Heat stress caused a small but statistically significant reduction in peak work capacity compared to temperate conditions (253 W vs 259 W) in young men, without altering myocardial functional responses.
Does environmental heat stress reduce maximal oxygen uptake, peak work capacity, or alter myocardial function during maximal exercise in healthy young men?
Environmental heat stress causes a small reduction in peak work capacity during maximal exercise in young men, but this is not explained by disturbances in myocardial functional responses.
Absolute Event Rate: 253% vs 259%
p-value: p=0.02
Both the extent and means by which maximal oxygen uptake (V̇O ₂₌₀ₗ) is depressed by elevated ambient temperature are uncertain. Particularly, information is currently unavailable regarding the possible influence of alterations in myocardial function on V̇O ₂₌₀ₗ and performance during exercise in the heat. This study investigated the effects of environmental heat on V̇O ₂₌₀ₗ, peak work capacity, and myocardial function during a standard, progressive cycle test to exhaustion. Twelve euhydrated men (aged 20. 7 ± 1. 7 years) performed a maximal cycle test in an environmental chamber in both heat stress 35°C, 30% relative humidity (RH) and temperate (20°C, 30% RH) conditions with measurement of standard gas exchange variables, core temperature, and echocardiographic measures of cardiac function. A small but statistically significant reduction of peak work capacity was observed in the heat stress versus temperate conditions (253 ± 30 and 259 ± 30 W, respectively, p = 0. 02). Mean V̇O ₂₌₀ₗ was not statistically different in the two conditions (p = 0. 16) but values were 3. 4% lower in the heat, and 9 of 12 participants demonstrated lower values in the heat stress trial. No differences in responses of heart rate, cardiac output, stroke volume, core temperature, hydration status, or myocardial systolic or diastolic function were observed between the two conditions, but perceived body temperature was higher in the heat. The small, negative impact of heat on exercise performance and V̇O ₂₌₀ₗ could not be explained by disturbances in myocardial functional responses to exercise in young adult males.
Smith et al. (Thu,) conducted a other in Healthy, physically active young men (n=12). Heat stress (35°C, 30% relative humidity) vs. Temperate condition (20°C, 30% relative humidity) was evaluated on Peak work capacity (p=0.02). Heat stress caused a small but statistically significant reduction in peak work capacity compared to temperate conditions (253 W vs 259 W) in young men, without altering myocardial functional responses.