An Examination of the Stretch-Shortening Cycle of the Dorsiflexors and Evertors in Uninjured and Functionally Unstable Ankles

Abstract

OBJECTIVE: To determine if there were differences in concentric peak torque/body-weight (PT/BW) ratios and concentric time to peak torque (TPT) of the dorsiflexors and evertors in uninjured and functionally unstable ankles using a stretch-shortening cycle (SSC) protocol on an isokinetic dynamometer. DESIGN AND SETTING: We employed a case-control study design to examine the test subjects in a climate-controlled athletic training/sports medicine research laboratory. SUBJECTS: Thirty subjects volunteered to participate in this study, 15 with unilateral functional ankle instability and 15 matched controls. MEASUREMENTS: Participants were assessed isokinetically using an SSC protocol for the dorsiflexors and evertors at 120 and 240 degrees.s(-1), bilaterally. Strength was assessed using PT values normalized for body mass. Concentric TPT measurements were also compared between the groups. RESULTS: No differences in concentric PT/BW ratios or concentric TPT were evident between the groups (P >.05). Additionally, there were no differences in these measurements between the ankles for the same motion and speed between the ankles in the subjects with functional instability. CONCLUSIONS: Using the SSC protocol as a measure of ankle function and the stretch-reflex phenomenon, we found no evidence to support the notion that differences in strength and TPT in the active, conscious state exist between those with functional ankle instability and a group of healthy control subjects.

Fig. 1

Significant ankle-by-speed-by-group interaction for dorsiflexion concentric time-to-peak-torque values. FAI indicates functionally unstable group; CON, control group.