During the golf swing, the reaction forces applied at the feet control translation and rotation of the body–club system. In this study, we hypothesized that skilled players using a 6-iron would regulate shot distance by scaling the magnitude of the resultant horizontal reaction force applied to the each foot with minimal modifications in force direction. Skilled players (n = 12) hit golf balls using a 6-iron. Shot distance was varied by hitting the ball as they would normally and when reducing shot distance using the same club. During each swing, reaction forces were measured using dual force plates (1200 Hz) and three-dimensional kinematics were simultaneously captured (110 Hz). The results indicate that, on average, the peak resultant horizontal reaction forces of the target leg were significantly less than normal (5%, p < 0.05) when reducing shot distance. No significant differences in the orientation of the peak resultant horizontal reaction forces were observed. Resultant horizontal reaction force–angle relationships within leg and temporal relationships between target and rear legs during the swing were consistent within player across shot conditions. Regulation of force magnitude with minimal modification in force direction is expected to provide advantages from muscle activation, coordination, and performance points of view.

This study investigates the effect of initial leg angle on horizontal jump performance. Eleven highly skilled male and female long jumpers (national and Olympic level) performed a series of horizontal jumps for distance. Within-jumper differences in initial leg angle, normalized horizontal and net vertical impulses, contact time, and average reaction force during the impact interval, post-impact interval, and in total were measured using highspeed video (240 or 300 Hz) and a force plate (1200 Hz). Pearson correlations, Winsorized correlations, and the HC4 method were used to determine significant correlations between variables (α = 0.05). Within-jumper analysis indicated that when jumpers initiate the takeoff phase with a larger leg angle they are able to generate significantly greater negative horizontal and positive net vertical impulse (n = 7). Increased impulse generation was the result of increased contact time (n = 5 of 7) and / or increased average reaction force (n = 4) during the impact interval ...

To improve performance and facilitate sport-specific skill acquisition, the challenges encountered by the athlete during competition must be understood. Quantitative evidence used to design and motivate specific modifications in movement technique often requires systematic experimentation conducted in realistic contexts. In some cases, laboratory-based experimentation and dynamic modeling can be integrated to determine how athletes are generating the forces causing the observed movements. These approaches help us ascertain why certain factors affect performance. Results can then be used as a basis for designing skill progressions used to improve performance. Examples provided in this article illustrate how the use of technology, software, and experimental-based engineering tools has facilitated skill acquisition and improved the performance of skills essential for competition in gymnastics, track and field, basketball, and volleyball.