(15) EFFECT OF SEASONAL ACCUMULATED WORKLOAD ON PHASE CHARACTERISTICS OF THE COUNTERMOVEMENT JUMP FORCE-TIME CURVE

Purpose: To examine the changes in countermovement jump (CMJ) braking and propulsion force-time characteristics for collegiate volleyball athletes who were players within the primary rotation.

Methods: 9 (age: 20.1 ± 0.5 years, body mass: 75.6 ± 11.7 kg, height: 169.9 ± 17.5 cm) National Collegiate Athletic Association (NCAA) Division III women volleyball athletes completed two CMJ testing sessions, which took place in the first week of the competitive season, and during the last week of the season. The primary rotation athletes played 25.1% more sets than the team average. Prior to each testing session, the subjects performed a standardized dynamic warm-up. Two maximal CMJ trials were performed on dual force plates and the force-time data were used to calculate braking mean force (BMF) and duration (BDur) and propulsion mean force (PMF) and duration (PDur) during each jump trial. The average performance between CMJ trials during each testing session were used to examine the changes in each variable. Hedge’s g effect sizes were used to determine the magnitude of change between the beginning and end of season tests. In addition, time-normalized force-time curves with 95% confidence limits were created for each subject to examine individual changes in performance.

Results: The CMJ force-time curves for each subject are displayed in Figure 1. There was a small increase in PMF (Beginning = 18.3 ± 1.6 N·kg^-1, End = 18.7 ± 1.6 N·kg^-1; g = 0.29) and small decrease in PDur (Beginning = 0.30 ± 0.05 s, End = 0.29 ± 0.05 s; g = -0.26). Further, there was both a trivial change in BMF (Beginning = 17.7 ± 1.9 N·kg^-1, End = 17.6 ± 1.7 N·kg^-1; g = -0.01) and BDur (Beginning = 0.17 ± 0.03 s, End = 0.17 ± 0.03 s; g = 0.02). Three out of the nine athletes displayed visible changes to their respective braking and propulsive force-time characteristics, whereas others maintained these traits throughout the season.

Conclusions: As a group, the primary rotation athletes applied more propulsive force over a shorter duration at the end of the season compared to the beginning. In contrast, there were minimal changes in CMJ braking force and duration. Finally, several players displayed unique changes in their CMJ force-time characteristics whereas others exhibited no changes. PRACTICAL APPLICATIONS: While it is integral to maintain or increase force production throughout the collegiate volleyball season, it is equally as important to monitor an athlete’s temporal phase characteristics during sport-specific tasks. The current results demonstrate that NCAA Division III volleyball players can increase their rapid force production characteristics by increasing force production over a shorter duration during a competitive season. Given the importance of rapid force production at the end of a season, it is recommended that practitioners monitor CMJ phase characteristics as these analyses may effectively identify any decrements in performance and guide training prescription.

Acknowledgements: None