The aim of the present study was to compare the frequency of oxygenation determined in the vastus lateralis by near-infrared spectroscopy (NIRS) in light exercise with that at rest. A subject rested in a recumbent position for 5 min and changed body position to a sitting position on a cycle ergometer for 9 min. Then exercise with low intensity (work rate of 60% of maximal oxygen uptake) was carried out for 30 min. Total hemoglobin and myoglobin (THb/Mb) suddenly decreased after the start of exercise and gradually increased until 6 min. Oxygenated hemoglobin and myoglobin (Hb/MbO2) suddenly decreased and returned to a steady state after the start of exercise. The difference between Hb/MbO2 and THb/Mb showed a sudden decrease and then a steady state. This difference was analyzed by fast Fourier transform. The peak frequencies of the power spectrum density (PSD) were 0.0169 + 0.0076 Hz at rest and 0.0117 + 0.0042 Hz in exercise. The peak frequency of PSD was significantly decreased in exercise. In exercise, the range of frequencies was expanded. It is concluded that there are oscillations at rest as well as in exercise and that the frequency of peak PSD becomes lower in exercise than at rest

The purpose of the present study was to examine how end tidal CO 2 pressure (PETCO 2 ) is controlled in impulse exercise. After pre-exercise at 25 watts for 5 min, impulse exercise for 10 sec with 200 watts followed by post exercise at 25 watts was performed.Ventilation (V ． E) significantly increased until the end of impulse exercise and significantly re-increased after a sudden decrease. Heart rate (HR) significantly increased until the end of impulse exercise and then decreased to the pre-exercise level.PETCO 2 remained constant during impulse exercise. PETCO 2 significantly increased momentarily after impulse exercise and then significantly decreased to the pre-exercise level. PETCO 2 showed oscillation. The average peak frequency of power spectral density in PETCO 2 appeared at 0.0078 Hz. Cross correlations were obtained after impulse exercise. The peak cross correlations between V ． E and PETCO 2 , HR and PETCO 2 , and V ． E and HR were 0.834 with a time delay of -7 sec, 0.813 with a time delay of 7 sec and 0.701 with a time delay of -15 sec, respectively. We demonstrated that PETCO 2 homeodynamics is interactively maintained by PETCO 2 itself, CO 2 transportation (product of cardiac output and mixed venous CO 2 content) into the lungs by heart pumping and CO 2 elimination by ventilation, and oscillates as a result of their interactions.

The purpose of the present study was to examine how oscillation of tissue oxygen index (TOI) in non-exercising exercise is affected during high-intensity and low-intensity exercises. Three exercises were performed with exercise intensities of 30% and 70% peak oxygen uptake (V o 2 peak) for 12 min and with exercise intensity of 70% V o 2 peak for 30 s. TOI in non-exercising muscle (biceps brachii) during the exercises for 12 min was determined by nearinfrared spectroscopy. TOI in the non-exercising muscle during the exercises was analyzed by fast Fourier transform (FFT) to obtain power spectra density (PSD). The frequency at which maximal PSD appeared (Fmax) during the exercise with 70% V o 2 peak for 12 min (0.00477 ± 0.00172 Hz) was significantly lower than that during the exercise with 30% V o 2 peak for 12 min (0.00781 ± 0.00338 Hz). There were significant differences in blood pH and blood lactate between the exercise with 70% V o 2 peak and the exercise with 30% V o 2 peak. It is concluded that TOI in nonexercising muscle oscillates during low-intensity exercise as well as during high-intensity exercise and that the difference in Fmax between the two exercises is associated with the difference in increase in blood lactate derived from the exercise.

The purpose of this study was to determine whether tissue oxygen indices (TOIs) in two muscle groups oscillated and were synchronized in repetition of impulse exercise with high intensity. Five impulse exercises of 400 watts for 10 s were repeated with intervals of 6 min. During this period, TOI was determined by near-infrared spectroscopy in the vastus lateralis and gastrocnemius muscles. TOIs in the two muscles oscillated at rest. The TOIs rapidly decreased during each impulse exercise and then recovered and overshot after each impulse. The TOIs oscillated during each interval period. During this test period, coherent and phase differences were determined. There was high coherence between TOIs in the two muscles with a peak value at 0.019 Hz. There was a phase difference of -45 ± 32.4 degrees between TOIs in the two muscles. This phase difference corresponded to about 6 s in time scale. It seemed from this time delay that impulse exercise was not a trigger factor for the starting point of TOIs in the two muscles. It has been concluded that TOIs oscillate and are synchronized between two muscles in repetition of impulse exercise with high intensity.Keywords: coherence, phase difference, tissue oxygen index, impulse exercise, oscillationIt is well known that glycolysis is a dissipative structure that shows oscillation in yeast (3). Richard (11) reported a review of chemical oscillation in yeast. In an anaerobic condition, a chemical substance in glycolysis oscillates by glucose continual input with an interval of about 10 min. By pulse input of glucose, NAD and NADH oscillate with a 37-sec interval, and their oscillations are gradually attenuated. Furthermore, when two yeast cell populations are mixed, the two oscillations are known to be synchronized. On the other hand, Satroutdinov et al. (12) described a different type of respiratory oscillation that is apparently not related to the cell. However, the cycle was around 40-50 min. Lloyd (6) has reported that there are three types of respiratory oscillation with periods of about one minute, about 40 min and one day. The time-keeping clock has been shown for oscillations of longer periods but not for oscillation of the shortest period in yeast. In humans, it has been reported that phosphocreatine (PCr) indicates damped oscillations during recovery from exercise (5) (that report is the first one to show a dissipative structure in which the order is self-organized in human skeletal muscle). This oscillation damps to resting level at 3-5 min during recovery. In visual inspection, the oscillation of PCr has

It was hypothesized that an oscillation of tissue oxygen index (TOI) determined by near-infrared spectroscopy during recovery from exercise occurs due to feedback control of adenosine triphosphate and that frequency of the oscillation is affected by blood pH. In order to examine these hypotheses, we aimed 1) to determine whether there is an oscillation of TOI during recovery from exercise and 2) to determine the effect of blood pH on frequency of the oscillation of TOI. Three exercises were performed with exercise intensities of 30 % and 70 % peak oxygen uptake (Vo2peak) for 12 min and with exercise intensity of 70 % Vo2peak for 30 s. TOI during recovery from the exercise was analyzed by fast Fourier transform in order to obtain power spectra density (PSD). There was a significant difference in the frequency at which maximal PSD of TOI appeared (Fmax) between the exercises with 70 % Vo2peak for 12 min (0.0039±0 Hz) and for 30 s (0.0061±0.0028 Hz). However, there was no significant difference in Fmax between the exercises with 30 % (0.0043±0.0013 Hz) and with 70 % Vo2peak for 12 min despite differences in blood pH and blood lactate from the warmed fingertips. It is concluded that there was an oscillation in TOI during recovery from the three exercises. It was not clearly shown that there was an effect of blood pH on Fmax.