宮本 忠吉

The purpose of this study was to examine the relation ships among muscle oxygenation level measured by a near-infrared spectroscopy (NIRS), blood lactate concentration (La) and substrate utilization during a prolonged 60-min steady-state exercise below the anaerobic threshold (AT). Ten healthy adult subjects (3 males and 7 females) completed an orientation trial, a maximal exercise test, and a submaximal exercise for 60 min. The oxygenated hemoglobin and myoglobin saturation (muscle oxygenation level) measured by NIRS was recorded continuously throughout the tests. The probe was located on the vastus lateralis muscle. At 30 mm after exercise, the calibration of NIRS was performed by the cuff occlusion at 260 mmHg for 10 min. The relative change in muscle oxygenation level was estimated by regarding muscle oxygenation level in the resting condition as 0% and that obtained during thigh occlusion as - 100%. Oxygen consumption (V^^・O_2), carbon dioxide production (V^^・CO_2), minute ventilation (V^^・E), respiratory exchange ratio (RER), heart rate (HR) and La were measured at rest and during exercise. Muscle oxygenation level decreased immediately after the onset of exercise and gradually increased from -24.2±10.8% at 5 min to -3.3± 11.8% at 60 min. From 10 to 60 min, muscle oxygenation level increased by 11.6±3.9% with a significant increase in total hemoglobin. Muscle oxygenation level indicated the balance between oxygen delivery and oxygen utilization. Therefore, the gradual increase in muscle oxygenation level during the prolonged cycle exercise may be affected by more increase in O_2 de livery to exercising muscles than O_2 utilization. From 10 to 60 min, La and RER significantly decreased while the muscle oxygenation level increased. Therefore, Change in muscle oxygenation level between 10 and 60 min was correlated with bothΔLa (r=-0.66, P<0.05) andΔRER (r=-0.71, P<0.05). These results indicated that increase in muscle oxygenation level might facilitate blood lactate disposal and fat oxidation during the prolonged exercise below AT.

一過性の中心血液量の増加は運動に対応する心循環系の調節機構に影響を及ぼし,運動負荷(強度レベル×時間)による生理学的ストレスを軽減する可能性が示唆された.それは,高強度運動レベルよりも低強度運動レベルで,顕著であることが示された

<jats:p>We propose a current confinement structure which can be self-formed by thermal annealing of a electrode metal with a self-aligning process. The migrated metal selectively destroys an AlAs/InP tunnel junction to form a high resistance isolation layer. The hole current can be injected through a preserved tunnel junction window. We confirmed its lateral confinement effect from the near-field pattern of fabricated GaInAsP/InP stripe lasers. The proposed current confinement structure is very simple and useful for the lateral injection in semiconductor optical devices including long-wavelength vertical-cavity surface-emitting lasers.</jats:p>

We demonstrate InP-based long-wavelength lasers with an AlAs/InP tunnel junction prepared in the upper cladding of a standard laser structure to convert electron current supplied by the upper n-electrode to hole current. A carbon auto-doped AlAs layer was employed as a heavy p-type layer required for the tunnel junction. The tunnel junction diode showed a small electrical resistance under a reverse-biased condition. In addition, a negative differential resistance characteristic was clearly observed under a forward-biased condition. The introduction of such a tunnel junction can eliminate the p-electrode which normally exhibits a high resistivity in InP-based lasers. In the fabricated lasers with tunnel junctions, it was observed that the tunnel junction can enhance lateral current spreading due to low resistance in the n-layer. The proposed structure for hole sources may be useful for reducing the resistance and homogenizing the carriers in the active region of long-wavelength vertical-cavity surface-emitting lasers (VCSEL).

A study was conducted to establish a method for quantitative evaluation of both the rate and degree of muscle oxygenation during ramp exercise using Near Infrared Spectroscopy (NIRS), and to determine the relationship of the indices to body composition and physical fitness. The subjects were 13 healthy men. After a warm-up period of 3 min at 20-W, the ramp exercise test was conducted. The exercise consisted of an increasing work rate at a slope of 20 W/min on a cycle ergometer performed until volitional fatigue. The NIRS probe used in the cycling exercise was placed on the vastus lateralis muscle. After 30 min of exercise, calibration was performed by cuff occlusion for 10 min with a pressure of 260 mmHg for quantitative determination of the NIRS curve. The oxygenation curve measured by NIRS during the exercise initially exhibited a linear decrease as the work rate increased. This rate of decrease in oxygenation was indicated by the NIRS slope (%/W) obtained from the calibration curve. In later stages of the exercise, the NIRS curve became flattened with increased work rate. The breaking point between the sloping phase and the flat phase was named the "NIRS Threshold 2, NT 2". In addition, the rate of decrease in oxygenation at the end of exercise per maximal NIRS decrease obtained from the calibration curve was indicated as the %NIRS fall. The mean NIRS slope and %NIRS fall were 0.3±0.1%/W (range, 0.13 to 0.50%/W) and 29.9±11.8% (range, 12.0 to 50.0%), respectively. NT 2 was observed in 8 of the 13 subjects. The subjects were divided into two groups (NT 2 (+) and NT 2 (-) ) based on the appearance of NT 2. Both the NIRS slope and %NIRS fall in the NT 2 (+) group were significantly higher than those in the NT 2 (-) group. The NIRS slope was significantly correlated with VO₂/wt at VT (r=0.73, p<0.05) and wattage at VT (r=0.86, p<0.0001) . The %NIRS fall was significantly correlated with VO₂/wt at peak (r=0.80, P<0.001) . The NIRS slope and %NIRS fall were not significantly correlated with body mass index, %fat or thigh circumference.<BR>These findings suggest that the NIRS slope indicates the efficiency of oxygen exchange in muscles activated during incremental exercise, and that the %NIRS fall indicates the ability to utilize Oxy-Hb+Mb against maximal oxygenation capacity in muscles. The NIRS slope and %NIRS fall can therefore be used as indices of muscular limitation during exercise, and as indices of muscular adaptation during exercise.

ランプ負荷運動中における筋内酸素動態に生じる低下反応(NIRS slope)と屈曲点(NT2)を用いて,吸入気ガス濃度(標準ガス,16%O2,40%O2濃度の酸素)の差が酸素動態に及ぼす影響について検討した.活動筋内のNIRS slopeは吸入気ガス濃度の影響を受けないが,酸素交換率の限界(NT2)に達する迄の時間は,低酸素吸入により早められることが明らかになった

健常男性19名を対象に漸増負荷検査を施行した.運動時の換気及びガス交換諸量の変化から無酸素性作業閾値(AT)及び呼吸性代償点(RC)を決定し,RCが検出された群(RC群;12名)と検出されなかった群(Non-RC群;7名)に分けた.同じ換気量(VE)のレベルでの運動中と回復期での一回換気量(VT)の差の平均を示すΔVTは,RC群がNon-RC群よりも高値を示し,RC群では回復期にVTが少なく,呼吸数(f)が多い浅速型の呼吸パターンを呈した.回復期の酸素摂取量(VO2)のfast-コンポーネントでの時定数[τVO2(f)]はRC群がNon-RC群よりも有意に延長したが,VO2のslow-コンポーネントでの時定数には両群間で有意差がなかった.運動終了10分後のVE/VO2の値から安静レベルの値を引いたΔVE/VO2についても,RC群が有意に高値を示した.ΔVTとτVO2(f)及びΔVE/VO2との間にそれぞれ有意な相関が認められた

健常人2例において,Ramp負荷運動中の脂肪酸化量はLT以下の運動中には顕著に増大した.更に1例では,Ramp負荷後の回復期にも安静時より増大することが認められた.但し,回復30分後の脂肪酸化量の増大には,運動中の血清脂質の動態や回復期においてリパーゼ活性に関与するアドレナリン,ノルアドレナリンやインスリンなどのホルモン動態が影響を与えることが推測された

A study was performed to clarify the relationships between oxygen uptake(VO_2)kinetics on recovery from incremental maximal exercise and blood lactate, glucose and alanine metabolism. Eight healthy males aged 21.6±3.3years were studied. The incremental exercise test was performed using a modified version of Bruce's protocol until 30min after exhaustion. The VO_2 responses on recovery were fitted by a two-component exponential model. Blood lactate concentration in the recovery phase was fitted by a bi-exponential time function to assess the velocity constant of the slowly decreasing component(γ2)expressing the rate of blood lactate removal. Both blood lactate and plasma alanine concentration were significantly increased from rest to maximal exercise, and were significantly decreased thereafter, but remained above resting values for 30min after the maximal stage. Blood glucose concentration was significantly decreased following maximal exercise and returned to the pre-exercise value by 30min after the maximal stage. Concentrations of plasma branched-chain amino acids(valine, leucine and isoleucine)were significantly decreased from the maximal stage until 30min after exhaustion. The time constant of the slow component on recovery VO_2[τVO_2(s)] was correlated with neither γ2 nor the degree of change in blood lactate from the maximal stage until 30min after exhaustion(Δlactate). However, τVO_2(s)was significantly correlated with both Δblood glucose and Δalanine. In addition, Δalanine was significantly correlated with Δblood glucose. From these results, we conclude that oxygen uptake kinetics after exhaustive maximal exercise is related to glucose resynthesis through alanine metabolism. as compared with that from lactate metabolism.

ランプ負荷法による自転車運動中において,近赤外分光法により測定された筋肉内酸素濃度の第2屈曲点(NT2)出現の遅延は,トレーニング効果によるものと推察された.このことは,従来よりトレーニング効果の指標として利用されているVO2max, VT, LTに加えNT2が一指標となり得る可能性が示唆された

定常負荷運動後におけるVO2の回復曲線の時定数は,運動能力を表わす指標になり得る可能性が示唆された.一方,VCO2の回復曲線に関しては,負荷量や回復時間を考慮して再検討を行う必要性が示された

健常男性7名(22.1±3.2歳)を対象にTreadmillによるstep運動負荷を施行し,breath-by-breathで求めたVO2の時定数は呼吸数の移動平均数を増すほど延長する傾向にあり,13呼吸以上の移動平均数ではbreath-by-breath値より有意差をもって延長した.更に対象毎に検討すると,2例では5呼吸や9呼吸の移動平均数でも時定数が延長した.これはVO2-kineticsの解析時に呼吸数の移動平均数を増すほど安静時や定常時の値が運動開始直後の値に加味される為に時定数が延長して算出されたと考えられた.又,運動開始前後の呼吸の乱れなども解析値に影響を及ぼす要因の一つとして考えられた

健常人の横隔膜水位では,肺気量の低下及び細気管支での閉塞所見が出現するのに関わらず,運動時の換気反応は良好に保たれ,水圧の換気に対する悪影響はみられなかった.特に,水中運動時では早期にATに至るが,ATを越えて炭酸ガスの排泄量が増した条件下でも換気の効率は良好であった

肥満者の水中歩行時では,浮力による体重減少の影響がより強く現れる為,非肥満者に比べ,陸上での換気循環反応及び自覚症状に及ぼす影響が軽減した

運動開始時のVO2-Kineticsの時定数を規定する要因として,運動筋への酸素輸送能,運動筋での酸素利用能に加え,運動筋からの静脈還流の因子が関与していることが示唆された

肥満者の水中歩行時には,陸上歩行時でみられる体重負荷の影響が浮力により軽減される一方,水中でのVTの早期出現及びrapid shallowな呼吸パターンへの移行が,換気反応の亢進や換気効率の悪化を引き起こし,自覚症状への影響も予想された

肥満者の安静時肺機能では,気道は正常に保たれているが,躯幹上半身の脂肪の為FRC及びTLCが低値を示した.更に運動時では過体重の負荷や,脂肪による胸郭の運動制限により運動中の換気効率が変化したと考えられる.そのためコントロール群よりVTが早期に出現し,VT後呼吸数が増加するのを反映して,呼吸困難感の上昇が認められたものと示唆された

中程度トレーニングの大学女子長距離選手(GR群),高度トレーニングの実業団女子長距離選手(ER群)及び年齢の一致した特別の運動経験を有さない女子大学生(SC群)を対象として,女性長距離選手の左室形態及び左室拡大パターンの特徴を明らかにしようとした. 1)GR群及びER群は,SC群と比較して有意に増大した左室内径,左室壁厚及び左室重量を示した.しかし,選手群の左室形態は,健常人の正常範囲内であった. 2)選手群(GR群,ER群)の左室内径に対する壁厚の比率は,非選手群(SC群)のそれと比較して有意差が認められなかった. 3)ER群の左室形態はGR群より高値を示すが,統計的有意差は選手群間に認められなかった.又,左室内径に対する左室壁厚の比率も同様に選手群間で有意差が認められなかった