Bilateral Ground Reaction Force Asymmetry During Supramaximal Drop Landings

Bilateral vertical ground reaction forces (vGRF) asymmetries have not been investigated during supramaximal drop heights. The first purpose of this study was to investigate the influence of drop height on impact and attenuation vGRF impulses. 19 young adults completed the protocol (14 males, 5 females, age: 21.3 ± 0.75 years, mass: 75.1 ± 10.2 kg, height: 171.4 ± 7.9 cm, 1RM back squat relative to mass: 1.72 ± 0.4), which included bilateral drop landings starting at 0.3 m going up to 1.52 m in increments of 0.152 m. Asymmetries were calculated from impact impulse, loading rate, peak vGRF, attenuation impulse, and total impulse. Linear regressions analyzed these variables with respect to drop height at the group and individual levels. All dependent variables measuring asymmetrical force production produced negative regression slopes at the group level, but the adjusted R2 values ranging 0.06 to 0.15 indicate drop height accounted for minimal variance in asymmetry variables. However, examination of individual asymmetry responses reveals noteworthy adjusted R2 values for athlete monitoring and return to play considerations in competitive sport. Seven participants displayed significant reductions in asymmetry values as drop height increased with R2 values ranging from 0.23-0.64. Practitioners and coaches using landing asymmetry measurements to support return to play decisions should consider the inclusion of larger drop heights to avoid false positive asymmetry results and encourage participants to land as quickly as possible with maximal effort.