The aim of this study was to compare low-frequency fatigue (LFF) after 100 drop jumps in boys (age = 12.7 ± 0.7 years, mean ± SD) and men (age = 25.6 ± 1.7 years). The force-generating-capacity test (FGCT) of knee extensor muscles was performed before the exercise, as well as 3 and 20 min after the exercise. Before exercise, men were stronger than boys, but twitch time characteristics did not differ between the groups. The 20:50 Hz torque ratio was similar in boys and men as well (0.71 ± 0.08 and 0.73 ± 0.08, respectively). After exercise, at 20 min of recovery, the 20:50 Hz ratio was depressed to 48.9 ± 11.6% of initial in men and to 74.5 ± 10.0% of initial in boys (p < .05). There was no significant difference between boys and men in ground-reaction forces of drop jumps when the values were normalized to body mass. It is argued that intrinsic differences in the muscle-tendon complex are responsible for less severe LFF in boys compared with men.
Streckis and Skurvydas are with the Laboratory of Human Motorics, Department of Applied Physiology and Health Education, Lithuanian Academy of Physical Education, Sporto 6, LT - 44221 Kaunas, Lithuania; Ratkevicius is with the University of Aberdeen, Department of Molecular Exercise Physiology, School of Medical Sciences, College of Life Sciences & Medicine, Foresterhill, Aberdeen, UK.