A comparison of landing strategies in volleyball players based on quadriceps strength

The purpose of this study was to compare the landing strategies utilized by healthy female volleyball players with differing quadriceps strength. The subjects were 15 collegiate volleyball players who performed landings following a jump smash of a volleyball. Three landing strategies were utilized: a self-selected landing style, a tall landing strategy, and a soft landing strategy. A CYBEX II isokinetic dynamometer was used to measure isometric quadriceps strength and the hamstrings-to-quadriceps strength ratio. The subjects were divided into weaker and stronger groups based on quadriceps strength. Sagittal plane motion was filmed with high speed videography and frontal plane motion was filmed with a conventional speed video camera. A Kistler force plate recorded peak vertical ground reaction force (PVGRF:) upon impact with each style of landing. The data were analyzed using a 2 x 3 analysis of variance with repeated measures. The results showed no significant difference ( p &le .05) between the strength groups in the kinetic and kinematic measures across all the landing strategies. Differences (p &le .05) existed between landing strategies and between strength groups within the landing strategies for PVGRF, the amount of hip flexion at toe touch and knee acceleration. Pearson's Correlation Coefficient was computed to test the relationship between the quadriceps strength measures and each of the landing strategy parameters. There was a significant (p &le .05) correlation between quadriceps strength and increased PVGRF in both the soft and tall landings. A significant (p &le .05) correlation also existed between the hamstrings-to-quadriceps strength ratio and an increase in right knee valgus with soft landing strategies. It was concluded that female, collegiate volleyball player with stronger quadriceps strength do not land from jumping different than weaker players for all landing strategies. Landing strategies that have greater amounts of hip and knee flexion result in decreased forces upon landing. Athletes with stronger quadriceps generate a greater amount of knee flexion deceleration regardless if landings are soft or stiff and that the increased PVGRFs upon landing in those jumps are related to increased quadriceps strength.