Effects of lower-extremity explosive strength on youth judo athletes adopting different types of power-based resistance training

Objective: The present study compared the effects of two different resistance types (pneumatic resistance and free weight) of 6-week squat training on the performance for young female judo athletes in linear speed and vertical jump by utilizing the maximum power of each set of squats in each training session as the monitoring vehicle. Monitoring data were used to assess the effects and trends of the two resistance types on 70% 1RM weight-bearing during the 6-week intervention training. Methods: In a 6 weeks squat training (2 reps/week with a constant load), 23 adolescent female judo athletes (Age span: 13–16 years, 14.58 ± 0.96) were randomly selected and then divided into the traditional barbell (FW) group (n = 12) and the pneumatic resistance (PN) (n = 11) group according to different resistance types (free weight and pneumatic resistance), with 10 in FW group and 9 in PN group actually completed the study. Before and after training, the 30-m Sprint time (T-30M), vertical jump height and relative power (countermovement jump, static-squat jump, and drop jump), reactive strength index (DJ-RSI), and maximal strength were assessed. One-Way ANOVA was used to examine the pre-test differences of groups (FW and PN). A 2-factor mixed-model analysis of variance was used to examine the independent effects of group (FW and PN) and time (pre and post) on each dependent measure. Scheffe post hoc comparisons were used to examine the differences. Pre- and post-experimental differences between the two groups were analyzed using independent samples t-tests and magnitude-based inferences (MBI) derived from their p values, and effect statistics were applied to compare the pre- and post-changes exhibited by each group to identify the potential beneficiary groups. Results: The PN group outperformed the FW group in terms of maximal power output per training session (822.5 ± 55.22 vs. 927.42 ± 48.15, conventional vs. pneumatic, p < 0.001, effect size = −2.02). After 6 weeks of training, the FW group showed significant increases in vertical jump height and relative strength (CMJ, SJ, DJ), with no significant gains observed in T-30 and maximal strength. The PN group showed significant improvements in maximal strength; however, no significant improvements were observed in the other tests. In addition, there was no significant difference in DJ-RSI between the two groups before and after training. Discussion: At 70% weight bearing, free weight resistance appears to be more conducive to vertical jump growth, while pneumatic resistance appears to be more conducive to maximal strength gains; however, the maximal strength gains from pneumatic resistance may not be well applied to athletic performance. In addition, the body adapts more quickly to pneumatic resistance than to free weight resistance.