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Effect of repeated hot water immersion on muscle strength, power, function and physical activity in healthy older adults: A randomised crossover trial

Daniel D. Piccolo, Jo Corbett, Timothy A. Exell, Joseph M. Moore, Amy Wright, Mohammad G. A. Alnajjar, Luke C. Hudson, Poppy A. Marsh, Veronika Praskacova, Melitta McNarry Orcid Logo, Kelly Mackintosh Orcid Logo, Zoe L. Saynor, Anthony I. Shepherd

Experimental Physiology

Swansea University Authors: Melitta McNarry Orcid Logo, Kelly Mackintosh Orcid Logo

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DOI (Published version): 10.1113/ep093501

Abstract

Ageing leads to an increased prevalence of sarcopenia and frailty, characterised by progressive declines in muscle strength, power and function and reduced physical activity. Hot water immersion (HWI) could potentially improve muscle function, but this is yet to be explored in older adults. Twelve m...

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Published in: Experimental Physiology
ISSN: 0958-0670 1469-445X
Published: Wiley 2026
Online Access: Check full text

URI: https://cronfa.swan.ac.uk/Record/cronfa71740
Abstract: Ageing leads to an increased prevalence of sarcopenia and frailty, characterised by progressive declines in muscle strength, power and function and reduced physical activity. Hot water immersion (HWI) could potentially improve muscle function, but this is yet to be explored in older adults. Twelve middle-aged to older adults completed a randomised, controlled, crossover trial (ClinicalTrials.gov ID NCT05618197), undergoing assessments before and after a 6-week HWI intervention (two to three 60-min HWIs per week) or control condition with a 6-week washout between study arms. During HWIs, body position was adjusted to maintain rectal temperature at 38.5–39.0°C. Pre- and post-intervention and control measurements of peripheral muscle strength (isokinetic and handgrip dynamometry), lower body power and functional performance (Short Physical Performance Battery consisting of balance, walking and sit to stand tests with motion and external force capture) and physical activity (accelerometry) were taken. Repeated HWI had no effect on the primary outcome peak quadriceps torque (P = 0.127, η2p = 0.125; n = 7), whilst grip strength increased in the control arm (P = 0.004) and decreased post-intervention compared to control (P = 0.039). SPPB total and component scores, lower body power, gait measures and physical activity levels were unchanged (all P > 0.05). Repeated HWI under the conditions employed did not improve strength, power, lower extremity function or physical activity levels in this cohort, and does not appear to be an effective method to improve indices of muscle function in healthy older adults.
Keywords: ageing, grip strength, lower body kinetics, lower extremity function, passive heating
College: Faculty of Science and Engineering
Funders: SPATEX and the British and Irish Spa and Hot Tub Association. Grant Number: 00229288; Ceperich Educational Trust