Restrictions in ankle dorsiflexion range of motion alter landing kinematics but not movement strategy when fatigued

Context: Ankle dorsiflexion range of motion (DF ROM) has been associated with a number of kinematic and kinetic variables associated with landing performance that increase injury risk. However, whether exercise-induced fatigue exacerbates compensatory strategies has not yet been established. Objectives: i) explore differences in landing performance between individuals with restricted and normal ankle DF ROM, and ii) identify the effect of fatigue on compensations in landing strategies for individuals with restricted and normal ankle DF ROM. Design: Cross-sectional. Setting: University research laboratory. Patients or Other Participants: 12 recreational athletes with restricted ankle DF ROM (restricted group) and 12 recreational athletes with normal ankle DF ROM (normal group). Main Outcome Measure(s): Participants performed five bilateral drop-landings, before and following a fatiguing protocol. Normalized peak vertical ground reaction force (vGRF), time to peak vGRF and loading rate were calculated, alongside sagittal plane initial contact angles, peak angles and joint displacement for the ankle, knee and hip. Frontal plane projection angles were also calculated. Results: At baseline, the restricted group landed with significantly less knee flexion (P = 0.005, effect size [ES] = 1.27) at initial contact and reduced peak ankle dorsiflexion (P < 0.001, ES = 1.67), knee flexion (P < 0.001, ES = 2.18) and hip flexion (P = 0.033, ES = 0.93) angles. Sagittal plane joint displacement was also significantly less for the restricted group for the ankle (P < 0.001, ES = 1.78), knee (P < 0.001, ES = 1.78) and hip (P = 0.028, ES = 0.96) joints. Conclusions: These findings suggest individuals with restricted ankle DF ROM adopt different landing strategies than those with normal ankle DF ROM. This is exacerbated when fatigued, although the functional consequences of fatigue on landing mechanics in individuals with ankle DF ROM restriction are unclear.