Sweating responses to a sustained static exercise is dependent on thermal load in humans

Area of Science:

• Physiology
• Thermoregulation
• Exercise Science

Background:

• The body's sweating response is crucial for thermoregulation.
• Understanding how internal temperature affects sweating during exercise is important for performance and health.
• Previous research has explored various factors influencing sweat rate, but the specific role of internal temperature magnitude requires further investigation.

Purpose of the Study:

• To investigate the hypothesis that internal temperature modulates the sweating response during sustained isometric handgrip exercise.
• To determine if different levels of internal temperature affect sweat rate from glabrous and non-glabrous skin.
• To explore the influence of non-thermal factors on sweating during exercise at varying internal temperatures.

Main Methods:

• Ten healthy males underwent leg immersion in hot water (43°C) to elevate internal temperature.
• Isometric handgrip exercise (IH) at 50% maximal voluntary contraction was performed at two stages of internal temperature increase.
• Oesophageal temperature (Tes), sweating rate (SR) from chest, forearm, and palm, mean arterial blood pressure, heart rate, and perceived effort were measured.

Main Results:

• Oesophageal temperature was significantly lower during the first exercise bout (37.54°C) compared to the second (37.84°C).
• Sweating rate from non-glabrous skin (chest and forearm) was significantly higher during the first exercise bout.
• Increases in blood pressure and palm sweating did not differ, while heart rate and perceived effort were higher in the second bout.

Conclusions:

• Sweating responses from non-glabrous skin during isometric handgrip exercise are modulated by the magnitude of thermal input, indicated by differing internal temperatures.
• Non-thermal factors appear to have a greater influence on sweating from non-glabrous skin at moderate internal temperatures (around 37.54°C) compared to higher temperatures (around 37.84°C).
• These findings highlight the complex interplay between thermal and non-thermal factors in regulating sweating during exercise.