Differences in Landing Forces in Individuals with and without Chronic Ankle Instability.

Abstract

As individuals with chronic ankle instability (CAI) re-sprain their ankles multiple times, it is important to understand the medio-lateral ground reaction force (GRF) loading during common sideward sport movements. PURPOSE: To determine if individuals with CAI display lower GRF during medial and lateral single leg jump landings when compared to a control (CON) group. METHODS: Seventy volunteer recreational athletes, (CAI 15 males, 22 females; CON 16 males, 17 females). CAI participants reported a history of multiple inversion ankle sprains and ≥2 episodes of the ankle "giving way" in the last year. Controls reported none. Participants performed 10 medial and 10 lateral single leg jump landings onto the unstable ankle side (CAI) or the matched side (CON). Participants jumped a distance of 70 cm at 50% of their maximum vertical jump height and had to balance for 3s upon landing. GRFs were normalized to body weight (BW). Maximum magnitudes were identified in each GRF direction. Independent t-tests assessed group differences (α=0.05). RESULTS: For lateral jumps, the CAI group displayed smaller peak lateral GRF (0.59±0.10 BW) than the CON group (0.65±0.10 BW) (p=0.029). No differences were found for peak medial (CON 0.06±0.01 BW; CAI 0.08±0.11 BW, p=0.34) or vertical GRFs (CON 4.24±0.90 BW; CAI 4.03±0.70 BW, p=0.26). For medial jumps, no differences were observed for peak lateral (CON 0.05±0.02 BW; CAI 0.05±0.01 BW, p=0.67), medial (CON 0.84±0.21 BW; CAI 0.82±0.16 BW, p=0.66), or vertical GRFs (CON 4.02±0.75 BW; CAI 3.90±0.63 BW, p=0.48). CONCLUSION: The CAI group may have displayed lower lateral peak force during lateral jumps in order to decrease loading on lateral ankle ligaments. This provides further evidence of altered neuromuscular control patterns in CAI participants. Researchers may need participants to perform movements in multiple planes to identify GRF differences. These GRF differences may reveal movement pattern differences between CAI and CON groups. Supported by University of Georgia Research Foundation Grant.