Forearm blood flow during body temperature transients produced by leg exercise

Area of Science:

• Physiology
• Thermoregulation
• Human Exercise Physiology

Background:

• Understanding the physiological responses to exercise in varying environmental conditions is crucial for performance and safety.
• Previous models of thermoregulation have explored the relationship between core and skin temperatures and blood flow, but further validation is needed.

Purpose of the Study:

• To investigate the independent and combined effects of core body temperature (esophageal temperature, Tes) and mean skin temperature (Tsk) on forearm blood flow (BF) during exercise.
• To determine if exercise intensity influences the relationship between temperature and BF.
• To compare the derived coefficients with existing thermoregulatory models.

Main Methods:

• Subjects performed 30-minute cycling exercise at 30%, 50%, and 70% of maximal aerobic power in controlled ambient temperatures (15°C, 25°C, 35°C).
• Esophageal temperature (Tes) and mean skin temperature (Tsk) were continuously monitored.
• Forearm blood flow (BF) was measured using electrocapacitance plethysmography.
• Forearm skin temperature was maintained at approximately 36.5°C.

Main Results:

• Forearm blood flow (BF) was accurately predicted by a linear equation incorporating esophageal temperature (Tes) and mean skin temperature (Tsk): BF = a1Tes + q2Tsk + b.
• This relationship remained consistent across different exercise intensities.
• The ratio of coefficients (a1/a2) derived from the data closely matched those from established thermoregulatory sweating models.

Conclusions:

• Core body temperature (Tes) and mean skin temperature (Tsk) are the primary determinants of forearm blood flow during exercise.
• Exercise intensity does not significantly alter the fundamental relationship between temperature and blood flow.
• The findings provide strong support for current physiological models of thermoregulation.