Purpose: Whereas cross-education has been extensively investigated with adults, there are far fewer youth investigations. Two studies suggested that children had greater global responses to unilateral knee extensor fatigue and training, respectively, than adults. The objective of this study was to compare global training responses and cross-education effects after unilateral elbow flexion (EFlex) and leg press (LP) training. Methods: Forty-three prepubertal youths (aged 10–13 y) were randomly allocated into dominant LP (n = 15), EFlex (n = 15) training groups, or a control (n = 13). Experimental groups trained 3 times per week for 8 weeks and were tested pretraining and posttraining for ipsilateral and contralateral 1-repetition maximum LP; knee extensor, knee flexors, elbow flexors; and handgrip maximum voluntary isometric contractions (MVIC), and countermovement jump. Results:In comparison to no significant changes with the control group, dominant elbow flexors training demonstrated significant ( P < .001) improvements only with ipsilateral and contralateral upper body testing (EFlex MVIC [15.9–21.5%], EFlex 1-repetition maximum [22.9–50.8%], handgrip MVIC [5.5–13.8%]). Dominant LP training similarly exhibited only significant ( P < .001) improvements for ipsilateral and contralateral lower body testing (LP 1-repetition maximum [59.6–81.8%], knee extensor MVIC [12.4–18.3%], knee flexor MVIC [7.9–22.3%], and countermovement jump [11.1–18.1%]). Conclusions: The ipsilateral and contralateral training adaptations in youth were specific to upper or lower body training, respectively.
Ben Othman, M. Chaouachi, Makhlouf, and A. Chaouachi are with Tunisian Research Laboratory “Sport Performance Optimisation,” National Center of Medicine and Science in Sports (CNMSS), Tunis, Tunisia. M. Chaouachi is also with Movement Sport and Health Sciences Laboratory, University of Rennes 2-ENS Cachan, Rennes, France. Farthing is with the College of Kinesiology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada. Granacher is with the Division of Training and Movement Science, University of Potsdam, Potsdam, Germany. Behm is with the School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John’s, Newfoundland and Labrador, Canada. A. Chaouachi is also with Sports Performance Research Institute New Zealand, AUT University, Auckland, New Zealand; and PVF Football Academy, Hang Yen, Vietnam.