Differences in Ground Reaction Forces When Collegiate Quarterbacks Throw Using Different Drop Patterns

Abstract

While there is limited research examining the kinematics of the quarterback passing throw, to date there have not been any studies reporting on ground reaction forces (GRF) during this type of throwing motion. Additionally, there have been no studies reporting how foot positions or drop patterns used by quarterbacks might change GRF parameters. This information would useful to both coaches and sports medicine professionals as it provides both performance and injury related insights. PURPOSE: Compare GRF parameters between three commonly used quarterback drop patterns: a one step (1S), a three step (3S), and a three plus one step (3P1) when performed with the rearfoot angled 90° relative to the throwing direction and 45° relative to the throwing direction. METHODS: Three NCAA Division I quarterbacks participated in this study. Participants performed three throws using each type of drop and each foot position. Two force plates were used to record GRF data at 1000 Hz. Trials were considered valid if both the front (FF) and rear (RF) feet landed on their respective force plates, with the RF foot in the appropriate orientation. For both the RF and FF, peak horizontal and vertical forces, and horizontal and vertical impulses were calculated. Differences between foot positions and drop patterns were evaluated using a 2x3 repeated measures ANOVA. RESULTS: There were no differences in any force metrics for the FF. For the RF, peak horizontal GRFs showed a main effect of drop (F2,4=43.9, p=.002), with peak forces being lower in the 3P1 (210.7 ± 13.5 N) than the 3S (476.7 ± 50.5 N) or 1S(378.7 ± 2.6 N) conditions. Peak vertical forces in the RF also showed a main effect of drop (F2,4=20.3, p=.008), with peak forces being lower in the 3P1 (1201.7 ± 39.8 N) than the 3S (1359.9 ± 105.8 N). Lastly, there was a main effect of drop for RF horizontal impulse (F2,4=55.7, p=.001), with impulses being lower in the 3P1 (58.2 ± 9.12 Ns) than the 3S(150.7 ± 4.5 Ns) or 1S (150.8 ± 5.1 Ns) conditions. CONCLUSION: A 3P1 drop pattern makes use of horizontal momentum, thus requiring the athlete to generate less force and smaller impulses with the RF during the throw. As such, coaches should emphasize pushing with the RF when using a 1S or 3S drop pattern. Changing foot positions does not appear to influence force parameters.