Post-exercise Circulatory Occlusion Research Articles

DECREASED MUSCLE AFFERENT ACTIVITY DURING ELECTRICALLY EVOKED EXERCISE IN CHRONIC HEART FAILURE PATIENTS

1069 This study was designed to examine the role of muscle afferent activity and central drive in controlling the cardiovascular system during exercise in patients with chronic heart failure (CHF). Isometric exercise of the triceps surae was performed for 2min at 30% of maximum voluntary strength using either voluntary (VOL) or electrically evoked (STIM) contraction, followed by 2min post exercise circulatory occlusion (PECO). In 7 CHF patients mean(sd) age 62(12) yr (NYHA class II-III), mean arterial pressure (MAP) rose by 10(4) and 17(11)mmHg at the end of STIM and VOL respectively. Previously reported values for young healthy subjects during STIM and VOL averaging 20mmHg. MAP fell to a level above resting during PECO attaining similar levels following STIM and VOL, 5(2) and 8(5)mmHg respectively. Heart rate rose by 5(3) and 9(8)b.min−1 during STIM and VOL respectively, returning to resting levels during PECO. These data support the view that muscle afferent activity is decreased during exercise in stable CHF patients, when both muscle mechanoreceptors and chemoreceptors may be active. During VOL exercise central command may compensate partially for this deficiency. Supported by BHF PG/97085

Sympathetic nerve activity to nonactive muscle of the exercising and nonexercising limb

The purpose of this study was to determine whether efferent sympathetic nerve activity is different to resting skeletal muscles from the exercising and nonexercising limb. MSNA was measured by microneurography in both legs (peroneal nerve) in six subjects during 2 min of unilateral isometric knee extension (IKE; 10-30% of maximum voluntary contraction (MVC)) followed by postexercise circulatory occlusion (PECO). Additional studies using isometric handgrip (30% MVC) followed by PECO were performed. IKE produced significant increases in mean arterial pressure (15 +/- 2 mm Hg) and heart rate (10 +/- 2 bpm). During PECO, mean arterial pressure remained significantly elevated (6 +/- 1 mm Hg) whereas heart rate returned to control. MSNA (bursts.min-1) was not different between the two limbs during control, IKE, PECO, and recovery. Seventy-five to eighty percent of all sympathetic nerve discharges occurred simultaneously in both legs, with the remaining percentage of sympathetic nerve discharges being divided almost equally between the nonexercising and exercising leg. Isometric handgrip produced significant increases in MSNA to the two resting legs with the percent of sympathetic discharges to the two legs being similar to that during IKE. These results indicate that MSNA is similar to the resting muscle in the exercising and nonexercising leg during brief, submaximal isometric exercise (< or = 30% MVC) and postexercise muscle ischemia.