Plantar flexor strength and size decrease following single-leg disuse in uninjured adults: A meta-analysis.

Introduction: Plantar flexors play a pivotal role in human locomotion and balance. Several original research studies and systematic reviews have characterised the impact of single-leg disuse on plantar flexor strength and size. However, no meta-analysis has quantified the effects of single-leg disuse on changes in plantar flexor strength and size in uninjured adults.

Aim: To quantify changes in plantar flexor strength and size in response to single-leg disuse.

Methods: Data were extracted from 19 studies captured in our previous systematic review on studies that employed a unilateral lower limb immobilisation model (cast or brace) and were published up to January 30, 2022. Random-effects meta-analyses were performed on original research studies reporting measures of plantar flexor strength (isometric, isokinetic, or repetition maximum) and size (magnetic resonance imaging or computed tomography) in uninjured adults.

Results: Single-leg disuse decreased plantar flexor strength (Hedges g_av = -0.71 [95% confidence interval: -0.93, -0.48], p < 0.001, 7-28 days, N = 16 studies, n = 121 participants including ≥13 females, ages 19-29) and plantar flexor size (-0.33 [-0.50, -0.15], p < 0.001, 14-35 days, N = 6, n = 49, 10 females, ages 22-27) across all durations of disuse.

Discussion: Single-leg disuse decreases plantar flexor strength and size in uninjured adults. This work adds to recent meta-analytic findings demonstrating the declines in knee extensors strength and size following single-leg disuse. The paucity of female and participants >30 years old in the single-leg disuse literature examining plantar flexors represents a priority of future work.