School of Health Sciences


Master of Science in Human Performance (MS)


Will Peveler


Sport, Ground Reaction Forces, Force Platform, Acute Load


Kinesiology | Sports Sciences


The purpose of this study was to determine if differences in vertical ground reaction forces (vGRFs) exist between single-leg take-off approaches (SL) and double-leg take-off approaches (DL) and if sex or positional differences existed in vGRFs in SL- or DL-style approaches. It was hypothesized that DL jumps would generate greater vGRFs, males would generate greater vGRFs in both styles, and middle blockers would have higher SL vGRFs while pin hitters would have higher DL vGRFs. Nine collegiate volleyball players (4 female; 5 male) (age: 20.44 ± 1.42 years; height: 186.02 ± 6.44 cm; body mass: 78.21 ± 10.63kg; body fat: 11.66 ±5.62%) were tested. An AMTI force plate collected vGRFs with three recorded trials per approach style per subject with randomization of jump-style order. The level of significance was set at p< 0.05. No significant differences were found between vGRFs and position or SL and DL vGRFs. Males had significantly higher vGRFs overall compared to females (p=0.007). Male SL vGRFs were significantly larger than females (p=0.017). DL, relative SL, and relative DL vGRFs were not significantly different between genders. Height, mass, and body fat percentage had at least moderate correlations to combined vGRFs, and height moderately correlated to DL vGRFs. These results suggest that both takeoffs have similar enough force load to be interchangeable. Strength coaches may use both styles to train their athletes and improve neural integration. Positional jump loads during practice or games may be tracked interchangeably in style regarding the take-off phase.