THE RATE OF PERIPHERAL CIRCULATORY ADJUSTMENT AT THE ONSET OF EXERCISE

• Published in: Japanese Journal of Physical Fitness and Sports Medicine Vol. 38; no. 5; pp. 167 - 174
• Main Author: KAGAYA, ATSUKO
• Format: Journal Article
• Language: English
• Published: The Japanese Society of Physical Fitness and Sports Medicine 1989
• Subjects: Calf blood flow; Rate of adjustment; Vo2 kinetics
• ISSN: 0039-906X; 1881-4751
• DOI: 10.7600/jspfsm1949.38.167

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% Vo2max. Calf blood flow was measured with a mercury-in-rubber strain gauge plethysmograph immediately after cessation of each bout of exercise. Heart rate and Vo2 were measured during running. Calf blood flow after 15-s exercise increased to 25.98±3.51 ml/100 ml/min (mean±SD), which corresponded to 70% of the mean calf blood flow (32.80 ml/100 ml/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 Vo2 after exercise of identical duration showed a smaller percentage increase in comparison with heart rate. The increase of calf blood flow or heart rate was fitted best by a monoexponential equation, Yt=C-ae-kt, 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. The present study therefore showed that the adjustment of the peripheral circulatory system at the commencement of treadmill runnning at an intensity of 70% Vo2max preceded the central circulatory adjustment.