Hiroshi Matsuo

Intermittent Hypoxia Improves Endurance Performance and Submaximal Exercise Efficiency

The purpose of the present study was to elucidate the influence of intermittent hypobaric hypoxia at rest on endurance performance and cardiorespiratory and hematological adaptations in trained endurance athletes. Twelve trained male endurance runners were assigned to either a hypoxic group (n = 6) or a control group (n = 6). The subjects in the hypoxic group were exposed to a simulated altitude of 4500 m for 90 min, three times a week for 3 weeks. The measurements of 3000 m running time, running time to exhaustion, and cardiorespiratory parameters during maximal exercise test and resting hematological status were performed before (Pre) and after 3 weeks of intermittent hypoxic exposure (Post). These measurements were repeated after the cessation of intermittent hypoxia for 3 weeks (Re). In the control group, the same parameters were determined at Pre, Post, and Re for the subjects not exposed to intermittent hypoxia. The athletes in both groups continued their normal training together at sea level throughout the experiment. In the hypoxic group, the 3000 m running time and running time to exhaustion during maximal exercise test improved. Neither cardiorespiratory parameters to maximal exercise nor resting hematological parameters were changed in either group at Post, whereas oxygen uptake (.V(O2)) during submaximal exercise decreased significantly in the hypoxic group. After cessation of intermittent hypoxia for 3 weeks, the improved 3000 m running time and running time to exhaustion tended to decline, and the decreased .V(O2) during submaximal exercise returned to Pre level. These results suggest that intermittent hypoxia at rest could improve endurance performance and submaximal exercise efficiency at sea level in trained endurance athletes, but these improvements are not maintained after the cessation of intermittent hypoxia for 3 weeks.

Effect of intermittent hypoxia on oxygen uptake during submaximal exercise in endurance athletes

The purpose of the present study was to clarify the following: (1) whether steady state oxygen uptake (V̇O2) during exercise decreases after short-term intermittent hypoxia during a resting state in trained athletes and (2) whether the change in V̇O2 during submaximal exercise is correlated to the change in endurance performance after intermittent hypoxia. Fifteen trained male endurance runners volunteered to participate in this study. Each subject was assigned to either a hypoxic group (n=8) or a control group (n=7). The hypoxic group spent 3xa0h per day for 14 consecutive days in normobaric hypoxia [12.3 (0.2)% inspired oxygen]. The maximal and submaximal exercise tests, a 3,000-m time trial, and resting hematology assessments at sea level were conducted before and after intermittent normobaric hypoxia. The athletes in both groups continued their normal training in normoxia throughout the experiment. V̇O2 during submaximal exercise in the hypoxic group decreased significantly (P<0.05) following intermittent hypoxia. In the hypoxic group, the 3,000-m running time tended to improve (P=0.06) after intermittent hypoxia, but not in the control group. Neither peak V̇O2 nor resting hematological parameters were changed in either group. There were significant (P<0.05) relationships between the change in the 3,000-m running time and the change in V̇O2 during submaximal exercise after intermittent hypoxia. The results from the present study suggest that the enhanced running economy resulting from intermittent hypoxia could, in part, contribute to improved endurance performance in trained athletes.

An intercomparison of measurement techniques for the determination of the dielectric properties of solids at near millimetre wavelengths

The results of a measurement intercomparison aimed at assessing the systematic errors in near-millimetre-wavelength dielectric measurements on reasonably transparent solid specimens are presented and discussed. Various monochromatic, broad band, guided wave and free space measurement methods were intercompared in the frequency region from 30 to 900 GHz using round-robin measurements of the refractive index and absorption coefficient of seven specimens. Typically, systematic errors of up to 1% were found in the refractive index results, while very much larger systematic errors were found in the absorption results. >

Ventilatory and circulatory responses at the onset of voluntary exercise and passive movement in sprinters

The purpose of this study was to clarify the characteristics of ventilatory and circulatory responses at the onset of voluntary exercise and passive movement in sprinters. Eleven male university sprinters and 11 male untrained subjects participated in the present study. Voluntary exercise consisted of leg extension–flexion movement for 20xa0s with weights corresponding to 5% of each subject’s body mass attached to each ankle. Passive movement was achieved without weights by the experimenter alternately pulling ropes that were connected to the subject’s ankles for the same period and frequency as during voluntary exercise. In the present study, the following results were found: (1) the magnitude of relative changes (gain) of minute ventilation at the onset of passive movement in the sprinters was significantly smaller than that in the untrained subjects [mean (SEM) 33.3 (2.9) vs 61.7 (6.4)%, P<0.05]; (2) the time for reaching one-half of the gain (response time) of heart rate at the onset of voluntary exercise and passive movement in the sprinters was significantly slower than that in the untrained subjects [2.5 (0.2) vs 1.7 (0.2)xa0s in voluntary exercise and 3.4 (0.8) vs 1.5 (0.1)xa0s in passive movement, P<0.05]; (3) the gain and response time of mean blood pressure at the onset of voluntary exercise and passive movement showed no significant differences between the two groups. It is concluded that sprinters show slowed heart rate response at the onset of voluntary exercise, and attenuated ventilatory and slowed heart rate responses at the onset of passive movement as compared with untrained subjects.

Changes in ventilatory responses to hypercapnia and hypoxia after intermittent hypoxia in humans

The purpose of this study was to clarify the changes in hypercapnic and hypoxic ventilatory responses (HCVR and HVR) after intermittent hypoxia and following the cessation of hypoxic exposure. Twenty-nine males were assigned to one of four groups, i.e., a hypoxic (EX1-H, n=7) or a control (EX1-C, n=7) group in Experiment 1, and a hypoxic (EX2-H, n=8) or a control (EX2-C, n=7) group in Experiment 2. In each experiment, the hypoxic tent system was utilized for intermittent hypoxia, and the oxygen levels in the tent were maintained at 12.3+/-0.2%. In Experiment 1, the EX1-H group spent 3 h/day in the hypoxic tent for 1 week. HCVR and HVR were determined before and after 1 week of intermittent hypoxia, and again 1 and 2 week after the cessation of hypoxic exposure. In Experiment 2, the subjects in the EX2-H group performed 3 h/day for 2 weeks in intermittent hypoxia. HCVR and HVR tests were carried out before and after intermittent hypoxia, and were repeated again after 2 weeks of the cessation of hypoxic exposure. The slope of the HCVR in the EX1-H group did not show a significant increase after 1 week of intermittent hypoxia, while HCVR in the EX2-H group increased significantly after 2 weeks of intermittent hypoxia. The HCVR intercept was unchanged following 1 or 2 weeks of intermittent hypoxia. There was a significant increase in the slope of the HVR after 1 and 2 weeks of intermittent hypoxia. The increased HCVR and HVR returned to pre-hypoxic levels after 2 weeks of the cessation of hypoxia. These results suggest that 3 h/day for 2 weeks of intermittent hypoxia leads to an increase in central hypercapnic ventilatory chemosensitivity, which is not accompanied by a re-setting of the central chemoreceptors, and that the increased hypercapnic and hypoxic chemosensitivities are restored within 2 weeks after the cessation of hypoxia.

Effect of menstrual cycle and gender on ventilatory and heart rate responses at the onset of exercise

To clarify the luteal-follicular and male–female differences in ventilatory and heart rate responses at the onset of exercise, seven women and seven men performed voluntary exercise and passive movement for 20xa0s (brief voluntary exercise and brief passive movement) and voluntary exercise for 3xa0min (long voluntary exercise) in a sitting position. Voluntary exercise consisted of alternate flexion-extensions of both lower legs with a weight corresponding to about 2.5% of the subjects body mass attached to each ankle, at a frequency of about 60xa0times min−1. Passive movement was carried out without weights by experimenters pulling ropes attached to both of the subjects ankles, in the same way as voluntary exercise. During these exercises and movements, minute inspiratory ventilation (V̇I) and heart rate (HR) were continuously measured by breath-by-breath and beat-to-beat techniques. We calculated relative changes of V̇I and HR (ΔV̇I and ΔHR). Additionally, we averaged ΔV̇I and ΔHR obtained during the exercise and movement for each subject, and performed a correlation analysis between the averaged ΔV̇I and ΔHR. It was clarified that: (1) ΔV̇I and ΔHR in the follicular phase were almost equal to those in the luteal phase; (2) there were no significant male–female differences in these parameters; (3) significant positive correlations were found in both genders only during brief voluntary exercise. We conclude that ventilatory and HR responses at the onset of voluntary exercise and passive movement are not affected by the menstrual cycle or gender.

Seven matched bolometers for millimeter wave observations

We have fabricated a millimeter wave observation system using an array of bolometric detectors. The performance of the system depends largely on obtaining identical performance from each bolometer. We achieved a variance in the responsivity of less than 4% except for one of the seven elements. The bolometers had an electrical NEP of 1.3×10−16 W/√Hz under radiation background loading of 30pW. We used an AC bridge readout circuit to significantly improve the stability of the array and showed that observations can be done without a mechanical beam switch. The bolometer array is now in use on the Nobeyama 45-m telescope for 150GHz observations.

Rocket-borne submillimeter radiometer.

We report the performance of a rocket-borne absolute radiometer which was designed to measure the diffuse brightness of the sky in six passbands between 100 microm and 1 mm. The radiometer consisted of a horn antenna and a photometer, both of which were cooled to 1.2 K by liquid (4)He. The performance of the instrument was satisfactory, but no astrophysical data were obtained during the flight because a lid covering the horn antenna failed to pen. Another flight of a similar apparatus is planned for 1986.

Calibration Source for Electron Cyclotron Emission Measurements

A high-temperature radiation source has been developed for the absolute calibration of diagnostic instruments for measuring electron cyclotron emission from high-temperature plasmas. The source has a radiation area of 150 mm and can be heated up to 500°C. The measured emissivity of the source is close to unity in the spectral region between 200 and 500 GHz. The grating polychromator has been calibrated using the radiation source developed. The obtained temperatures agree with those by the pulse height analysis of soft X-rays and Thomson scattering measurement within 10%.

Submillimeter-wave telescope onboard a sounding rocket

We have made a submillimeter-wave telescope for a Japanese sounding rocket, S- 520-17, which is dedicated for an observation of cold dust in Orion molecular cloud region. The system is now under test for launch in Jan. 1995. The telescope include an off-axis Gregorian telescope with aperture of 30 cm, focal plane bolometer array, cryogenic cooling system down to 0.3 K, and a star sensor using charge modulation device. A very low emissivity optical arrangement of less than 1% is achieved using pure aluminum mirror, off axis reflector and cold optics. Single moded conical feed horn is effectively coupled with bolometers with efficiency of more than 90%. The focal plane array consists of 12-element bolometers, six for 250 micrometers observation and six for 500 micrometers observation. NEPs of the bolometers are 5 X 10-17W/√Hz which is read out by AC bridge read-out circuit. Total system gives sensitivities of about 10-12W/cm2 X sr for diffuse objects or 2 Jy for compact objects at 500 micrometers over 100 deg2 region with a beam sizes of 10 arcmin. This observation gives unique data on cold dust distribution, which is believed to dominate the dust mass distribution, over Orion Molecular Cloud region.