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Evaporative Heat Loss and Changes in Core Temperature Set‐Point during Different Absolute Workloads
Author(s) -
Jay Ollie,
Kenny Glen
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.956.18
Subject(s) - set point , zoology , chemistry , core temperature , core (optical fiber) , workload , rectal temperature , analytical chemistry (journal) , medicine , materials science , chromatography , biology , control engineering , computer science , engineering , composite material , operating system
Previous work suggests changes in core temperature set‐point during exercise are determined by relative workload (i.e. % of VO 2max ). Concurrent rates of metabolic heat production (M‐W), whole‐body evaporative (EHL) and dry heat loss (DHL) were measured by whole‐body direct calorimetry in 5 males throughout 90‐min of cycling at 3 absolute oxygen uptakes of 1.82±0.05 (hi), 1.26±0.05 (med) and 0.65±0.03 (low) L‐min’ at 30°C and 30% RH. Due to the variation in VO 2max between participants (3.24 to 4.44 L·min −1 ) these workloads corresponded to a range of relative workloads within each condition. Rectal temperature (T re ) was also measured throughout. Sustained levels of M‐W obtained throughout exercise were 500±17 (hi), 348±10 (med) and 203±10 W (low). After 90‐min, T re was steady at 0.96±0.13, 0.70±0.10 and 0.23±0.03°C above rest for hi, med and low respectively. EHL was 423±18, 290±10 and 150±16 W respectively and DHL was 41±10, 45±15 and 58±14 W. Within condition, EHL varied little between participants despite relative workloads differing by 15–20%. End‐exercise EHL appears to be determined by absolute metabolic workload rather than relative workload. Variations in core temperature set‐point within condition are attributed to individual differences in sweating sensitivity during the early stages of exercise; and effects of body mass and composition upon the ‘passive’ system. Supported by NSERC Grant.