Unilateral Elbow Flexion and Leg Press Training Induce Cross-Education But Not Global Training Gains in Children

Effects of different supervised and structured physical exercise on the physical fitness trainability of children and adolescents: a meta-analysis and meta-regression : Physical fitness trainability in children and adolescents' health

BACKGROUND

Physical fitness has been considered an important health indicator. Several factors can impact the increase in physical fitness in children and adolescents, including chronological age, sex and BMI, in addition to training variables such as weekly frequency, session and intervention duration, and types of exercises performed. To know the importance of variables that can impact physical fitness, it is important for health professionals to identify the most efficient way of prescribing physical exercises for children and adolescents. The aim is review and meta-analyses of the effects of supervised and structured physical exercise on the physical fitness trainability of children and adolescents.

METHODS

Relevant articles were searched in the PubMed, Cochrane Library, Embase and Scopus platform databases and selected based on the following criteria: children and adolescents aged between 7 and 17 years who performed any type of structured physical exercise compared to a control group without exercise and evaluating physical fitness (strength or muscular power, cardiorespiratory fitness (CRF) or speed. The results are reported in accordance with PRISMA 2020.

RESULTS

Eighty studies were included with a total of 5769 participants. Strength exercises (ES: 1.073; 95% CI, 0.612-1.533; P < 0.001; I2: 74%), concurrent (ES: 1.054; 95% CI, 0.255-1.853; P < 0.010; I2: 72%) and sports (ES: 0.573; 95% CI, 0.015 to 1.132; P < 0.044; I2: 34%) seem to be the most effective in increasing muscular strength. Aerobic activities (ES: 0.400; 95% CI, 0.258-0.542; P < 0.001; I2: 74%), sports (ES: 0.271; 95% IC, 0.148-0.394; P < 0.001; I2: 15), or HIIT (ES: 0.668; 95% IC, 0.333-1.003; P < 0.001; I2: 29%) resulted in increased CRF (ES: 0.514; 95% IC, 0.220-1.808; P < 0.001; I2: 66%). The practice of physical exercise increased muscular power (ES: 0.241; 95% CI, 0.053-0.429; P = 0.012; I2: 0%). The practice of HIIT impacts MAS gains (ES: 0.048; 95% CI, 0.050 - 0.026; P = 0.029; I2: 44%).

CONCLUSION

Supervised and structured physical exercise can improve muscular strength (15-35%), CRF (5.4-8.5%), muscular power (5.6-11.8%), and MAS (5.4%) trainability in children and adolescents. Sex, BMI of the subjects and type of exercise performed (aerobic activities, exclusive to strength, HIIT or sports) should be considered when prescribing the exercise.

Age, Sex, and Training Specific Effects on Cross-Education Training

An extensive number of publications have examined cross-education effects with adults, primarily investigating contralateral homologous (same) muscles. There are far fewer investigations on cross-education effects on contralateral heterologous (different) muscles and age (youth vs adult) and no studies investigating sex differences. Hence, the objective was to compare cross-education in female and male youth and young adults to contralateral homologous (chest press [CP], elbow flexors and extensors, handgrip isometric strength, and shot put) and heterologous (leg press, knee extension isometric strength, and countermovement jump) muscles. Twenty-eight female adults, 28 female youth, 28 male adults, and 28 male youth (total: 112) were examined before and after an 8-week (3 sessions/wk) unilateral, dominant arm, CP training program. Unilateral testing assessed dominant and nondominant leg press and CP 1-repetition maximum, knee extensors, elbow extensors, elbow flexors, and handgrip maximum voluntary isometric contraction (MVIC) strength, as well as shot put distance and countermovement jump height. Unilateral CP training induced training specific (CP 1-repetition maximum) and nonspecific (elbow extensors, elbow flexors, handgrip MVIC force, and shot put distance) improvements (P < .04, η2: .45-.85) but no significant lower body improvements. There was evidence for testing limb specificity as the dominant arm provided significantly (P < .021, η2: .17-.75) greater training gains than the nondominant arm. Youth's training adaptations exceeded with unilateral CP 1-repetition maximum, elbow extensors MVIC force, and shot put distance (P < .049, η2: .14-.49). No sex main effect differences were apparent. In conclusion, cross-education was training specific (greatest gains with upper body and dominant limbs) with greater benefits for youth and generally no sex differences with the exception of elbow extensors MVIC.

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.

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.

Exercise prescription and strategies to promote the cross-education of strength: a scoping review

The cross-education of strength is moderated by exercise design and prescription in clinical and non-clinical populations. This review synthesizes the available evidence regarding exercise design strategies for unilateral resistance training and provides evidence-based recommendations for the prescription of unilateral training to maximize the cross-education of strength. Greater insights regarding the timing and effectiveness of cross-education interventions in clinical scenarios will strengthen the use of unilateral resistance training for individuals who may benefit from its use.

Long-Term Adaptations in the Squat, Bench Press, and Deadlift: Assessing Strength Gain in Powerlifting Athletes

PURPOSE

Understanding strength changes with resistance training is important in human performance. It also enables better understanding into the expected magnitude of strength increase and factors that influence this change over time.

METHODS

Squat, bench press, and deadlift scores were collated from 407 powerlifting meets (n = 1896 unique competitors: ~625 females, ~1270 males) between 2003 and 2018. Absolute (in kilograms) and relative starting strength (in kilograms per body weight) for each lift type was expressed for both sexes. Maximum and overall strength gain per day and per year (in kilograms) was calculated by comparing first and final, or maximum scores for each lift, respectively, and considered based on strength quartile classification. Paired and independent t-tests compared strength changes from baseline and between sexes. One-way ANOVAs compared strength changes between quartiles. Pearson correlations assessed relationships between strength changes over time, and baseline strength, number of competitions, and total days competing.

RESULTS

Maximum strength adaptations were greater for squat (20.2-25.4 kg·yr-1) and deadlift (18.1-21.1 kg·yr-1) compared with bench press (10.5-12.8 kg·yr-1, P ≤ 0.001). However, the change in absolute (all lifts: P = 0.247-0.379) and relative strength (all lifts: P = 0.641-0.821) did not differ between sexes. For females, maximum strength gain per day did not differ by quartile (all lifts: P = 0.091-0.746), nor did overall strength gain per day (P = 0.151-0.575). Conversely, males in the fourth quartile generally displayed lower maximum and overall strength gain per day.

CONCLUSIONS

These findings show differences in strength gain between upper- and lower-body lifts, but not sex differences in the change in strength. In line with previous research, the strongest males likely gain strength more slowly than weaker counterparts. Professionals should consider this information in the training, assessment, and long-term benchmarking of athletes whose sports require a focus on muscular strength.

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.