Temperature of Ingested Water during Exercise Does Not Affect Body Heat Storage

Lamarche, Dallon T.; Meade, Robert D.; McGinn, Ryan; Poirier, Martin P.; Friesen, Brian J.; Kenny, Glen P.

doi:10.1249/mss.0000000000000533

Cited by 18 publications

(17 citation statements)

References 36 publications

(51 reference statements)

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“…A study from our research group (1) subsequently demonstrated using partitional calorimetry that the lower sweat production with the ingestion of cold (1.5-C) and cool (10-C) fluid relative to a thermoneutral fluid (37-C) leads to a reduction in estimated skin surface evaporative heat loss that is approximately equal to the greater internal heat exchange with the ingested cold fluid, thereby resulting in similar net heat loss and therefore similar changes in body heat storage irrespective of fluid temperature. This finding has been recently corroborated using direct measurements of evaporative heat loss via direct calorimetry (19).…”

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confidence: 59%

“…In the present study, ICE ingestion during exercise, relative to 37-C fluid ingestion, led to a disproportionately greater reduction in E sk compared to the difference in H fluid with ICE ingestion. In a recent publication investigating the effect of warm (50-C) and cold (1.5-C) water ingestion on heat balance during exercise using direct calorimetry (19), the authors observed no difference in body heat storage between trials indicating proportional changes in E sk with different levels of H fluid . Using the partitional calorimetry method, we previously observed a similar finding with 1.5-C, 10-C, and 37-C fluid ingestion (1).…”

Section: Discussionmentioning

confidence: 99%

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Ice Slurry Ingestion Leads to a Lower Net Heat Loss during Exercise in the Heat

Morris

Coombs

Jay

2016

Medicine &Amp; Science in Sports &Amp; Exercise

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Relative to 37 °C, ICE ingestion caused disproportionately greater reductions in Esk relative to Hfluid, resulting in a lower HLnet and greater S. Mechanistically, LSR and possibly SkBF were suppressed independently of Tre or Tsk, reaffirming the concept of human abdominal thermoreception. From a heat balance perspective, recommendations for ICE ingestion during exercise in warm, dry conditions should be reconsidered.

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confidence: 59%

Section: Discussionmentioning

confidence: 99%

Ice Slurry Ingestion Leads to a Lower Net Heat Loss during Exercise in the Heat

Morris

Coombs

Jay

2016

Medicine &Amp; Science in Sports &Amp; Exercise

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“…; Lamarche et al . )), these conditions provided all individuals with respective net heat loads of approximately 400, 500 and 600 W. The first and lowest heat load used was selected to be greater than the net heat load used in previous research (∼340 W; Jay et al . ; Cramer & Jay, ).…”

Section: Introductionmentioning

confidence: 99%

“…To achieve our objective, we used an exercise model consisting of three successive bouts of semi-recumbent cycling performed at progressively greater fixed rates of metabolic heat production (and therefore heat load) in hot, dry conditions (40°C, 12% relative humidity). After accounting for the additional dry heat gain from the environment to the skin (estimated from our previous work to be ß100 W (Gagnon et al 2013;Lamarche et al 2015)), these conditions provided all individuals with respective net heat loads of approximately 400, 500 and 600 W. The first and lowest heat load used was selected to be greater than the net heat load used in previous research (ß340 W; Jay et al 2011;Cramer & Jay, 2015). We hypothesized that fitness-related differences in whole-body evaporative heat loss are heat-load dependent and that the magnitude of those differences would be greater with progressive increases in net heat load.…”

Section: Introductionmentioning

confidence: 99%

Fitness‐related differences in the rate of whole‐body evaporative heat loss in exercising men are heat‐load dependent

Lamarche

Notley

Louie

et al. 2017

Experimental Physiology

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What is the central question of this study? Aerobic fitness modulates heat loss, but the heat-load threshold at which fitness-related differences in heat loss occur in young healthy men remains unclear. What is the main finding and its importance? We demonstrate using direct calorimetry that aerobic fitness modulates heat loss in a heat-load-dependent manner, with fitness-related differences occurring between young men who have low and high fitness when the heat load is ∼≥500 W. Although aerobic fitness has been known for some time to modulate heat loss, our findings define the precise heat-load threshold at which fitness-related differences occur. The effect of aerobic fitness (defined as rate of peak oxygen consumption) on heat loss during exercise is thought to be related to the level of heat stress. However, it remains unclear at what combined exercise and environmental (net) heat-load threshold these fitness-related differences occur. To identify this, we assessed whole-body heat exchange (dry and evaporative) by direct calorimetry in young (22 ± 3 years) men matched for physical characteristics with low (Low-fit; 39.8 ± 2.5 ml O kg min ), moderate (Mod-fit; 50.9 ± 1.2 ml O kg min ) and high aerobic fitness (High-fit; 62.0 ± 4.4 ml O kg min ; each n = 8), during three 30 min bouts of cycling in dry heat (40°C, 12% relative humidity) at increasing rates of metabolic heat production of 300 (Ex1), 400 (Ex2) and 500 W (Ex3), each followed by a 15 min recovery period. Each group was exposed to a similar net heat load (metabolic plus ∼100 W dry heat gain; P = 0.83) during each exercise bout [∼400 (Ex1), ∼500 (Ex2) and ∼600 W (Ex3); P < 0.01]. Although evaporative heat loss was similar between groups during Ex1 (P = 0.33), evaporative heat loss was greater in the High-fit (Ex2, 466 ± 21 W; Ex3, 557 ± 26 W) compared with the Low-fit group (Ex2, 439 ± 22 W; Ex3, 511 ± 20 W) during Ex2 and Ex3 (P ≤ 0.03). Conversely, evaporative heat loss for the Mod-fit group did not differ from either the High-fit or Low-fit group during all exercise bouts (P ≥ 0.09). We demonstrate that aerobic fitness modulates heat loss in a heat-load-dependent manner, such that young, highly fit men display greater heat-loss capacity only at heat loads ∼≥500 W compared with their lesser trained counterparts.

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“…We appreciate the interest of Bain et al (2) in our work (6). Recently, Bain et al (1) argued that the reported reductions in body heat storage with cold water ingestion (7,8) were likely due to the inherent underestimation of body heat storage associated with thermometry (5).…”

Section: R E S P O N S Ementioning

confidence: 87%

On the Maintenance of Human Heat Balance during Cold and Warm Fluid Ingestion

Bain

Morris

Cramer

et al. 2015

Medicine &Amp; Science in Sports &Amp; Exercise

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Dear Editor-in-Chief,The influence of ingested fluid temperature on thermo regulatory responses during exercise has attracted consider able attention during the past decade. To date, however, it has remained unclear whether body heat storage is truly al tered. A thermometric model is generally considered inac curate for estimating heat storage during exercise (2). Therefore, we previously assessed the influence of ingested fluid temperature on this parameter using partitional calo rimetry (1). In a follow-up study, we demonstrated that thermoreceptors in the abdomen-not mouth-might inde pendently mediate fluid-temperature-dependent alterations in sweating (4). A recent study by Lamarche et al. (3), published in Medicine & Science in Sports & Exercise®, duplicated the design of our earlier study but importantly assessed heat storage using direct, rather than partitional, calorimetry-the former, ostensibly, being more accurate. Their precis suggested observations different from our two previous studies and questioned the validity of employing partitional calorimetry. However, upon closer examination, their study seemingly yielded similar findings, with one important exception that helps highlight the limitations of partitional calorimetry.Arguably, the most practically relevant finding from our previous study (1) was that ingestion of cold fluids (10°C or 1.5°C), compared to thermoneutral (37°C) fluids, during exercise does not lead to lower body heat storage due to a reduction in evaporation that is proportional to the heat energy exchanged internally with ingested fluids. Lamarche et al. (3) reproduced the same finding (for 1.5°C), thus demonstrating that partitional calorimetry provides an apparently reliable assessment of heat storage at least during cold fluid ingestion.No statistical difference in forehead sweat rate was ob served between ingestion of 50°C water and ingestion of 1.5°C water, whereas upper back sweat rate was only sta tistically different after the third bolus ingestion (3). To gether, these observations were reported to contradict our other previous study (4). However, a clear separation be tween conditions appears evident-particularly on the fore head ( Fig. 3D in [3])-after ingestion, indicating that statistical significance may have been attained with a larger sample size.With direct calorimetry, our previous conclusion of a disproportionately greater increase in evaporation from the skin relative to the heat gained internally with ingestion of 50°C water (1) is now shown to be potentially incorrect (3). These conflicting reports can probably be explained by a better maintenance of sweating efficiency with circulating airflow in a direct calorimeter, as opposed to our forward facing airflow. Although the accuracy of both calorimetric methods is limited to combinations of activity and climate that induce complete evaporation, the present study indicates that the upper limit of these conditions is likely cooler and drier for a given metabolic rate when employing partitional calorimetry. Thes...

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Temperature of Ingested Water during Exercise Does Not Affect Body Heat Storage

Cited by 18 publications

References 36 publications

Ice Slurry Ingestion Leads to a Lower Net Heat Loss during Exercise in the Heat

Ice Slurry Ingestion Leads to a Lower Net Heat Loss during Exercise in the Heat

Fitness‐related differences in the rate of whole‐body evaporative heat loss in exercising men are heat‐load dependent

On the Maintenance of Human Heat Balance during Cold and Warm Fluid Ingestion

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