%0 Journal Article
%T The optimal exercise intensity for the unbiased comparison of thermoregulatory responses between groups unmatched for body size during uncompensable heat stress
%A Matthew Cramer
%A Nicholas Ravanelli
%A Ollie Jay
%A Pascal Imbeault
%J Archive of "Physiological Reports".
%D 2017
%R 10.14814/phy2.13099
%X We sought to identify the appropriate exercise intensity for unbiased comparisons of changes in rectal temperature (¦¤Tre) and local sweat rates (LSR) between groups unmatched for body size during uncompensable heat stress. Sixteen males vastly different in body morphology were separated into two equal groups [small (SM): 65.8 ¡À 6.2 kg, 1.8 ¡À 0.1 m2; large (LG): 100.0 ¡À 13.1 kg, 2.3 ¡À 0.1 m2], but matched for sudomotor thermosensitivity (SM: 1.3 ¡À 0.6; LG: 1.1 ¡À 0.4 mg¡¤cm£¿2¡¤min£¿1¡¤¡ãC£¿1). The maximum potential for evaporation (Emax) for each participant was assessed using an incremental humidity protocol. On separate occasions, participants then completed 60 min of cycling in a 35¡ãC and 70% RH environment at (1) 50% of VO 2max, (2) a heat production (Hprod) of 520 W, (3) Hprod relative to mass (6 W¡¤kg£¿1), and (4) Hprod relative to mass above Emax (3 W¡¤kg£¿1>Emax). Emax was similar between LG (347 ¡À 39 W, 154 ¡À 15 W¡¤m£¿2) and SM (313 ¡À 63 W, 176 ¡À 34 W¡¤m£¿2, P > 0.12). ¦¤Tre was greater in SM compared to LG at 520 W (SM: 1.5 ¡À 0.5; LG 0.8 ¡À 0.3¡ãC, P < 0.001) and at 50% of VO 2max (SM: 1.4 ¡À 0.5; LG 0.9 ¡À 0.3¡ãC, P < 0.001). However, ¦¤Tre was similar between groups when Hprod was either 6 W¡¤kg£¿1 (SM: 0.9 ¡À 0.3; LG 0.9 ¡À 0.2¡ãC, P = 0.98) and 3 W¡¤kg£¿1>Emax (SM: 1.4 ¡À 0.5; LG 1.3 ¡À 0.4¡ãC, P = 0.99). LSR was similar between LG and SM irrespective of condition, suggesting maximum LSR was attained (SM: 1.10 ¡À 0.23; LG: 1.07 ¡À 0.35 mg¡¤cm£¿2¡¤min£¿1, P = 0.50). In conclusion, systematic differences in ¦¤Tre and LSR between groups unmatched for body size during uncompensable heat stress can be avoided by a fixed Hprod in W¡¤kg£¿1 or W¡¤kg£¿1>Emax
%K Body morphology
%K core temperature
%K evaporation
%K hyperthermia
%K sweating
%U https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5350162/