Work Rate during Self-paced Exercise is not Mediated by the Rate of Heat Storage

Brian J Friesen, Julien D Périard, Martin P Poirier, Martin Lauzon, Denis P Blondin, Francois Haman, Glen P Kenny

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

PURPOSE: To date, there have been mixed findings on whether greater anticipatory reductions in self-paced exercise intensity in the heat are mediated by early differences in rate of body heat storage. The disparity may be due to an inability to accurately measure minute-to-minute changes in whole-body heat loss. Thus, we evaluated whether early differences in rate of heat storage can mediate exercise intensity during self-paced cycling at a fixed rate of perceived exertion (RPE of 16; hard-to-very-hard work effort) in COOL (15°C), NORMAL (25°C) and HOT (35°C) ambient conditions.

METHODS: On separate days, nine endurance-trained cyclists exercised in COOL, NORMAL and HOT conditions at a fixed RPE until work rate (measured after first 5-min of exercise) decreased to 70% of starting values. Whole-body heat loss and metabolic heat production were measured by direct and indirect calorimetry respectively.

RESULTS: Total exercise time was shorter in HOT (57±20 min) relative to both NORMAL (72±23 min, P=0.004) and COOL (70±26 min, P=0.045). Starting work rate was lower in HOT (153±31 W) compared to NORMAL (166±27 W, P=0.024) and COOL (170±33 W, P=0.037). Rate of heat storage was similar between conditions during the first 4 min of exercise (all P>0.05). Thereafter, rate of heat storage was lower in HOT relative to NORMAL and COOL until 30-min of exercise (last common time-point between conditions; all P<0.05). Further, rate of heat storage was significantly higher in COOL compared to NORMAL at 15- (P=0.026) and 20-min only (P=0.020). No differences were measured at end-exercise.

CONCLUSIONS: We show that rate of heat storage does not mediate exercise intensity during self-paced exercise at a fixed RPE in cool to hot ambient conditions.

Original languageEnglish
Pages (from-to)159-168
Number of pages9
JournalMedicine and Science in Sports and Exercise
Volume50
Issue number1
Early online date8 Sep 2017
DOIs
Publication statusPublished - Jan 2018

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Hot Temperature
Indirect Calorimetry
Thermogenesis

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Friesen, Brian J ; Périard, Julien D ; Poirier, Martin P ; Lauzon, Martin ; Blondin, Denis P ; Haman, Francois ; Kenny, Glen P. / Work Rate during Self-paced Exercise is not Mediated by the Rate of Heat Storage. In: Medicine and Science in Sports and Exercise. 2018 ; Vol. 50, No. 1. pp. 159-168.
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abstract = "PURPOSE: To date, there have been mixed findings on whether greater anticipatory reductions in self-paced exercise intensity in the heat are mediated by early differences in rate of body heat storage. The disparity may be due to an inability to accurately measure minute-to-minute changes in whole-body heat loss. Thus, we evaluated whether early differences in rate of heat storage can mediate exercise intensity during self-paced cycling at a fixed rate of perceived exertion (RPE of 16; hard-to-very-hard work effort) in COOL (15°C), NORMAL (25°C) and HOT (35°C) ambient conditions.METHODS: On separate days, nine endurance-trained cyclists exercised in COOL, NORMAL and HOT conditions at a fixed RPE until work rate (measured after first 5-min of exercise) decreased to 70{\%} of starting values. Whole-body heat loss and metabolic heat production were measured by direct and indirect calorimetry respectively.RESULTS: Total exercise time was shorter in HOT (57±20 min) relative to both NORMAL (72±23 min, P=0.004) and COOL (70±26 min, P=0.045). Starting work rate was lower in HOT (153±31 W) compared to NORMAL (166±27 W, P=0.024) and COOL (170±33 W, P=0.037). Rate of heat storage was similar between conditions during the first 4 min of exercise (all P>0.05). Thereafter, rate of heat storage was lower in HOT relative to NORMAL and COOL until 30-min of exercise (last common time-point between conditions; all P<0.05). Further, rate of heat storage was significantly higher in COOL compared to NORMAL at 15- (P=0.026) and 20-min only (P=0.020). No differences were measured at end-exercise.CONCLUSIONS: We show that rate of heat storage does not mediate exercise intensity during self-paced exercise at a fixed RPE in cool to hot ambient conditions.",
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Work Rate during Self-paced Exercise is not Mediated by the Rate of Heat Storage. / Friesen, Brian J; Périard, Julien D; Poirier, Martin P; Lauzon, Martin; Blondin, Denis P; Haman, Francois; Kenny, Glen P.

In: Medicine and Science in Sports and Exercise, Vol. 50, No. 1, 01.2018, p. 159-168.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Work Rate during Self-paced Exercise is not Mediated by the Rate of Heat Storage

AU - Friesen, Brian J

AU - Périard, Julien D

AU - Poirier, Martin P

AU - Lauzon, Martin

AU - Blondin, Denis P

AU - Haman, Francois

AU - Kenny, Glen P

PY - 2018/1

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N2 - PURPOSE: To date, there have been mixed findings on whether greater anticipatory reductions in self-paced exercise intensity in the heat are mediated by early differences in rate of body heat storage. The disparity may be due to an inability to accurately measure minute-to-minute changes in whole-body heat loss. Thus, we evaluated whether early differences in rate of heat storage can mediate exercise intensity during self-paced cycling at a fixed rate of perceived exertion (RPE of 16; hard-to-very-hard work effort) in COOL (15°C), NORMAL (25°C) and HOT (35°C) ambient conditions.METHODS: On separate days, nine endurance-trained cyclists exercised in COOL, NORMAL and HOT conditions at a fixed RPE until work rate (measured after first 5-min of exercise) decreased to 70% of starting values. Whole-body heat loss and metabolic heat production were measured by direct and indirect calorimetry respectively.RESULTS: Total exercise time was shorter in HOT (57±20 min) relative to both NORMAL (72±23 min, P=0.004) and COOL (70±26 min, P=0.045). Starting work rate was lower in HOT (153±31 W) compared to NORMAL (166±27 W, P=0.024) and COOL (170±33 W, P=0.037). Rate of heat storage was similar between conditions during the first 4 min of exercise (all P>0.05). Thereafter, rate of heat storage was lower in HOT relative to NORMAL and COOL until 30-min of exercise (last common time-point between conditions; all P<0.05). Further, rate of heat storage was significantly higher in COOL compared to NORMAL at 15- (P=0.026) and 20-min only (P=0.020). No differences were measured at end-exercise.CONCLUSIONS: We show that rate of heat storage does not mediate exercise intensity during self-paced exercise at a fixed RPE in cool to hot ambient conditions.

AB - PURPOSE: To date, there have been mixed findings on whether greater anticipatory reductions in self-paced exercise intensity in the heat are mediated by early differences in rate of body heat storage. The disparity may be due to an inability to accurately measure minute-to-minute changes in whole-body heat loss. Thus, we evaluated whether early differences in rate of heat storage can mediate exercise intensity during self-paced cycling at a fixed rate of perceived exertion (RPE of 16; hard-to-very-hard work effort) in COOL (15°C), NORMAL (25°C) and HOT (35°C) ambient conditions.METHODS: On separate days, nine endurance-trained cyclists exercised in COOL, NORMAL and HOT conditions at a fixed RPE until work rate (measured after first 5-min of exercise) decreased to 70% of starting values. Whole-body heat loss and metabolic heat production were measured by direct and indirect calorimetry respectively.RESULTS: Total exercise time was shorter in HOT (57±20 min) relative to both NORMAL (72±23 min, P=0.004) and COOL (70±26 min, P=0.045). Starting work rate was lower in HOT (153±31 W) compared to NORMAL (166±27 W, P=0.024) and COOL (170±33 W, P=0.037). Rate of heat storage was similar between conditions during the first 4 min of exercise (all P>0.05). Thereafter, rate of heat storage was lower in HOT relative to NORMAL and COOL until 30-min of exercise (last common time-point between conditions; all P<0.05). Further, rate of heat storage was significantly higher in COOL compared to NORMAL at 15- (P=0.026) and 20-min only (P=0.020). No differences were measured at end-exercise.CONCLUSIONS: We show that rate of heat storage does not mediate exercise intensity during self-paced exercise at a fixed RPE in cool to hot ambient conditions.

KW - CALORIMETRY

KW - HEAT LOSS

KW - HEAT STRESS

KW - PERFORMANCE

KW - RATING OF PERCEIVED EXERTION

KW - THERMOMETRY

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