Forearm endurance training attenuates sympathetic nerve response to isometric handgrip in normal humans

Abstract

Recent evidence indicates that muscle ischemia and activation of the muscle chemoreflex are the principal stimuli to sympathetic nerve activity (SNA) during isometric exercise. We postulated that physical training would decrease muscle chemoreflex stimulation during isometric exercise and thereby attenuate the SNA response to exercise. We investigated the effects of 6 wk of unilateral handgrip endurance training on the responses to isometric handgrip (IHG: 33% of maximal voluntary contraction maintained for 2 min). In eight normal subjects the right arm underwent exercise training and the left arm sham training. We measured muscle SNA (peroneal nerve), heart rate, and blood pressure during IHG before vs. after endurance training (right arm) and sham training (left arm). Maximum work to fatigue (an index of training efficacy) was increased by 1,146% in the endurance-trained arm and by only 40% in the sham-trained arm. During isometric exercise of the right arm, SNA increased by 111 +/- 27% (SE) before training and by only 38 +/- 9% after training (P less than 0.05). Endurance training did not significantly affect the heart rate and blood pressure responses to IHG. We also measured the SNA response to 2 min of forearm ischemia after IHG in five subjects. Endurance training also attenuated the SNA response to postexercise forearm ischemia (P = 0.057). Sham training did not significantly affect the SNA responses to IHG or forearm ischemia. We conclude that endurance training decreases muscle chemoreflex stimulation during isometric exercise and thereby attenuates the sympathetic nerve response to IHG.

Endurance training reduces renal vasoconstriction to orthostatic stress

“…With this association between MSNA and RSNA established, the training-induced MSNA reduction during leg exercise training suggests that there is a concurrent reduction in RSNA during training (14). Additionally, other studies have found that training is associated with an attenuation of exerciseinduced increases of MSNA (14,19,20). Therefore, the lack of renal vasoconstriction that we observed in the present study is likely a result of training-induced RSNA reductions.…”

Effects of Prolonged Immobilization of the Limb on Radial Artery Mechanical Properties

“…Physical activity should thus be regarded as a mechanism involved in the determination of arterial mechanical function in all subjects, its role coexisting with other mechanisms involved in the tonic modulation of these functions, eg, sympathetic nerve activity. 4,21,23,[25][26][27] Our study does not clarify the mechanisms responsible for the effect of an ordinary level of physical activity on arterial distensibility. We can speculate, however, that both structural and functional factors are involved.…”

“…Key Words: arterial distensibility Ⅲ training Ⅲ exercise Ⅲ vessels Ⅲ circulation E xercise training is associated with several changes in cardiac and arteriolar structure and function. [1][2][3][4][5][6][7][8][9] There is evidence, however, that large and conduit artery mechanical properties are also modified by training and that the modification consists of an increase in distensibility 10 -13 that is particularly evident in the arteries of the limbs most involved in the physical activity.14 Whether arterial mechanical properties are modified also by ordinary levels of physical activity (rather than becoming manifest only during exercise training) has never been investigated. In the present study, we addressed this issue by measuring radial artery diameter and distensibility in subjects in whom 1 arm was immobilized in plaster for 30 days because of an elbow fracture.…”

Effect of Isometric Handgrip Exercise Training on Resting Blood Pressure in Normal Healthy Adults

“…Various authors have shown that during isometric training, chemoreceptor reflex responsible for sympathetic nerve activity is reduced and thus causing attenuation of sympathetic nerve response to sympathetic nerve activity which is responsible for decrease in resting blood pressure over a period of time [23].…”