Monitoring markers of muscle damage during a 3 week periodized drop-jump exercise programme.

The aim of this study was to examine changes in indirect markers of muscle damage during 3 weeks of stretch-shortening exercise with a progressively increasing load and continued modulation of various key training variables. Eight healthy untrained men performed a drop-jump programme involving a progressive increase in load impact with respect to the number of jumps performed, drop (platform) height, squat depth amplitude, and addition of weights. Maximal concentric and isometric knee extensor strength were assessed immediately before and 10 min after each training session. Voluntary and 100 Hz-stimulation-evoked torque decreased acutely after each training session relative to pre-exercise values (P < 0.05) but recovered before the subsequent training session. Post-exercise plasma creatine kinase activity increased from 162.2 ± 56.2 IU · l(-1) to 284.3 ± 116.3 IU · l(-1) at 48 h after the first training session (P < 0.05) and remained marginally elevated throughout the training period. The present results indicate that detrimental muscle damage can be avoided with drop-jump training even with the gradual introduction of more demanding exercise induced by increasing the volume, intensity, and muscle stretch amplitude. These findings suggest that the human neuromuscular system is highly adaptable to progressively varied loading demands during stretch-shortening exercise training.