Persistence of functional sympatholysis post-exercise in human skeletal muscle

Abstract

Blunting of sympathetic vasoconstriction in exercising muscle is well-established. Whether it persists during the early post-exercise period is unknown. This study tested the hypothesis that it persists in human skeletal muscle during the first 10 min of recovery from exercise. Eight healthy young males (21.4 ± 0.8 yrs, SE) performed 7 min of forearm rhythmic isometric handgrip exercise at 15% below forearm critical force (fCF). In separate trials, a cold pressor test (CPT) of 2 min duration was used to evoke forearm sympathetic vasoconstriction in each of Rest (R), Steady State Exercise (Ex), 2–4 min Post-Exercise (PEearly), and 8–10 min Post-Exercise (PElate). A 7 min control exercise trial with no CPT was also performed. Exercising forearm brachial artery blood flow, arterial blood pressure, cardiac output (CO), heart rate (HR), forearm deep venous catecholamine concentration, and arterialized venous catecholamine concentration were obtained immediately prior to and following the CPT in each trial. CPT resulted in a significant increase in forearm venous plasma norepinephrine concentration in all trials (P = 0.007), but no change in arterialized plasma norepinephrine (P = 0.32). CPT did not change forearm venous plasma epinephrine (P = 0.596) or arterialized plasma epinephrine concentration (P = 0.15). As assessed by the %reduction in forearm vascular conductance (FVC) the CPT evoked a robust vasoconstriction at rest that was severely blunted in exercise (R = −39.9 ± 4.6% vs. Ex = 5.5 ± 7.4%, P < 0.001). This blunting of vasoconstriction persisted at PEearly (-12.3 ± 10.1%, P = 0.02) and PElate (-18.1 ± 8.2%, P = 0.03) post-exercise. In conclusion, functional sympatholysis remains evident in human skeletal muscle as much as 10 min after the end of a bout of forearm exercise. Persistence of functional sympatholysis may have important implications for blood pressure regulation in the face of a challenge to blood pressure following exercise.

Does oxygen delivery explain interindividual variation in forearm critical impulse?

“…However, addition of subjects from previously published studies (Moynes et al. ; Kellawan and Tschakovsky ) as well as unpublished data from ongoing investigations increasing the total n to 47 identified a weak, albeit statistically significant,, relationship between critical impulse and MVC (Fig. ; r 2 = 0.125, P = 0.015).…”

“…However, when we included data from published studies (Moynes et al. ; Kellawan and Tschakovsky ) and other ongoing unpublished work, there was a weak, albeit statistically significant, relationship between MVC and critical impulse.…”

Cardiovascular Adaptations to Exercise Training

“…Remensnyder and co-workers (351) demonstrated in 1962 in dogs that the responsiveness of a vascular bed to adrenergic stimulation at rest diminishes significantly with a small increase in oxygen uptake. It was more recently shown in humans that following an exercise bout, a blunting of sympathetic vasoconstriction was evident in the skeletal muscle previously engaged in exercise (299). This residual effect of acute exercise indicates that exercise training is central for stimulating the signaling pathways that are important for functional sympatholysis.…”

Neural control of the circulation during exercise in health and disease

“…Interestingly, this is likely extended to post exercise as well. Indeed, Moynes et al (2013) demonstrate a persistent attenuation of vascular responses to sympathetic activation acutely after the cessation of exercise that may have important implications for blood pressure regulation and immediate post exercise hypotension. Lastly, it is important to remember that not all vascular beds respond alike.…”