INTERACTION BETWEEN MUSCLE TEMPERATURE AND BLOOD FLOW ON MUSCLE SYMPATHETIC OUTFLOW DURING FOREARM EXERCISE
2001; Lippincott Williams & Wilkins; Volume: 33; Issue: 5 Linguagem: Inglês
10.1097/00005768-200105001-01123
ISSN1530-0315
AutoresAndrew C. Ertl, Nikolai Dahl, Chester A. Ray,
Tópico(s)Infrared Thermography in Medicine
ResumoPrevious studies from our laboratory have shown that altering muscle temperature of the exercising forearm elicits changes in muscle sympathetic nerve activity (MSNA) during is-chemic isometric handgrip. The purpose of the current study was to determine the effect of muscle temperature on MSNA responses during rhythmic handgrip (RHG). Eight subjects performed 3 bouts of graded RHG to fatigue followed by 2 min of postexercise muscle ischemia (PEMI). Forearm muscle temperatures during the 3 bouts were 30○C (cold), 34○C (ambient), and 38○C (warm). Mean arterial pressure and heart rate increased in a linear fashion during graded RHG (P < 0.05), but were not affected by muscle temperature. MSNA (burst frequency and total activity) at fatigue and PEMI were elevated in all conditions (P < 0.05). However, MSNA responses were not different among temperature conditions. To ascertain the effects of blood flow, 8 additional subjects completed 2 trials of ischemic RHG under ambient or warm conditions followed by 2 min of PEMI. MSNA, expressed as burst frequency and total activity, was significantly greater in the warm compared to the ambient trial (Δ14 ± 3 and Δ9 ± 2 bursts/30s, and Δ1234 ± 260 and Δ751 ± 199 units/30s, respectively). This finding supports the concept that muscle heating sensitizes skeletal muscle afferents during muscle contractions in humans. Based on these studies, we conclude that muscle blood flow minimizes the effect of muscle temperature on MSNA during exercise. Supported by NIH HL58503 and NASA NAG 9–1034
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