Received September 24, 2003
Revised November 24, 2003
Accepted after revision January 23, 2004
Human/environmental and exercise physiology
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Dissociation between the time courses of femoral artery blood flow and pulmonary VO2 during repeated bouts of heavy knee extension exercise in humans
Yoshiyuki Fukuba 1*,
Yukie Ohe 1,
Akira Miura 1,
Asami Kitano 1,
Masako Endo 1,
Hironori Sato 2,
Motohiko Miyachi 3,
Shunsaku Koga 4,
Osamu Fukuda 5
1 Hiroshima Prefectural Women's University
2 Hiroshima Institute of Technology
3 National Institute of Health and Nutrition
4 Kobe Design University
5 National Institute of Advanced Industrial Science and Technology
* To whom correspondence should be addressed. E-mail: fukuba{at}hirojo-u.ac.jp.
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Abstract |
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It has frequently been demonstrated that prior heavy cycling exercise facilitates pulmonary VO2 kinetics at the onset of subsequent heavy exercise. This might be due to improved muscle perfusion via acidosis-induced vasodilating effects. However, it is difficult to measure the blood flow (BF) to the working muscles (via the femoral artery) during cycling exercise. We, therefore, selected supine knee extension (KE) exercise as an alternative, and investigated whether the faster VO2 kinetics in the 2nd bout was matched by proportionally faster BF kinetics to the exercising muscle. Nine healthy subjects (aged 21-44 years) volunteered to participate in this study. The protocol consisted of two consecutive 6-min KE exercise bouts in a supine position (work rate: 70-75 % of peak power) separated by a 6-min baseline rest (EX1 to EX2). During the protocol, a pulsed Doppler ultrasound technique was utilized to continuously measure the BF in the right femoral artery. The protocol was repeated at least 6 times to characterize the precise kinetics. In agreement with previous studies using cycling exercise, the VO2 kinetics in the 2nd bout were facilitated compared with that in the 1st bout [mean±S.D. of the 'effective' time constant (<font face=symbol>t</font>): EX1: 68.6 ±15.9 vs. EX2: 58.0±14.4 s; phase II-<font face=symbol>t</font>: EX1: 48.7 ±9.0 vs. EX2: 41.2±13.3 s; and empirical index of the slow component (<font face=symbol>D</font>VO2(6-3)): EX1: 78±44 vs. EX2: 57±36 ml/min (P<0.05)]. However, no substantial difference was observed for the facilitation of the femoral artery BF response to the 1st and 2nd exercise bouts [i.e., the 'effective' <font face=symbol>t</font> of the femoral artery BF: EX1: 40.8±16.9 vs. EX2: 39.0±17.1 s (P>0.05)]. It was concluded that the faster pulmonary VO2 kinetics during heavy KE exercise following prior heavy exercise was not associated with a similar modulation in the BF to the working muscles.
Key Words:
Circulation, Exercise, Respiratory control
