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Enhanced chemosensitivity after intermittent hypoxic exposure does not affect exercise ventilation at sea level. 査読有り

Katayama, K., Y. Sato, N. Shima, J. Qiu, K. Ishida, S. Mori, and M. Miyamura.

Eur. J. Appl. Physiol 87 巻頁： 187-191 2002年

記述言語：英語掲載種別：研究論文（学術雑誌）

The purpose of the present study was to test the hypothesis that the ventilatory response to exercise at sea level may increase after intermittent hypoxic exposure for 1 week, accompanied by an increase in hypoxic or hypercapnic ventilatory chemosensitivity. One group of eight subjects (hypoxic group) were decompressed in a chamber to 432 torr (where 1 torr=1.0 mmHg, simulating an altitude of 4,500 m) over a period of 30 min and maintained at that pressure for 1 h daily for 7 days. Oxygen uptake and pulmonary ventilation (V(E)) were determined at 40%, 70%, and 100% of maximal oxygen uptake at sea level before (Pre) and after (Post) 1 week of daily exposures to hypoxia. The hypoxic ventilatory response (HVR) was determined using the isocapnic progressive hypoxic method as an index of ventilatory chemosensitivity to hypoxia, and the hypercapnic ventilatory response (HCVRSB) was measured by means of the single-breath carbon dioxide method as an index of peripheral ventilatory chemosensitivity to hypercapnia. The same parameters were measured in another group of six subjects (control group). In the hypoxic group, resting HVR increased significantly ( P<0.05) after intermittent hypoxia and HCVRSB increased at Post, but the change was not statistically significant ( P=0.07). In contrast, no changes in HVR and HCVRSB were found in the control group. There were no changes in either V(E) or the ventilatory equivalent for oxygen during maximal and submaximal exercise at sea level throughout the experimental period in either group. These results suggest that the changes in resting hypoxic and peripheral hypercapnic chemosensitivities following short-term intermittent hypoxia have little effect on exercise ventilation at sea level.

DOI： 10.1007/s00421-002-0594-4

Effect of intermittent hypoxia on cardiovascular adaptations and response to progressive hypoxia in humans. 査読有り

Katayama, K., N. Shima, Y. Sato, J. Qiu, K. Ishida, S. Mori, and M. Miyamura.

High Alt. Med. Biol. 2 巻頁： 501-508 2001年

記述言語：英語掲載種別：研究論文（学術雑誌）

The aim of the present study was to elucidate (1) the cardiovascular adaptations and response to hypoxic stimuli during short-term intermittent hypoxia and (2) whether the change in cardiovascular response to hypoxia is correlated to the change in hypoxic ventilatory chemosensitivity. Fourteen subjects were decompressed in a chamber to 432 torr, simulating an altitude of 4500 m, over a period of 30 min and were maintained at that pressure for 1 h daily for 7 days. Ventilatory (DeltaV(I)/DeltaSa(O2); Sa(O2) is arterial oxygen saturation), systolic and diastolic blood pressure (DeltaSBP/DeltaSa(O2) and DeltaDBP/DeltaSa(O2)), and heart rate (DeltaHR/DeltaSa(O2)) responses to progressive isocapnic hypoxia were measured before and after intermittent hypoxia. Resting ventilation, SBP, DBP, and HR did not change after intermittent hypoxia. DeltaSBP/DeltaSa(O2) and DeltaDBP/DeltaSa(O2) increased significantly after intermittent hypoxia accompanied by an enhanced DeltaV(I)/DeltaSa(C2), but there was no change in DeltaHR/DeltaSa(C2). There were significant correlations between the change in DeltaV(I)/DeltaSa(O2) and both the changes in DeltaSBP/DeltaSa(O2) and DeltaDBP/DeltaSa(O2) following intermittent hypoxic exposure. These results suggest that short-term intermittent hypoxia leads to the enhanced arterial BP response to hypoxic stimuli in humans, and that the enhanced peripheral chemosensitivity to hypoxia after intermittent hypoxia may play an important role in the increased arterial BP response.

DOI： 10.1089/152702901753397063

Intermittent hypoxia increases ventilation and SaO2 during hypoxic exercise and hypoxic chemosensitivity. 査読有り

Katayama, K., Y. Sato, Y. Morotome, N. Shima, K. Ishida, S. Mori, and M. Miyamura.

J. Appl. Physiol. 90 巻頁： 1431-1440 2001年

記述言語：英語掲載種別：研究論文（学術雑誌）

The purpose of this study was 1) to test the hypothesis that ventilation and arterial oxygen saturation (Sa(O2)) during acute hypoxia may increase during intermittent hypoxia and remain elevated for a week without hypoxic exposure and 2) to clarify whether the changes in ventilation and Sa(O2) during hypoxic exercise are correlated with the change in hypoxic chemosensitivity. Six subjects were exposed to a simulated altitude of 4,500 m altitude for 7 days (1 h/day). Oxygen uptake (VO2), expired minute ventilation (VE), and Sa(O2) were measured during maximal and submaximal exercise at 432 Torr before (Pre), after intermittent hypoxia (Post), and again after a week at sea level (De). Hypoxic ventilatory response (HVR) was also determined. At both Post and De, significant increases from Pre were found in HVR at rest and in ventilatory equivalent for O2 (VE/VO2) and Sa(O2) during submaximal exercise. There were significant correlations among the changes in HVR at rest and in VE/VO2 and Sa(O2) during hypoxic exercise during intermittent hypoxia. We conclude that 1 wk of daily exposure to 1 h of hypoxia significantly improved oxygenation in exercise during subsequent acute hypoxic exposures up to 1 wk after the conditioning, presumably caused by the enhanced hypoxic ventilatory chemosensitivity.

DOI： 10.1152/jappl.2001.90.4.1431

Ventilatory and circulatory responses at the onset of voluntary exercise and passive movement in children 査読有り

Y Sato, K Katayama, K Ishida, M Miyamura

EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY 83 巻 ( 6 ) 頁： 516 - 523 2000年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SPRINGER-VERLAG

The purpose of this study was to investigate whether or not the ventilatory and circulatory responses at the onset of voluntary exercise and passive movement, especially at the initial stage (phase I), in children are the same as in adults. Ten pre-teenage male children and ten adult men participated in this study. Voluntary exercise and passive movement were performed in a sitting position for about 20 s. Both the exercise and the movement consisted of flexion-extensions of the lower leg from a vertical to horizontal position, either voluntarily or passively, with a frequency of about 60.min(-1). Inspiratory minute ventilation ((V) over dot(I)), tidal volume (V-T), respiratory frequency, partial pressure of end-tidal CO2 and O-2, heart rate (f(c)) and mean blood pressure ((BP) over bar) before, during and after exercise or movement were measured using breath-by-breath and beat-to-beat techniques. Cardiorespiratory responses at the onset of voluntary exercise and passive movement were compared with the relative change (Delta), which was estimated from the value at rest (100%). In the present study, it was found that: (1) the V-I during voluntary exercise were significantly lower in the children, mainly due to lower DeltaV(T); (2) the Deltaf(c) during voluntary exercise was almost the same in both groups, while Deltaf(c) was significantly lower in the children during the last part of passive movement; (3) in the voluntary exercise and passive movement, the (BP) over bar in the children was increased a little or remained close to the value at rest, while it was significantly decreased in the adults. As a result, there were significant differences in Delta(BP) over bar between the two groups during voluntary exercise. These results suggest that the cardiorespiratory responses at the onset of voluntary exercise and passive movement may be modified during the growth process.

DOI： 10.1007/s004210000290

Web of Science

Cardiovascular response to hypoxia after endurance training at altitude and sea level and after detraining 査読有り

K Katayama, Y Sato, Y Morotome, N Shima, K Ishida, S Mori, M Miyamura

JOURNAL OF APPLIED PHYSIOLOGY 88 巻 ( 4 ) 頁： 1221 - 1227 2000年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSIOLOGICAL SOC

The pur pose of this study was to elucidate 1) the effects of endurance exercise training during hypoxia or normoxia and of detraining on ventilatory and cardiovascular responses to progressive isocapnic hypoxia and 2) whether the change in the cardiovascular response to hypoxia is correlated to changes in the hypoxic ventilatory response (HVR) after training and detraining. Seven men (altitude group) performed endurance training using a cycle ergometer in a hypobaric chamber of simulated 4,500 m, whereas the other seven men (sea-level group) trained at sea level (K. Katayama, Y. Sate, Y. Morotome, N. Shima, K. Ishida, S. Mori, and M. Miyamura. J. Appl. Physiol. 86: 1805-1811, 1999). The HVR, systolic and diastolic blood pressure responses (Delta SBP/Delta Sa(O2), Delta DBP/Delta Sa(O2)), and heart rate response (Delta HR/Delta Sa(O2) Sa(O2) is arterial oxygen saturation) to progressive isocapnic hypoxia were measured before and after training and during detraining. Delta SBP/Delta Sa(O2) increased significantly in the altitude group and decreased significantly in the sea-level group after training. The changed Delta SBP/Delta Sa(O2) in both groups was restored during 2 wk of detraining, as were the changes in HVR, whereas there were no changes in the Delta DBP/Delta Sa(O2) and Delta HR/Delta Sa(O2) throughout the experimental period. The changes in Delta SBP/Delta Sa(O2)? after training and detraining were significantly correlated with those in HVR. These results suggest that Delta SBP/Delta Sa(O2), to progressive isocapnic hypoxia is variable after endurance training during hypoxia and normoxia and after detraining, as is HVR, but Delta DBP/Delta Sa(O2) and Delta HR/Sa(O2) are not. It also suggests that there is an interaction between the changes in Delta SBP/Delta Sa(O2) and HVR after endurance training or detraining.

DOI： 10.1152/jappl.2000.88.4.1221

Web of Science

Cardiovascular response to isocapnic hypoxia after endurance training at altitude, sea level, and detraining. 査読有り

Katayama, K., Y. Sato, Y. Morotome, N. Shima, K. Ishida, S. Mori, and M. Miyamura

J. Appl. Physiol. 88 巻頁： 1221-1227 2000年

記述言語：英語掲載種別：研究論文（学術雑誌）

The purpose of this study was to elucidate 1) the effects of endurance exercise training during hypoxia or normoxia and of detraining on ventilatory and cardiovascular responses to progressive isocapnic hypoxia and 2) whether the change in the cardiovascular response to hypoxia is correlated to changes in the hypoxic ventilatory response (HVR) after training and detraining. Seven men (altitude group) performed endurance training using a cycle ergometer in a hypobaric chamber of simulated 4,500 m, whereas the other seven men (sea-level group) trained at sea level (K. Katayama, Y. Sato, Y. Morotome, N. Shima, K. Ishida, S. Mori, and M. Miyamura. J. Appl. Physiol. 86: 1805-1811, 1999). The HVR, systolic and diastolic blood pressure responses (DeltaSBP/DeltaSa(O(2)), DeltaDBP/DeltaSa(O(2))), and heart rate response (DeltaHR/DeltaSa(O(2)); Sa(O(2)) is arterial oxygen saturation) to progressive isocapnic hypoxia were measured before and after training and during detraining. DeltaSBP/DeltaSa(O(2)) increased significantly in the altitude group and decreased significantly in the sea-level group after training. The changed DeltaSBP/DeltaSa(O(2)) in both groups was restored during 2 wk of detraining, as were the changes in HVR, whereas there were no changes in the DeltaDBP/DeltaSa(O(2)) and DeltaHR/DeltaSa(O(2)) throughout the experimental period. The changes in DeltaSBP/DeltaSa(O(2)) after training and detraining were significantly correlated with those in HVR. These results suggest that DeltaSBP/DeltaSa(O(2)) to progressive isocapnic hypoxia is variable after endurance training during hypoxia and normoxia and after detraining, as is HVR, but DeltaDBP/DeltaSa(O(2)) and DeltaHR/DeltaSa(O(2)) are not. It also suggests that there is an interaction between the changes in DeltaSBP/DeltaSa(O(2)) and HVR after endurance training or detraining.

Ventilatory chemosensitive adaptations to intermittent hypoxic exposure with endurance training and detraining 査読有り

K Katayama, Y Sato, Y Morotome, N Shima, K Ishida, S Mori, M Miyamura

JOURNAL OF APPLIED PHYSIOLOGY 86 巻 ( 6 ) 頁： 1805 - 1811 1999年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSIOLOGICAL SOC

The present study was performed to clarify the effects of intermittent exposure to an altitude of 4,500 m with endurance training and detraining on ventilatory chemosensitivity. Seven subjects (sea-level group) trained at sea level at 70% maximal oxygen uptake ((V) over doto(2max)) for 30 min/day, 5 days/wk for 2 wk, whereas the other seven subjects (altitude group) trained at the same relative intensity (70% altitude (V) over doto(2max)) in a hypobaric chamber. (V) over doto(2max) hypoxic ventilatory response (HVR), and hypercapnic ventilatory response, as an index of central hypercapnic chemosensitivity (HCVR) and as an index of peripheral chemosensitivity (HCVRSB), were measured. In both groups (V) over doto(2max) increased significantly after training, and a significant loss of (V) over doto(2max) occurred during 2 wk of detraining. HVR tended to increase in the altitude group but not significantly, whereas it decreased significantly in the sea-level group after training. HCVR and HCVRSB did not change in each group. After detraining, HVR returned to the pretraining level in both groups. These results suggest that ventilatory chemosensitivity to hypoxia is more variable by endurance training and detraining than that to hypercapnia.

DOI： 10.1152/jappl.1999.86.6.1805

Web of Science

Ventilatory chemosensitive adaptations to intermittent hypoxic exposure with endurance training and detraining. 査読有り

Katayama, K., Y. Sato, Y. Morotome, N. Shima, K. Ishida, S. Mori, and M. Miyamura.

J. Appl. Physiol 86 巻頁： 1805-1811 1999年

記述言語：英語掲載種別：研究論文（学術雑誌）

The present study was performed to clarify the effects of intermittent exposure to an altitude of 4,500 m with endurance training and detraining on ventilatory chemosensitivity. Seven subjects (sea-level group) trained at sea level at 70% maximal oxygen uptake (VO2 max) for 30 min/day, 5 days/wk for 2 wk, whereas the other seven subjects (altitude group) trained at the same relative intensity (70% altitude VO2 max) in a hypobaric chamber. VO2 max, hypoxic ventilatory response (HVR), and hypercapnic ventilatory response, as an index of central hypercapnic chemosensitivity (HCVR) and as an index of peripheral chemosensitivity (HCVRSB), were measured. In both groups VO2 max increased significantly after training, and a significant loss of VO2 max occurred during 2 wk of detraining. HVR tended to increase in the altitude group but not significantly, whereas it decreased significantly in the sea-level group after training. HCVR and HCVRSB did not change in each group. After detraining, HVR returned to the pretraining level in both groups. These results suggest that ventilatory chemosensitivity to hypoxia is more variable by endurance training and detraining than that to hypercapnia.

DOI： 10.1152/jappl.1999.86.6.1805

Effects of maximal interval training on arterial oxygen desaturation and ventilation during heavy exercise Open Access

Motohiko Miyachi, Keisho Katayama

Japanese Journal of Physiology 49 巻 ( 5 ) 頁： 401 - 407 1999年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：The Physiological Society of Japan

The purpose of the present study was to clarify longitudinally the effects of exercise training on arterial O2 saturation (Sa(O)2) and ventilation during heavy exercise. A group of six subjects (training group) volunteered to train four times a week for 12 weeks. Each training session consisted of five 3-min periods of exercise on a cycle ergometer at a power output of 100% maximal O2 uptake (V̇O(2 max)), interspersed with 2 min recovery period cycling at 50% V̇O(2 max). During the training, V̇O(2 max), Sa(O)2, the ventilatory equivalent for oxygen (V̇E/V̇O2), and the end- tidal partial pressure of O2 (PET(O)2) during heavy exercise were measured periodically. The same parameters were measured simultaneously in another group of five subjects (control group) who led normal lives. Maximal interval training increases V̇O(2 max), with little change in V̇E(max) and pulmonary functions at rest. The training decreased PET(O)2, V̇E/V̇O2, and Sa(O)2 during heavy exercise. Sa(O)2 is significantly related to V̇E/V̇O2 (r2 = 0.49). These results suggest that less hyperventilatory response to exercise occurs with progress in physical training because the adaptability of ventilatory capacity is less than that of aerobic work capacity, which half induces arterial O2 desaturation during heavy exercise. PET(O)2 as well as V̇E/V̇O2 and V̇O(2 max) did not change anymore after the 6th week, nevertheless Sa(O)2 kept decreasing up to the last 2 weeks. In addition, when the Sa(O)2-V̇E/V̇O2 plot was compared between the two groups, the regression line of the training group was steeper than that of the control groups
i.e., compared at a lower level of V̇E/V̇O2 (~30 ml · ml-1), the Sa(O)2 of the trained subjects exercising at a higher V̇O2 level was lower than that of the control subjects. Predominance of less hyperventilation and another factor, increased A-aDO2, in the genesis of arterial hypoxemia and O2 desaturation may be dependent upon V̇O2 levels in heavy exercise and the state of training.

DOI： 10.2170/jjphysiol.49.401

Scopus

PubMed

The effects of intermittent exposure to hypoxia during endurance exercise training on the ventilatory responses to hypoxia and hypercapnia in humans 査読有り

Keisho Katayama, Yasutake Sato, Koji Ishida, Shigeo Mori, Miharu Miyamura

European Journal of Applied Physiology and Occupational Physiology 78 巻 ( 3 ) 頁： 189 - 194 1998年8月

記述言語：英語掲載種別：研究論文（学術雑誌）

The present study was performed to investigate the effects of a combination of intermittent exposure to hypoxia during exercise training for short periods on ventilatory responses to hypoxia and hypercapnia (HVR and HCVR respectively) in humans. In a hypobaric chamber at a simulated altitude of 4500 m (barometric pressure 432 mmHg), seven subjects (training group) performed exercise training for 6 consecutive days (30 min·day-1), while six subjects (control group) were inactive during the same period. The HVR, HCVR and maximal oxygen uptake (V̇O(2max)) for each subject were measured at sea level before (pre) and after exposure to intermittent hypoxia. The post exposure test was carried out twice, i.e. on the 1st day and 1 week post exposure. It was found that HVR, as an index of peripheral chemosensitivity to hypoxia, was increased significantly (P &lt
0.05) in the control group after intermittent exposure to hypoxia. In contrast, there was no significant increase in HVR in the training group after exposure. The HCVR in both groups was not changed by intermittent exposure to hypoxia, while V̇O(2max) increased significantly in the training group. These results would suggest that endurance training during intermittent exposure to hypoxia depresses the increment of chemosensitivity to hypoxia, and that intermittent exposure to hypoxia in the presence or absence of exercise training does not induce an increase in the chemosensitivity to hypercapnia in humans.

DOI： 10.1007/s004210050406

Scopus

PubMed

The effects of intermittent exposure to hypoxia during endurance exercise training on the ventilatory responses to hypoxia and hypercapnia in humans. 査読有り

Katayama, K., Y. Sato, K. Ishida, S. Mori, and M. Miyamura.

Eur. J. Appl. Physiol. 78 巻頁： 189-194 1998年

記述言語：英語掲載種別：研究論文（学術雑誌）

The present study was performed to investigate the effects of a combination of intermittent exposure to hypoxia during exercise training for short periods on ventilatory responses to hypoxia and hypercapnia (HVR and HCVR respectively) in humans. In a hypobaric chamber at a simulated altitude of 4,500 m (barometric pressure 432 mmHg), seven subjects (training group) performed exercise training for 6 consecutive days (30 min x day(-1)), while six subjects (control group) were inactive during the same period. The HVR, HCVR and maximal oxygen uptake (VO2max) for each subject were measured at sea level before (pre) and after exposure to intermittent hypoxia. The post exposure test was carried out twice, i.e. on the 1st day and 1 week post exposure. It was found that HVR, as an index of peripheral chemosensitivity to hypoxia, was increased significantly (P < 0.05) in the control group after intermittent exposure to hypoxia. In contrast, there was no significant increase in HVR in the training group after exposure. The HCVR in both groups was not changed by intermittent exposure to hypoxia, while VO2max increased significantly in the training group. These results would suggest that endurance training during intermittent exposure to hypoxia depresses the increment of chemosensitivity to hypoxia, and that intermittent exposure to hypoxia in the presence or absence of exercise training does not induce an increase in the chemosensitivity to hypercapnia in humans.

DOI： 10.1007/s004210050406

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