Effect of repeated hot water immersion on muscle strength, power, function and physical activity in healthy older adults: a randomised crossover trial
Effect of repeated hot water immersion on muscle strength, power, function and physical activity in healthy older adults: a randomised crossover trial
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, η
2
p = 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.
ageing, grip strength, lower body kinetics, lower extremity function, passive heating
Piccolo, Daniel
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Corbett, Jo
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Exell, Timothy
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Moore, Joseph
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Wright, Amy
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Alnajjar, Mohammed
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Hudson, Luke
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Marsh, Poppy
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Praskacova, Veronika
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McNarry, Melitta
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Mackintosh, Kelly
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Saynor, Zoe
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Shepherd, Anthony
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Piccolo, Daniel
54d9b6dd-ea75-4f77-8640-46336a414214
Corbett, Jo
34197d16-28c7-4d78-9b57-b5634022ce97
Exell, Timothy
fab0e27c-c606-4204-bdc7-f408d4eb994b
Moore, Joseph
d9dd7c5c-663b-4989-a05b-147dc0ad49ad
Wright, Amy
24d38091-a030-4ee3-88a7-d52d8362f679
Alnajjar, Mohammed
27e88f84-c604-4fbf-9f9f-262b62297407
Hudson, Luke
72fff732-22a4-4184-878a-331960547e78
Marsh, Poppy
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Praskacova, Veronika
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McNarry, Melitta
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Mackintosh, Kelly
2ced9b9f-f349-46f0-b848-df202c1568df
Saynor, Zoe
a4357c7d-db59-4fa5-b24f-58d2f7e74e39
Shepherd, Anthony
f40e2412-3279-4bef-ac59-7c63bfb1d5f9
Piccolo, Daniel, Corbett, Jo, Exell, Timothy, Moore, Joseph, Wright, Amy, Alnajjar, Mohammed, Hudson, Luke, Marsh, Poppy, Praskacova, Veronika, McNarry, Melitta, Mackintosh, Kelly, Saynor, Zoe and Shepherd, Anthony
(2026)
Effect of repeated hot water immersion on muscle strength, power, function and physical activity in healthy older adults: a randomised crossover trial.
Experimental Physiology.
(doi: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 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, η
2
p = 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.
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Experimental Physiology - 2026 - Piccolo - Effect of repeated hot water immersion on muscle strength power function and (1)
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Repeated HWI and Muscle Function in Healthy Older Adults
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Accepted/In Press date: 23 March 2026
e-pub ahead of print date: 20 April 2026
Additional Information:
Publisher Copyright:
© 2026 The Author(s). Experimental Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society.
Keywords:
ageing, grip strength, lower body kinetics, lower extremity function, passive heating
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Local EPrints ID: 511046
URI: http://eprints.soton.ac.uk/id/eprint/511046
ISSN: 0958-0670
PURE UUID: 26d47b99-3c64-4cf3-b148-0916776a75f9
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Date deposited: 29 Apr 2026 16:40
Last modified: 30 Apr 2026 02:14
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Contributors
Author:
Daniel Piccolo
Author:
Jo Corbett
Author:
Timothy Exell
Author:
Joseph Moore
Author:
Amy Wright
Author:
Mohammed Alnajjar
Author:
Luke Hudson
Author:
Poppy Marsh
Author:
Veronika Praskacova
Author:
Melitta McNarry
Author:
Kelly Mackintosh
Author:
Zoe Saynor
Author:
Anthony Shepherd
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