Authors:T. Yano, T. Yunoki, R. Matsuura, T. Arimitsu and T. Kimura
The purpose of the present study was to examine the effect of change in blood volume in skin plus active muscle on heart rate drift during moderate exercise and heavy exercise for 30 min. Total hemoglobin concentration (Total Hb) in the vastus lateralis muscle plus its skin was determined by near-infrared spectroscopy. Total Hb significantly increased and remained stable from 20 min in moderate exercise and from 10 min in heavy exercise. Heart rate (HR) rapidly increased until 3 min and showed a steady state in moderate exercise. HR at 30 min was significantly higher than that at 3 min in moderate exercise. HR rapidly increased until 3 min and then gradually but significantly increased in heavy exercise. Increase in total Hb was not significantly related with HR after 3 min of exercise when HR was around 120 beats per min in moderate exercise. Increase in total Hb was significantly related with HR from 3 min to 10 min in the heavy exercise (correlation coefficients ranged from 0.959 to 0.702). It is concluded that an increase in the blood volume in skin plus active muscle is not simply associated with HR drift.
Authors:R. Matsuura, T. Arimitsu, T. Yunoki, T. Kimura, R. Yamanaka and T. Yano
The purpose of the present study was to determine the effects of deception for exercise intensity on surface electromyogram (SEMG) activity and blood lactate concentration during intermittent cycling exercise (ICE) tests. Sixteen healthy male were randomly assigned to two groups who completed two ICE [three 4-min cycling at 80% peak power output (PPO) with 3-min passive recovery periods followed by exhaustive cycling] tests (ICE-1 and ICE-2). The experimental group (ICED) was deceived of the actual cycling intensity, while the control group (ICEC) was informed of the actual protocol in ICE-2. In ICE-1, both groups were informed of the actual protocol. In ICE-2, root mean square (RMS) calculated from SEMG during submaximal cycling was significantly higher in the ICEC than in the ICED and blood lactate concentration ([La−]) was significantly higher in the ICEC than in the ICED. In particular, the difference in RMS between the groups was also observed during the first 4-min cycling, in which there was no difference in [La−] between the groups. These results suggest that the CNS modulates skeletal muscle recruitment due to the prior deception for exercise intensity.
Authors:T. Yano, R. Afroundeh, R. Yamanaka, T. Arimitsu, C.S. Lian, K. Shirakawa and T. Yunoki
The purpose of the present study was to examine 1) whether O2 uptake (V̇O2) oscillates during light exercise and 2) whether the oscillation is enhanced after impulse exercise. After resting for 1 min on a bicycle seat, subjects performed 5-min pre-exercise with 25 watts work load, 10-s impulse exercise with 200 watts work load and 15-min post exercise with 25 watts work load at 80 rpm. V̇O2 during pre-exercise significantly increased during impulse exercise and suddenly decreased and re-increased until 23 s after impulse exercise. In the cross correlation between heart rate (HR) and V̇O2 after impulse exercise, V̇O2 strongly correlated to HR with a time delay of −4 s. Peak of power spectral density (PSD) in HR appeared at 0.0039 Hz and peak of PSD in V̇O2 appeared at 0.019 Hz. The peak of the cross power spectrum between V̇O2 and HR appeared at 0.0078 Hz. The results suggested that there is an oscillation in O2 uptake during light exercise that is associated with the oscillation in O2 consumption in active muscle. The oscillation is enhanced not only by change in O2 consumption but also by O2 content transported from active muscle to the lungs.
Authors:T. Yano, C. Lian, T. Arimitsu, R. Yamanaka, R. Afroundeh, K. Shirakawa and T. Yunoki
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 for 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.
Authors:T. Yano, R. Afroundeh, R. Yamanak, T. Arimitsu, C. Lian, K. Shirkawa and T. Yunoki
The purpose of the present study was to examine how end tidal CO2 pressure (PETCO2) 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 (V̇E) 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. PETCO2 remained constant during impulse exercise. PETCO2 significantly increased momentarily after impulse exercise and then significantly decreased to the pre-exercise level. PETCO2 showed oscillation. The average peak frequency of power spectral density in PETCO2 appeared at 0.0078 Hz. Cross correlations were obtained after impulse exercise. The peak cross correlations between V̇E and PETCO2, HR and PETCO2, and V̇E 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 PETCO2 homeodynamics was interactively maintained by PETCO2 itself, CO2 transportation (product of cardiac output and mixed venous CO2 content) into the lungs by heart pumping and CO2 elimination by ventilation, and it oscillates as a result of their interactions.
Authors:E. Yunoki, T. Kataoka, K. Michihiro, H. Sugiyama, M. Shimizu and T. Mori
The distribution of226Ra and238U in various soils has been studied. Supposing that radioactive equilibrium were in existence, the average activities of226Ra and238U would show a nearly 11 correlation. As weathering affects radioactive equilibrium in surface soil, radioactive equilibrium was not in existence. Therefore, four kinds of soil were selected from different weathering conditions, viz. river bed soil, paddy field soil, field soil and uncropped soil. The226Ra/238U ratio of various soils lies in the range of 1.63 to 2.41. The activity concentrations of226Ra were greater than238U in various soils. The ratio226Ra/238U can be shown to be a quantitative index of weathering. Phosphatic manure contains238U and its daughter isotopes in concentrations far exceeding the average abundance in the earth's crust. But the cultivated soils (paddy field soil, field soil) are not affected by fertilizers in Kamisaibara.
Authors:E. Yunoki, T. Kataoka, K. Michihiro, H. Sugiyama, M. Shimizu and T. Mori
The238U and226Ra contents of small-volume aerosols are determined by a chemical analysis technique. Mean activity concentrations of238U and226Ra in aerosols over approximately ten years are 0.29·10–5 and 0.93·10–5 Bq/m3, respectively. The yearly variation of238U and226Ra in aerosols is small. The concentrations of226Ra are always larger than those of238U in the same sampling time. The correlation of238U and226Ra cannot be recogonized (r=0.18). The concentrations of summer samples are greater than those of winter samples for238U. One of the causes of seasonal difference may be due to the fact that the components of aerosols are different according to soil size, soil components, weathering states, etc.
Authors:E. Yunoki, T. Kataoka, K. Michiro, H. Sugiyama, M. Shimizu and T. Mori
Distributions of238U and226Ra in agricultural samples and cultivated soils have been studied over ten years. The crops are rice, spinach and Chinese cabbage. Two investigated areas have been selected (35° 18 N, 113° 35 E). The agricultural samples and soils were collected annually from May 1982 through October 1991. The activity concentrations of226Ra in agricultural samples are greater than those of238U. The transfer factors of238U,226Ra are from 0.06·10–3 to 1.2·10–3. The226Ra/238U ratios for three agricultural samples have their characteristic values.
Authors:T Yano, W Widjaja, K Shirakawa, C-S Lian, Z Xiao and T Yunoki
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.
Authors:T Yano, R Afroundeh, K Shirakawa, C-S Lian, K Shibata, Z Xiao and T Yunoki
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 (Vo2peak) for 12 min and with exercise intensity of 70% Vo2peak 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% Vo2peak for 12 min (0.00477 ± 0.00172 Hz) was significantly lower than that during the exercise with 30% Vo2peak for 12 min (0.00781 ± 0.00338 Hz). There were significant differences in blood pH and blood lactate between the exercise with 70% Vo2peak and the exercise with 30% Vo2peak. 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.