Effect of sauna‑based heat acclimation on plasma volume and heart rate variability

Stanley, Jamie, Halliday, Aaron, D'Auria, Shaun, Buchheit, Martin, and Leicht, Anthony S. (2015) Effect of sauna‑based heat acclimation on plasma volume and heart rate variability. European Journal of Applied Physiology, 115 (4). pp. 785-794.

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Abstract

Purpose: We investigated the effect of post-exercise sauna bathing on plasma volume (PV) expansion and whether such responses can be tracked by changes in heart rate (HR)-based measures.

Methods: Seven, well-trained male cyclists were monitored for 35 consecutive days (17 days baseline training, 10 days training plus sauna, 8 days training). Sauna exposure consisted of 30 min (87 °C, 11 % relative humidity) immediately following normal training. Capillary blood samples were collected while resting seated to assess PV changes. HR (HRwake) and vagal-related HR variability (natural logarithm of square root mean squared differences of successive R–R intervals, ln rMSSDwake) were assessed daily upon waking. A sub-maximal cycle test (5 min at 125 W) was performed on days 1, 8, 15, 22, 25, 29, and 35 and HR recovery (HRR60s) and ln rMSSDpostex were assessed post-exercise. Effects were examined using magnitude-based inferences.

Results: Compared with baseline, sauna resulted in: (1) peak PV expansion after four exposures with a likely large increase [+17.8 % (90 % confidence limits, 7.4; 29.2)]; (2) reduction of HRwake by a trivial-to-moderate amount [−10.2 % (−15.9; −4.0)]; (3) trivial-to-small changes for ln rMSSDwake [4.3 % (1.9; 6.8)] and ln rMSSDpostex [−2.4 % (−9.1; 4.9)]; and (4) a likely moderate decrease in HRR60s [−15.6 % (−30.9; 3.0)]. Correlations between individual changes in PV and HR measures were all unclear.

Conclusions: Sauna bathing following normal training largely expanded PV in well-trained cyclists after just four exposures. The utility of HR and HRV indices for tracking changes in PV was uncertain. Future studies will clarify mechanisms and performance benefits of post-training sauna bathing.

Item ID: 39044
Item Type: Article (Research - C1)
ISSN: 1439-6327
Keywords: heat exposure; blood volume; cardiac parasympathetic activity; post-exercise; cyclists
Funders: Centre of Excellence for Applied Sport Science Research at Queensland Academy of Sport
Date Deposited: 02 Jun 2015 23:00
FoR Codes: 11 MEDICAL AND HEALTH SCIENCES > 1106 Human Movement and Sports Science > 110602 Exercise Physiology @ 100%
SEO Codes: 92 HEALTH > 9299 Other Health > 929999 Health not elsewhere classified @ 100%
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