Lower extremity kinematics and ground reaction forces after prophylactic lace-up ankle bracing

Context: Long-term effects of ankle bracing on lower extremity kinematics and kinetics are unknown. Ankle motion restriction may negatively affect the body's ability to attenuate ground reaction forces (GRFs). Objective: To evaluate the immediate and long-term effects of ankle bracing on lower extremity kinematics and GRFs during a jump landing. Design: Experimental mixed model (2 [group] x 2 [brace] x 2 [time]) with repeated measures. Setting: Sports medicine research laboratory. Patients or Other Participants: A total of 37 healthy subjects were assigned randomly to either the intervention (n = 11 men, 8 women; age = 19.63 +/- 0.72 years, height = 176.05 +/- 10.58 cm, mass = 71.50 +/- 13.15 kg) or control group (n = 11 men, 7 women; age = 19.94 +/- 1.44 years, height 179.15 +/- 8.81 cm, mass = 74.10 +/- 10.33 kg). Intervention(s): The intervention group wore braces on both ankles and the control group did not wear braces during all recreational activities for an 8-week period. Main Outcome Measure(s): Initial ground contact angles, maximum joint angles, time to reach maximum joint angles, and joint range of motion for sagittal-plane knee and ankle motion were measured during a jump-landing task. Peak vertical GRF and the time to reach peak vertical GRF were assessed also. Results: While participants were wearing the brace, ankle plantar flexion at initial ground contact (brace = 35 degrees +/- 13 degrees, no brace = 38 degrees +/- 15 degrees, P = .024), maximum dorsiflexion (brace = 21 degrees +/- 7 degrees, no brace = 22 degrees +/- 6 degrees, P = .04), dorsiflexion range of motion (brace = 56 degrees +/- 14 degrees, no brace = 59 degrees +/- 16 degrees, P = .001), and knee flexion range of motion (brace = 79 degrees +/- 16 degrees, no brace = 82 degrees +/- 16 degrees, P = .036) decreased, whereas knee flexion at initial ground contact increased (brace = 12 degrees +/- 9 degrees, no brace = 9 degrees +/- 9 degrees, P = .0001). Wearing the brace for 8 weeks did not affect any of the outcome measures, and the brace caused no changes in vertical GRFs (P > .05). Conclusions: Although ankle sagittal-plane motion was restricted with the brace, knee flexion upon landing increased and peak vertical GRF did not change. The type of lace-up brace used in this study appeared to restrict ankle motion without increasing knee extension or vertical GRFs and without changing kinematics or kinetics over time.