Purpose: The main purpose of this study was to determine the relationships between countermovement jump (CMJ) variables and acceleration and maximum speed performance. Methods: Twenty-three elite Australian football players were tested on a CMJ, which yielded several kinematic and kinetic variables describing leg muscle function. A 40 m sprint was also conducted to assess acceleration (10 m time) and an estimate of maximum speed (flying 20 m time). Players from one Australian Football League (AFL) club were tested and Pearson correlations for CMJ variables and sprint performance were calculated. Results: Jump height, peak velocity, peak force, and peak power had less than 50% common variance, and therefore represented independent expressions of CMJ performance. Generally, the correlations between CMJ variables and sprinting performance were stronger for maximum speed (small to large effect sizes) than for acceleration (trivial to moderate sizes). The variable that produced the strongest correlation with acceleration was jump height (r = -0.430, P = .041) and with maximum speed was peak power/weight (r = -0.649, P = .001). Conclusions: The results indicate that if an integrated system comprising a position transducer and a force platform is available for CMJ assessment, jump height and peak power/weight are useful variables to describe leg muscle explosive function for athletes who perform sprints.
The aim of this study was to establish the effectiveness of a resistance training programme, designed to improve vertical jumping ability, on the grab, swing and rear-weighted track starts in swimming. Twenty-three female non-competitive swimmers participated (age 19.9±2.4 years; mean±s). The diving techniques were practised weekly for 8 weeks. The participants were randomly assigned to a control group (n = 11) or a resistance-training group (n = 12), which trained three times a week for 9 weeks. The tests before and after the training programme involved performing each dive technique and six dry-land tests: two countermovement jumps (with and without arms), two isokinetic squats (bar speeds of 0.44 and 0.70 rad.s-1) and two overhead throws (with and without back extension). A repeated-measures multivariate analysis of variance was used to show that resistance training improved performance in the dry-land tests (P < 0.0001). No significant improvements due to training were found for any temporal, kinematic or kinetic variables within the grab or swing starts. Significant improvements (P < 0.05) were found for the track start for take-off velocity, take-off angle and horizontal impulse. The results suggest that the improved skill of vertical jumping was not transferred directly to the start, particularly in the grab technique. Non-significant trends towards improvement were observed within all starts for vertical force components, suggesting the need to practise the dives to retrain the changed neuromuscular properties.