The effectiveness of isometric protocols using an external load or voluntary effort on jump height enhancement in trained females

This study aimed to examine the effectiveness of isometric post-activation performance enhancement protocols using an external load (EXL) or voluntary effort (VE) on jump height (JH) in trained females divided into EXL (n = 15), VE (n = 14), and control (CON; n = 12) groups. JH was assessed using countermovement jumps at baseline and the third, fifth, seventh, and ninth minutes after the protocols. The EXL performed three sets of back squats with a 70%-repetition maximum load for four seconds, with one-minute breaks. The VE performed three sets of pushing against an immovable bar in the back squat position for five seconds, with one-minute breaks. The CON group ran on a treadmill at 6 km/h for four minutes. A RM-ANOVA showed a significant interaction for group-time (p < 0.01). The EXL protocol provided JH improvement at the third minute compared to baseline (p = 0.01), though it decreased in subsequent minutes (p < 0.05). JH declined in the VE group at the third and fifth minutes (p < 0.05), then peaked, surpassing baseline, after nine minutes (p = 0.04). No significant differences were found between the protocols in the relative effect (best-baseline) (p = 0.09), though the EXL group appeared to gain more (effect size [ES] = 0.76). Both protocols improved JH, but caution is required due to peak performance time and potential JH reduction.

Automated summary

This study aimed to examine the effectiveness of isometric post-activation performance enhancement protocols using an external load (EXL) or voluntary effort (VE) on jump height (JH) in trained females. The results showed that both EXL and VE groups improved JH at different time points. The importance of this study is rated 7 out of 10.