RESUMEN
Respiro-circulatory responses to forearm and calf exercise performed simultaneously were compared with corresponding responses to forearm or calf exercise performed separately in 9 active women aged 21.1 yr on average. Handgrip exercise and plantar flexion were carried out for 60 s in a supine position at a frequency of 60 times·min<SUP>-1</SUP> and the load was adjusted to 1/3 MVC. Forearm blood flow (FBF) increased to 9.64±1.00 m<I>l</I>·100 m<I>l</I><SUP>-1</SUP>·min<SUP>-1</SUP> immediately after handgrip exercise, and calf blood flow (CBF) to 12.72±0.72 m<I>l</I>·100 m<I>l</I><SUP>-1</SUP>·min<SUP>-1</SUP> after plantar flexion. These increases in FBF and CBF were not significantly different from those after combined arm and leg exercise. Blood flow to inactive limbs showed no significant changes. Rises in systolic and diastolic blood pressure at the end of exercise were significantly higher after handgrip exercise than after plantar flexion. However, no significant difference was found in mean blood pressure among the three types of exercise. Vo<SUB>2</SUB> and HR in combined exercise were significantly higher than those during handgrip exercise, but no significant difference was found between combined exercise and plantar flexion.<BR>Thus the present results indicated that the circulation to active limbs was not restricted when exercise was performed at 1/3 MVC, and that inhibitory summation shown in the central respiro-circulatory response to increased active muscle mass could occur without restriction of the peripheral circulation to the active muscle.
RESUMEN
The rate of peripheral circulatory adjustment at the onset of exercise was studied in six active women aged 2022 yrs. Five bouts of exercise with different duration of 15, 30, 60, 120 and 180 s were performed on a level treadmill at an intensity of 70% Vo<SUB>2</SUB>max. Calf blood flow was measured with a mercury-in-rubber strain gauge plethysmograph immediately after cessation of each bout of exercise. Heart rate and Vo<SUB>2</SUB> were measured during running.<BR>Calf blood flow after 15-s exercise increased to 25.98±3.51 m<I>l</I>/100 m<I>l</I>/min (mean±SD), which corresponded to 70% of the mean calf blood flow (32.80 m<I>l</I>/100 m<I>l</I>/min) immediately after 180-s exercise. The relative increases in calf blood flow after 15- and 30-s exercise were significantly higher than those of heart rate. The Vo<SUB>2</SUB> after exercise of identical duration showed a smaller percentage increase in comparison with heart rate.<BR>The increase of calf blood flow or heart rate was fitted best by a monoexponential equation, Yt=C-ae<SUP>-kt</SUP>, where Yt is the response at time t (s) expressed as a percentage of the value at 180-s exercise, C is 100 in the present study, and k is a rate constant. The rate constant k in the equations ranged from 0.025 to 0.179 for blood flow and 0.025 to 0.036 for the heart rate. The calculated half-times (t1/2) for the increase in blood flow averaged 12.85 s, ranging from 5.6 to 20.0 s. This was significantly (p<0.05) shorter than HRt 1/2, which averaged 21.7 s.<BR>The present study therefore showed that the adjustment of the peripheral circulatory system at the commencement of treadmill runnning at an intensity of 70% Vo<SUB>2</SUB>max preceded the central circulatory adjustment.