To report a joint-centered mechanism of performance decrements caused by overtraining.
Eleven weight-trained men, 1 (subject A) with overload injury of the knees.
High-intensity squat resistance-exercise overtraining for 2 weeks.
1RM lower-body strength, isokinetic and isometric knee-extension strength, and stimulated isometric knee-extension strength.
Subject A’s 1RM strength decreased 40.3 kg, and the other overtrained subjects (OT) exhibited significant (P < .05) 1RM decrements (x = –9.3 kg). Isokinetic knee-extension strength decreased for all subjects. For the OT group, voluntary isometric knee-extension strength did not change and stimulated isometric knee-extension strength decreased. Subject A exhibited increased values for both these variables.
These data indicate that muscle strength was attenuated for subject A only during dynamic activity. It is theorized that subject A exhibited a joint-centered overtraining syndrome, with afferent inhibition from the affected joints impairing dynamic strength.