A pilot study to determine whether repeated post-exercise cryotherapy exposure augments physiological and perceptual responses to cold

INTRODUCTION:
Cold water immersion (CWI) is a popular recovery strategy employed by athletes attempting to expedite recovery following strenuous exercise. Cold exposure is known to upregulate the production of the potent vasoconstrictor endothelin-1 (ET-1) which could augment the cooling potential, and efficacy, of CWI over time. Therefore, the aim of this study was to investigate the influence of repeated post exercise CWI on circulating ET-1 and perceptions of thermal comfort and sensation.
METHODS:
Seven resistance trained males (age 26 ± 6 years; height 1.71 ± 0.06 m; mass 74.8 ± 8.3 kg) completed an 8 week lower body resistance training program. Participants completed 2 training sessions per week with each session followed by a CWI protocol (10 min at 10°C ± 0.5°). At the first and last training session (sessions 1 and 16 respectively) blood samples were taken to analyse circulating levels of ET-1, and measures of thermal sensation and comfort were recorded after 5 minutes of the post-exercise CWI protocol. Participants were asked to rate their thermal sensation on a nine point standard scale. Participants were asked ‘How are you feeling now?’ and responded by pointing to the scale where 4 = very hot, 3 = hot, 2 = warm, 1 = slightly warm, 0 = neutral, -1 = slightly cool, -2 = cool, -3 = cold and -4 = very cold. Thermal comfort was also assessed using a five-point scale (‘Do you find this,’ 0 =comfortable, 1 = slightly uncomfortable, 2 = uncomfortable, 3 = very uncomfortable, 4 = extremely uncomfortable). Data were analysed using T-tests to assess changes in thermal sensation, thermal comfort and ET-1 from session 1 to 16.
RESULTS:
The results demonstrated that thermal sensation was significantly increased (t(6) = -2.75, p = 0.03) and thermal comfort was significantly improved (t(6) = 4.07, p = 0.006) from session 1 to session 16. Despite an increase in mean scores from session 1 to 16, there was no statistically significant alteration in ET-1 (t(5) = -0.69, p = 0.52).
CONCLUSION:
The findings from this study demonstrate that participants felt ‘warmer’ and experienced less discomfort during CWI from session 1 to 16. This indicates that individuals regularly using CWI as a recovery intervention are likely to experience perceptual habituation as a result of repeated exposure. Further investigation is warranted to understand the potential influence of CWI on ET-1 and the impact this may have on peripheral blood flow and skeletal muscle cooling.