(13) The effect of a competitive season on jump performance measures in starter vs non-starters in female Division 1 volleyball athletes

Purpose: The purpose of the study to examine the influence of fatigue in starters vs. non-starters over the course of a volleyball season on modified reactive strength index, jump height, relative peak power, and vertical velocity at takeoff.

Methods: Fourteen NCAA Division 1 volleyball athletes (Starters: n= 7 vs Non-Starters: n = 7) completed volunteered to complete 14 testing sessions over the course of the season (4 months). The athletes completed 3 maximal countermovement jumps (CMJ) on a set of bilateral force plates within 2-3 days post completion of the weekend series (3 games over 2 days). All jumps occurred at approximately (± 1 hr)the same time of day before the strength and conditioning sessions. Athletes were instructed to jump as high as possible and get off the ground as quickly as possible while using their arms. Athletes were given 10 seconds of rest between jumps. The average of the three maximal CMJs were collected. From these jumps, jump height (JH; in), relative peak power (rPP; W), Vertical Velocity at takeoff (s), modified-reactive strength index (m-RSI) were calculated. The athlete’s JH was calculated using flight time and converted to inches. The rPP was calculated as the power the athlete produced during the jump normalized to the athlete’s body weight (kgs). Additionally, VVT was calculated as the highest velocity achieved once the athlete’s feet left the force plate. The m-RSI was determined as the ratio between jump height (cm) and time to takeoff (s). Bayesian generalized linear models with Markov Chain Monte Carlo (MCMC) estimation were used for data analysis using the MCMCglmm package in R version 4.2.2. Reported parameter estimates include the posterior mean and the 95% credible intervals (CI). Parameter estimates were interpreted as statistically significant if the 95% credible intervals did not include zero and pMCMC values calculated in MCMCglmm were less than 0.05. Percent decline was evaluated from pre-post testing for each variable.

Results: There were no significant interactions or main effects for m-RSI or vertical velocity at takeoff (p > 0.05). For JH and rPP, no significant interaction effects were observed when looking at starting status across sessions. However, a main effect for session in JH (Pre season: 13.27 ± 4.04 in vs. Post season: 9.60 ± 1.97 in, % decline = 28%, b = -0.23 [95% CI: -0.31, -0.16], p <span style="mso-bidi-font-family: Calibri; mso-bidi-theme-font: minor-latin;">≤ 0.001) and rPP (Pre season: 52.89 ± 8.38 W vs. Post season: 38.24 ± 15.09 W, % decline = 28%, b = -0.74 [95% CI: -1.27, -0.23], p = 0.004).

Conclusion: The main effects for testing session suggests a small decline in jump height and relative peak power over the course of the season. These data suggest that playing status did not influence fatigue over the course of the season. Jump volume throughout the season may play an important role in performance. Practical applications: Practitioners and Strength and Conditioning professionals can use these data to optimize resistance exercise or practice intensity to maintain performance across a competitive volleyball season.

Acknowledgements: N/A