Assessment of Immediate Traction Manipulation of the Ankle Joint on the Peroneus Longus, Gluteus Medius and Tensor Fascia Lata Muscles in Healthy People: A Randomized Double-Blind Study

Objectives: This study aimed to evaluate the effect of a superior ankle traction manipulation on the strength and electrical activity (surface EMG) of the peroneus longus, gluteus medius, and tensor fasciae latae muscles in healthy young adults. Methods: In total, 30 healthy participants (26 men and 4 women) were enrolled in a prospective, randomized, double-blind, controlled study. Participants were randomly assigned to a Manipulation or Sham group. Muscle activity was recorded using surface EMG, and isometric strength was assessed with a Biodex dynamometer. EMG signals were normalized to session-specific maximal voluntary isometric contractions (MVIC) and expressed as %MVIC for amplitude and median frequency. Baseline differences were examined with Welch’s t-tests. The primary analysis used analysis of covariance (ANCOVA) on POST values adjusted for PRE, with partial eta squared (η2p) as an effect size. Change-score comparisons (Δ = POST − PRE) and Hedges-corrected Cohen’s d were reported as sensitivity analyses. False discovery rate (FDR) correction was applied across outcomes. Results: No significant between-group differences were observed after adjustment for baseline in any %MVIC amplitude or median frequency outcome (p > 0.05, all FDR-adjusted q > 0.05). Within-group analyses showed small, nonsignificant changes in both groups, with the Manipulation group tending toward slightly greater increases in peroneus longus %MVIC amplitude (Δ = +3.1%, p = 0.033, d = 0.79, not significant after FDR correction). Descriptive data indicated similar PRE and POST values across groups for all muscles. Conclusions: When EMG activity is expressed relative to MVIC and baseline differences are controlled, a single superior ankle traction manipulation does not produce statistically significant acute changes in peroneus longus, gluteus medius, or tensor fasciae latae activity compared with a sham procedure. These findings suggest that previously reported differences may have reflected unadjusted baseline variability rather than true intervention effects.