| Autor: |
Yamaoka Endo, Masako, Kobayakawa, Mayumi, Kinugasa, Ryuta, Kuno, Shinya, Akima, Hiroshi, Rossiter, Harry B., Miura, Akira, Fukuba, Yoshiyuki |
| Předmět: |
|
| Zdroj: |
American Journal of Physiology: Regulatory, Integrative & Comparative Physiology; Aug2007, Vol. 293, pR812-R820, 9p, 3 Charts, 5 Graphs |
| Abstrakt: |
The mechanisms underlying the oxygen uptake (Vo2) slow component during supra-lactate threshold (supra-LT) exercise are poorly understood. Evidence suggests that the Vo2 slow component may be caused by progressive muscle recruitment during exercise. We therefore examined whether leg muscle activation patterns [from the transverse relaxation time (T2) of magnetic resonance images] were associated with supra-LT Vo2 kinetic parameters. Eleven subjects performed 6-min cycle ergometry at moderate (80% LT), heavy (70% between LT and critical power; CP), and very heavy (7% above CP) intensities with breath-by-breath pulmonary Vo2 measurement. T2 in 10 leg muscles was evaluated at rest and after 3 and 6 min of exercise. During moderate exercise, nine muscles achieved a steady-state T2 by 3 min; only in the vastus medialis did T2 increase further after 6 min. During heavy exercise, T2 in the entire vastus group increased between minutes 3 and 6, and additional increases in T2 were seen in adductor magnus and gracilis during this period of very heavy exercise. The Vo2 slow component increased with increasing exercise intensity (being functionally zero during moderate exercise). The distribution of T2 was more diverse as supra-LT exercise progressed: T2 variance (ms) increased from 3.6 ± 0.2 to 6.5 ± 1.7 between 3 and 6 min of heavy exercise and from 5.5 ± 0.8 to 12.3 ± 5.4 in very heavy exercise (rest = 3.1 ± 0.6). The 12 distribution was significantly correlated with the magnitude of the Vo2 slow component (P < 0.05). These data are consistent with the notion that the Vo2 slow component is an expression of progressive muscle recruitment during supra-LT exercise. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
|
