Changes in specific jumping performance after detraining period.

Aim: The purpose of this study was to examine the effects of a detraining period after specific plyometric training on vertical jump performance and mechanical properties of aponeurosis of medial gastrocnemius (MG).
Methods: Twenty participants were assigned into two groups and performed plyometric training on incline (IP, N.=10) and plane ground (PP, N.=10), respectively. Vertical jumping (squat jump [SJ], countermovement jump [CMJ], slow and fast drop jumps from 20 and 40 cm [DJ20, DJ40, DJf20, DJf40]) and aponeurosis strain of MG have been re-evaluated four weeks after the end of the training period. The electromyographic (EMG) activity of MG and tibialis anterior (TA) muscles and MG architecture were also recorded after a 4 week of detraining period.
Results: After detraining period, jumping height was decreased from 31.20±3.3 cm to 27.5±2 cm and from 31.8±2.9 cm to 29.5±1.9 cm for DJf20 and DJf40, respectively. For the IP group, these changes were accompanied by a significantly lower MG activity during the propulsion phase (from 0.93%±0.09 to 0.77±0.09% and from 0.89±0.09% to 0.60%±0.06 for DJf20 and DJf40, respectively). Similarly, strain was decreased from 22.7% (±0.05) to 16.3% (±0.05) after detraining period.
Conclusion: These findings suggest that after four weeks of detraining, ankle muscle tendon complex properties withdraw to the pre-training values with lower performance, possible reflecting a different working length of the muscle.