of gross motor function across the lifespan in health and disease.

Effects of Combined Balance and Plyometric Training on Athletic Performance in Female Basketball Players

Bouteraa, I, Negra, Y, Shephard, RJ, and Chelly, MS. Effects of combined balance and plyometric training on athletic performance in female basketball players. J Strength Cond Res 34(7): 1967-1973, 2020-The purpose of this study was to examine the effect of 8 weeks combined balance and plyometric training on the physical fitness of female adolescent basketball players. Twenty-six healthy regional-level players were randomly assigned to either an experimental group (E; n = 16, age = 16.4 ± 0.5) or a control group (C; n = 10, age = 16.5 ± 0.5). C maintained their normal basketball training schedule, whereas for 8 weeks E replaced a part of their standard regimen by biweekly combined training sessions. Testing before and after training included the squat jump (SJ), countermovement jump (CMJ), drop jump (DJ), 5-, 10-, and 20-m sprints, Stork balance test (SBT), Y-balance test (YBT) and modified Illinois change of direction test (MICODT). Results indicated no significant intergroup differences in SJ and CMJ height; however, E increased their DJ height (p < 0.05, Cohens'd = 0.11). No significant intergroup differences were found for sprint performance or SBT, but dynamic YBT tended to a significant group interaction (p = 0.087, d = 0.006). Post hoc analysis also showed a significant increase of MICODT for E (Δ 6.68%, p = 0.041, d = 0.084). In summary, the addition of 8 weeks of balance and plyometric training to regular in-season basketball training proved a safe and feasible intervention that enhanced DJ height, balance, and agility for female adolescent basketball players relative to the standard basketball training regimen.

Multiple athletic performances, maturation, and Functional Movement Screen total and individual scores across different age categories in young soccer players

The purpose of this study was to evaluate differences in multiple athletic performances, and to examine associations between athletic performance and Functional Movement Screen (FMS) in young soccer players. Forty-one soccer players were tested on peak height velocity (PHV), 5-, 10-, and 30-m sprint times, 505 change of direction (505 COD), Y-reactive agility tests, countermovement jump (CMJ), and squat jump (SJ) height. Significant main effects (P<0.01) were recorded in all tests except FMS total score whereas the U16 group outperformed U12 and U14 in almost each test. However, when the results were adjusted to the PHV 7 of 11 tests were nonsignificant. Significant associations were recorded between trunk stability push-up (TSPU) and 5 m (P=0.04) and 505 COD (preferred) times (P=0.01), and SJ height (P=0.03) in the U12. In the U14, significant associations were recoded between TSPU and SJ (P<0.01) and CMJ height (P=0.03). In the U16, significant associations were recorded between deep overhead squat and 5-m sprint time (P=0.02) and CMJ height (P=0.04). Results of this study indicate that athletic performance in young soccer players is multidimensional in nature, and it is a consequence of several factors including maturation, different training strategies, and movement proficiency.

Comparison of Cross-Education and Global Training Effects in Adults and Youth After Unilateral Strength Training

Chaouachi, A, Ben Othman, A, Chaouachi, M, Hechmi, A, Farthing, JP, Granacher, U, and Behm, DG. Comparison of cross-education and global training effects in adults and youth after unilateral strength training. J Strength Cond Res XX(X): 000-000, 2020-Youth strength training research examining contralateral, homologous (cross-education), and heterologous (global training) effects after unilateral training have provided mixed results and the relationship to adults has not been compared. The objective was to compare adult and youth cross-education and global training effects on dominant and nondominant limb testing. Initially, 15 men and 15 prepubertal boys volunteered for each unilateral chest press (CP), handgrip training, and control groups (n = 89). Individuals trained their dominant limb 3 times per week for 8 weeks and had their dominant and nondominant limbs tested for CP and leg press 1 repetition maximum (1RM), handgrip, knee extension and flexion, and elbow extension and flexion maximum voluntary isometric contractions (MVICs). Adult CP training gains were significantly greater than youth with lower-body testing (p = 0.002-0.06), whereas youth CP training gains exceeded adults with upper-body tests (p = 0.03-0.07). Training specificity was evident with greater CP 1RM increases with CP vs. handgrip training for both youth (p < 0.0001) and adults (p < 0.0001). Handgrip training elicited greater gains in handgrip MVICs compared with other strength tests (p < 0.0001). In conclusion, only contralateral CP 1RM showed a training advantage for unilateral CP over unilateral handgrip training. Adults showed greater gains with lower-body testing, whereas youth showed greater gains with upper-body testing.

Short-Term Compound Training on Physical Performance in Young Soccer Players

This study aimed to investigate the effects of a five-week compound training (with strength and plyometric exercises performed on separate days) on sprint, change of direction, and vertical jump in young soccer players. Eighteen novices in strength and plyometric training were assigned to either a compound training (CMPT) or a control condition (CNT). Both groups trained three times per week. One session was dedicated to soccer-specific drills. The other two weekly sessions were dedicated to circuit-based training routines employing on one-day strength exercises and on the other day plyometric exercises in the CMPT group. At the same time, the CNT group performed two weekly soccer-specific training sessions. All players were tested by 15-m sprint, change-of-direction and acceleration test (CODAT), squat jump, and countermovement jump with arms swing tests. CMPT group improved CODAT, squat jump and countermovement jump to a higher extent compared to CNT group (large vs small or trivial effects, p < 0.05), while both groups had similar 15-m sprint performance (p > 0.05). These results support the use of compound training to improve change of direction and vertical jump performances in young novice soccer players, which are unfamiliar with structured and advanced strength and plyometric training.

The Effects of 6 Weeks Eccentric Training on Speed, Dynamic Balance, Muscle Strength, Power, and Lower Limb Asymmetry in Prepubescent Weightlifters

Hammami, R, Duncan, MJ, Nebigh, A, Werfelli, H, and Rebai, H. The effects of 6 weeks eccentric training on speed, dynamic balance, muscle strength, power and lower limb asymmetry in prepubescent weightlifters. J Strength Cond Res XX(X): 000-000, 2020-This study examined whether 6 weeks of twice-weekly in-season hamstring eccentric training would enhance selected performance-related abilities in prepubescent male weightlifters. Twenty elite weightlifters (11.1 ± 0.8 years) were randomly split into an eccentric training intervention group (INT n = 10) or a control group (CON) that maintained their standard in-season regimen (n = 10). Pre-intervention and postintervention speed, dynamic balance, muscle strength, power, and lower limb (LL) asymmetry were assessed. Analysis of covariance controlling for maturation was used to determine any differences in the performance variables. There were no significant changes in muscle strength, dynamic balance, or LL asymmetry (all p < 0.05) because of the intervention. Both 10-m (p = 0.001) and 30-m (p = 0.007) sprint speed and agility (p = 0.049) improved to a greater extent in INT compared with the CON group. Similar results were evident for the standing long jump (p = 0.015) and 3 hop test (p = 0.004) where performance improved to a greater magnitude in INT compared with CON groups. This study suggests that eccentric training, undertaken twice weekly for 6-weeks results in positive changes in sprint speed, change of direction speed, and power performance, but not muscle strength, dynamic balance, or LL asymmetry in prepubertal weightlifters.