(10) OPTIMIZING ENERGY TRANSFER IN THE GOLF SWING: INTRODUCING A NEW METRIC BEYOND SMASH FACTOR

Purpose: Smash factor is a golf swing metric derived from the ratio of club head speed to ball speed. This metric is commonly used to assess energy transfer into a golf ball but does not account for ball flight characteristics, such as angle of attack (AoA). The purpose of the study was to develop a new metric that quantifies the efficiency of energy transfer in relation to driving distance rather than just ball speed. Methods: Eight elite female collegiate golfers participated in this study (height = 167.9 ± 3.8 cm, weight = 64.3 ± 5.5 kg, driver club head weight = 198 ± 4 g). All testing was conducted on a driving range using a Trackman 4 Launch Monitor to collect and calculate the swing metrics. The participant completed a 10-minute swing session to measure maximal effort driver club head speed (CHS), ball speed (BS), AoA, and total driving distance (TD). Once swing metrics were collected, calculations were performed to determine club head kinetic energy (CHKE), ball kinetic energy (BKE), total kinetic energy (TKE), and TD to TKE ratio (DKE ratio). DKE ratio was calculated by taking total distance in yards and dividing it by TKE. This ratio describes how many yards one Joule of energy produces. CHKE was derived from KE=1/2mv² where mass (m) was taken from the known club head and velocity (v) from the club head peak velocity. BKE was derived from KE=1/2m(vsinθ2 ) where mass (m) was taken from a known golf ball, velocity (v) from golf ball exit velocity and 𝜃 taken from AoA. The metrics were analyzed using Pearson product-moment correlations and linear regression models with SPSS. Results: DKE Ratio had a moderately strong correlation with AoA (r = 0.706) and was statistically significant (p = .050). While smash factor was moderately correlated with AoA (r = 0.494) and was not statistically significant (p = .209). A linear regression model combining AoA, CHKE, BKE, and DKE ratio, significantly predicted total driving distance, F(4, 3) = 67.295, p = .003, and an adjusted R2 = 0.974, thus the model explained 97.4% of the variance in driving distance. Conclusions: Since AoA is a strong contributor to driving distance, it proves its importance in energy transfer to a golf ball. Poor AoA results in poor energy transfer. The DKE ratio takes this into consideration by calculating the kinetic energy transferred to a golf ball based on the AoA. Golfers may have an ideal smash factor while still having a poor DKE ratio, indicating that smash factor does not fully capture energy transfer. Since mishits can initially show similar ball speeds to well struck shots, this introduces error to smash factor. The DKE ratio provides a more valuable assessment of energy transfer into a golf ball, making it great for optimizing performance. Practical Applications: Unlike smash factor, the DKE ratio provides golfers with insight into their actual strike efficiency and energy transfer. This ratio should be used by coaches and practitioners for injury prevention by identifying instances where high intensity swings produce low energy output, eliminating potential excessive strain or lack of efficiency in force application. Coaches and practitioners should also use the DKE ratio to better evaluate swing efficiency. Future research should include other ball striking metrics, such as spin rate, club path, face angle, launch angle and spin axis, to enhance the accuracy of measuring energy transfer. Acknowledgements: None