The effect of underwater massage during hot water immersion on acute cardiovascular and mood responses

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Purpose: There is emerging evidence that demonstrates the health benefits of hot water immersion including improvements to cardiovascular health and reductions in stress and anxiety. Many commercially available hot tubs offer underwater massage systems which purport to enhance many benefits of hot water immersion, however, these claims have yet to be studied.

Methods: Twenty participants (4 females) completed three, 30-minute sessions of hot-water immersion (beginning at 39°C) in a crossover randomized design: with air massage (Air Jet), water massage (Hydro Jet) or no massage (Control). Cardiovascular responses comprising; heart rate, blood pressure and superficial femoral artery blood flow and shear rate were measured. State trait anxiety, basic affect, and salivary cortisol were recorded before and after each trial. Data were analysed using a mixed effects model.

Results: Post immersion, heart rate increased (Δ31bpm, P < 0.001, = 1.38), mean arterial blood pressure decreased (Δ16 mmHg, P<0.001, d = −0.66), with no difference between conditions. Blood flow and mean shear rate increased following immersion (P < 0.001, Δ362 ml/min, d = 1.20 and Δ108 s−1, d = 1.00), but these increases were blunted in the Air Jet condition (P < 0.001,Δ171 ml/min, d = 0.43 and Δ52 s−1, d = 0.52). Anxiety and salivary cortisol were reduced (P = 0.003, d = −0.20, P = 0.014, d = −0.11), but did not vary between conditions. Enjoyment did not vary between conditions.

Conclusion: These data demonstrate positive acute responses to hot water immersion on markers of cardiovascular function, anxiety, and stress. There was no additional benefit of water-based massage, while air-basedmassage blunted some positive vascular responses due to lower heat conservation of the water.
Original languageEnglish
Article number103858
Number of pages8
JournalJournal of Thermal Biology
Publication statusPublished - 25 Apr 2024

Bibliographical note

This is an open access article under the CC BY-NC-ND license (


The work was funded by Bestway International Limited, however, the company had no input into the collection and interpretation of the data, writing of the manuscript or the decision to publish the results.


  • Passive heating
  • Hot water immersion
  • Massage
  • Health benefits


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