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.

Lack of Evidence for Crossover Fatigue with Plantar Flexor Muscles.

The occurrence and mechanisms underlying non-local or crossover muscle fatigue is an ongoing issue. This study aimed to investigate crossover fatigue of the plantar flexor muscles. Sixteen recreationally active males (n = 6) and females (n = 10) visited the laboratory for four sessions and performed a single 5-s pre-test maximal voluntary isometric contraction (MVIC) with each plantar flexors muscle. Thereafter, the fatigue intervention involved two 100-s MVICs (60-s recovery) with their dominant plantar flexors or rested for 260-s (control). Subsequently, in two separate sessions, Hoffman reflexes (H-reflex) were evoked in the non-dominant, non-exercised, leg before and following the dominant leg fatigue or control intervention (Fatigue-Reflex and Control-Reflex conditions). MVIC forces and volitional (V)-waves were monitored in the non-dominant leg in the other two sessions (Fatigue-MVIC and Control-MVIC) before and after the intervention (fatigue or control) as well as during 12 repeated MVICs and immediately thereafter. Despite the force reduction in the dominant leg (42.4%, p = 0.002), no crossover force deficit with single (F(1,9) = 0.02, p = 0.88, pƞ2 = 0.003) or repeated (F(1,9) = 0.006, p = 0.93, pƞ2 = 0.001) MVIC testing were observed. The H-reflex did not change after the fatigue (F(1,7) = 0.51; p = 0.49; pƞ2 = 0.06) or repeated MVICs (F(1,8) = 0.27; p = 0.61; pƞ2 = 0.03). There were also no crossover effects of fatigue on the V-wave with single (F(1,8) = 3.71, p = 0.09, pƞ2 = 0.31) or repeated MVICs (F(1,6) = 1.45, p = 0.27, pƞ2 = 0.19). Crossover fatigue was not evident with the plantar flexors nor any significant changes in H-reflex and V-waves in the soleus muscle. This finding suggests that crossover fatigue may not necessarily occur in slow-twitch predominant muscle groups.

Foam Rolling Prescription: A Clinical Commentary.

Behm, DG, Alizadeh, S, Hadjizadeh Anvar, S, Mahmoud, MMI, Ramsay, E, Hanlon, C, and Cheatham, S. Foam rolling prescription: a clinical commentary. J Strength Cond Res 34(11): 3301-3308, 2020-Although the foam rolling and roller massage literature generally reports acute increases in range of motion (ROM) with either trivial or small performance improvements, there is little information regarding appropriate rolling prescription. The objective of this literature review was to appraise the evidence and provide the best prescriptive recommendations for rolling to improve ROM and performance. The recommendations represent studies with the greatest magnitude effect size increases in ROM and performance. A systematic search of the rolling-related literature found in PubMed, ScienceDirect, Web of Science, and Google Scholar was conducted using related terms such as foam rolling, roller massage, ROM, flexibility, performance, and others. From the measures within articles that monitored ROM (25), strength (41), jump (41), fatigue (67), and sprint (62) variables; regression correlations and predictive quadratic equations were formulated for number of rolling sets, repetition frequency, set duration, and rolling intensity. The analysis revealed the following conclusions. To achieve the greatest ROM, the regression equations predicted rolling prescriptions involving 1-3 sets of 2-4-second repetition duration (time for a single roll in one direction over the length of a body part) with a total rolling duration of 30-120-second per set. Based on the fewer performance measures, there were generally trivial to small magnitude decreases in strength and jump measures. In addition, there was insufficient evidence to generalize on the effects of rolling on fatigue and sprint measures. In summary, relatively small volumes of rolling can improve ROM with generally trivial to small effects on strength and jump performance.