Ischemic preconditioning does not alter muscle sympathetic responses to static handgrip and metaboreflex activation in young healthy men

Abstract

Ischemic preconditioning (IPC) has been hypothesized to elicit ergogenic effects by reducing feedback from metabolically sensitive group III/IV muscle afferents during exercise. If so, reflex efferent neural outflow should be attenuated. We investigated the effects of IPC on muscle sympathetic nerve activity (MSNA) during static handgrip (SHG) and used post‐exercise circulatory occlusion (PECO) to isolate for the muscle metaboreflex. Thirty‐seven healthy men (age: 24 ± 5 years [mean ± SD]) were randomized to receive sham (n = 16) or IPC (n = 21) interventions. Blood pressure, heart rate, and MSNA (microneurography; sham n = 11 and IPC n = 18) were collected at rest and during 2 min of SHG (30% maximal voluntary contraction) and 3 min of PECO before (PRE) and after (POST) sham or IPC treatment (3 × 5 min 20 mmHg or 200 mmHg unilateral upper arm cuff inflation). Resting mean arterial pressure was higher following sham (79 ± 7 vs. 83 ± 6 mmHg, P < 0.01) but not IPC (81 ± 6 vs. 82 ± 6 mmHg, P > 0.05), while resting MSNA burst frequency was unchanged (P > 0.05) with sham (18 ± 7 vs. 19 ± 9 bursts/min) or IPC (17 ± 7 vs. 19 ± 7 bursts/min). Mean arterial pressure, heart rate, stroke volume, cardiac output, and total vascular conductance responses during SHG and PECO were comparable PRE and POST following sham and IPC (All P > 0.05). Similarly, MSNA burst frequency, burst incidence, and total MSNA responses during SHG and PECO were comparable PRE and POST with sham and IPC (All P > 0.05). These findings demonstrate that IPC does not reduce hemodynamic responses or central sympathetic outflow directed toward the skeletal muscle during activation of the muscle metaboreflex using static exercise or subsequent PECO.

Effect of Ischemic Preconditioning on the Recovery of Cardiac Autonomic Control From Repeated Sprint Exercise

“…Mulliri et al ( 2016 ) reported IPC did not change central and peripheral hemodynamic parameters during exercise, but IPC decreased mean arterial pressure during post-exercise circulatory occlusion due to a venous return-induced reduction of stroke volume and cardiac output. Of note, however, Incognito et al ( 2017 ) and Mulliri et al ( 2016 ) did not provide enough data to interpret the IPC effect under normal free flow recovery from exercise, like we did in the present study. In addition, cardiovascular responses to handgrip exercise are very different from those provoked by dynamic exercise involving large muscle mass (Lewis et al, 1985 ).…”

“…In contrast, in our study HR surpassed 180 bpm. Therefore, methodological dissimilarities preclude comparison of the IPC effect on post-exercise cardiovascular parameters between former studies (Mulliri et al, 2016 ; Incognito et al, 2017 ) and the present one.…”

“…Both studies used handgrip exercise and employed circulatory occlusion during recovery from exercise to isolate the activation of the muscle metaboreflex. Incognito et al ( 2017 ) reported IPC did not change arterial pressure, HR and muscle sympathetic nerve activity during exercise and post-exercise circulatory occlusion. Mulliri et al ( 2016 ) reported IPC did not change central and peripheral hemodynamic parameters during exercise, but IPC decreased mean arterial pressure during post-exercise circulatory occlusion due to a venous return-induced reduction of stroke volume and cardiac output.…”

“…In addition, cardiovascular responses to handgrip exercise are very different from those provoked by dynamic exercise involving large muscle mass (Lewis et al, 1985 ). For example, Incognito et al ( 2017 ) and Mulliri et al ( 2016 ) reported mean HR to achieve 102 and 72 bpm, respectively. In contrast, in our study HR surpassed 180 bpm.…”

Conduit Artery Diameter During Exercise Is Enhanced After Local, but Not Remote, Ischemic Preconditioning

“…Lower SNA has been observed following limb ischemia reperfusion injury preceded by IPC using the gold standard microneurography ( Lambert et al, 2016 ). However, it has recently been reported that no change in SNA was present during static handgrip at 30% MVC, following IPC versus a SHAM condition ( Incognito et al, 2017 ). Based on the available evidence, we cannot currently elucidate this mechanism.…”