Effects of lower limb joint manipulation on squat strength and ankle range of motion: a sham-controlled double-blind randomised cross-over trial

BACKGROUND: The back squat is a commonly prescribed exercise for developing lower body strength. The ability to squat can be affected by reduced ankle dorsiflexion range of motion (DF-ROM), leading to limited squat depth and dysfunctional compensatory movement patterns. OBJECTIVE: To investigate the effect of high-velocity low-amplitude lower limb manipulations on 1 repetition maximum (1RM) back squat strength, sagittal plane ankle kinematics during a squat, and active DF-ROM in individuals with asymptomatic deficits in DF-ROM. METHODS: Twenty-six enrolled; Twenty-four analysed resistance-trained participants with asymptomatic deficits in DF-ROM participated in this double-blind randomised sham-controlled cross-over trial. Interventions involved high-velocity low-amplitude joint manipulations targeting ankle DF-ROM, and a sham which mimicked the manipulations using a mechanical drop mechanism. The primary outcome was a change in back squat 1RM between baseline to post-intervention, with secondary outcomes being maximal ankle DF-ROM during the 1RM squat using 3D motion capture, and change in DF-ROM during the weightbearing lunge test. RESULTS: There was no statistically significant difference between interventions for back squat 1RM (p = 0.27). From baseline, the 1RM increased by 4.75 kg (3.6%) following manipulation and 2.75 kg (2.1%) following the sham. There were no statistically significant differences between interventions on maximal DF-ROM during the back squat (p = 0.24) and no statistically significant differences in ankle DF-ROM immediately following either intervention (p = 0.39). CONCLUSION: Based on these results a single session of high-velocity low-amplitude manipulations targeting ankle DF-ROM does not significantly improve 1RM back squat strength compared to sham, and does not influence short-term ankle DF-ROM. Trial registration The study was pre-registered with ANZCTR (ACTRN12622000811707).