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1.
This study investigated the possible influence of oral caffeine administration on endogenous glucose production and energy
substrate metabolism during prolonged endurance exercise. Twelve trained endurance athletes [seven male, five female; peak
oxygen consumption (
) = 65.5 ml·kg–1·min–1] performed 60 min of cycle ergometry at 65%
twice, once after oral caffeine administration (6 mg·kg–1) (CAF) and once following consumption of a placebo (PLA). CAF and PLA were administered in a randomized double-blind manner
75 min prior to exercise. Plasma glucose kinetics were determined with a primed-continuous infusion of [6,6-2H]glucose. No differences in oxygen consumption (
), and carbon dioxide production (
) were observed between CAF and PLA, at rest or during exercise. Blood glucose concentrations were similar between the two
conditions at rest and also during exercise. Exercise did lead to an increase in serum free fatty acid (FFA) concentrations
for both conditions; however, no differences were observed between CAF and PLA. Both the plasma glucose rate of appearance
(
) and disappearance (
) increased at the onset of exercise (P<0.05), but were not affected by CAF, as compared to PLA. CAF did lead to a higher plasma lactate concentration during exercise
(P<0.05). It was concluded that an acute oral dose of caffeine does not influence plasma glucose kinetics or energy substrate
oxidation during prolonged exercise in trained endurance athletes. However, CAF did lead to elevated plasma lactate concentrations.
The exact mechanism of the increase in plasma lactate concentrations remains to be determined.
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2.
The purpose of the present study was to examine comprehensively the kinetics of oxygen uptake (
) during treadmill running across the moderate, heavy and severe exercise intensity domains. Nine subjects [mean (SD age,
27 (7) years; mass, 69.8 (9.0) kg; maximum
,
, 4,137 (697) ml·min–1] performed a series of "square-wave" rest-to-exercise transitions of 6 min duration at running speeds equivalent to 80% and
100% of the
at lactate threshold (LT; moderate exercise); and at 20%, 40%, 60%, 80% and 100% of the difference between the
at LT and
(Δ, heavy and severe exercise). Critical velocity (CV) was also determined using four maximal treadmill runs designed to result
in exhaustion in 2–15 min. The
response was modelled using non-linear regression techniques. As expected, the amplitude of the
primary component increased with exercise intensity [from 1,868 (136) ml·min–1 at 80% LT to 3,296 (218) ml·min–1 at 100% Δ, P<0.05]. However, there was a non-significant trend for the "gain" of the primary component to decrease as exercise intensity
increased [181 (7) ml·kg–1·km–1 at 80% LT to 160 (6) ml·kg–1·km–1 at 100% Δ]. The time constant of the primary component was not different between supra-LT running speeds (mean value range
= 17.9–19.1 s), but was significantly shorter during the 80% LT trial [12.7 (1.4) s, P<0.05]. The
slow component increased with exercise intensity from 139 (39) ml·min–1 at 20% Δ to 487 (57) ml·min–1 at 80% Δ (P<0.05), but decreased to 317 (84) ml·min–1 during the 100% Δ trial (P<0.05). During both the 80% Δ and 100% Δ trials, the
at the end of exercise reached
[4,152 (242) ml·min–1 and 4,154 (114) ml·min–1, respectively]. Our results suggest that the "gain" of the primary component is not constant as exercise intensity increases
across the moderate, heavy and severe domains of treadmill running. These intensity-dependent changes in the amplitudes and
kinetics of the
response profiles may be associated with the changing patterns of muscle fibre recruitment that occur as exercise intensity
increases.
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3.
Ventilatory work during heavy endurance exercise has not been thought to influence systemic lactate concentration. We evaluated
the effect of maximal isocapnic volitional hyperpnoea upon arterialised venous blood lactate concentration ([lac−]B) during leg cycling exercise at maximum lactate steady state (MLSS). Seven healthy males performed a lactate minimum test
to estimate MLSS, which was then resolved using separate 30 min constant power tests (MLSS=207±8 W, mean ± SEM). Thereafter,
a 30 min control trial at MLSS was performed. In a further experimental trial, the control trial was mimicked except that
from 20 to 28 min maximal isocapnic volitional hyperpnoea was superimposed on exercise. Over 20–28 min minute ventilation,
oxygen uptake, and heart rate during the control and experimental trials were 87.3±2.4 and 168.3±7.0 l min−1 (P<0.01), the latter being comparable to that achieved in the maximal phase of the lactate minimum test (171.9±6.8 l min−1), 3.46±0.20 and 3.83 ± 0.20 l min−1 (P<0.01), and 158.5±2.7 and 166.8±2.7 beats min−1 (P<0.05), respectively. From 20 to 30 min of the experimental trial [lac−]B increased from 3.7±0.2 to 4.7±0.3 mmol l−1 (P<0.05). The partial pressure of carbon dioxide in arterialised venous blood increased approximately 3 mmHg during volitional
hyperpnoea, which may have attenuated the [lac−]B increase. These results show that, during heavy exercise, respiratory muscle work may affect [lac−]B. We speculate that the changes observed were related to the altered lactate turnover in respiratory muscles, locomotor muscles,
or both. 相似文献
4.
This study evaluated whether the heart rate (HR) response to exercise depends on body position and on the active muscle mass.
The HR response to ergometer rowing (sitting and using both arms and legs) was compared to treadmill running (upright exercise
involving mainly the legs) using a progressive exercise intensity protocol in 55 healthy men [mean (SD) height 176 (5) cm,
body mass 71 (6) kg, age 21 (3) years]. During rowing HR was lower than during running at a blood lactate concentration of
2 mmol·l–1 [145 (13) compared to 150 (11) beat·min–1, P<0.05], 4 mmol·l–1 [170 (10) compared to 177 (13) beat·min–1, P<0.05], and 6 mmol·l–1 [182 (10) compared to 188 (10) beat·min–1, P<0.05]. Also during maximal intensity rowing, HR was lower than during maximal intensity running [194 (9) compared to 198 (11) beat·min–1, P<0.05]. These results were accompanied by a higher maximal oxygen uptake during rowing than during running [rowing compared
to running, 4.50 (0.5) and 4.35 (0.4) l·min–1, respectively, P<0.01]. Thus, the oxygen pulse, as an index of the stroke volume of the heart, was higher during rowing than during running
at any given intensity. The results suggest that compared to running, the seated position and/or the involvement of more muscles
during rowing facilitate venous return and elicit a smaller HR response for the same relative exercise intensity.
Electronic Publication 相似文献
5.
Summary The purposes of this investigation were to determine the validity of critical power (CP) as a measure of the work rate that can be maintained for a very long time without fatigue and to determine whether this corresponded with the maximal lactate steady-state (lass,max). Eight highly trained endurance cyclists (maximal oxygen uptake 74.1 ml · kg–1 · min–1, SD 5.3) completed four cycle ergometer tests to exhaustion at predetermined work rates (360, 425, 480 and 520 W). From these four co-ordinates of work and time to fatigue the regression of work limit on time limit was calculated for each individual (CP). The cyclists were then asked to exercise at their CP for 30 min. If CP could not be maintained, the resistance was reduced minimally to allow the subject to complete the test and maintain a blood lactate plateau. Capillary blood was sampled at 0, 5, 10, 20 and 30 min into exercise for the analysis of lactate. Six of the eight cyclists were unable to maintain CP for 30 min without fatigue. In these subjects, the mean power attained was 6.4% below that estimated by CP. Mean blood lactates (n = 8) reached a steady-state (8.9 mmol · l–1, SD 1.6) during the last 20 min of exercise indicating that CP slightly overestimated lass, max. Individual blood lactates during the last 20 min of exercise were more closely related to the y-intercept of the CP curve (r=0.78, P<0.05) than either CP (0.34, NS) or mean power output (r=0.42, NS). The present investigation has shown that highly trained endurance cyclists can tolerate previously unreported levels of blood lactate during 30 min of exercise at or near their CP. Blood lactates during continuous exercise are higher than at the same work rate during an incremental test. The CP provides a simple and inexpensive means of assessing the exercise intensity which can be maintained continuously, while avoiding the methodological difficulties associated with ventilatory and lactate thresholds. 相似文献
6.
The relationship between critical velocity, maximal lactate steady-state velocity and lactate turnpoint velocity in runners 总被引:2,自引:0,他引:2
In cycle exercise, it has been suggested that critical power, maximal lactate steady state, and lactate turnpoint all demarcate
the transition between the heavy exercise domain (in which blood lactate is elevated above resting values but remains stable
over time) and the very heavy exercise domain (in which blood lactate increases continuously throughout constant-intensity
exercise). The purpose of the present study was to assess the level of agreement between critical velocity (CV), maximal lactate
steady-state velocity (MLSSV), and lactate turnpoint velocity (LTPV) during treadmill running. Eight male subjects [mean (SD)
age 28 (5) years, body mass 71.2 (8.0) kg, maximum oxygen uptake 54.9 (3.2) ml·kg–1·min–1) performed an incremental treadmill test for the determination of LTPV (defined as a sudden and sustained increase in blood
lactate concentration ([La]) at ≅2.0–5.0 mM). The subjects returned to the laboratory on eight or nine occasions for the determination
of CV and MLSSV. The CV was determined from four treadmill runs at velocities that were chosen to result in exhaustion within
2–12 min. The MLSSV was determined from four or five treadmill runs of up to 30 min duration and defined as the highest velocity
at which blood [La] increased by no more than 1.0 mM after between 10 and 30 min of exercise. Analysis of variance revealed
no significant differences between [mean (SD)] CV [14.4 (1.1) km·h–1], MLSSV [13.8 (1.1) km·h–1] and LTPV [13.7 (0.6) km·h–1]. However, the bias ±95% limits of agreement for comparisons between CV and MLSSV [0.6 (2.2) km·h–1], CV and LTPV [0.7 (2.7) km·h–1], and MLSSV and LTPV [0.1 (1.8) km·h–1] suggest that the extent of disagreement is too great to allow one variable to be estimated accurately from another in individual
subjects. Direct determination of MLSSV is necessary if precision is required in experimental studies.
Electronic Publication 相似文献
7.
Effects of prior heavy exercise,prior sprint exercise and passive warming on oxygen uptake kinetics during heavy exercise in humans 总被引:3,自引:0,他引:3
Prior heavy exercise (above the lactate threshold, Thla) increases the amplitude of the primary oxygen uptake (VO2) response and reduces the amplitude of the VO2 slow component during subsequent heavy exercise. The purpose of this study was to determine whether these effects required
the prior performance of an identical bout of heavy exercise, or if prior short-duration sprint exercise could cause similar
effects. A secondary purpose of this study was to determine the effect of elevating muscle temperature (through passive warming)
on VO2 kinetics during heavy exercise. Nine male subjects performed a 6-min bout of heavy exercise on a cycle ergometer 6 min after:
(1) an identical bout of heavy exercise; (2) a 30-s bout of maximal sprint cycling; (3) a 40-min period of leg warming in
a hot water bath at 42°C. Prior sprint exercise elevated blood [lactate] prior to the onset of heavy exercise (by ≅5.6 mM)
with only a minor increase in muscle temperature (of ≅0.7°C). In contrast, prior warming had no effect on baseline blood lactate
concentration, but elevated muscle temperature by ≅2.6°C. Both prior heavy exercise and prior sprint exercise significantly
increased the absolute primary VO2 amplitude (by ≅230 ml·min–1 and 260 ml·min–1, respectively) and reduced the amplitude of the VO2 slow component (by ≅280 ml·min–1 and 200 ml·min–1, respectively) during heavy exercise, whereas prior warming had no significant effect on the VO2 response. We conclude that the VO2 response to heavy exercise can be markedly altered by both sustained heavy-intensity submaximal exercise and by short-duration
sprint exercise that induces a residual acidosis. In contrast, passive warming elevated muscle temperature but had no effect
on the VO2 response.
Electronic Publication 相似文献
8.
J. M. Le Chevalier H. Vandewalle C. Thépaut-Mathieu J. F. Stein L. Caplan 《European journal of applied physiology》2000,81(1-2):120-127
The hypothesis that critical power (CP) is significantly lower than the maximal aerobic power of the knee extensors has been
tested in nine endurance-trained subjects, seven gymnasts and seven weight lifters. CP was calculated as being equal to the
slope of the linear relationship between exhaustion time and work performed at exhaustion on a knee-extension ergometer. CP
was compared with the power output at the end of a progressive knee-extension exercise (P
peak) and the power outputs corresponding to exhaustion times equal to 4 (P
4 min), 6 (P
6 min), 8 (P
8 min) and 10 min (P
10 min), calculated according to the linear relationship between work and exhaustion time. The hypothesis that CP corresponds to
a steady state in metabolic and physiological parameters was tested in the gymnasts and the weight lifters by comparing CP
with the fatigue thresholds of the integrated electromyogram (iEMGFT), lactate level (LaFT), oxygen uptake (V˙O2FT) and heart rate (HRFT). The results of the present study demonstrate that the value of CP of a local exercise cannot be considered as the equivalent
of the maximal aerobic power for general exercises. The values of P
4 min, P
6 min, P
8 min, P
10 min and P
peak were significantly higher than CP, and corresponded to 138, 126, 119, 115 and 151% CP, respectively. The results of the present
study indicate that CP can be considered as an index of muscular endurance. Indeed, LaFT, iEMG FT, V˙O2FT and HRFT were not significantly different from CP. All of these fatigue thresholds were significantly correlated with CP (r > 0.92). Moreover, the highest coefficient of correlation (r=0.71; P < 0.01) between the percentage of maximal aerobic power in cycling that corresponds to a blood lactate concentration of 4 mmol · l−1 (OBLA%) and the different local aerobic indices was observed with CP.
Received: 22 February 1999 / Accepted: 16 June 1999 相似文献
9.
Oxygen uptake during whole-body vibration exercise: comparison with squatting as a slow voluntary movement 总被引:2,自引:0,他引:2
In this study we investigated metabolic power during whole-body vibration exercise (VbX) compared to mild resistance exercise.
Specific oxygen consumption (
) and subjectively perceived exertion (rating of perceived exertion, RPE; Borg scale) were assessed in 12 young healthy subjects
(8 female and 4 male). The outcome parameters were assessed during the last minute of a 3-min exercise bout, which consisted
of either (1) simple standing, (2) squatting in cycles of 6 s to 90° knee flexion, and (3) squatting as before with an additional
load of 40% of the subject's body weight (35% in females). Exercise types 1–3 were performed with (VbX+) and without (VbX–)
platform vibration at a frequency of 26 Hz and an amplitude of 6 mm. Compared to the VbX– condition, the specific
was increased with vibration by 4.5 ml·min–1·kg–1. Likewise, squatting and the additional load were factors that further increased
. Corresponding changes were observed in RPE. There was a correlation between VbX– and VbX+ values for exercise types 1–3
(r=0.90). The correlation coefficient between squat/no-squat values (r=0.70 without and r=0.71 with the additional load) was significantly lower than that for VbX–/VbX+. Variation in specific
was significantly higher in the squatting paradigm than with vibration. It is concluded that the increased metabolic power
observed in association with VbX is due to muscular activity. It is likely that this muscular activity is easier to control
between individuals than is simple squatting.
Electronic Publication 相似文献
10.
Maximal strength-training with an emphasis on maximal mobilization during cross-country skiing increases exercise economy
when double-poling. The aim of this experiment was to investigate whether the mechanism of this increase is a change in the
force-velocity relationship and the mechanical power output. A group of 19 cross-country skiers having an average peak oxygen
uptake of 255 ml·kg–0.67 body mass·min–1 or 61 ml·kg–1·min–1 were randomly assigned to either a high resistance-training group (n=10) or a control group (n=9). Upper body endurance was tested on a ski ergometer. The high-resistance-training group trained for 15 min on three occasions
a week for 9 weeks. Training consisted of three series of five repetitions using 85% of one repetition maximum (1RM), with
emphasis on high velocity in the concentric part of the movement. Upper body exercise economy, 1RM and time to exhaustion
increased significantly in the high resistance-training group, but was unchanged in the control group. Peak power and the
velocities for a given load increased significantly, except for the two lowest loads. We conclude that the increased exercise
economy after a period of upper body high resistance-training can be partly explained by a specific change in the force-velocity
relationship and the mechanical power output.
Electronic Publication 相似文献
11.
Effect of prior metabolic rate on the kinetics of oxygen uptake during moderate-intensity exercise 总被引:1,自引:0,他引:1
Brittain CJ Rossiter HB Kowalchuk JM Whipp BJ 《European journal of applied physiology》2001,86(2):125-134
Pulmonary oxygen uptake (
) dynamics during moderate-intensity exercise are often assumed to be dynamically linear (i.e. neither the gain nor the time
constant (τ) of the response varies as a function of work rate). However, faster, slower and unchanged
kinetics have been reported during work-to-work transitions compared to rest-to-work transitions, all within the moderate-intensity
domain. In an attempt to resolve these discrepancies and to improve the confidence of the parameter estimation, we determined
the
response dynamics using the averaged response to repeated exercise bouts in seven healthy male volunteers. Each subject initially
performed a ramp-incremental exercise test for the estimation of the lactate threshold (
). They then performed an average of four repetitions of each of three constant-work-rate (WR) tests: (1) between 20 W and
a work rate of 50% (WR50) between 20 W and 90%
(step 1→2), (2) between WR50 and 90%
(step 2→3), and (3) between 20 W and 90%
(step 1→3); 6 min was spent at each work rate increment and decrement. Parameters of the kinetic response of phase II
were established by non-linear least-squares fitting techniques. The kinetics of
were significantly slower at the upper reaches of the moderate-intensity domain (step 2→3) compared to steps 1→2 and 1→3 [group
mean (SD) phase II τ: step 1→2 25.3 (4.9) s, step 2→3 40.0 (7.4) s and step 1→3 32.2 (6.9) s]. The off-transient values of
τ were not significantly different from each other: 36.8 (16.3) s, 38.9 (11.6) s and 30.8 (5.7) s for steps 1→2, 2→3 and 1→3,
respectively. Surprisingly, the on-transient gain (G,
) was also found to vary among the three steps [G=10.56 (0.42) ml·min–1·W–1, 11.85 (0.64) ml·min–1·W–1 and 11.23 (0.52) ml·min–1·W–1 for steps 1→2, 2→3 and 1→3, respectively]; the off-transient G did not vary significantly and was close to that for the on-transient step 1→3 in all cases. Our results do not support a
dynamically linear system model of
during cycle ergometer exercise even in the moderate-intensity domain. The greater oxygen deficit per unit power increment
in the higher reaches of the moderate-intensity domain necessitates a greater transient lactate contribution to the energy
transfer, or a greater phosphocreatine breakdown, or possibly both.
Electronic Publication 相似文献
12.
The aim of this investigation was to examine the effect of water ingestion on physiological responses to prolonged cycling
(CYC) and running (RUN). A group of 11 men with mean (SEM) maximal oxygen uptake (V˙O2max) 48.5 (1.8) ml·kg–1·min–1 on a cycle-ergometer and 52.1 (2.2) ml·kg–1·min–1 on a treadmill (P<0.01) exercised for 90 min on four occasions, twice on each ergometer, at 60% of mode specific V˙O2max. No fluid was taken (D) in one trial on each ergometer, whereas 60% of fluid losses were replaced by drinking water in the
other trial (W). In CYC, water ingestion attenuated the change in cardiac output (
) and the reduction in stroke volume (ΔSV) [ΔSV: –22.7 (3.8) in D, –10.7 (2.9) ml·beat–1 in W, P<0.01;
: –1.9 (0.5) in D, –0.2 (0.4) l·min–1 in W at 85 min, P<0.01], but did not affect rectal temperature [T
re at 90 min: 38.8 (0.1)°C in D, 38.7 (0.1)°C in W]. In contrast, fluid replacement reduced hyperthermia in RUN [T
re at 90 min: 39.6 (0.2) in D, 39.1 (0.2)°C in W, P<0.01], and this was linked with a higher skin blood flow [RUN-W 88.9 (8.5), RUN-D 70.7 (8.4)%, P<0.05]. The
and ΔSV were also attenuated with water ingestion in this mode of exercise (P<0.05). It is concluded that water ingestion improves physiological function in both cycling and running, but that the underlying
mechanism is different in the two modes of exercise.
Electronic Publication 相似文献
13.
Laursen PB Rhodes EC Langill RH McKenzie DC Taunton JE 《European journal of applied physiology》2002,87(4-5):433-440
The purpose of this study was, firstly, to investigate the intensity of exercise performanceof highly trained ultra-endurance
triathletes during the cycling portion of an Ironman triathlon, and, secondly, to examine the anaerobic threshold and its
relationship to this performance. Following a peak oxygen consumption (VO2peak) test on a cycle ergometer to determine the heart rate (HRTh,vent) and power output (POTh,vent) at the ventilatory threshold (Thvent), 11 highly trained male triathletes [mean (SEM) age 35.8 (1.6) years, body fat 11.7 (1.2)%. VO2peak 67.5 (1.0) ml·kg–1·min–1] who were participating in an Ironman triathlon, in random order: (1) cycled at their POTh,vent (BiTh,vent) until they were exhausted, and (2) cycled for 5 h at a self-selected intensity (BiSSI). Cycling power output (PO), oxygen uptake (VO2), heart rate (HR) and blood lactate concentration ([La–]b) were recorded at regular intervals during these trials, while performance HR was recorded during the cycling phase of the
Ironman triathlon. Significantly greater (P<0.05) values were attained during BiTh,vent than during BiSSI for PO [274 (9) compared to 188 (9) W], VO2 [3.61 (0.15) compared to 2.64 (0.09) l·min–1], and [La–]b [6.7 (0.8) compared to 2.8 (0.4) mmol·l–1]. Moreover, mean HR during the Ironman triathlon cycle phase [146.3 (2.4) beats·min–1; n=7] was significantly greater than mean HR during BiSSI [130 (4) beats·min–1], and significantly less than mean HR during BiTh,vent [159 (3) beats·min–1; all P<0.05]. However, HR during the cycle portion of the Ironman triathlon was highly related to (r=0.873; P<0.05) and not significantly different to HRTh,vent [150 (4) beats·min–1]. These data suggest that ultra-endurance triathletes cycle during the Ironman triathlon at a HR intensity that approximates
to HRTh,vent, but at a PO that is significantly below POTh,vent.
Electronic Publication 相似文献
14.
Beta-endorphin immunoreactivity during high-intensity exercise with and without opiate blockade 总被引:3,自引:2,他引:1
Angelopoulos TJ 《European journal of applied physiology》2001,86(1):92-96
Nine highly fit men [mean (SE) maximum oxygen uptake,
: 63.9 (1.7) ml·kg–1·min–1; age 27.6 (1.6) years] were studied during two treadmill exercise trials to determine plasma β-endorphin immunoreactivity
during intense exercise (80%
). A double-blind experimental design was used, and subjects performed the two exercise trials in counterbalanced order. Exercise
trials were 30 min in duration and were conducted 7 days apart. One exercise trial was undertaken following administration
of naloxone (1.2 mg; 3 cm3) and the other after receiving a placebo (0.9% NaCl saline; 3 cm3). Prior to each experimental trial, a flexible catheter was placed into an antecubital vein and baseline blood samples were
collected. Thereafter, each subject received either a naloxone or placebo bolus injection. Blood samples were also collected
after 10, 20 and 30 min of continuous exercise. β-Endorphin was higher (P<0.05) during exercise when compared to pre-exercise in both trials. However, no statistically significant difference was
found (P>0.05) between exercise time points within either experimental trial. β-endorphin immunoreactivity was greater (P<0.05) in the naloxone than in the placebo trial during each exercise sampling time point [10 min: 63.7 (3.9) pg·ml–1 vs 78.7 (3.8) pg·ml–1; 20 min: 68.7 (4.1) pg·ml–1 vs 83.8 (4.3) pg·ml–1; 30 min: 71.0 (4.3) pg·ml–1 vs 82.5 (3.2) pg·ml–1]. These data suggest that intense exercise induces significant increases in β-endorphin that are maintained over time during
steady-rate exercise. Exercise and naloxone had an interactive effect on β-endorphin release that warrants further investigation.
Electronic Publication 相似文献
15.
In this study we examined the oxygenation trend of the vastus medialis muscle during sustained high-intensity exercise. Ten
cyclists performed an incremental cycle ergometer test to voluntary exhaustion [mean (SD) maximum oxygen uptake 4.29 (0.63) l·min–1; relative to body mass 60.8 (2.4) ml·kg–1·min–1] and a simulated 20-km time trial (20TT) on a wind-loaded roller system using their own bicycle (group time = 23–31 min)
in two separate sessions. Cardiorespiratory responses were monitored using an automated metabolic cart and a wireless heart
rate monitor. Tissue absorbency, which was used as an index of muscle oxygenation, was recorded simultaneously from the vastus
medialis using near-infrared spectroscopy. Group mean values for oxygen uptake, ventilation, heart rate, respiratory exchange
ratio, power output, and rating of perceived exhaustion were significantly (P≤0.05) higher during the incremental test compared to the 20TT [4.29 (0.63) l·min–1 vs 4.01 (0.55) l·min–1, 120.4 (26) l·min–1 vs 97.6 (16.1) l·min–1, 195 (8) beats·min–1 vs 177 (9) beats·min–1, 1.15 (0.06) vs 0.93 (0.06), 330.1 (31) W vs 307.2 (24.5) W, and 19 (1.5) vs 16 (1.7), respectively]. Oxygen uptake and heart
rate during the 20TT corresponded to 93.5% and 90.7%, respectively, of the maximal values observed during the incremental
test. Comparison of the muscle oxygenation trends between the two tests indicated a significantly greater degree of deoxygenation
during the 20TT [–699 (250) mV vs –439 (273) mV; P≤0.05] and a significant delay in the recovery oxygenation from the 20TT. The mismatching of whole-body oxygen uptake and
localised tissue oxygenation between the two tests could be due to differences in muscle temperature, pH, localised blood
flow and motor unit recruitment patterns between the two tests.
Electronic Publication 相似文献
16.
Acute EPOC response in women to circuit training and treadmill exercise of matched oxygen consumption 总被引:2,自引:0,他引:2
The purpose of the study was to evaluate the effects of circuit training (CT) and treadmill exercise performed at matched rates of oxygen consumption and exercise duration on elevated post-exercise oxygen consumption (EPOC) in untrained women, while controlling for the menstrual cycle. Eight, untrained females (31.3±9.1 years; 2.04±0.26 l min–1 estimated VO2max; BMI=24.6±3.9 kg/m2) volunteered to participate in the study. Testing was performed during the early follicular phase for each subject to minimize hormonal variability between tests. Subjects performed two exercise sessions approximately 28 days apart. Resting, supine energy expenditure was measured for 30 min preceding exercise and for 1 h after completion of exercise. Respiratory gas exchange data were collected continuously during rest and exercise periods via indirect calorimetry. CT consisted of three sets of eight common resistance exercises. Pre-exercise and exercise oxygen consumption was not different between testing days (P>0.05). Thus, exercise conditions were appropriately matched. Analysis of EPOC data revealed that CT resulted in a significantly higher (p<0.05) oxygen uptake during the first 30 min of recovery (0.27±0.01 l min–1 vs 0.23±0.01 l min–1); though, at 60 min, treatment differences were not present. Mean VO2 remained significantly higher (0.231±0.01 l min–1) than pre-exercise measures (0.193±0.01 l min–1) throughout the 60-min EPOC period (p<0.05). Heart rate, RPE, VE and RER were all significantly greater during CT (p<0.05). When exercise VO2 and exercise duration were matched, CT was associated with a greater metabolic disturbance and cost during the early phases of EPOC. 相似文献
17.
Effect of ageing on the ventilatory response and lactate kinetics during incremental exercise in man
Jacques Prioux Michèle Ramonatxo Maurice Hayot Patrick Mucci Christian Préfaut 《European journal of applied physiology》2000,81(1-2):100-107
We investigated the effects of age on breathing pattern, mouth occlusion pressure, the ratio of mouth occlusion pressure
to mean inspiratory flow, and venous blood lactate kinetics during incremental exercise. Mouth occlusion pressure was used
as an index of inspiratory neuromuscular activity, and its ratio to mean inspiratory flow was used as an index of the “effective
impedance” of the respiratory system. Nine elderly male subjects [mean (SD) age: 68.1 (4.8) years] and nine young male subjects
[mean (SD) age: 23.4 (1.3) years] performed an incremental exercise test on a bicycle ergometer. After a warm-up at 30 W,
the power was increased by 30 W every 1.5 min until exhaustion. Our results showed that at maximal exercise, power output,
breathing pattern, and respiratory exchange values, with the exception of tidal volume and the “effective impedance” of the
respiratory system, were significantly higher in the young subjects. The power output and oxygen consumption values at the
anaerobic threshold were also significantly higher in the young men. At the same power output, the elderly subjects showed
significantly higher values for minute ventilation, respiratory equivalents for oxygen uptake and carbon dioxide output (CO2), mean inspiratory flow, occlusion pressure and lactate concentration than the young subjects. At the same CO2 below the anaerobic threshold (0.5, 0.75, 1.00 and 1.25 l · min−1), minute ventilation and lactate concentration were also significantly higher in the elderly subjects. We observed a significantly
higher minute ventilation at CO2 values of 0.5, 0.75, 1.00 (P < 0.001) and 1.25 l · min−1 (P < 0.05) in the elderly men, and a significantly higher lactate concentration at CO2 values of 1.00 (P < 0.05) and 1.25 l · min−1 (P < 0.01). In conclusion, the ventilatory response in elderly subjects is elevated in comparison with that in young subjects,
both below and above the anaerobic threshold. This study demonstrates for the first time that this ventilatory increase, both
below and above the threshold, is partly due to an increased lactate concentration.
Received: 30 March 1999 / Accepted: 24 June 1999 相似文献
18.
Santa-Clara H Fernhall B Mendes M Sardinha LB 《European journal of applied physiology》2002,87(6):568-575
Weight-training is recommended as a complement to conventional aerobic-training for most low to moderate risk patients suffering
from coronary artery disease (CAD). The purpose of this study was to evaluate the effect of a 1 year exercise programme combining
weight- and aerobic-training on peak oxygen uptake (VO2,peak) and ventilatory threshold (VT). We studied 40 men suffering CAD who were divided into three groups: 14 subjects to weight-training
plus aerobic-training [mean (SD] [combined exercise group, age 55 (10) years], 14 to aerobic-training only [aerobic-training
group, age 57 (11) years], and 12 to a control group [standard care, age 57 (11) years]. A symptom-limited graded exercise
test using the standard Bruce protocol was performed using a 12-lead electrocardiogram, and gas analysis techniques. Muscle
strength was determined only in the combined exercise group using the one-repetition maximum method on each of eight weight
exercises. Arm and leg strength increased by 21.9% and 27.8% respectively (P<0.0001) from pre to post-tests. The VO2,peak did not differ between the combined and aerobic-training groups but their adjusted means were greater than those of the control
group [39 (1.8) and 35.3 (1.8) compared to 26.2 (2.7) ml·kg–1·min–1 (P<0.001)]. The oxygen uptake at VT was higher in the combined group [24.7 (1.4) ml·kg–1·min–1] compared to aerobic [18.7 (1.4) ml·kg–1·min–1] and control [13.6 (1.7) ml·kg–1min–1] groups (P<0.001). Similar results were found for exercise tolerance (treadmill time to peak and at VT). Combined exercise training
increased the VT more than aerobic-training alone. Combined exercise training did not improve the VO2,peak or the functional capacity more than aerobic-training alone.
Electronic Publication 相似文献
19.
To determine the effect of acute plasma volume (PV) expansion on substrate utilization, blood metabolites and catecholamines
to prolonged, moderate intensity cycle exercise, eight untrained men mean maximal oxygen uptake,O2max 4.10 (SEM 0.32) l · min−1 were infused (10 ml·kg−1) with a 6% dextran (DEX) solution. These responses were also compared to those elicited using a short-term training (TR)
protocol involving cycling for 90 to 120 min · day−1 at 60% O2max for 3 consecutive days. In general DEX, which resulted in a calculated expansion of PV by 23.9%, was without effect in modifying
exercise oxygen uptake or the reduction in the respiratory exchange ratio (R) observed during prolonged exercise. In addition,
the concentrations of blood glucose, glycerol, alanine and serum free fatty acids, although altered (P < 0.05) by exercise, were not altered by DEX. Blood lactate concentration was only higher (P < 0.05) at 30 min of exercise during DEX compared to the control. With the exception of blood lactate concentration, which
was reduced (P < 0.05), TR did not change R or the concentrations of other blood metabolites. The concentrations of nonadrenaline and adrenaline, were depressed (P < 0.05) by DEX and TR at 60 and 90 min of exercise. These results would suggest that mechanisms as yet undefined can compensate
for the estimated 10% reduction in arterial oxygen content mediated by acute PV expansion and enable prolonged exercise to
be performed without adjustments in substrate selection and substrate mobilization.
Accepted: 23 August 1996 相似文献
20.
The slope of the expired alveolar partial pressure of carbon dioxide profile increases during exercise. Its relationship
to metabolic rate, however, remains to be determined at high exercise intensities. We therefore determined the slope of alveolar
partial pressures of carbon dioxide and oxygen (
,
, respectively) during incremental cycle ergometer exercise (an increment of 40 W each minute) to exhaustion in 11 normal
subjects. The
and
increased as linear functions of carbon dioxide production and oxygen uptake (
), respectively, up to the estimated lactate threshold (θLa
–). At higher intensities
increased disproportionately but
continued to increase at the same rate in 7 subjects but increased more rapidly in the remainder. The rate of change in
per unit rate of change in
averaged 3.15 (SD 1.05) (mmHg·s–1)·(l·min–1)–1 while the rate of change in
per unit rate of change in
averaged –3.53 (SD 0.79) (mmHg·s–1)·(l·min–1)–1 over this range. The more rapid increase in
above θLa
– was consistent with an accelerated CO2 exchange, whereas the more rapid rate of change in
in 3 of the subjects may have reflected the development of an increased distribution of the ventilation perfusion ratio in
addition to the effects of hyperventilation.
Electronic Publication 相似文献