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@article{Stacey:2017:10.1007/s00421-017-3758-y,
author = {Stacey, MJ and Delves, SK and Woods, DR and Britland, SE and Macconnachie, L and Allsopp, AJ and Brett, SJ and Fallowfield, JL},
doi = {10.1007/s00421-017-3758-y},
journal = {European Journal of Applied Physiology},
pages = {165--174},
title = {Heart rate variability and plasma nephrines in the evaluation of heat acclimatisation status},
url = {http://dx.doi.org/10.1007/s00421-017-3758-y},
volume = {118},
year = {2017}
}

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TY  - JOUR
AB  - PurposeHeat adaptation (HA) is critical to performance and health in a hot environment. Transition from short-term heat acclimatisation (STHA) to long-term heat acclimatisation (LTHA) is characterised by decreased autonomic disturbance and increased protection from thermal injury. A standard heat tolerance test (HTT) is recommended for validating exercise performance status, but any role in distinguishing STHA from LTHA is unreported. The aims of this study were to (1) define performance status by serial HTT during structured natural HA, (2) evaluate surrogate markers of autonomic activation, including heart rate variability (HRV), in relation to HA status.MethodsParticipants (n = 13) were assessed by HTT (60-min block-stepping, 50% VO2peak) during STHA (Day 2, 6 and 9) and LTHA (Day 23). Core temperature (Tc) and heart rate (HR) were measured every 5 min. Sampling for HRV indices (RMSSD, LF:HF) and sympathoadrenal blood measures (cortisol, nephrines) was undertaken before and after (POST) each HTT.ResultsSignificant (P < 0.05) interactions existed for Tc, logLF:HF, cortisol and nephrines (two-way ANOVA; HTT by Day). Relative to LTHA, POST results differed significantly for Tc (Day 2, 6 and 9), HR (Day 2), logRMSSD (Day 2 and Day 6), logLF:HF (Day 2 and Day 6), cortisol (Day 2) and nephrines (Day 2 and Day 9). POST differences in HRV (Day 6 vs. 23) were + 9.9% (logRMSSD) and − 18.6% (logLF:HF).ConclusionsEarly reductions in HR and cortisol characterised STHA, whereas LTHA showed diminished excitability by Tc, HRV and nephrine measures. Measurement of HRV may have potential to aid real-time assessment of readiness for activity in the heat.
AU  - Stacey,MJ
AU  - Delves,SK
AU  - Woods,DR
AU  - Britland,SE
AU  - Macconnachie,L
AU  - Allsopp,AJ
AU  - Brett,SJ
AU  - Fallowfield,JL
DO  - 10.1007/s00421-017-3758-y
EP  - 174
PY  - 2017///
SN  - 1439-6319
SP  - 165
TI  - Heart rate variability and plasma nephrines in the evaluation of heat acclimatisation status
T2  - European Journal of Applied Physiology
UR  - http://dx.doi.org/10.1007/s00421-017-3758-y
UR  - http://hdl.handle.net/10044/1/53077
VL  - 118
ER  -

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