Prepubescent males are less susceptible to neuromuscular fatigue following resistance exercise

Abstract

To determine if prepubescent and adult males have similar fatigue profiles following high and lower intensity knee extensions. Ten male children and ten adults completed two sessions of three sets of high repetition (17 typical muscle endurance training) high repetition (High RM) or low repetition (seven typical strength training) maximum (Low RM) dynamic knee extensions. Voluntary and evoked contractile properties, heart rate (HR), and rating of perceived exertion (RPE) were assessed before and after each knee extension RM. Knee extension RM measures revealed that boys performed more (children set 2, 6.7 ± 0.5; set 3, 5.7 ± 0.5 vs. adult set 2, 5.2 ± 0.4; set 3, 3.5 ± 0.5; P < 0.001) repetitions, had a faster (children 39.9 ± 8.6 vs. adult 9.4 ± 3.7 bpm; P < 0.001) HR recovery and lower (6.4 ± 0.43; P < 0.001) RPE compared to adults (8.0 ± 0.4). Post-knee extension measures also revealed a smaller MVC force decrement (P < 0.001) with boys (94.3 % ± 6.1 vs. 76.3 % ± 4.1). Unlike adults, there were no significant decrements to children's evoked contractile properties or EMG. The greater boys' antagonist activation (children 125.7 % ± 9.2 vs. adult: 103.5 % ± 6.7; P < 0.001) post-knee extension would suggest muscle coordination changes as a primary mechanism for MVC force decrements. The lower RPE and similar agonist EMG activity may also indicate an inability of boys to perceive or produce a maximal effort. Independent of High or Low RM knee extensions, boys had greater neuromuscular fatigue resistance and recovered faster than adults.