Vascular and central hemodynamic changes following exercise-induced heat stress

Abstract

This study examined the effects of moderate exercise-induced heat stress (EIHS) on vascular function, central hemodynamic load and indices of coronary perfusion. Vascular-hemodynamic measures were collected in 12 healthy men (aged 22±3 years) pre and post 100 minutes of moderate, intermittent exercise in two randomized conditions: heat stress (HS; wearing firefighter personal protective equipment (PPE)), and no heat stress (NHS; wearing a cooling shirt and equivalent PPE weight). Aortic blood pressure, reflected wave pressure (Pb), systolic (SPTI) and diastolic pressure time-integral (DPTI), and aortic stiffness were assessed before and after each condition. SPTI was significantly greater, and DPTI and Pb were significantly lower for HS-post compared to NHS-post (p<0.05). Pulse wave velocity was not different between conditions. In conclusion, EIHS does not affect aortic stiffness, but increases indices of myocardial work and reduces indices of coronary perfusion which may be related to chronotropic responses to EIHS. The mismatch between oxygen demand and oxygen supply may increase cardiac vulnerability to ischemia during strenuous work in the heat.

Physiological Evaluation of Cooling Devices in Conjunction With Personal Protective Ensembles Recommended for Use in West Africa

“…[12][13][14] Additionally, it has been shown that HR response and cardiovascular strain are increased during exercise in a hot and humid environment and that this is attenuated with the use of a CD. [13][14][15][16] Weight loss has also been shown to be reduced when using a CD during exercise in the heat. 16,17 Previously, PCM CDs have been reported to offer a cooling effect that is "quick and strong," mimicking the results seen in this study.…”

Cardiovascular health effects following exposure of human volunteers during fire extinction exercises

“…Several studies have demonstrated that exposure to heat, associated with increased body temperature, increases the peripheral arterial compliance, shear stress and blood flow [ 5 , 6 ]. Exercise also increases the body temperature and evokes a number of hemodynamic changes, including vasodilation [ 7 ]. Above all, these results demonstrate an immediate and possibly transient effect of exercise and increased body temperature on the cardiovascular physiology.…”

Exercise‐induced heat stress disrupts the shear–dilatory relationship

“…Blood pressures (systolic, diastolic and mean arterial pressure) were examined pre‐ and postexercise and were not different between conditions, suggesting that the blood pressures at which the FMD measurements were made were not likely to be a contributing factor to the reduction in vascular function in response to EIHS (Lefferts et al . ). Although no direct measures of sympathetic activity were assessed in this study, heart rate remained significantly elevated postexercise in the EIHS trail, suggestive of less parasympathetic tone and a greater unveiling of sympathetic nerve activity.…”

“…; Lefferts et al . ) and in vitro (Ives et al . ), peripheral vascular function in relation to heat stress has remained largely unstudied.…”

“…Although the effects of EIHS on the heart and central blood vessels (i.e. aorta) have been explored in vivo (Ganio et al 2011;Fehling et al 2015;Lefferts et al 2015) and in vitro (Ives et al 2012), peripheral vascular function in relation to heat stress has remained largely unstudied.…”