Effects of forearm muscle metaboreceptors activation on sweating and cutaneous vascular responses during passive heating and cycle exercising in humans
Extreme Physiology & Medicine volume 4, Article number: A99 (2015)
Muscle metaboreceptors are afferent signals from working muscles that enhance sweating and attenuate cutaneous vasodilation during a passive heat stress in humans . However, it remains unclear if metaboreceptor activation during an exercise-induced heat stress may have comparable effects on heat loss responses. This study investigates the influence of forearm muscle metaboreceptors activation on the core temperature onset thresholds and thermosensitivity (slopes) of the sweating and cutaneous vascular responses during a passive (study Ι) and exercise (study ΙΙ) induced heat stresses associated with the different modification of the responses between heating conditions .
Study Ι: Fourteen (8 females, 6 males) young adults were passively heated for 15.5 min using a upper body water perfused suit (34 °C) and immersing the participant's legs in hot water (43 °C). During the heating period, the participants performed 1.5 minutes of isometric hand-grip exercise at 40 % of maximum voluntary contraction with or without (Control) post exercise occlusion of the limb with a pressure cuff to stimulate muscle metaboreceptors for 9 minutes. Study ΙΙ: Twelve (6 for each sex) young subjects performed the similar forearm muscle metaboreceptors stimulation while cycling for 13.5 minutes at the exercise intensity of 40 % maximum oxygen consumption while wearing the water perfused suit.
Study Ι: Forearm muscle metaboreceptors stimulation significantly lowered Δmean body temperature thresholds for sweating and cutaneous vasodilation on the oppositional arm of hand-grip exercise during passive heating compared with Control (P <0.05) without differences in thermosensitivity of the responses. Study ΙΙ: Forearm muscle metaboreceptors stimulation did not significantly (P > 0.05) affect the onset threshold and thermosensitivity for sweating and cutaneous vasodilation during exercise.
Our results suggest that forearm muscle metaboreceptors activation can modulate heat loss responses during a passive heat stress only. The acceleration of sweating and cutaneous vasodilation through a reduction in the core temperature thresholds of the responses would suggest a central modulation of temperature regulation . It is thought that any of overriding factors associated with dynamic exercise may be masking the influence of forearm muscle metaboreceptors activation.
Forearm muscle metaboreceptors activation lowers core temperature thresholds for heat loss responses during passive heating but not during exercise.
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Amano, T., Inoue, Y., Nishiyasu, T. et al. Effects of forearm muscle metaboreceptors activation on sweating and cutaneous vascular responses during passive heating and cycle exercising in humans. Extrem Physiol Med 4 (Suppl 1), A99 (2015). https://doi.org/10.1186/2046-7648-4-S1-A99
- Maximum Voluntary Contraction
- Passive Heating
- Cutaneous Vasodilation
- Onset Threshold
- Lower Core Temperature