Altered Vertical Ground Reaction Forces in Participants With Chronic Ankle Instability While Running.

CONTEXT: Altered gait kinetics may increase the risk of long-term injuries in participants with chronic ankle instability (CAI). Vertical ground reaction forces (vGRFs) can provide insight into how body loading is altered.

OBJECTIVE

To compare the components of vGRFs while running in participants with or without CAI.

DESIGN

Cohort study.

SETTING

University biomechanics laboratory.

PATIENTS OR OTHER

PARTICIPANTS

Twenty-four experienced, college-aged runners. Groups were categorized by the presence (CAI group) or absence (control group) of CAI through self-reported questionnaires.

INTERVENTION(S): After a warm-up period, all participants ran on an instrumented treadmill for 5 minutes at 3.3 m/s. Data were collected during the last 30 seconds. Five continuous trials of heel-to-toe running were identified per participant and averaged for statistical analysis.

MAIN OUTCOME MEASURE(S): The dependent variables were impact peak force (N/body weight [BW]), active peak force (N/BW), time to impact peak force (milliseconds), time to active peak force (milliseconds), and average loading rate ([N/BW]/s).

RESULTS

A difference was found between groups (P = .002). The CAI group had higher impact peak forces (P = .001) and active peak forces (P = .002) compared with the control group. The CAI group also had an increased loading rate (P = .001) and a shorter time to reach the active peak force (P = .001) compared with the control group. No difference was seen between groups in the time to reach the impact peak force (P = .952).

CONCLUSIONS

Participants with CAI produced altered vGRFs and loading rates while running. Altered loading rates could predispose individuals with CAI to stress-related injuries and repetitive sprains.