Effects of Passive Foot Flexions on Muscular Oxygenation and Performance Recovery Following an Isometric Task

Background: Passive movement-based recovery strategies may support post-exercise recovery without additional metabolic demand. Objective: To examine the acute effects of passive foot flexions during recovery on isometric task performance after repeated exercise. Methods: Fourteen physically active men completed two randomized crossover sessions—passive rest and passive foot flexions—separated by a 7-day washout. Each session included a sustained static isometric plantar flexion task at 75% of maximal voluntary contraction (MVC), a 15 min recovery period, and a repeated isometric task. Work capacity was assessed as holding time. Cardiovascular, autonomic, and peripheral responses were recorded throughout the protocol. Results: Baseline holding time did not differ between the conditions. During the repeated isometric task, holding time was significantly longer following passive foot flexions compared to passive rest (67.7 ± 10.4 s vs. 52.9 ± 9.7 s; p < 0.05), with a large effect size (d ≈ 1.5). Passive foot flexions were associated with a greater increase in parasympathetic modulation, reflected by higher root mean square of successive differences (RMSSD) during recovery and altered muscle oxygenation dynamics, including faster post-exercise re-oxygenation. For both conditions, heart rate and systolic and diastolic blood pressure exhibited similar exercise–recovery patterns with no between-condition differences. Only minor changes in muscle stiffness were observed following the passive foot flexions. Conclusions: Passive foot flexions may support short-term recovery between repeated isometric efforts, particularly with respect to holding time and RMSSD.