Impact Variability among Skilled Female Volleyball Players

Abstract

Understanding how individuals accommodate impact forces is important relative to risk reduction of impact-related injuries. Although it has been demonstrated that individuals respond differentially to controlled landings, the effects of between-leg variability have not been investigated. PURPOSE: To examine the variability (magnitude and timing) of selected vertical ground reaction force values for the preferred (P) and non-preferred (NP) limb across trials for controlled bilateral step-off landings. METHODS: Skilled collegiate female volleyball players (n = 10; 19.1±0.9yrs; 69.8±12.8 kg; 176±9 cm) performed landings from specific heights and distances onto a force platform (height = 80% of maximum vertical jump; distance = 50% of maximum vertical jump). Subjects completed five bilateral landings onto a force platform (1080 Hz) for both P and NP limbs. F1 (first maximum vertical force), FM (first minimum vertical force, and F2 (second maximum vertical force) and their respective times (T1, TM, T2) were evaluated/analyzed for all trials. RESULTS: Repeated measures ANOVAresults identified no significant differences (? = 0.05) for “leg” (P vs. NP) across subjects, suggesting trial independence. Variability measures (standard deviation, sd; coefficient of variation) were compared across trials using repeated measures ANOVAs (? = 0.05). RESULTS: identified one significant difference (TM sd) between conditions. However, 67% of the variability measures were greater for the NP limb. In addition, individual subjects exhibited limb variability dominance with 50% of the subjects (n = 5) exhibiting greater limb variability for NP, 30% for P and 20% exhibited no pattern. CONCLUSIONS: The results did not identify strong statistically significant differences for the group. The observed individual performance variability showed variation among subjects and could be the result of individual limb preference. Possible causative factors could include limb strength, task demands, experience, or other performance aspects. Further study is warranted to ascertain mechanisms for the observed NP variability trends. Partially funded by Stimulation/Implementation/Transition/Enhancement Award; University of Nevada, Las Vegas.