REDUCED ARTERIAL DIAMETER DURING STATIC EXERCISE IN HUMANS

In eight subjects luminal diameter of the resting limb radial and dors alis pedis arteries was determined by high-resolution ultrasound (20 M Hz). This measurement was followed during rest and during 2 min of sta tic handgrip or of one-leg knee extension at 30% of maximal voluntary contraction of another limb. Static exercise increased heart rate and mean arterial pressure, which were largest during one-leg knee extensi on. After exercise heart rate and mean arterial pressure returned to t he resting level. No changes were recorded in arterial carbon dioxide tension, and the rate of perceived exertion was similar to 15 units af ter both types of exercise. The dorsalis pedis arterial diameter was 1 .50 +/- 0.20 mm (mean and se) and the radial AD 2.45 +/- 0.12 mm. Duri ng both types of contractions the luminal diameters decreased similar to 3.5% within the first 30 s (P < 0.05), and during one-leg knee exte nsion they continued to decrease to a final exercise value 7.6 +/- 1.1 % lower than at rest (P < 0.05). Thus, they became smaller than during the handgrip. After exercise resting values were reestablished. When the arterial diameter was expressed in relation to mean arterial press ure for the radial and dorsalis pedis artery was 22 +/- 3 and 28 +/- 3 % lower during handgrip than the relation during rest, respectively. A fter one-leg knee extension both arteries reached 30 +/- 4% lower valu es. This study demonstrated arterial constriction in the resting limbs within the first 30 s of static exercise, and continued constriction during one-leg knee extension. These results support to the hypothesis that central command and/or muscle mechanoreceptors influence arteria l tone, and that the exercise presser reflex becomes important with th e involvement of a large muscle mass.