It has been hypothesized that the signals of near infrared spectroscopy (NIRS) would reflect muscle O 2 uptake (mV̇O 2). Although it is not definite that NIRS signals accurately reflect mV̇O 2, there is every possibility that NIRS signals at least reflect regional O 2 uptake (rV̇O 2). The phase II kinetics of pulmonary oxygen uptake (pV̇O 2) is regarded as reflecting mV̇O 2 at the onset of exercise. To examine whether the rV̇O 2 on-kinetics measured by NIRS reflects the mV̇O 2 on-kinetics at the onset of exercise, we compared the rV̇O 2 as measured by NIRS with the phase II kinetics of pV̇O 2 at the onset of exercise. Twelve healthy male subjects cycled a Monark ergometer at three different intensities: below the ventilatory threshold (VT) level (below-VT), on the VT level (on-VT), and above the VT level (above-VT), for 6 minutes on three separate occasions. The rV̇O 2 was calculated from the concentration of oxyhemoglobin and deoxyhemoglobin, as measured by NIRS every 3 seconds. The pV̇O 2 was determined by the breath-by-breath method. A significant relationship between the amount of increases of pV̇O 2 and rV̇O 2 from rest to the end of exercise among all levels of exercise intensity was found (r=0.935, P<0.001). The time constants of rV̇O 2 (rV̇O 2-Tc: below-VT: 6.514±2.159s, on-VT: 7.760±2.035 s, above-VT: 9.532±2.342 s) were significantly faster than the time constants of pV̇O 2 (pV̇O 2-Tc: below-VT: 23.8±4.4 s, on-VT: 25.9±5.1 s, above-VT: 26.3±5.7 s) (P<0.001). There was no significant relationship between rV̇O 2-Tc and pV̇O 2-Tc for each intensity (P>0.05). We conclude that the rV̇O 2 on-kinetics measured by NIRS does not necessarily reflect the mV̇O 2 kinetics at the onset of exercise.
|Number of pages||6|
|Journal||Journal of physiological anthropology and applied human science|
|Publication status||Published - May 1 2003|
All Science Journal Classification (ASJC) codes
- Social Sciences(all)