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Rate of heat storage does not influence exercise intensity at a fixed rating of perceived exertion
Author(s) -
Cramer Matthew N.,
Molgat-Seon Yannick,
Carlsen Anthony N.,
Jay Ollie
Publication year - 2012
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.26.1_supplement.1084.11
Subject(s) - rating of perceived exertion , zoology , perceived exertion , intensity (physics) , exercise intensity , medicine , exertion , heart rate , vastus lateralis muscle , chemistry , biology , skeletal muscle , physics , quantum mechanics , blood pressure
This study investigated whether different rates of decline in self‐selected work rate ( W ) were mediated by early differences in heat storage. Five males cycled at a W to maintain a perceived exertion of 16 (Borg scale) at 35°C and 25°C. Heat production ( H prod ) was estimated via indirect calorimetry. Esophageal (T es ) and skin (T sk ) temperatures, as well as local sweat rates on the lower back (LSR back ) and thigh (LSR thigh ), were measured throughout. The level of muscle activation in vastus lateralis (VL) was assessed via integrated surface electromyography (iEMG). While dry heat loss was lower at 35°C (P<0.01), sweating responses were elevated, indicated by greater LSR thigh at 2 min (P<0.05), a trend toward greater LSR back (P=0.07), and earlier onsets at both sites (P=0.02). Similar H prod and rates of change in T es were found in both conditions (P>0.05), yet at 35°C, exercise time was shorter (35°C: 22.6±4.9 min; 25°C: 32.1±10.4 min; P=0.03), and W (% of initial W ) declined more rapidly by 15 min (35°C: 89.2±8.2%; 25°C: 82.2±8.0%; P<0.01). Mean T sk was lower throughout exercise at 25°C (P<0.01). Similar changes in VL iEMG activity were found at 25°C and 35°C (P=0.28). In conclusion, reductions in W occur without early differences in heat storage between air temperatures, implicating factors other than the rate of heat storage, such as T sk , in the regulation of exercise intensity. Supported by a NSERC Discovery Grant (O. Jay)