EFFECTS OF FOOTBATH INTERVENTION ON SKELETAL MUSCLE OXYGENATION RECOVERY: GROUP-LEVEL AND INDIVIDUAL-LEVEL ANALYSES USING MDC95

Riki Tanaka; Kensei Tsujimoto; Tetsushi Moriguchi

doi:10.20319/icrlsh.2026.7088

Authors

Riki Tanaka Faculty of Sports & Health Science, Fukuoka University, Fukuoka, Japan
Kensei Tsujimoto Graduate School of Sport and Health Science, Fukuoka University, Fukuoka, Japan
Tetsushi Moriguchi Department of Public Health and Sports Medicine, Faculty of Sports Science, Fukuoka University, Fukuoka, Japan

DOI:

https://doi.org/10.20319/icrlsh.2026.7088

Keywords:

Foot Bathing, Ashiyu, Muscle Oxygenation, Near-Infrared Spectroscopy

Abstract

Foot bathing (ashiyu) is a traditional and widely practiced recovery method in Japan; however, its physiological effects on skeletal muscle recovery and the sources of inter-individual variability remain unclear. This study investigated the effects of foot bathing on skeletal muscle oxygenation recovery kinetics, focusing on both group-level outcomes and clinically meaningful individual responses. Fifteen healthy young men completed a randomized crossover protocol consisting of a control rest condition and a foot bathing condition following a standardized calf-raise exercise. Muscle oxygenation of the medial gastrocnemius was continuously assessed using near-infrared spectroscopy. Recovery rate (Slope) and recovery half-time (Halftime) were analyzed at both the group and individual levels. Individual responsiveness was classified using the minimal detectable change at the 95% confidence level (MDC₉₅), assuming an intraclass correlation coefficient of 0.90. Group-level analyses revealed no statistically significant differences between conditions for either Slope or Halftime. In contrast, individual-level analysis demonstrated substantial heterogeneity in responses. Five participants exceeded MDC₉₅ for improved recovery rate following foot bathing, whereas others showed minimal change or deterioration. No participants exceeded MDC₉₅ for Halftime improvement. These findings indicate that foot bathing does not exert uniform effects on muscle oxygenation recovery. Incorporating MDC₉₅-based individual analysis provides a more clinically relevant framework for evaluating recovery interventions and highlights the importance of personalized recovery strategies.

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