Quantifying Functional Ankle Rehabilitation Progression Criteria Using GPS: A Preliminary Study

Context: Contemporary developments in Global Positioning System (GPS) technology present a means of quantifying mechanical loading in a clinical environment with high ecological validity. However, applications to date have typically focused on performance rather than rehabilitation. Objective: To examine the efficacy of GPS microtechnology in quantifying the progression of loading during functional rehabilitation from ankle sprain injury, given the prevalence of reinjury and need for quantifiable monitoring. Furthermore, to examine the influence of unit placement on the clinical interpretation of loading during specific functional rehabilitation drills. Design: Repeated measures. Setting: University athletic facilities. Participants: Twenty-two female intermittent team sports players. Intervention: All players completed a battery of 5 drills (anterior hop, inversion hop, eversion hop, diagonal hop, and diagonal hurdle hop) designed to reflect the mechanism of ankle sprain injury, and progress functional challenge and loading. Main Outcome Measures: GPS-mounted accelerometers quantified uniaxial PlayerLoad for each drill, with units placed at C7 and the tibia. Main effects for drill type and GPS location were investigated. Results: There was a significant main effect for drill type (P < .001) in the mediolateral (η² = .436), anteroposterior (η² = .480), and vertical planes (η² = .516). The diagonal hurdle hop elicited significantly greater load than all other drills, highlighting a nonlinear progression of load. Only the mediolateral load showed evidence of progressive increase in loading. PlayerLoad was significantly greater at the tibia than at C7 for all drills, and in all planes (P < .001, η² ≥ .662). Furthermore, the tibia placement was more sensitive to between-drill changes in mediolateral load than the C7 placement. Conclusions: The placement of the GPS unit is imperative to clinical interpretation, with both magnitude and sensitivity influenced by the unit location. GPS does provide efficacy in quantifying multiplanar loading during (p)rehabilitation, in a field or clinical setting, with potential in extending GPS analyses (beyond performance metrics) to functional injury rehabilitation and prevention.