Warm Skin Alters Cardiovascular Responses to Cycling after Preheating and Precooling

Lee, Joshua F.; Christmas, Kevin M.; Machin, Daniel R.; McLean, Blake D.; Coyle, Edward F.

doi:10.1249/mss.0000000000000539

Cited by 10 publications

(12 citation statements)

References 28 publications

(52 reference statements)

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“…normothermia) (204,205,225,327,990). The tachycardic response in the early stages of exercise in the heat is suggested to stem from a thermoregulatory-mediated rise in cutaneous blood flow (205,530). As thermal strain develops, the increase in heart rate has been attributed to withdrawal of parasympathetic outflow and increased cardiac sympathetic neural activity in response to baroreflex modulation and/or a hyperadrenergic state (230,284,373,493,808,1038), along with the direct effect of blood temperature on the sinoatrial node (i.e.…”

Section: Maximal Aerobic Power In the Heatmentioning

confidence: 99%

Exercise under heat stress: thermoregulation, hydration, performance implications, and mitigation strategies

Périard

Eijsvogels²,

Daanen

2021

Physiological Reviews

217

166

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A rise in body core temperature and loss of body water via sweating are natural consequences of prolonged exercise in the heat. This review provides a comprehensive and integrative overview of how the human body responds to exercise under heat stress and the countermeasures that can be adopted to enhance aerobic performance under such environmental conditions. The fundamental concepts and physiological processes associated with thermoregulation and fluid balance are initially described, followed by a summary of methods to determine thermal strain and hydration status. An outline is provided on how exercise-heat stress disrupts these homeostatic processes, leading to hyperthermia, hypohydration, sodium disturbances and in some cases exertional heat illness. The impact of heat stress on human performance is also examined, including the underlying physiological mechanisms that mediate the impairment of exercise performance. Similarly, the influence of hydration status on performance in the heat and how systemic and peripheral hemodynamic adjustments contribute to fatigue development is elucidated. This review also discusses strategies to mitigate the effects of hyperthermia and hypohydration on exercise performance in the heat, by examining the benefits of heat acclimation, cooling strategies and hyperhydration. Finally, contemporary controversies are summarized and future research directions provided.

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Section: Maximal Aerobic Power In the Heatmentioning

confidence: 99%

Exercise under heat stress: thermoregulation, hydration, performance implications, and mitigation strategies

Périard

Eijsvogels²,

Daanen

2021

Physiological Reviews

217

166

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“…As the core:skin gradient narrows, increased blood flow to the skin results in a reduction in cardiac output, which in turn impairs V0 O 2max (Périard et al 2011;Lee et al 2015). Furthermore, elevated T SKIN influences thermal comfort and RPE, which are associated with voluntary reductions of exercise intensity in the heat (Schlader et al 2011a, Schlader et al 2011b, Barwood et al 2015.…”

Section: Effect Of Training On Gxt and Time Trial Performancementioning

confidence: 99%

Short-term heat acclimation improves the determinants of endurance performance and 5-km running performance in the heat

James

Richardson

Watt

et al. 2017

Appl. Physiol. Nutr. Metab.

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This study investigated the effect of 5 days of controlled short-term heat acclimation (STHA) on the determinants of endurance performance and 5-km performance in runners, relative to the impairment afforded by moderate heat stress. A control group (CON), matched for total work and power output (2.7 W·kg), differentiated thermal and exercise contributions of STHA on exercise performance. Seventeen participants (10 STHA, 7 CON) completed graded exercise tests (GXTs) in cool (13 °C, 50% relative humidity (RH), pre-training) and hot conditions (32 °C, 60% RH, pre- and post-training), as well as 5-km time trials (TTs) in the heat, pre- and post-training. STHA reduced resting (p = 0.01) and exercising (p = 0.04) core temperature alongside a smaller change in thermal sensation (p = 0.04). Both groups improved the lactate threshold (LT, p = 0.021), lactate turnpoint (LTP, p = 0.005) and velocity at maximal oxygen consumption (vV̇O; p = 0.031) similarly. Statistical differences between training methods were observed in TT performance (STHA, -6.2(5.5)%; CON, -0.6(1.7)%, p = 0.029) and total running time during the GXT (STHA, +20.8(12.7)%; CON, +9.8(1.2)%, p = 0.006). There were large mean differences in change in maximal oxygen consumption between STHA +4.0(2.2) mL·kg·min (7.3(4.0)%) and CON +1.9(3.7) mL·kg·min (3.8(7.2)%). Running economy (RE) deteriorated following both training programmes (p = 0.008). Similarly, RE was impaired in the cool GXT, relative to the hot GXT (p = 0.004). STHA improved endurance running performance in comparison with work-matched normothermic training, despite equality of adaptation for typical determinants of performance (LT, LTP, vV̇O). Accordingly, these data highlight the ergogenic effect of STHA, potentially via greater improvements in maximal oxygen consumption and specific thermoregulatory and associated thermal perception adaptations absent in normothermic training.

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“…Such error is not acceptable for scientific studies or exercise models. Exercise can hemoconcentrate blood~10 -15% and permit differences between skin and core temperatures, rising as high as 12°C (18). Hemoconcentration alone drops gas solubility by at least the amount of water displaced, and temperature increasing at exercising muscle can reduce solubility at the working muscle by as much as 25% compared with the cooler periph-eral tissues.…”

Section: Discussionmentioning

confidence: 99%

Equations for O₂and CO₂solubilities in saline and plasma: combining temperature and density dependences

Christmas

Bassingthwaighte

2017

Journal of Applied Physiology

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Solubilities of respiratory gasses in water, saline, and plasma decrease with rising temperatures and solute concentrations. Henry's Law, C = α·P, states that the equilibrium concentration of a dissolved gas is solubility times partial pressure. Solubilities in the water of a solution depend on temperature and the content of other solutes. Blood temperatures may differ more than 20°C between skin and heart, and an erythrocyte will undergo that range as blood circulates. The concentrations of O and CO are the driving forces for diffusion, exchanges, and for reactions. We provide an equation for O and CO solubilities, α, that allows for continuous changes in temperature, T, and solution density, ρ, in dynamically changing states:[Formula: see text]This two-exponential expression with a density scalar γ, and a density exponent β, accounts for solubility changes due to density changes of an aqueous solution. It fits experimental data on solubilities in water, saline, and plasma over temperatures from 20 to 40°C, and for plasma densities, ρ up to 1.020 g/ml with ~0.3% error. The amounts of additional bound O (to Hb) and CO (bicarbonate and carbamino) depend on the concentrations in the local water space and the reaction parameters. During exercise, solubility changes are large; both ρ and T change rapidly with spatial position and with time. In exercise hemoconcentration plasma, ρ exceeds 1.02, whereas T may range over 20°C. The six parameters for O and the six for CO are constants, so solubilities are calculable continuously as T and ρ change. Solubilities for oxygen and carbon dioxide are dependent on the density of the solution, on temperature, and on the partial pressure. We provide a brief equation suitable for hand calculators or mathematical modeling, accounting for these factors over a wide range of temperatures and solution densities for use in rapidly changing conditions, such as extreme exercise or osmotic transients, with better than 0.5% accuracy.

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Warm Skin Alters Cardiovascular Responses to Cycling after Preheating and Precooling

Abstract: These data suggest that when TSK is elevated during exercise, HR and TC will rise but SV will only be reduced when TC is also elevated above 38°C. Furthermore, changes in SV are not related to changes in SkBF.

Cited by 10 publications

References 28 publications

Exercise under heat stress: thermoregulation, hydration, performance implications, and mitigation strategies

Exercise under heat stress: thermoregulation, hydration, performance implications, and mitigation strategies

Short-term heat acclimation improves the determinants of endurance performance and 5-km running performance in the heat

Equations for O₂and CO₂solubilities in saline and plasma: combining temperature and density dependences

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Warm Skin Alters Cardiovascular Responses to Cycling after Preheating and Precooling

Abstract: These data suggest that when TSK is elevated during exercise, HR and TC will rise but SV will only be reduced when TC is also elevated above 38°C. Furthermore, changes in SV are not related to changes in SkBF.

Cited by 10 publications

References 28 publications

Exercise under heat stress: thermoregulation, hydration, performance implications, and mitigation strategies

Exercise under heat stress: thermoregulation, hydration, performance implications, and mitigation strategies

Short-term heat acclimation improves the determinants of endurance performance and 5-km running performance in the heat

Equations for O2and CO2solubilities in saline and plasma: combining temperature and density dependences

Contact Info

Product

Resources

About

Equations for O₂and CO₂solubilities in saline and plasma: combining temperature and density dependences