Can amateur athletes benefit from passive heat acclimation?

Thermal acclimation, widely used to increase endurance in elite athletes training for competition in hot environments, could also benefit amateur sportspeople¹. The findings, reported in the journal Human Physiology, support the broader use of thermal acclimation techniques for improved fitness and conditioning.

A team of researchers, led by Oleg Glazachev at Sechenov First Moscow State Medical University, set out to investigate whether the thermal acclimation approach might also benefit amateur sportspeople. In a randomized controlled study, they explored the effects of adaptation to passive elevation of body temperature (hyperthermia) on physical performance and cardiorespiratory endurance in amateur athletes during increasingly intense exercise carried out under laboratory conditions.

An initial cohort of 28 male subjects – all aged in their early 20s, of similar height and weight, who had each played amateur team sport for up to seven years – was randomly split into an experimental group and control group. Over a 10-week period, the experimental group underwent passive hyperthermic procedures involving lying down in an ergonomic chamber for their body to be exposed to infrared heating, while their heads, outside the chamber, were blown with cool air from a fan.

During the same period, the control group underwent training on an elliptical trainer machine, subjecting them to moderate physical stress, but with no thermal exposure.

Halfway through the study and at its completion, the two groups were assessed using a standard stress cardiopulmonary treadmill test. The researchers found that the experimental group showed an increase in several key indicators of fitness, including improved aerobic and cardiac performance. They concluded that it was the course of passive thermal acclimation that had led to improved aerobic performance, although further research is needed to be able to translate the impacts of this to professional athletes.

“The work identified specific indicators reflecting an increase in physical performance tested under normal thermal conditions,” Glazachev explains. “The results provide a basis for the introduction of passive thermal acclimation techniques to improve fitness and health in sports clubs and wellness centres, especially in complex programs combined with physical training.”

In related work, Glazachev’s team is also exploring the potential impact of passive thermal acclimation on performance-related hormones.

“We are currently testing the hypothesis that the effects of passive thermal acclimation, in terms of physical performance and cardiorespiratory endurance, are related to thermal stimulation of the production of a number of myokines by skeletal muscles and other organs, in particular irisin and MNTPs,” Glazachev says.