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Repeated muscle damage blunts the increase in heat strain during subsequent exercise heat stress

Dolci, A. and Fortes, M.B. and Walker, F.S. and Haq, A. and Riddle, T. and Walsh, N.P. (2015) Repeated muscle damage blunts the increase in heat strain during subsequent exercise heat stress. European Journal of Applied Physiology, 115 (7). pp. 1577-1588. DOI: 10.1007/s00421-015-3143-7

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Abstract

Purpose Exercise-induced muscle damage (EIMD) has recently been shown to increase heat strain during exercise heat stress (HS), and represents a risk factor for exertional heat illness (EHI). We hypothesised that a repeated bout of EIMD blunts the increase in rectal temperature (T re) during subsequent endurance exercise in the heat. Methods Sixteen non-heat-acclimated males were randomly allocated to EIMD (n = 9) or control (CON, n = 7). EIMD performed a downhill running treatment at -10 % gradient for 60 min at 65 % V. O2max in 20 °C, 40 % RH. CON participants performed the same treatment but at +1 % gradient. Following treatment, participants rested for 30 min, then performed HS (+1 % gradient running for 40 min at 65 % V. O2max in 33 °C, 50 % RH) during which thermoregulatory measures were assessed. Both groups repeated the treatment and subsequent HS 14 days later. Isometric quadriceps strength was assessed at baseline, and 48 h post-treatment. Results The decrease in leg strength 48 h post-EIMD trial 1 (-7.5 %) was absent 48 h post-EIMD trial 2 (+2.9 %) demonstrating a repeated bout effect. Final T re during HS was lower following EIMD trial 2 (39.25 ± 0.47 °C) compared with EIMD trial 1 (39.59 ± 0.49 °C, P < 0.01), with CON showing no difference. Thermal sensation and the T re threshold for sweating onset were also lower during HS on EIMD trial 2. Conclusion The repeated bout effect blunted the increase in heat strain during HS conducted after EIMD. Incorporating a muscle-damaging bout into training could be a strategy to reduce the risk of EHI and improve endurance performance in individuals undertaking heavy exercise with an eccentric component in the heat.

Item Type: Article
Subjects: Research Publications
Departments: College of Health and Behavioural Sciences > School of Sport, Health and Exercise Sciences
Date Deposited: 14 Mar 2015 03:16
Last Modified: 04 Mar 2016 03:15
ISSN: 1439-6319
Publisher's Statement: The final publication is available at Springer via http://dx.doi.org/10.1007/s00421-015-3143-7
URI: http://e.bangor.ac.uk/id/eprint/3653
Identification Number: DOI: 10.1007/s00421-015-3143-7
Publisher: Springer
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