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1.
Tetsuro Ogaki Atsushi Saito Shozo Kanaya Takehiko Fujino 《European journal of applied physiology》1995,72(1-2):6-11
The prolonged effects of steady-state exercise and meals on plasma sulpho-conjugated catecholamines (CA) after exercise were examined. Seven male subjects exercised on 2 separate days for 60 min at 50% and 70% of maximal oxygen uptake (
) on a cycle ergometer and then rested, for 8 h sitting in an armchair. A control trial without any exercise was also performed. At 2 h after the end of exercise the subjects were given a meal. The plasma free and sulphated CA, oxygen uptake (
) and heart rate (HR) were all measured before exercise, during exercise and hourly during the 8-h recovery period. The sulphated noradrenaline (NA-S) and adrenaline (A-S) concentrations increased after exercise, and, furthermore, only the NA-S concentrations remained elevated for 6 h after exercise at 50%
and for 8 h at 70%
trial, compared with the control trial. There were no changes in either the plasma NA-S or A-S concentrations after consuming a meal, whereas the dopamine sulphate concentration demonstrated a dynamic change. A significantly higher excess postexercise
was observed at 2 h postexercise at 50%
and at 6 h postexercise at 70%
trials. The mean HR was still elevated at 6 and 8 h after exercise, which closely correlated with the duration of the elevated NA-S concentrations. These results suggest that sulphated CA, especially NA-S, could represent an additional index of sympathetic nerve activity after exercise, and that a meal containing small amounts of the amines would seem to have no effect on plasma NA-S and A-S concentrations. 相似文献
2.
Takayoshi Yoshida Koji Yamamoto Masao Udo 《European journal of applied physiology》1993,66(2):155-160
Summary The purpose of the present study was to assess the relationship between the rapidity of increased gas exchange (i.e. oxygen uptake
) and increased cardiac output (
) during the transient phase following the onset of exercise. Five healthy male subjects performed multiple rest-exercise or light exercise (25 W)-exercise transitions on an electrically braked ergometer at exercise intensities of 50, 75, or 100 W for 6 min, respectively. Each transition was performed at least eight times for each load in random order. The
was obtained by a breath-by-breath method, and
was measured by an impedance method during normal breathing, using an ensemble average. On transitions from rest to exercise,
rapidly increased during phase I with time constants of 6.8–7.3 s. The
also showed a similar rapid increment with time constants of 6.0–6.8 s with an apparent increase in stroke volume (SV). In this phase I,
increased to about 29.7%–34.1% of the steady-state value and
increased to about 58.3%–87.0%. Thereafter, some 20 s after the onset of exercise a mono-exponential increase to steady-state occurred both in
and
with time constants of 26.7–32.3 and 23.7–34.4 s, respectively. The insignificant difference between
and
time constants in phase I and the abrupt increase in both
and SV at the onset of exercise from rest provided further evidence for a cardiodynamic contribution to
following the onset of exercise from rest. 相似文献
3.
Summary Six trained male cyclists and six untrained but physically active men participated in this study to test the hypothesis that the use of percentage maximal oxygen consumption (%
, as a normalising independent variable is valid despite significant differences in the absolute
of trained and untrained subjects. The subjects underwent an exercise test to exhaustion on a cycle ergometer to determine
and lactate threshold. The subjects were grouped as trained (T) if their
exceeded 60 ml ·kg–1 ·min–1, and untrained (UT) if their
was less than 50 ml · kg–1 · min-–1. The subjects were required to exercise on the ergometer for up to 40 min at power outputs that corresponded to approximately 50% and 70%
The allocation of each exercise session (50% or 70%
was random and each session was separated by at least 5 days. During these tests venous blood was taken 10 min before exercise (–10 min), just prior to the commencement of exercise (–10 min), after 20 min of exercise (20 min), at the end of exercise and 10 min postexercise (+ 10 min) and analysed for concentrations of cortisol, [Na+], [K+], [CI–], glucose, free fatty acid, lactate [la-], [NH3], haemoglobin [Hb] and for packed cell volume. The oxygen consumption (
) and related variables were measured at two time intervals (14–15 and 34–35 min) during the prolonged exercise tests. Rectal temperature was measured throughout both exercise sessions. There was a significant interaction effect between the level of training and exercise time at 50%
for heart rate (
c:) and venous [la–]. At 70%
and ventilation (
) for the T group and
and carbon dioxide production for the UT group increased significantly with time and there was a significant interaction effect forf
c, ]Ia–1], [Hb] and [NH3]. The change in body mass at 50% and 70%
was significantly greater in the T group. The present study found that when two groups of male subjects with different absolute
exercised at a similar percentage of
some effector responses were significantly different, questioning the validity of selecting %
as a normalising independent variable. 相似文献
4.
A. R. Lind R. R. Rochelle J. S. Rinehart J. S. Petrofsky R. L. Burse 《European journal of applied physiology》1982,49(2):243-254
Summary Three subjects were trained in leg extensor isometric contractions and in cycling. They then cycled for three consecutive
bouts, each of 2.75 min at a constant level of
, from 20 to 80%
max. Fifteen seconds after each bout of cycling the subjects exerted an isometric contraction of the right leg at 40% of
the maximum voluntary contraction. In each experiment, the duration of the three successive isometric contractions decreased
as in hand-grip contractions. There was also a linear reduction in isometric endurance as the severity of the preceding rhythmic
exercise increased. In other experiments, after three bouts of rhythmic exercise at 20%
max (each followed by a fatiguing contraction at 40% MVC), further bouts of cycling at increasing levels of severity up to
60%
max resulted in a linear fall in isometric endurance which could be reversed by interposing a lighter level of cycling. The
heart rates during these experiments showed a steady increase during the isometric exercise, to about 150 beats·min−1, as the bouts of preceding rhythmic exercise became progressively more severe. The isometric contractions had little influence
on the heart rate during cycling. But the rhythmic cycling exercise markedly increased the heart rate achieved at the end
of the isometric contractions while decreasing theincrement in heart rateduring the contraction.
Supported by HEW Contract HSM 99-71-21, and U.S.N. Grant N00014-77-0640 相似文献
5.
Tetsuo Takaishi Takashi Ono Yoshifumi Yasuda 《European journal of applied physiology》1992,65(4):335-339
Summary The surface electromyogram (EMG) from active muscle and oxygen uptake (
) were studied simultaneously to examine changes of motor unit (MU) activity during exercise tests with different ramp increments. Six male subjects performed four exhausting cycle exercises with different ramp slopes of 10, 20, 30 and 40 W · min–1 on different days. The EMG signals taken from the vastus lateralis muscle were stored on a digital data recorder and converted to obtain the integrated EMG (iEMG). The
was measured, with 20-s intervals, by the mixing chamber method. A non-linear increase in iEMG against work load was observed for each exercise in all subjects. The break point of the linear relationship of iEMG was determined by the crossing point of the two regression lines (iEMGbp). Significant differences were obtained in the exercise intensities corresponding to maximal oxygen uptake (
) and the iEMGbp between 10 and 30, and 10 and 40 W · min –1 ramp exercises (P < 0.05). However, no significant differences were obtained in
and
corresponding to the iEMGbp during the four ramp exercises. With respect to the relationship between
and exercise intensity during the ramp increments, the
-exercise intensity slope showed significant differences only for the upper half (i.e. above iEMGbp). These results demonstrated that the
and
at which a nonlinear increase in iEMG was observed were not varied by the change of ramp slopes but by the exercise intensity corresponding to
and the iEMGbp was varied by the change of ramp slopes. In addition, the significant differences in the
exercise intensity slopes for the upper half of the tests would suggest that the recruitment patterns of MU and/or muscle metabolic state might be considerably altered depending upon the ramp slope increments. 相似文献
6.
T. B. R. J. Smith W. G. Hopkins N. A. S. Taylor 《European journal of applied physiology》1994,69(1):44-49
The position of the body and use of the respiratory muscles in the act of rowing may limit ventilation and thereby reduce maximal aerobic power relative to that achieved in cycling or running, in spite of the greater muscle mass involved in rowing. This hypothesis was investigated for three groups of male subjects: nine elite senior oarsmen, eight former senior oarsmen and eight highly trained athletes unskilled in rowing. The subjects performed graded exercise to maximal effort on a rowing ergometer, cycle ergometer and treadmill while respiratory minute volume
and oxygen consumption
were monitored continuously. The VE at a given
during intense submaximal exercise (greater than 75% of maximal
) was not significantly lower in rowing compared with that in cycling and treadmill running for any group, which would suggest that submaximal rowing does not restrict ventilation. At maximal effort,
and
for rowing were less than those for the other types of exercise in all the groups, although the differences were not statistically significant in the elite oarsmen. These data are consistent with a ventilatory limitation to maximal performance in rowing that may have been partly overcome by training in the elite oarsmen. Alternatively, a lower maximal VE in rowing might have been an effect rather than a cause of a lower maximal
if maximal
was limited by the lower rate of muscle activation in rowing. 相似文献
7.
J. M. Steinacker T. R. Marx U. Marx W. Lormes 《European journal of applied physiology》1986,55(3):240-247
Summary Oxygen consumption (
) when rowing was determined on a mechanically braked rowing ergometer (RE) with an electronic measuring device.
was measured by an open spirometric system. The pneumotachograph valve was fixed to the sliding seat, thus reducing movement
artefacts. A multi-stage test was performed, beginning with a work load of 150 W and increasing by 50 W every 2 minutes up
to exhaustion. Serum lactate concentrations were determined in a 30 s break between the work stages. 61 examinations of oarsmen
performing at maximum power of 5 W · kg−1 or more were analysed.
and heart rate (HR) for each working stage were measured and the regression line of
on the work load (P) and an estimation error (sxy) were calculated:
(ml · min−1) (Sxy = ± 337 ml,r = 0.98)
Good reproducibility was found in repeated examinations.
Similar spiroergometry was carried out on a bicycle ergometer (BE) with 10 well trained rowers and 6 trained cyclists.
of rowing was about 600 ml · min−1 higher than for bicycling in the submaximal stages for both groups. The
of RE exercise was 2.6% higher than for oarsmen on BE, and the cyclists reached a greater
on BE than the oarsmen. No differences were found between RE and BE exercise heart rate. The net work efficiency when rowing
was 19% for both groups, experienced and inexperienced: when cycling it was 25% for cyclists and 23% for oarsmen. 相似文献
8.
Acute effects of cigarette smoking and inhalation of carbon monoxide during maximal exercise 总被引:2,自引:0,他引:2
Summary The acute effect of inhaling the smoke of three cigarettes was compared to the effect of inhalation of an amount of carbon
monoxide (CO), giving the same CO-saturation of the arterial blood as smoking during rest and during maximal exercise on a
Krogh cycle ergometer. Sixteen male subjects were tested in the morning (1) after about 8 h without smoking (control), (2)
after inhalation of the smoke of three cigarettes (smoke), and (3) after CO-inhalation (CO). It was found that the average
maximal rate of O2-uptake (
max) decreased during both smoke and CO by about 7%. Endurance time at
max decreased 20% during smoke but only 10% during CO. A significant decrease in maximal heart rate (HR), and an increase
in HR at rest, was demonstrated only during smoke. The peak lactate concentration (HLa) following maximal exercise was significantly
decreased after smoke. The results suggest that the decrease in
max during smoke is due to the CO-saturation of the blood, and hence to a decrease in the oxygen capacity of the blood, while
the decrease in endurance time during smoke is a combined effect of the CO-saturation and an increased cost of breathing caused
by the smoke particles. It is further suggested that nicotine, or possibly some other components of the smoke, have an enhancing
effect on the heart at rest, while an inhibition is seen during maximal exercise. Finally it was found that the subjects who
had a
max above the average for all subjects investigated were less susceptible to the effects of smoking than subjects with a
max below the average.
Supported by a grant from The Danish Sports Research Council 相似文献
9.
Thimm Franz Dienstel Ellen Meier zu Verl Elisabeth 《European journal of applied physiology》1986,55(3):273-280
Summary In a rat with an isolated hind leg circulation perfused with varying tyrode solutions, heart rate (HR) changes were studied
in dependence of
in the isolated hind leg and of
, [K+], pH and lactic acid concentration ([Lac]) measured in the venous outflow of the isolated hind leg. In experimental series
I the inflow
was kept constantly high (either about 65 or 72 kPa). The perfusion pressure alternated between 16 and 24 kPa leading to
flow rates in isolated hind legs (
) from 30 to 50 ml · 100 g−1 · min−1. The
depended on the momentary
(flow-limited oxygen uptake). The [K+] and [Lac], the pH and the
remained nearly constant while the
was lower at small flow rates. The HR decreases some 4 min after initial enhancement of
and
. Series II comprised experiments with low flow rates and a medium oxygen supply (
=2.5−17.4 ml · 100 g−1 · min−1),
=17.5−62.7 kPa). The
ranged between 0.02 and 0.2 ml · 100 g−1 · min−1. The [K+] and [Lac], the
and the HR increased while the pH decreased. The [Lac] in the outflow showed a strong dependence on oxygen uptake and — at
a weak oxygen supply — on the time. Cross-correlation analyses between the parameters confirmed that the HR was best temporally
correlated to the [Lac] in the outflow. In series III a 17 min perfusion of normoxic solution (
=65.3 kPa) was followed by perfusion with a hypoxic tyrode solution (
=8.7 kPa).
was 30 ml · 100 g−1 · min−1. The [Lac], the
and the HR increased accompanied by a decrease in pH. However a HR increase was observed only when the actual values of [Lac],
and pH exceeded their normal ranges for a resting muscle. The results support the hypothesis that heart rate is additionally
influenced by metabolic muscle receptors measuring lactic acid concentration in working muscle. 相似文献
10.
J. Beillot F. Carré G. Le Claire P. Thoumie B. Perruoin-Verbe A. Cormerais A. Courtillon E. Tanguy G. Nadeau P. Rochcongar J. Dassonville 《European journal of applied physiology》1996,73(3-4):376-381
The energy cost of walking using a reciprocating gait orthosis (RGOII) with functional electrical stimulation (FES) was assessed
in 14 patients with spastic complete paraplegia from six rehabilitation centres. Before and after training asing RGOII with
FES, the subjects performed a progressive maximal test on an arm-crank ergometer to obtain their laboratory peak oxygen uptake
heart rate (HR) and blood lactate concentration changes. At the end of the training session, oxygen uptake
was measured during a walking test with orthosis at different speeds (6 min steady state at 0.1 m · s−1, followed by 2-min stages at progressively increasing speeds up to exhaustion). Of the subjects 4 repeated this test using
orthosis without FES. At a speed of 0.1 m · s−1,
represented 47 (SD 23)% of
, mean HR was 137 (SD 21) beats · min−1 and mean blood lactate concentration 2.4 (SD 1.4) mmol · l−1. Maximal speed ranged from 0.23 to 0.5 m · s−1. At maximal speed,
was 91 (SD 18) % of
mean HR reached 96 (SD 7)% and mean blood lactate concentration only 52 (SD 19)% of the maximal values measured during the
laboratory test. Walking without electrical stimulation induced an increase in HR but there was no difference in
and blood lactate compared to walking with stimulation. The training period did not result in any improvement in maximal
physiological data. We concluded that the free cadence walking speed with orthosis remains much lower than that of able-bodied
people or wheelchair users. The metabolic cost at a given speed is much higher even if, using a stimulation device, the cardiovascular
stress is reduced. 相似文献
11.
Lois M. Sheldahl Nancy A. Wilke Richard D. Hanna Sara M. Dougherty Felix E. Tristani 《European journal of applied physiology》1996,72(4):357-364
The primary purpose of the present study was to determine oxygen uptake (
) and heart rate (HR) responses of patients with coronary artery disease (CAD) to common lawn-care activities. The study was conducted in three phases. In phase I, 8 men with CAD performed 30 min of push motorized lawn mowing at a self-paced rate. In phase II, 9 men with CAD performed push (no power) mowing, trimming (power and manual), and raking for 8 min each. In phase III, age-matched men and women with and without CAD (9–11 per group) performed self-propelled motorized mowing and push motorized mowing. In phase I,
averaged 17.3 (SEM 3.8) ml · kg–1 · min–1 during 30 min of mowing. Relative effort was 68 (SEM 1) and 76 (SEM 4)% of treadmill maximal
(
) and HR, respectively. In phase II, mean
ranged from 8.6 (SEM 0.4) with grass trimming to 22.2 (SEM 1.6) ml · kg–1 · min–1 with push manual mowing. With self-propelled mowing at three speeds in phase III, mean
of the CAD groups ranged from 9.5 (SEM 0.3) to 13.8 (SEM 1.4) ml · kg–1 · min–1 and represented 37%–62%
. The results indicated that lawn mowing is often performed at an exercise intensity recommended for aerobic exercise training; patients who achieve a treadmill peak capacity of 4 times resting metabolic rate (4 METs) should be able to perform self-propelled motorized lawn mowing (slow speed) and grass trimming at less than 80% peak
; and
demands of lawn mowing can be adjusted by equipment selection and/or pace. 相似文献
12.
H. A. deVries Robert A. Wiswell PhD G. Romero T. Moritani R. Bulbulian 《European journal of applied physiology》1982,49(2):277-286
Summary Five older men (aged 60–69 yr) and five young men (aged 21–29 yr) with approximately equal levels of age-corrected
max were compared with respect to oxygen kinetics at equal absolute workloads (100 watts) and at equal relative workloads
(45%
max) on a cycle ergometer. At 45%
max, half times for
response to instantaneous transition from unloaded pedalling were 30.0 s and 27.4 s for old and young respectively (t=0.260,p<0.80). No significant differences were found in the
response and by inference none existed in O2 extraction. Mean half times for heart rate responses at a workload of 100 W were 24.2 s and 20.6 s for old and young groups
respectively (t=0.722,p<0.49). Mechanical efficiency estimated from steady state data at 100 W was 19.8% and 20.5% for old and young groups respectively
(t=0.574). The close similarity in responses to submaximal work in old and young subjects of equivalent fitness suggests caution
in the interpretation of agewise decrements observed in physiological variables which may be sensitive to physical fitness
status. 相似文献
13.
Summary The individual anaerobic threshold (IAT) has been defined as the highest metabolic rate at which blood lactate (La) concentrations are maintained at a steady state during prolonged exercise. The validity of this definition, however, has not been substantiated. Eleven men [maximum oxygen uptake (
), mean (SD), 57.8 (6.9) ml·kg–1 · min–1) did two maximal incremental cycle exercise tests (30 W and 4 min per step). Blood was sampled repeatedly during exercise and for 9 min during the subsequent recovery period with light activity. The subjects then exercised at the power output equivalent of IAT for 45 min, until they could no longer continue or until rectal temperature reached 39°C. Subjects performed two additional exercise tests. The intensity of these tests depended upon the LA and acid-base responses during the last 15 min of at least 30 min of exercise at IAT. If a steady state was achieved (La, pH and PCO2 changed by less than 0.5 mmol·l–1, 0.005 pH units and 0.3 kPa, respectively) or decreasing La and increasing pH values were observed, then the second test was performed at IAT + 5%
and the third session at either IAT + 2.5% or +7.5%
. Conversely if a steady state was not achieved during exercise at the calculated IAT, the intensity of the second test was set at IAT–5%
. Depending on the La and acid-base responses during this test, the final session was performed at either IAT –2.5% or –7.5%
. Test-retest reliability for the determination of IAT was high (r = 0.98; estimated SE was 8 W or about 2%
) and the method was reproducible [mean (SD); 240.3 (41.7) W for test 1 and 236.6 (42.9) W for test 2]. However, only 4 subjects completed at least 30 min of exercise at IAT with steady-state La and acid-base responses. None of these subjects showed steady-state responses at +5%
above IAT, and only 1 met the criteria at +2.5%
above IAT. Therefore, for these individuals the incremental exercise test underestimated the true IAT by less than 5%
. For the other 7 subjects, 4 met the steady-state criteria at both –5% and –2.5%
below the calculated IAT, suggesting the true IAT was overestimated by less than 2.5%
. For 2 of the remaining subjects, the incremental exercise test over-estimated the true IAT by at least 7.5%
. Therefore, the maximal incremental exercise test followed by a light active recovery period will produce a reliable and reproducible estimate of IAT which is valid for the majority of subjects. However, since the method overestimates the true IAT for some individuals, the procedure cannot be assumed (without verification) to be valid for all subjects. 相似文献
14.
Summary These experiments examined the effect of exercise intensity and duration on the magnitude of the abrupt change in ventilation at the start (
) and end (
) of exercise. Five subjects performed constant load treadmill exercise at 50% and 80% of their maximum oxygen consumption (
) for 6 and 10 min while inspiring atmospheric air. The subjects also completed additional exercise tests at 80%
for 10 min while inspiring an oxygen-enriched gas mixture. During each exercise trial ventilation was measured breath-by-breath. The
and
were determined by using non-linear curve-fitting techniques. The results showed that
was greater at the start of the 80-% exercise tests compared to the 50-% tests and that
at each level of exercise was greater than
. The results also demonstrated that
was inversely related to the intensity and duration of exercise. Furthermore, the
was not altered subsequent to the inspiration of oxygen-enriched air. These findings have led us to postulate that the stimulus responsible for
is reduced during exercise and that the degree of reduction is related to the intensity and duration of exercise. In addition, it was concluded that these changes might occur independently of peripheral chemoreceptor activity. 相似文献
15.
M. -T. Linossier D. Dormois R. Fouquet A. Geyssant C. Denis 《European journal of applied physiology》1996,74(5):420-427
A group of 15 untrained male subjects pedalled on a friction-loaded cycle ergometer as fast as possible for 5–7 s to reach
the maximal velocity (V{immax}) against different braking forces (F
B). Power was averaged during a complete crank rotation by adding the power dissipated againstF
B to the power necessary to accelerate the flywheel. For each sprint, determinations were made of peak power output (
) power output attained atV
max (
) calculated as the product ofV
max andF
B and the work performed to reachV
max expressed in mean power output (
). The relationships between these parameters andF
B were examined. A biopsy taken from the vastus lateralis muscle and tomodensitometric radiographs of both thighs were taken
at rest to identify muscle metabolic and morphometric properties. The
value was similar for allF
B. Therefore, the average of values was defined as corrected maximal power (
). This value was 11 higher than the maximal power output uncorrected for the acceleration. Whereas the
determination did not require high loads, the highest
value (
) was produced when loading was heavy, as evidenced by the
-F
B parabolic relationship. For each subject, the braking force (
) giving
was defined as optimal. The
, equal to 0.844 (SD 0.108) N · kg−1 bodymass, was related to thigh muscle area (r = 0.78,P < 0.05). The maximal velocity (
) reached against this force seemed to be related more to intrinsic fibre properties (% fast twitch b fibre area and adenylate
kinase activity). Thus, from the
determination, it is suggested that it should be possible to predict the conditions for optimal exercise on a cycle ergometer. 相似文献
16.
Stephen P. Keith Ira Jacobs Tom M. McLellan 《European journal of applied physiology》1992,65(4):316-323
Summary The individual anaerobic threshold (Than) is the highest metabolic rate at which blood lactate concentrations can be maintained at a steady-state during prolonged exercise. The purpose of this study was to test the hypothesis that training at the Than would cause a greater change in indicators of training adaptation than would training around the Than. Three groups of subjects were evaluated before, and again after 4 and 8 weeks of training: a control group, a group which trained continuously for 30 min at the Than intensity (SS), and a group (NSS) which divided the 30 min of training into 7.5-min blocks at intensities which alternated between being below the Than [Than–30% of the difference between Than and maximal oxygen consumption (
)] and above the Than (Than + 30% of the difference between Than and
). The
increased significantly from 4.06 to 4.271 · min–1 in SS and from 3.89 to 4.061-min–1 in NSS. The power output (W) at Than increased from 70.5 to 79.8%
in SS and from 71.1 to 80.7%
in NSS. The magnitude of change in
,W at Than, %
at Than and in exercise time to exhaustion at the pretraining Than was similar in both trained groups. Vastus lateralis citrate synthase and 3-hydroxyacyl-CoA-dehydrogenase activities increased to the same extent in both trained groups. While all of these training-induced adaptations were statistically significant (P<0.05), there were no significant changes in any of these variables for the control subjects. These results suggest that the relative stimulus for physiological adaptation to training was similar in SS and NSS. These results also demonstrate that, when training intensity is set relative to the Than, it is the mean intensity during training that determines the extent of adaptation regardless of whether the exercise is performed intermittently or continuously. 相似文献
17.
Ryszard Grucza Yoshimi Nakazono Yoshimi Miyamoto 《European journal of applied physiology》1989,59(1-2):59-67
Summary Twenty young, untrained men performed two tests on cycle ergometer in order to verify whether the kinetics of the cardiorespiratory
reactions exhibit any relation to maximal oxygen uptake (
) in the untrained state. On the 1st day, the subjects exercised at work intensities of 50 and 100 W, the increase as a step
function, for periods of 10 min each. The next day, they performed exercise at a relative intensity of 50%
for 10 min. Respiratory frequency, tidal volume, minute ventilation (
), heart rate (HR), stroke volume (SV), and cardiac output (
) were measured continuously. The SV was measured by impedance plethysmography. All the cardiorespiratory variables increased
rapidly at the onset of both absolute and relative intensity of work, with a faster response for
than for
. The increase in absolute intensity of work from 50 to 100 W caused a significantly slower cardiorespiratory reaction than
at the beginning of exercise. The SV increased by 20 ml during first 20 s of both absolute and relative intensities of work
and then began to decrease after 6 and 4 min of the exercise, respectively. The decrease in SV was associated with an increase
in HR and a stable value of
. Acceleration at the beginning of, and deceleration during recovery from, the relative intensity of work for
, HR, and
were well correlated with individual levels of
in the tested men. It is concluded that the kinetics of cardiorespiratory reaction to a constant, relative intensity of work
is related to
in untrained men, and that the kinetics probably constitute a physiological feature of an individual. 相似文献
18.
Summary Thermoregulatory responses were studied in seven women during two separate experimental protocols in the follicular (F, days
4–7) phase and during the luteal (L, days 19–22) phase of the menstrual cycle. Continuous measurements of esophageal temperature
(T
es), mean skin temperature (
), oxygen uptake and forearm sweating (
) were made during all experiments. Protocol I involved both passive heat exposure (3 h) and cycle exercise at ∼80%
peak during which the environmental chamber was controlled atT
a=50.0° C, rh=14% (P
w=1.7 kPa). In protocol II subjects were tested during thirty-five minutes of exercise at ∼85%
peak atT
a=35° C and rh=25% (P
w=1.4 kPa). The normal L increase in restingT
es (≈0.3° C) occurred in all seven subjects.
was higher during L than F in all experiments conducted at 50° C. During exercise and passive heat exposure, theT
es threshold for sweating was higher in L, with no change in the thermosensitivity (slope) of
toT
es between menstrual cycle phases. This rightward or upward shift inT
es threshold for initiation of sweating averaged 0.5° C for all experiments. The data indicate the luteal phase modulation in
the control of sweating in healthy women is also apparent during severe exercise and/or heat stress. 相似文献
19.
André L. Vallerand Gustave Savourey Anne-Marie Hanniquet Jacques H. M. Bittel 《European journal of applied physiology》1992,65(3):286-294
Summary The aim of this study was to determine whether in humans there are differences in the heat storage calculated by partitional calorimetry (S, the balance of heat gains and heat losses) compared to the heat storage obtained by conventional methods (thermometry) via either core temperature or mean body temperatures (
, whereT
c is core temperature and
is mean skin temperature) when two different sites are used as an index ofT
c [rectal (T
re) and auditory canal (T
ac) temperatures]. Since women respond to the heat differently than men, both sexes were studied. After a stabilisation period at thermal neutrality, six men and seven women were exposed to a globe temperature of 50°C, relative humidity of 17% and wind speed of 0.8–1.0 m·s–1 for 90 min semi-nude at rest, whereT
re,T
ac,
, metabolic rate, dry (radiant+convective heat exchange) and evaporative heat losses,S, heat storage byT
c (
) and heat storage by
were assessed every minute. In the men,S was equal to 350.8(SEM 49.6) kJ whereas
amounted to only 114.6(SEM 16.2) and 196.7(SEM 32.3) kJ forT
re andT
ac, respectively (P<0.05). Final
underestimatedS by 49% [177.7(SEM 23.0) kJ;P<0.05] whereas
was not significantly different than S [255.7(SEM 37.9) kJ]. In the women,S corresponded to a total of 294.3(SEM 23.2) kJ, a value that was very similar to the
262.6(SEM 31.0) kJ], whereas
underpredicted by 35% [190.4(SEM 26.3) kJ;P<0.05]. As in the men,S
T
c was much lower thanS [116.6(SEM 19.9) and 190.3(SEM 24.2) kJ forT
re andT
ac, respectively;P<0.05]. Using seven other well-known
weighting coefficients,
could under- and overestimateS by up to 55% and 11%, respectively. In all subjects, a large portion of the variance (68% and 75%) in the difference betweenS and
, could be explained primarily by the T
ac. The results demonstrated that although some estimates of thermometric heat storage matched the calorimetricS, other predictions underestimated it by up to 67% during passive heating. It is suggested that these differences can be explained in part by he site chosen to representT
c, the use of eitherT
c or
in the heat storage calculation, and the thermoneutral/hot weighting coefficient(s) chosen to determine
. Until more representative measurements of body temperatures at different depths (core, shell and intermediate) are possible, the use of
and
-derived heat storage is difficult to justify. 相似文献
20.
François Carré Josette Dassonville Jocelyne Beillot Jean-Yves Prigent Pierre Rochcongar 《European journal of applied physiology》1994,69(3):258-261
A group of 18 well-trained white-water kayakers performed maximal upper body exercise in the laboratory and during.a field test. Laboratory direct peak oxygen uptake (
) values were compared, firstly by a
backward extrapolation estimation and secondly by an estimation calculated from
measured during the first 20 s of exercise recovery. Direct peak
correlated with
backward extrapolation (r=0.89), but the results of this study showed that the backward extrapolation method tended to overestimate significantly peak
by [0.57 (SD 0.31) 1·min–1 in the laboratory, and 0.66 (SD 0.33) 1·min–1 in the field,P<0.001]. The
measured during the first 20 s of recovery, whether the exercise was performed in the laboratory or in the field, correlated well with the laboratory direct peak
(r=0.92 andr=0.91, respectively). The use of the regression equation obtained from field data
2f20s, that is peak
2=0.23+1.08
2f20s, gave an estimated peak
2, the mean difference of which compared with direct peak
was 0.22 (SD 0.13) 1·min–1. In conclusion, we propose the use of a regression equation to estimate peak
from a single sample of the gas expired during the first 20 s of recovery after maximal exercise involving the upper part of the body. 相似文献