Decreased muscle oxygenation and increased arterial blood flow in the non-exercising limb during leg exercise.
ABSTRACT We evaluated arterial blood flow, muscle tissue oxygenation and muscle metabolism in the non-exercising limb during leg cycling exercise. Ten healthy male volunteers performed a graded leg cycling exercise at 0, 40, 80, 120 and 160 watts (W) for 5 min each. Tissue oxygenation index (TOI) of the non-exercising left forearm muscle was measured using a near-infrared spatially resolved spectroscopy (NIR(SRS)), and non-exercising forearm blood flow ((NONEX)FBF) in the brachial artery was also evaluated by a Doppler ultrasound system. We also determined O(2) consumption of the non-exercising forearm muscle (NONEXV(O)(2mus)) by the rate of decrease in O(2)Hb during arterial occlusion at each work rate. TOI was significantly decreased at 160 W (p < 0.01) compared to the baseline. The (NONEX)V(O)(2mus) at each work rate was not significantly increased. In contrast, (NONEX)FBF was significantly increased at 120 W (p < 0.05) and 160 W (p < 0.01) compared to the baseline. These results suggest that the O(2) supply to the non-exercising muscle may be reduced, even though (NONEX)FBF increases at high work rates during leg cycling exercise.
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ABSTRACT: Recent investigations using direct (microneurographic) recordings of MSNA have provided a substantial amount of new information on the regulation of sympathetic nervous system control of nonactive skeletal muscle blood flow during exercise in humans. Some of the new conclusions from these studies discussed in this review include: 1. The direction, pattern and magnitude of the MSNA response to exercise depend on the collective influence of a number of factors, including the mode (isometric or rhythmic), intensity, and duration of the exercise, the size of the contracting muscle mass, and possibly the level of conditioning (physical training) of the exercising muscles. The MSNA response also appears to be tightly coupled with the onset and progression of muscle fatigue, at least during sustained, isometric contractions. 2. Increases in MSNA evoked during exercise with the arms are fairly uniform among different skeletal muscle nerves, and these responses correlate strongly with changes in venous plasma norepinephrine concentrations, limb vascular resistance and arterial blood pressure. Thus, increases in this neural activity during exercise are associated with the expected physiological responses. 3. The MSNA response to the same level of exercise varies markedly among healthy subjects but appears to be consistent over time within a particular subject. 4. The muscle metaboreflex (muscle chemoreflex) is the primary-mechanism by which MSNA is stimulated during small-muscle, isometric exercise in humans. In contrast, central command has a relatively weak influence on MSNA during this type of exercise. 5. Muscle metaboreflex-stimulation of MSNA also occurs during dynamic exercise, but only at or above moderate, submaximal intensities (i.e., not during mild exercise). 6. Muscle metaboreflex-evoked increases in MSNA during exercise are strongly associated with glycogenolysis and the consequent cellular accumulation of hydrogen ions in the contracting muscles. 7. Sympathoinhibitory cardiopulmonary reflexes do not appear to modulate the MSNA responses to isometric exercise in the healthy human. However, arterial baroreflexes exert a potent inhibitory effect on MSNA during this form of exercise. The mechanisms involved in the regulation of MSNA during large-muscle, dynamic leg exercise is an important topic for future investigations, as is the relationship between MSNA and sympathetic outflow to other regional circulations (e.g., heart, viscera, skin) during various forms of exercise.Exercise and Sport Sciences Reviews 02/1991; 19:313-49. · 5.28 Impact Factor
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ABSTRACT: This study was carried out to determine whether hemodynamics in inactive forearm muscle during ramp leg cycling is affected from the ventilatory threshold (VT) and respiratory compensation point (RCP), at which the rate of increase in ventilation (VE) against power output begins to increase abruptly. Change in hemodynamics was evaluated by change in oxygenation index (difference between concentrations of oxygenated hemoglobin and deoxygenated hemoglobin, HbD) measured using near-infrared spectrometry (NIRS). Each subject (n=9) performed 4-min constant-work-rate leg cycling and subsequent ramp leg cycling at an increasing rate of 10 watts.min(-1) in power output. The work rates at VT, RCP and peak oxygen uptake (VO(2 peak)) were 107 +/- 11, 172 +/- 21 and 206 +/- 20 watts, respectively. The rates of increase in VE between 10-watt leg cycling, VT, RCP and VO(2 peak) were 0.19 +/- 0.03, 0.44 +/- 0.07 and 1.32 +/- 0.47 l.min(-1).watts(-1), respectively. In one subject, HbD started to decrease during ramp exercise from the VT, and the rate of decrease increased at a high intensity of exercise. In eight subjects, although no decrease in HbD from the VT was observed, HbD showed a sudden drop at a high intensity of exercise. The work rate at which HbD began to decrease at a high intensity of exercise was 174 +/- 23 watts. This work rate was not significantly different from that at the RCP and was significantly correlated with that at the RCP (r=0.72, P<0.05). The results suggest that the abrupt increase in VE from the RCP affects hemodynamics, resulting in a decrease in HbD in inactive forearm muscle.Journal of PHYSIOLOGICAL ANTHROPOLOGY and Applied Human Science 01/2004; 23(1):7-17.
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ABSTRACT: Regular exercise augments endothelium-dependent vasodilatory capacity in the vasculature located in the nonworking limbs. We determined whether blood flow as well as shear stress would change in inactive limbs during acute incremental exercise. Eight young healthy female subjects performed graded exercise on arm and leg cycle ergometers that had been modified to minimize the movement of nonworking limbs and to facilitate the placement of Doppler transducers. Both brachial and femoral blood flow was monitored using Doppler ultrasonography. EMG activity was also measured to document that there was no muscular activity in nonworking muscles. During leg exercise, brachial blood flow and calculated shear stress gradually and curvilinearly increased (P < 0.05). At the peak work rate, there was an approximately fourfold increase in blood flow in the brachial artery (19 +/- 6 vs 77 +/- 16 mL x min(-1)). Femoral blood flow and calculated shear stress increased progressively and linearly during arm exercise (P < 0.05). We concluded that blood flow to the nonworking limbs increases markedly in proportion to the work intensity. These results suggest that the conduit arteries in the nonworking limbs are exposed to increases in blood flow and shear stress during exercise.Medicine & Science in Sports & Exercise 01/2006; 38(1):81-5. · 4.48 Impact Factor