A Comparison of Vertical Ground Reaction Forces in Single-leg Jump Take-offs and Double-leg Jump Take-offs in Indoor Collegiate Volleyball Players

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\u3c 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

Effects of Normobaric Hypoxia on Oculomotor Dynamics of Aviator Students during a Simulated Flight Task

Hypoxia occurs when the body\u27s tissues are unable to obtain adequate oxygen supply and is the primary environmental factor present when pilots are exposed to increasing altitude levels. Hypoxia leads to impaired vision, cognition, and motor control function, which can negatively affect performance and become deadly if a pilot becomes incapacitated. Thus, objective identification of early-onset hypoxia is critical to increase the time of useful consciousness and prevent physiological episodes. Of the few studies utilizing eye-tracking, there is disagreement and mixed results concerning saccadic eye metrics as a means to measure and detect hypoxia. Therefore, the purpose of this study was to investigate saccadic velocity changes driven by acute normobaric hypoxia. Using a noninvasive infrared-based eye-tracking device, we recorded saccadic average peak velocity during flight tasks at simulated altitudes of 0 ft, 12,500 ft, and 19,000 ft. No changes were observed in saccadic average peak velocity among different altitude exposures. As time on task increased, saccadic average peak velocity decreased, suggesting that eye metrics can serve as an indicator of mental fatigue

Influence of Ankle Flexibility on the Single Leg Balance Test Using a Dynamic Balance System

Graduat

The Effects of Hindfoot Eversion Taping on Foot and Ankle Kinematics During Treadmill Running

Graduate & Undergraduat