Is there a role for GPS in determining functional ankle rehabilitation progression criteria? A preliminary study

Context: Contemporary developments in GPS technology present a means of quantifying mechanical loading in a clinical environment with high ecological validity. However, applications to date have typically focussed on performance rather than rehabilitation. Objective: To examine the efficacy of GPS micro-technology in quantifying the progression of loading during functional rehabilitation from ankle sprain injury, given the prevalence of re-injury 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: 22 female intermittent team sports players. Intervention: All players completed a battery of 5 drills (anterior hop, inversion hop, eversion hop, diagonal hop, 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 uni-axial 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<0.001) in the medio-lateral (ɳ2=0.436), anterio-posterior (ɳ2=0.480), and vertical planes (ɳ2=0.516). The diagonal hurdle hop elicited significantly greater load than all other drills, highlighting a non-linear progression of load. Only medio-lateral 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<0.001, ɳ2≥0.662). Furthermore, the tibia placement was more sensitive to between-drill changes in medio-lateral 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 multi-planar 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.