Received February 13, 2006
Revised March 13, 2006
Accepted after revision April 24, 2006
Cardiovascular Control [210]
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Forearm vascular responses to combined muscle metaboreceptor activation in the upper and lower limbs in humans
Ken Tokizawa 1,
Masaki Mizuno 1,
Isao Muraoka 1*
1 Waseda University
* To whom correspondence should be addressed. E-mail: imuraoka{at}waseda.jp.
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Abstract |
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Our previous studies showed that venous occlusion or passive stretch of the lower limb, assuming a mechanical stimulus, attenuates the vasoconstriction in the nonexercised forearm during postexercise muscle ischaemia (PEMI) of the upper limb. In this study, we investigated whether a metabolic stimulus to the lower limb induces a similar response. Eight subjects performed a 2 min static handgrip exercise at 30% maximal voluntary contraction (MVC) followed by 3 min PEMI of the upper limb, concomitant with or without 2 min static ankle dorsiflexion at 30% MVC followed by 2 min PEMI of the lower limb. During PEMI of the upper limb alone, forearm blood flow (FBF) and forearm vascular conductance (FVC) in the nonexercised arm decreased significantly, whereas during combined PEMI of the upper and lower limbs, the decreases in FBF and FVC produced by PEMI of the upper limb was attenuated. FBF and FVC were significantly greater during combined PEMI of the upper and lower limbs than during PEMI of the upper limb alone. When PEMI of the lower limb was released after combined PEMI of the upper and lower limbs (only PEMI of the upper limb was maintained continuously), the attenuated decreases in FBF and FVC observed during combined PEMI of the upper and lower limbs was not observed. Thus, forearm vascular responses differ when muscle metaboreceptor are activated in the upper limb and when there is combined activation of muscle metaboreceptor in both the upper and lower limbs.
Key Words:
Blood pressure, Sympathetic nervous system, Vascular blood flow
