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 (V(.)o(2)peak) for 12 min and with exercise intensity of 70 % V(.)o(2)peak 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 % V(.)o(2)peak 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 % V(.)o(2)peak 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.
- MeSH
- analýza krevních plynů metody MeSH
- biologické hodiny fyziologie MeSH
- cvičení fyziologie MeSH
- kosterní svaly fyziologie MeSH
- lidé MeSH
- mladiství MeSH
- mladý dospělý MeSH
- spotřeba kyslíku fyziologie MeSH
- svalová kontrakce fyziologie MeSH
- zátěžový test metody MeSH
- Check Tag
- lidé MeSH
- mladiství MeSH
- mladý dospělý MeSH
- mužské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
Time delay in the mediation of ventilation (V(.)E) by arterial CO(2) pressure (PaCO(2)) was studied during recovery from short impulse-like exercises with different work loads of recovery. Subjects performed two tests including 10-s impulse like exercise with work load of 200 watts and 15-min recovery with 25 watts in test one and 50 watts in test two. V(.)E, end tidal CO(2) pressure (PETCO(2)) and heart rate (HR) were measured continuously during rest, warming up, exercise and recovery. PaCO(2) was estimated from PETCO(2) and tidal volume (V(T)). Results showed that predicted arterial CO(2) pressure (PaCO(2 pre)) increased during recovery in both tests. In both tests, V(.)E increased and peaked at the end of exercise. V(.)E decreased in the first few seconds of recovery but started to increase again. The highest correlation coefficient between PaCO(2 pre) and V(.)E was obtained in the time delay of 7 s (r=0.854) in test one and in time delays of 6 s (r=0.451) and 31 s (r=0.567) in test two. HR was significantly higher in test two than in test one. These results indicate that PaCO(2 pre) drives V(.)E with a time delay and that higher work intensity induces a shorter time delay.
- MeSH
- cvičení fyziologie MeSH
- energetický metabolismus fyziologie MeSH
- kyselina mléčná krev MeSH
- lanthan krev MeSH
- lidé MeSH
- mechanika dýchání fyziologie MeSH
- mladý dospělý MeSH
- oxid uhličitý krev MeSH
- srdeční frekvence fyziologie MeSH
- Check Tag
- lidé MeSH
- mladý dospělý MeSH
- mužské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The aim of the present study was to compare the oscillations of oxygenation in skeletal muscle between early and late phases in prolonged exercise. During prolonged exercise at 60 % of peak oxygen uptake (V(.)o(2)) for 60 min and at rest, oxygenated hemoglobin/myoglobin (Hb/MbO(2)) and total Hb/Mb (THb/Mb) were determined by near-infrared spectroscopy in the vastus lateralis. Power spectra density (PSD) for the difference between Hb/MbO(2) and THb/Mb (-HHb/MbO(2): deoxygenation) was obtained by fast Fourier transform at rest, in the early phase (1-6 min) and in the late phase (55-60 min) in exercise. Peak PSD in the early phase was significantly higher than that at rest. There were at least three peaks of PSD in exercise. The highest peak was a band around 0.01 Hz, the next peak was a band around 0.04 Hz, and the lowest peak was a band around 0.06 Hz. PSD in the early phase was not significantly different from that in the late phase in exercise. Heart rate (HR) showed a continuous significant increase from 3 min in exercise until the end of exercise. Skin blood flow (SBF) around the early phase was significantly lower than that around the late phase. It was concluded that oscillation of oxygenation in the muscle oxygen system in the early phase is not different from that in the late phase in prolonged exercise despite cardiovascular drift.
- MeSH
- biologické hodiny fyziologie MeSH
- cvičení fyziologie MeSH
- dospělí MeSH
- fyzická vytrvalost fyziologie MeSH
- fyziologická adaptace fyziologie MeSH
- kosterní svaly fyziologie MeSH
- kyslík metabolismus MeSH
- lidé MeSH
- spotřeba kyslíku fyziologie MeSH
- svalová kontrakce fyziologie MeSH
- Check Tag
- dospělí MeSH
- lidé MeSH
- mužské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- srovnávací studie MeSH
We investigated ventilation (V(.)E) control factors during recovery from light impulse-like exercise (100 watts) with a duration of 20 s. Blood ions and gases were measured at rest and during recovery. V(.)E, end tidal CO(2) pressure (PETCO(2)) and respiratory exchange ratio (RER) were measured continuously during rest, exercise and recovery periods. Arterial CO(2) pressure (PaCO(2) (pre) was estimated from PETCO(2) and tidal volume (V(T)). RER at 20 s of exercise and until 50 s during recovery was significantly lower than RER at rest. Despite no change in arterialized blood pH level, PaCO(2) (pre) was significantly higher in the last 10 s of exercise and until 70 s during recovery than the resting value. V(.)E increased during exercise and then decreased during recovery; however, it was elevated and was significantly higher than the resting value until 155 s (p<0.05). There was a significant relationship between V(.)E and PaCO(2) (pre) during the first 70 s of recovery in each subject. The results suggest that PaCO(2) drives V(.)E during the first 70 s of recovery after light impulse-like exercise. Elevated V(.)E in the interval from 70 s until 155 s during recovery might be due to neural factors.
- MeSH
- acidóza krev patofyziologie MeSH
- analýza rozptylu MeSH
- biologické markery krev MeSH
- časové faktory MeSH
- cvičení * MeSH
- cyklistika MeSH
- koncentrace vodíkových iontů MeSH
- lidé MeSH
- mladý dospělý MeSH
- obnova funkce MeSH
- oxid uhličitý krev MeSH
- parciální tlak MeSH
- plicní ventilace * MeSH
- zátěžový test MeSH
- Check Tag
- lidé MeSH
- mladý dospělý MeSH
- mužské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
The purpose of the present study was to examine whether excessive CO2 output (V . co2excess) is dominantly attributable to hyperventilation during the period of recovery from repeated cycling sprints. A series of four 10-sec cycling sprints with 30-sec passive recovery periods was performed two times. The first series and second series of cycle sprints (SCS) were followed by 360-sec passive recovery periods (first recovery and second recovery). Increases in blood lactate (?La) were 11.17±2.57 mM from rest to 5.5 min during first recovery and 2.07±1.23 mM from the start of the second SCS to 5.5 min during second recovery. CO2 output (V . co2) was significantly higher than O2 uptake (V . o2) during both recovery periods. This difference was defined as V . co2excess. V . co2excess was significantly higher during first recovery than during second recovery. V . co2excess was added from rest to the end of first recovery and from the start of the second SCS to the end of second recovery (CO2excess). ?La was significantly related to CO2excess (r=0.845). However, ventilation during first recovery was the same as that during second recovery. End-tidal CO2 pressure (PETco2) significantly decreased from the resting level during the recovery periods, indicating hyperventilation. PETco2 during first recovery was significantly higher than that during second recovery. It is concluded that V . co2excess is not simply determined by ventilation during recovery from repeated cycle sprints.
To determine the relationship between hyperventilation and recovery of blood pH during recovery from a heavy exercise, short-term intense exercise (STIE) tests were performed after human subjects ingested 0.3 g · kg-1 body mass of either NaHCO3 (Alk) or CaCO3 (Pla). Ventilation (V . E) - CO2 output (V . co2) slopes during recovery following STIE were significantly lower in Alk than in Pla, indicating that hyperventilation is attenuated under the alkalotic condition. However, this reduction of the slope was the result of unchanged V . E and a small increase in V . co2. A significant correlation between V . E and blood pH was found during recovery in both conditions. While there was no difference between the V . E - pH slopes in the two conditions, V . E at the same pH was higher in Alk than in Pla. Furthermore, the values of pH during recovery in both conditions increased toward the preexercise levels of each condition. Thus, although V . E - V . co2 slope was decreased under the alkalotic condition, this could not be explained by the ventilatory depression attributed to increase in blood pH. We speculate that hyperventilation after the end of STIE is determined by the V . E - pH relationship that was set before STIE or the intensity of the exercise performed.
Inactive forearm muscle oxygenation has been reported to begin decreasing from the respiratory compensation point (RCP) during ramp leg cycling. From the RCP, hyperventilation occurs with a decrease in arterial CO2 pressure (PaCO2). The aim of this study was to determine which of these two factors, hyperventilation or decrease in PaCO2, is related to a decrease in inactive biceps brachii muscle oxygenation during leg cycling. Each subject (n = 7) performed a 6-min two-step leg cycling. The exercise intensity in the first step (3 min) was halfway between the ventilatory threshold and RCP (170±21 watts), while that in the second step (3 min) was halfway between the RCP and peak oxygen uptake (240±28 watts). The amount of hyperventilation and PaCO2 were calculated from gas parameters. The average cross correlation function in seven subjects between inactive muscle oxygenation and amount of hyperventilation showed a negative peak at the time shift of zero (r = -0.72, p<0.001), while that between inactive muscle oxygenation and calculated PaCO2 showed no peak near the time shift of zero. Thus, we concluded that decrease in oxygenation in inactive arm muscle is closely coupled with increase in the amount of hyperventilation.
- MeSH
- blízká infračervená spektroskopie metody využití MeSH
- ergometrie metody využití MeSH
- hyperventilace krev metabolismus MeSH
- kosterní svaly fyziologie metabolismus MeSH
- lidé MeSH
- oxid uhličitý krev škodlivé účinky MeSH
- paže fyziologie krevní zásobení MeSH
- spotřeba kyslíku fyziologie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- srovnávací studie MeSH
The purpose of this study was to examine how oxygen uptake (V . o2) in decrement-load exercise (DLE) is affected by changing rate of decrease in power output. DLE was performed at three different rates of decrease in power output (10, 20 and 30 watts·min-1: DLE10, DLE20 and DLE30, respectively) from power output corresponding to 90 % of peak V . o2. V . o2 exponentially increased and then decreased, and the rate of its decrease was reduced at low power output. The values of V . o2 in the three DLE tests were not different for the first 2 min despite the difference in power output. The relationship between V . o2 and power output below 50 watts was obtained as a slope to estimate excessive V . o2 (ex-V . o2) above 50 watts. The slopes were 10.0±0.9 for DLE10, 9.9±0.7 for DLE20 and 10.2±1.0 ml·min-1·watt-1 for DLE30. The difference between V . o2 estimated from the slope and measured V . o2 was defined as ex-V . o2. The peak value of ex-V . o2 for DLE10 (189±116 ml·min-1) was significantly greater than those for DLE20 and for DLE30 (93±97 and 88±34 ml·min-1). The difference between V . o2 in DLE and that in incremental-load exercise (ILE) below 50 watts (?V . o2) was greater in DLE30 and smallest in DLE10. There were significant differences in ?V . o2 among the three DLE tests. The values of ?V . o2 at 30 watts were 283±152 for DLE10, 413±136 for DLE20 and 483±187 ml·min-1 for DLE30. Thus, a faster rate of decrease in power output resulted in no change of V . o2 at the onset of DLE, smaller ex-V . o2 and greater ?V . o2. These results suggest that V . o2 is disposed in parallel in each motor unit released from power output or recruited in DLE.
The aim of this study was to determine whether excessive oxygen uptake (V . o2) occurs not only during exercise but also during recovery after heavy exercise. After previous exercise at zero watts for 4 min, the main exercise was performed for 10 min. Then recovery exercise at zero watts was performed for 10 min. The main exercises were moderate and heavy exercises at exercise intensities of 40 % and 70 % of peak V . o2, respectively. V . o2 kinetics above zero watts was obtained by subtracting V . o2 at zero watts of previous exercise (?V . o2). ? V . o2 in moderate exercise was multiplied by the ratio of power output performed in moderate and heavy exercises so as to estimate the ? V . o2 applicable to heavy exercise. The difference between ? V . o2 in heavy exercise and ? V . o2 estimated from the value of moderate exercise was obtained. The obtained V . o2 was defined as excessive V . o2. The time constant of excessive V . o2 during exercise (1.88±0.70 min) was significantly shorter than that during recovery (9.61±6.92 min). Thus, there was excessive V . o2 during recovery from heavy exercise, suggesting that O2/ATP ratio becomes high after a time delay in heavy exercise and the high ratio continues until recovery.
The purpose of the present study was to examine whether the level of oxygen uptake (Vo2) at the onset of decrementload exercise (DLE) is lower than that at the onset of constant-load exercise (CLE), since power output, which is the target of Vo2 response, is decreased in DLE. CLE and DLE were performed under the conditions of moderate and heavy exercise intensities. Before and after these main exercises, previous exercise and post exercise were performed at 20 watts. DEL was started at the same power output as that for CLE and power output was decreased at a rate of 15 watts per min. Vo2 in moderate CLE increased at a fast rate and showed a steady state, while Vo2 in moderate DLE increased and decreased linearly. Vo2 at the increasing phase in DLE was at the same level as that in moderate CLE. Vo2 immediately after moderate DLE was higher than that in the previous exercise by 98±77.5 ml/min. Vo2 in heavy CLE increased rapidly at first and then slowly increased, while Vo2 in heavy DLE increased rapidly, showing a temporal convexity change, and decreased linearly. Vo2 at the increasing phase of heavy DLE was the same level as that in heavy CLE. Vo2 immediately after heavy DLE was significantly higher than that in the previous exercise by 156±131.8 ml/min. Thus, despite the different modes of exercise, Vo2 at the increasing phase in DLE was at the same level as that in CLE due to the effect of the oxygen debt expressed by the higher level of Vo2 at the end of DLE than that in the previous exercise.
