Post-Activation Performance Enhancement in Sledge Ankle Hops after a 6-seconds maximal Isometric Plantar Flexion

Abstract: Aim The aim of this study was to investigate the effects of a 6-second maximal voluntary isometric contraction (MVIC) of the plantar-flexors on subsequent ankle hops performed only by plantar flexing at the ankle. Methods 10 physically active university students were recruited to volunteer in this study. All subjects were free from injury in the right ankle. The tests were performed in a single session, even though this study is a part of a bigger study that involved several visits to GIH. The 6-sec MVIC was performed in an isokinetic dynamometer and the ankle hops were performed in a custom built backwards tilted jumping sledge. Each subject performed two baseline jumps with one minute of rest between them. Right after the baseline, subjects performed the 6-sec MVIC followed by another two jumps at 30 seconds, 90 seconds, 3 minutes, 5 minutes, 8 minutes and 15 minutes after MVIC. Results A significant difference was found for peak force at 30 seconds when compared to pre-test 1 (p= 0.020). No significant difference could be found between either pre-test 1 or pre-test 2 at any time frames for average rate of force development, Rate of force development between 0- 50 milliseconds, Rate of force development between 0-90 milliseconds, Time in the air and Time to take off . Conclusion A 6-sec MVIC of the plantar flexors did not improve isolated plantar flexor jump performance. While such conditioning contractions has previously been shown to temporarily potentiate the contractile properties of the plantar flexors as assessed by a single twitch, such effects may not be readily transferred to functional voluntary tasks.