Hyperthermia modifies muscle metaboreceptor and baroreceptor modulation of heat loss in humans
| Autor: | Narihiko Kondo, Aaron Lynn, Konrad Binder, Glen P. Kenny, Daniel Gagnon |
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| Rok vydání: | 2011 |
| Předmět: |
Hyperthermia
Adult Male medicine.medical_specialty Baroreceptor Hot Temperature Adolescent Physiology Ischemia Blood Pressure Pressoreceptors Baroreflex Young Adult Esophagus Physiology (medical) Internal medicine medicine Humans Exercise physiology Muscle Skeletal Sweat Exercise Skin Hand Strength Chemistry Heat losses Thermoregulation medicine.disease Heat stress Anesthesia Cardiology Body Temperature Regulation |
| Zdroj: | American journal of physiology. Regulatory, integrative and comparative physiology. 302(4) |
| ISSN: | 1522-1490 |
| Popis: | The relative influence of muscle metabo- and baroreflex activity on heat loss responses during post-isometric handgrip (IHG) exercise ischemia remains unknown, particularly under heat stress. Therefore, we examined the separate and integrated influences of metabo- and baroreceptor-mediated reflex activity on sweat rate and cutaneous vascular conductance (CVC) under increasing levels of hyperthermia. Twelve men performed 1 min of IHG exercise at 60% of maximal voluntary contraction followed by 2 min of ischemia with simultaneous application of lower body positive pressure (LBPP, +40 mmHg), lower body negative pressure (LBNP, −20 mmHg), or no pressure (control) under no heat stress. On separate days, trials were repeated under heat stress conditions of 0.6°C (moderate heat stress) and 1.4°C (high heat stress) increase in esophageal temperature. For all conditions, mean arterial pressure was greater with LBPP and lower with LBNP than control during ischemia (all P ≤ 0.05). No differences in sweat rate were observed between pressure conditions, regardless of the level of hyperthermia ( P > 0.05). Under moderate heat stress, no differences in CVC were observed between pressure conditions. However, under high heat stress, LBNP significantly reduced CVC by 21 ± 4% ( P ≤ 0.05) and LBPP significantly elevated CVC by 14 ± 5% ( P ≤ 0.05) relative to control. These results show that sweating during post-IHG exercise ischemia is activated by metaboreflex stimulation, and not by baroreflexes. In contrast, our results suggest that baroreflexes can influence the metaboreflex modulation of CVC, but only at greater levels of hyperthermia. |
| Databáze: | OpenAIRE |
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