Central command and the increase in middle cerebral artery blood flow velocity during static arm exercise in women.

We examined the role of central command in static exercise-induced increase in middle cerebral artery mean blood flow velocity (V(MCA)). Eleven young female subjects performed static elbow flexion for 2 min at 30% maximal voluntary contraction without (control exercise; CONT) and with vibrations to the biceps brachii tendon (EX+VIB) in order to reduce the effort needed to maintain the set contraction intensity. The rating of perceived exertion in exercising muscle (Arm RPE) at the end of EX+VIB was lower than that of CONT (mean +/- s.d.; 4.8 +/- 1.1 for CONT versus 3.5 +/- 1.0 for EX+VIB; P < 0.05). The increases in mean arterial pressure (36 +/- 8 versus 22 +/- 7%; P < 0.05), heart rate (36 +/- 16 versus 21 +/- 7%; P < 0.05) and cardiac output (56 +/- 26 versus 39 +/- 14%; P < 0.05) during EX+VIB were also lower than those during CONT. Similarly, the increase in the V(MCA) during EX+VIB was lower than that during CONT (29 +/- 5 versus 17 +/- 14%; P < 0.05). These results suggest that the influence of central command contributes to cerebral blood flow regulation during static exercise and the decrease in V(MCA) is likely to be caused by attenuated brain activation in the central command network and/or by the reduction in cardiac output.

Perceived exertion is not necessarily associated with altered brain activity during exercise.

Previous studies have investigated the relationship between prefrontal cortex activation and perceived exertion during prolonged exercise. However, the effect of perceived exertion on prefrontal cortex activity is confounded by exercise intensity. Therefore, the changes in prefrontal cortex activity in response to perceived exertion remain unclear. The purpose of the present study was to investigate the relationship between the activation (oxygenation) of the prefrontal cortex and perceived exertion during constant work-rate elbow-flexion exercise with or without muscle-spindle stimulation. Ten healthy, right-handed subjects participated in the study. Near-infrared spectroscopy with probes positioned over the prefrontal cortex measured its activation throughout elbow-flexion exercise. Subjects performed sustained elbow-flexion exercise at 25-35% of the maximal voluntary contraction (MVC) with or without muscle-spindle stimulation (vibration), which can decrease perceived exertion. The ratings of perceived exertion were significantly lower during exercise with vibration (Ex-Vib) than during exercise without vibration (Ex) (p<0.05). The oxygenation of the prefrontal cortex during Ex-Vib did not significantly differ from that during Ex (p>0.05). These results indicated that perceived exertion was not necessarily associated with prefrontal cortex activation during exercise.

Transient increase in femoral arterial blood flow to the contralateral non-exercising limb during one-legged exercise.

We studied the effect of exercise intensity and duration on blood flow to the non-exercising leg during one-legged dynamic knee extension. Femoral arterial blood flow (FBF) to the non-exercising leg, blood pressure (BP), and heart rate (HR) were monitored during one-legged dynamic knee extension exercise at 15, 30, and 45% maximal voluntary contraction (MVC) in seven healthy females. There was an interaction between exercise intensity and duration for FBF and FVC (P < 0.01). During the initial phase of contralateral leg exercise at all intensities, FBF and femoral vascular conductance (FVC) of non-exercising leg increased, and the increase was larger at higher intensities (P < 0.01). After initial vasodilatation, FBF and FVC decreased to baseline, which suggests the vasoconstriction. However, FBF and FVC gradually increased during exercise at 15% MVC. We conclude that transient vasodilatation at the onset of exercise is followed by gradual change to vasoconstriction in non-exercising limb during dynamic one-legged exercise and these changes are exercise intensity- and duration-dependent.