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1.
Miura A Endo M Sato H Sato H Barstow TJ Fukuba Y 《European journal of applied physiology》2002,87(3):238-244
For high-intensity cycle ergometer exercise, the relationship between power output (P) and its tolerable duration (t) has been well characterized by the hyperbolic relationship: (P–θ
F)·t=W′, where θF has been termed the "critical power" or "fatigue threshold". The curvature constant (W′) reflects a constant amount of work
which can be performed above θF, and it may be regarded as a muscle energy store. The relationship of this energy store to muscle mass is not known. Therefore,
the purpose of this study was to determine the relationships among W′, accumulated peak oxygen deficit (accumulated peak O2-deficit), and muscle cross-sectional area (CSA) of the thigh for high-intensity cycle ergometry in humans. A group of 17 healthy
male subjects (aged 21–41 years) participated in this study. The θF and W′ of the P-t hyperbolic relationship and the accumulated peak O2-deficit was calculated by standard procedures. The CSA of muscle, fat and bone in the right thigh were measured using ultrasonography.
The mean (SD) of θF, W′, accumulated peak O2-deficit, and muscle CSA of the thigh were 200.0 (17.8) W, 12.60 (2.94) kJ, 2.29 (0.41) l, and 185.3 (22.6) cm2, respectively. The muscle CSA of the thigh was positively correlated with W′ (r=0.59, P<0.01) and with accumulated peak O2-deficit (r=0.54, P<0.05). The relationship between W′ and accumulated peak O2-deficit also showed a positive correlation (r=0.63, P<0.005). Our results indicated that W′ derived from the P-t hyperbolic curve as anaerobic working capacity is related to the CSA of muscle.
Electronic Publication 相似文献
2.
Han Houdijk Eveline A. M. Heijnsdijk Jos J. de Koning Gert de Groot Maarten F. Bobbert 《European journal of applied physiology》2000,83(4-5):283-288
The present study investigates which physiological sources support the increase in mechanical power output (W˙
out) that can be obtained using klapskates in speed skating. It was hypothesized that the increase in W˙
out could be achieved through an increase in gross efficiency or an increase in aerobic power (W˙
aer). Six speed skaters performed a submaximal and maximal 1600-m skating test with both klapskates and conventional skates,
to measure gross efficiency and maximal W˙
aer during speed skating. The rate of oxygen uptake (V˙O2) and post-exercise blood lactate concentrations ([La]) were measured and video recordings were made. W˙
aer was calculated from V˙O2. W˙
out was derived from the power needed to overcome air and ice friction. Gross efficiency was calculated as the ratio of W˙
out and W˙
aer. In the maximal tests, the subjects skated faster with klapskates compared to conventional skates (10.0 vs 9.6 m · s−1). They sustained the resulting higher W˙
out with klapskates with an equal V˙O2. [La] was, however, 1.7 mmol · l−1 higher when klapskates were used, which might reflect an increase in anaerobic power. During the submaximal tests the skaters
generated equal W˙
out with both types of skate. Although not statistically significant, V˙O2 and W˙
aer were, on average, lower when klapskates were used compared to conventional skates [mean (SD) 0.3 (0.43) l · min−1, 105 (143) W]. Despite the lack of a statistically significant difference in W˙
aer, gross efficiency was shown to be significantly higher with klapskates compared to conventional skates (16.3% vs 14.8%, P=0.02). We conclude that the increase in W˙
out when the subjects were using klapskates could be explained by an increase in gross efficiency rather than an increase in
W˙
aer.
Accepted: 20 July 2000 相似文献
3.
The aim of the study was to examine to what extent prior high- or low-intensity cycling, yielding the same amount of external
work, influenced the oxygen uptake (V˙O2) slow component of subsequent high-intensity cycling. The 12 subjects cycled in two protocols consisting of an initial 3 min
period of unloaded cycling followed by two periods of constant-load exercise separated by 3 min of rest and 3 min of unloaded
cycling. In protocol 1 both periods of exercise consisted of 6 min cycling at a work rate corresponding to 90% peak oxygen
uptake (V˙O2peak). Protocol 2 differed from protocol 1 in that the first period of exercise consisted of a mean of 12.1 (SD 0.8) min cycling
at a work rate corresponding to 50% V˙O2peak. The difference between the 3rd min V˙O2 and the end V˙O2 (ΔV˙O2(6−3)) was used as an index of the V˙O2 slow component. Prior high-intensity exercise significantly reduced ΔV˙O2(6−3). The ΔV˙O2(6−3) was also reduced by prior low-intensity exercise despite an unchanged plasma lactate concentration at the start of the second
period of exercise. The reduction was more pronounced after prior high- than after prior low-intensity exercise (59% and 28%,
respectively). The results of this study show that prior exercise of high as well as low intensity reduces the V˙O2 slow component and indicate that a metabolic acidosis is not a necessary condition to elicit a reduction in ΔV˙O2(6−3).
Accepted: 8 July 2000 相似文献
4.
Billat VL Morton RH Blondel N Berthoin S Bocquet V Koralsztein JP Barstow TJ 《European journal of applied physiology》2000,82(3):178-187
The purpose of this study was to characterise the relationship between running velocity and the time for which a subject
can run at maximal oxygen uptake (V˙O2
max), (t
lim
V˙O2
max). Seven physical education students ran in an incremental test (3-min stages) to determine V˙O2
max and the minimal velocity at which it was elicited (νV˙O2
max). They then performed four all-out running tests on a 200-m indoor track every 2 days in random order. The mean times to
exhaustion t
lim at 90%, 100%, 120% and 140% νV˙O2
max were 13 min 22 s (SD 4 min 30 s), 5 min 47 s (SD 1 min 50 s), 2 min 11 s (SD 38 s) and 1 min 12 s (SD 18 s), respectively.
Five subjects did not reach V˙O2
max in the 90% νV˙O2
max test. All the subjects reached V˙O2
max in the runs at 100% νV˙O2
max. All the subjects, except one, reached V˙O2
max in the runs at 120%νV˙O2
max. Four subjects did not reach V˙O2
max in the 140% νV˙O2
max test. Time to achieve V˙O2
max was always about 50% of the time to exhaustion irrespective of the intensity. The time to exhaustion-velocity relationship
was better fitted by a 3- than by a 2-parameter critical power model for running at 90%, 100%, 120%, 140% νV˙O2
max as determined in the previous incremental test. In conclusion, t
lim
V˙O2
max depended on a balance between the time to attain V˙O2
max and the time to exhaustion t
lim. The time to reach V˙O2
max decreased as velocity increased. The t
lim
V˙O2
max was a bi-phasic function of velocity, with a peak at 100% νV˙O2
max.
Accepted: 2 February 2000 相似文献
5.
Hiroshi Takaki Kenji Sunagawa Masaru Sugimachi Yasushi Hara Toru Kawada Takashi Kurita Yoichi Goto 《European journal of applied physiology》1998,78(4):333-339
The transient response of oxygen uptake (V˙O2) to submaximal exercise, known to be abnormal in patients with cardiovascular disorders, can be useful in assessing the functional
status of the cardiocirculatory system, however, a method for evaluating it accurately has not yet been established. As an
alternative approach to the conventional test at constant exercise intensity, we applied a random stimulus technique that
has been shown to provide relatively noise immune responses of system being investigated. In 27 patients with heart failure
and 24 age-matched control subjects, we imposed cycle exercise at 50 W intermittently according to a pseudo-random binary
(exercise-rest) sequence, while measuring breath-by-breath V˙O2. After determining the transfer function relating exercise intensity (W˙) to V˙O2 and attenuating the high frequency ranges (>6 exercise-rest cycles · min−1), we computed the high resolution band-limited (0–6 cycles · min−1) V˙O2 response (0–120 s) to a hypothetical step exercise. The V˙O2 response showed a longer time constant in the patients than in the control subjects [47 (SD 37) and 31 (SD 8) s, respectively,
P < 0.05]. Furthermore, the amplitude of the V˙O2 response after the initial response was shown to be significantly smaller in the patients than in the control subjects [176
(SD 50) and 267 (SD 54) ml · min−1 at 120 s]. The average amplitude over 120 s correlated well with peak V˙O2 (r = 0.73) and ΔV˙O2/ΔW˙ (r = 0.70), both of which are well-established indexes of exercise tolerance. The data indicated that our band-limited V˙O2
step response using random exercise was more markedly attenuated and delayed in the patients with heart failure than in the normal controls
and that it could be useful in quantifying the overall functional status of the cardiocirculatory system.
Accepted: 6 January 1998 相似文献
6.
The primary aim of this study was to examine any change in performance caused by a fatiguing interval training session (TS).
A secondary aim of this study was to examine the change in oxygen uptake (V˙O2) during moderate and severe intensity running, and the relationship with the change in performance. Seven male runners [mean
age 24 (SD 6) years, height 1.79 (SD 0.06) m, body mass 67.9 (SD 7.6) kg, maximal oxygen uptake (V˙O2max) 4.14 (SD 0.49) l · min−1] were studied. The V˙O2 during moderate and severe intensity running and running performance were studied immediately prior to, 1 h following, and
72 h following TS. The TS was performed on a treadmill, and consisted of six bouts of 800 m at 1 km · h−1 below the velocity at V˙O2max (v
V˙
O2max), with 3-min rest intervals. Performance was also assessed at 1 km · h−1 below v
V˙
O2max, in the form of time to exhaustion (t
lim). The V˙O2 and heart rate (f
c) were assessed both during the severe intensity performance trial, and the moderate intensity run at 50% v
V˙
O2max. Whilst a significant change was observed in running performance and the V˙O2 during both moderate and severe intensity running prior to and following TS, no relationship was observed between the magnitude
of change in these variables. At 1 h following TS, t
lim had decreased by 24%, V˙O2 during moderate intensity running had increased by 2%, and the difference in V˙O2 between 2 min 45 s and the end of severe intensity running had increased by 91% compared with values recorded prior to TS.
At 1 h following TS, ƒc had also increased significantly during moderate intensity running by 5% compared to the value recorded prior to TS. These
findings demonstrated that TS resulted in a reduction in performance, and that the relationship between running performance
and V˙O2 during running may be altered under conditions of prolonged fatigue.
Accepted: 16 September 1999 相似文献
7.
Kawaguchi K Tabusadani M Sekikawa K Hayashi Y Onari K 《European journal of applied physiology》2001,84(1-2):158-161
To examine whether the kinetics of local muscle oxygenation reflect systemic oxygen intake, we measured the kinetics of local
muscle oxygenation and systemic oxygen consumption (V˙O
2). This study included 16 healthy males who performed an exercise tolerance test on a bicycle ergometer. During the exercise
test, expiratory gas analysis was performed with an expiratory gas analyzer, and the kinetics of vastus lateralis muscle oxygenation
were determined by near-infrared spectroscopy (NIRS). Oxygenated hemoglobin (OxyHb) and tissue blood oxygen saturation (S
tO2) gradually decreased during the exercise test, while deoxygenated hemoglobin (DeoxyHb) gradually increased. We examined correlations
between the mean values of these parameters, which were calculated by time-integrating the values obtained using NIRS and
dividing them by the integral time, and V˙O
2. There was a marked positive correlation between DeoxyHb and V˙O
2 (r=0.893 − 0.986), and a marked negative correlation between S
tO2 and V˙O
2 (r=0.859 − 0.995). There was a negative correlation between V˙O
2 and OxyHb (r=0.726 − 0.978), and no correlation between TotalHb and V˙O
2. These results suggest that the kinetics of peripheral muscle oxygenation reflect systemic V˙O
2.
Accepted: 23 October 2000 相似文献
8.
Marzorati M Perini R Milesi S Veicsteinas A 《European journal of applied physiology》2000,81(4):275-280
There have been many studies on the effects of isokinetic exercise on muscle performance in training and rehabilitative programmes.
On the other hand, the cardiovascular and metabolic responses elicited by this type of exercise have been poorly investigated.
This study was specifically designed to describe the relationships, if any, between metabolic and cardiorespiratory responses
and power output during maximal intermittent knee isokinetic exercise when a steady state is reached. A group of 18 healthy
subjects (10 men and 8 women, age range 25–30 years) were requested to perform at maximal concentric isokinetic knee extensions/flexions
60° · s−1 and 180° · s−1 for 5 min, with a 5-s pause interposed between consecutive repetitions. The power output (W˙) was calculated; before and during the tasks heart rate (f
c) and arterial blood pressure (APa) were continuously monitored. Pulmonary ventilation (V˙
E) and oxygen uptake (V˙O2) were measured at the 4th and at the 5th min of exercise and blood lactate concentration at rest and at the 3rd min of recovery.
From the 4th to the 5th min only a slight decrease in W˙ was observed, both at 60° · s−1 and 180° · s−1. The V˙O2, V˙
E, f
c and APa showed similar values in the last 2 min of exercise, suggesting that a steady state had been reached. The V˙O2 increased linearly as a function of W˙, showing a significantly steeper slope at 60° · s−1 than at 180° · s−1. The f
c, in spite of a large interindividual variation, was linearly related to metabolic demand, and was not affected by angular
velocity. Systolic and diastolic APa were not related either to V˙O2 or to angular velocity. In conclusion it would appear that the metabolic response to maximal intermittent knee isokinetic
exercise resembles that of dynamic exercise. Conversely, the cardiocirculatory responses would seem to reflect a relevant
role of the isometric postural component, the importance of which should be carefully evaluated in each subject.
Accepted: 21 September 1999 相似文献
9.
Previous findings of a narcosis-induced reduction in heat production during cold water immersion, as reflected in oxygen
uptake (V˙O2), have been attributed to the attenuation of the shivering response. The possibility of reduced oxygen utilization (V˙O2) by the muscles could not, however, be excluded. Accordingly, the present study tested the hypothesis that mild narcosis,
induced by inhalation of a normoxic gas mixture containing 30% nitrous oxide (N2O), would affect V˙O2. Nine male subjects participated in both maximal and submaximal exercise trials, inspiring either room air (AIR) or a normoxic
mixture containing 30% N2O. In the submaximal trials, the subjects exercised at 50% of maximal exercise intensity (W˙
max
) as determined in the maximal AIR trial. Though the subjects attained the same W˙
max
in the AIR and N2O trials, maximal V˙O2 was significantly higher (P < 0.05) during the N2O condition [58.9 (SEM 3.1) ml · kg−1 · min−l] compared to the AIR condition [55.0 (SEM 2.4) ml · kg−1 · min−l]. However, the V˙O2-relative exercise intensity relationship was similar during both maximal AIR and maximal N2O at submaximal exercise intensities. There were no significant differences in the responses of oesophageal temperature, sweating
rate, heart rate and ventilation between AIR and N2O in the maximal and submaximal tests. It was concluded that the previously reported narcosis-induced reductions in V˙O2 observed during cold water immersion can be attributed solely to a reduction in the shivering response rather than to decreased
oxygen utilization by the muscles.
Accepted: 6 February 2000 相似文献
10.
Hoogeveen AR 《European journal of applied physiology》2000,82(1-2):45-51
The purpose of this study was to investigate the effects of endurance training on the ventilatory response to acute incremental
exercise in elite cyclists. Fifteen male elite cyclists [mean (SD) age 24.3 (3.3) years, height 179 (6) cm, body mass 71.1
(7.6) kg, maximal oxygen consumption (V˙O2max) 69 (7) ml · min−1 · kg−1] underwent two exercise tests on a cycle ergometer. The first test was assessed in December, 6 weeks before the beginning
of the cycling season. The second test was performed in June, in the middle of the season. During this period the subjects
were expected to be in a highly endurance-trained state. The ventilatory response was assessed during an incremental exercise
test (20 W · min−1). Oxygen consumption (V˙O2), carbon dioxide production (V˙CO2), minute ventilation (V˙
E), and heart rate (HR) were assessed at the following points during the test: at workloads of 200 W, 250 W, 300 W, 350 W,
400 W and at the subject's maximal workload, at a respiratory exchange ratio (R) of 1, and at the ventilatory threshold (Thvent) determined using the V-slope-method. Post-training, the mean (SD) V˙O2max was increased from the pre-training level of 69 (7) ml · min−1 · kg−1 (range 61.4–78.6) to 78 (6) ml · min−1 · kg−1 (range 70.5–86.3). The mean post-training V˙O2 was significantly higher than the pre training value (P < 0.01) at all work rates, at Thvent and at R=1. V˙O2 was also higher at all work rates except for 200 W and 250 W. V˙
E was significantly higher at Thvent and R=1. Training had no effect on HR at all workloads examined. An explanation for the higher V˙O2 cost for the same work rate may be that in the endurance-trained state, the adaptation to an exercise stimulus with higher
intensity is faster than for the less-trained state. Another explanation may be that at the same work rate, in the less-endurance-trained
state power is generated using a significantly higher anaerobic input. The results of this study suggest the following practical
recommendations for training management in elite cyclists: (1) the V˙O2 for a subject at the same work rate may be an indicator of the endurance-trained state (i.e., the higher the V˙O2, the higher the endurance-trained capacity), and (2) the need for multiple exercise tests for determining the HR at Thvent during a cycling season is doubtful since at Thvent this parameter does not differ much following endurance training.
Accepted: 19 October 1999 相似文献
11.
The aim of the present study was to examine the effect of prior exercise at a remote site on the V˙O2 kinetics during subsequent heavy cycle exercise using a model that allowed us to discriminate between the V˙O2 fast and slow component responses. Ten male subjects completed a constant-load exercise of 6 min cycling at 90% of the V˙O2peak in three conditions: without prior exercise (LE-C), after heavy cycling exercise (6 min at 90% of the V˙O2peak) (LE-L) and after heavy arm-cranking exercise (6 min at 90% of the arm V˙O2peak) (LE-A). Subjects performed four repetitions of each exercise protocol, separated by at least 1 day. V˙O2 was measured on a breath-by-breath basis and V˙O2 kinetics were determined with a biexponential model. There were no significant differences in the V˙O2 fast component parameters between LE-C, LE-L and LE-A. However, the V˙O2 slow component amplitude was significantly reduced in LE-L and LE-A compared to LE–C, but the reduction was less pronounced
in LE-A [the value of the V˙O2 slow exponential term at the end of exercise, A
2′, was 657 (SD 200) ml.min–1 in LE-C versus 384 (SD 136) ml.min–1 in LE-L and 551 (SD 169) ml.min–1 in LE-A; P<0.05]. The results of this study demonstrate that prior heavy arm exercise alters V˙O2 kinetics during cycling exercise by reducing the V˙O2slow component amplitude, though this reduction is smaller than the reduction observed following prior heavy leg exercise.
These data indicate that the primary factor causing changes in the V˙O2 kinetics is probably located in the involved muscle.
Electronic Publication 相似文献
12.
The purpose of the present study was to determine whether the linear relationship between CO2 output (V˙CO2) and pulmonary ventilation (V˙
E) is altered during incremental cycling performed after exercise-induced metabolic acidosis. Ten untrained, female subjects
performed two incremental cycling tests (15 W · min−1 up to 165 W) on separate days. One incremental exercise test was conducted without prior exercise, whereas the other test
was preceded by a 1-min bout of maximal cycling. The ventilatory equivalent for O2 (V˙
E/V˙O2) was only elevated above control values at 15–60 W during incremental cycling performed after high-intensity exercise. In
contrast, the ventilatory equivalent for CO2 (V˙
E/V˙CO2) was significantly increased above control levels at nearly every work stage of incremental work (all except 165 W). Hyperventilation
relative to V˙CO2 was confirmed by the significantly lower end-tidal CO2 tension (P
ETCO2) obtained throughout the incremental cycling that was performed after high-intensity exercise (except at 165 W). V˙
E and V˙CO2 were significantly correlated under both treatment conditions (r > 0.99; P < 0.001). Moreover, both the slope and y-intercept of the linear regression were found to be significantly elevated during the incremental cycling performed after
high-intensity cycling compared to control conditions (P < 0.01). The increase in the slope of the V˙
E-V˙CO2 relationship during incremental exercise performed under these conditions does not represent an uncoupling of V˙
E from V˙CO2, but could be accounted for by the significantly lower P
ETCO2 observed during exercise.
Accepted: 20 June 1997 相似文献
13.
Olivier Hue Daniel Le Gallais Didier Chollet Alain Boussana Christian Préfaut 《European journal of applied physiology》1997,77(1-2):98-105
The aim of the present study was to determine the effects of 40 km of cycling on the biomechanical and cardiorespiratory
responses measured during the running segment of a classic triathlon, with particular emphasis on the time course of these
responses. Seven male triathletes underwent four successive laboratory trials: (1) 40 km of cycling followed by a 10-km triathlon
run (TR), (2) a 10-km control run (CR) at the same speed as TR, (3) an incremental treadmill test, and (4) an incremental
cycle test. The following ventilatory data were collected every minute using an automated breath-by-breath system: pulmonary
ventilation (V˙
E, l · min−1), oxygen uptake (V˙O2, ml · min−1 · kg−1), carbon dioxide output (ml · min−1), respiratory equivalents for oxygen (V˙
E/V˙O2) and carbon dioxide (V˙
E/V˙CO2), respiratory exchange ratio (R) respiratory frequency (f, breaths · min−1), and tidal volume (ml). Heart rate (HR, beats · min−1) was monitored using a telemetric system. Biomechanical variables included stride length (SL) and stride frequency (SF) recorded
on a video tape. The results showed that the following variables were significantly higher (analysis of variance, P < 0.05) for TR than for CR: V˙O2 [51.7 (3.4) vs 48.3 (3.9) ml · kg−1 · min−1, respectively], V˙
E [100.4 (1.4) l · min−1 vs 84.4 (7.0) l · min−1], V˙
E/V˙O2 [24.2 (2.6) vs 21.5 (2.7)] V˙
E/V˙CO2 [25.2 (2.6) vs 22.4 (2.6)], f [55.8 (11.6) vs 49.0 (12.4) breaths · min−1] and HR [175 (7) vs 168 (9) beats · min−1]. Moreover, the time needed to reach steady-state was shorter for HR and V˙O2 (1 min and 2 min, respectively) and longer for V˙
E (7 min). In contrast, the biomechanical parameters, i.e. SL and SF, remained unchanged throughout TR versus CR. We conclude
that the first minutes of the run segment after cycling in an experimental triathlon were specific in terms of V˙O2 and cardiorespiratory variables, and nonspecific in terms of biomechanical variables.
Accepted: 7 July 1997 相似文献
14.
The objective of this study was to evaluate the viability of using a single test in which cardiorespiratory variables are
measured, to establish training guidelines in running and/or cycling training activities. Six triathletes (two females and
four males), six runners (two females and four males) and six males cyclists, all with 5.5 years of serious training and still
involved in racing, were tested on a treadmill and cycle ergometer. Cardiorespiratory variables [e.g., heart rate (HR), minute
ventilation, carbon dioxide output (V˙CO2)] were calculated relative to fixed percentages of maximal oxygen uptake (V˙O2max; from 50 to 100%). The entire group of subjects had significantly (P < 0.05) higher values of V˙O2max on the treadmill compared with the cycle ergometer [mean (SEM) 4.7 (0.8) and 4.4 (0.9) l · min−1, respectively], and differences between tests averaged 10.5% for runners, 6.1% for triathletes and 2.8% for cyclists. A three-way
analysis of variance using a 3 × 2 × 6 design (groups × tests × intensities) demonstrated that all factors yielded highly
significant F-ratios (P < 0.05) for all variables between tests, even though differences in HR were only 4 beats · min−1. When HR was plotted against a fixed percentage of V˙O2max, a high correlation was found between tests. These results demonstrate that for triathletes, cyclists and runners, the relationship
between HR and percentage of V˙O2max, obtained in either a treadmill or a cycle ergometer test, may be used independently of absolute V˙O2max to obtain reference HR values that can be used to monitor their running and/or cycling training bouts.
Received: 3 November 1998 / Accepted: 29 July 1999 相似文献
15.
Billat VL Slawinski J Bocquet V Demarle A Lafitte L Chassaing P Koralsztein JP 《European journal of applied physiology》2000,81(3):188-196
The conventional method used to estimate the change in mean body temperature (dMBT) is by taking X% of a body core temperature
and (1−X)% of weighted mean skin temperature, the value of X being dependent upon ambient temperature. This technique is used
widely, despite opposition from calorimetrists. In the present paper we attempt to provide a better method. Minute-by-minute
changes in dMBT, as assessed using calorimetry, and 21 (20 if esophageal temperature was unavailable) various regional temperatures
(dRBTs), as assessed using thermometry, including 6 subcutaneous measures, were collected from 7 young male adults at 6 calorimeter
temperatures. Since a calorimeter measures only changes in heat storage, which can be converted to dMBT, all body temperatures
are expressed as changes from the reasonably constant pre-exposure temperatures. The following three aspects were investigated.
(1) The prediction of dMBT from the 21 (or 20) dRBTs with multi-linear regression analysis (MLR). This yields two results,
model A with rectal temperature (dT
re) alone, and model B with dT
re and esophageal temperature (dT
es). (2) The prediction of dMBT from dT
re with or without dT
es and 13 skin surface temperatures combined to one weighted mean skin temperature (dTˉ
sk), using MLR. This results in models C and D. Six more models (E–J) were added, representing the above two sets in various
combinations with four factors. (3) The conventional method calculated with four values for X. Model A predicted better than
0.3 °C in 70% of the cases. Model I was the best amongst the models with 13 weighted skin temperatures (better than 0.3 °C
in 60% of the cases). The conventional method was erratic.
Accepted: 14 January 2000 相似文献
16.
Spengler CM Knöpfli-Lenzin C Birchler K Trapletti A Boutellier U 《European journal of applied physiology》2000,81(5):368-374
The aim of the present study was to investigate whether the changes in breathing pattern that frequently occur towards the
end of exhaustive exercise (i.e., increased breathing frequency, f
b, with or without decreased tidal volume) may be caused by the respiratory work itself rather than by leg muscle work. Eight
healthy, trained subjects performed the following three sessions in random order: (A) two sequential cycling endurance tests
at 78% peak O2 consumption (V˙O2peak) to exhaustion (A1, A2); (B) isolated, isocapnic hyperpnea (B1) at a minute ventilation (V˙
E) and an exercise duration similar to that attained during a preliminary cycling endurance test at 78% V˙O2peak, followed by a cycling endurance test at 78% V˙O2peak (B2); (C) isolated, isocapnic hyperpnea (C1) at a V˙
E at least 20% higher than that of the preliminary cycling test and the same exercise duration as the preliminary cycling test,
followed by a cycling endurance test at 78% V˙O2peak (C2). Neither of the two isocapnic hyperventilation tasks (B1 or C1) affected either the breathing pattern or the endurance
times of the subsequent cycling tests. Only cycling test A2 was significantly shorter [mean (SD) 26.5 (8.3) min] than tests
A1 [41.0 (9.0) min], B2 [41.9 (6.0) min], and C2 [42.0 (7.5) min]. In addition, compared to test A1, only the breathing pattern
of test A2 was significantly different [i.e., V˙
E: +10.5 (7.6) l min−1, and f
b: +12.1 (8.5) breaths min−1], in contrast to the breathing patterns of cycling tests B2 [V˙
E: −2.5 (6.2) l min−1, f
b: +0.2 (3.6) breaths min−1] and C2 [V˙
E: −3.0 (7.0) l min−1, f
b: +0.6 (6.1) breaths min−1]. In summary, these results suggest that the changes in breathing pattern that occur towards the end of an exhaustive exercise
test are a result of changes in the leg muscles rather than in the respiratory muscles themselves.
Accepted: 7 October 1999 相似文献
17.
Robert G. McMurray M. J. Bauman J. S. Harrell S. Brown S. I. Bangdiwala 《European journal of applied physiology》2000,81(1-2):132-139
In this study we determined the influence of improving aerobic power (V˙O2max) on basal plasma levels of insulin and glucose of 11- to 14-year-old children, while accounting for body fat, gender, pubertal
status, and leisure-time physical activity (LTPA) levels. Blood samples were obtained from 349 children after an overnight
fast and analyzed for plasma insulin and glucose. Height, mass, body mass index (BMI), and sum of skinfolds (Σ triceps + subscapular
sites) were measured. LTPA levels and pubertal status were estimated from questionnaires, and V˙O2max was predicted from a cycle ergometry test. Regardless of gender, insulin levels were significantly correlated (P = 0.0001) to BMI, skinfolds, pubertal stage, and predicted V˙O2max, but were not related to LTPA levels. Fasting glucose levels were not correlated to measures of adiposity or exercise (LTPA
score, V˙O2max) for females; however, BMI and skinfolds were correlated for males (P < 0.006). The children then took part in an 8-week aerobic exercise program. The 60 children whose V˙O2max improved (≥3 ml · kg−1 · min−1) had a greater reduction in circulating insulin than the 204 children whose V˙O2max did not increase −16 (41) vs −1 (63) pmol · l−1; P = 0.028. The greatest change occurred in those children with the highest initial resting insulin levels. Plasma glucose levels
were slightly reduced only in those children with the highest insulin levels whose V˙O2max improved (P < 0.0506). The results of this study indicate that in children, adiposity has the most significant influence on fasting insulin
levels; however, increasing V˙O2max via exercise can lower insulin levels in those children with initially high levels of the hormone. In addition, LTPA does
not appear to be associated with fasting insulin status, unless it is sufficient to increase V˙O2max.
Accepted: 2 June 1999 相似文献
18.
Oxygen consumption at steady state (V˙O
2, l · min−1) and mechanical power (W˙, W) were measured in five subjects riding a human-powered vehicle (HPV, the Karbyk, a four-wheeled recumbent cycle) on a
flat concrete road at constant sub-maximal speeds. The external mechanical work spent per unit of distance (W, J · m−1), as calculated from the ratio of W˙ to the speed (v, m · s−1), was found to increase with the square of v: W˙=8.12+(0.262 ·v
2) (r=0.986, n=31), where the first term represents the mechanical energy wasted, over a unit of distance, against frictional forces (rolling
resistance, Rr), and the second term (k · v
2) is the work performed, per unit distance, to overcome the air drag. The rolling coefficient (Cr, obtained dividing Rr by m · g, where m is the overall mass and g is the acceleration of gravity) amounted to [mean (SD)] 0.0084 (0.0008), that is about 60% higher than that of a racing bicycle.
The drag coefficient was calculated from the measured values of k, air density (ρ) and frontal area (A) [Cx=k · (0.5 · A · ρ)−1], and amounted to 1.067 (0.029), that is about 20% higher than that of a racing bicycle. The energy cost of riding the HPV
(Ck, J · m−1) was measured from the ratio of metabolic power above rest (net V˙O
2, expressed in J · s−1) to the speed (v, m · s−1); the value of this parameter increased with the square of v, as described by: Ck=61.45 + (0.675 · v
2) (r=0.711, n=23). The net mechanical efficiency (η) was calculated from the ratio of W to Ck: over the investigated speed range this turned out to be 0.22 (0.021). Best performance times (BPTs) of a “typical”élite
athlete riding the Karbyk were calculated over the distances of 1, 5 and 10 km: these were about 8% longer than the BPTs calculated,
on the same subjects, when riding a conventional racing bicycle.
Accepted: 7 August 2000 相似文献
19.
This study examined the oxygen uptake (V˙O2) and heart rate (HR) kinetics during arm cranking and leg cycling at work rates above the anaerobic threshold (AT). Ten untrained
male subjects [21.6 (1.3) years] completed two 7 min 15 s constant-load arm cranking and two leg cycling tests at a power
output halfway between the mode-specific AT and peak V˙O2. The time constants for phase II V˙O2 (τ) and HR (τ) kinetics were determined by fitting a monoexponential curve from the end of phase I until 3 min of exercise.
V˙O2 τ and HR τ values were significantly (P<0.001) slower in arm cranking [V˙O2 τ = 66.4 (3.0) s; HR τ = 74.7 (4.4) s] than in leg cycling [V˙O2 τ = 42.0 (1.9) s; HR τ = 55.6 (3.5) s]. The V˙O2 slow component (V˙O2SC) accounted for a significantly (P<0.001) greater percentage of the total exercise response during arm cranking [23.8 (1.6)%] than during leg cycling [14.2
(1.5)%]. The greater relative V˙O2SC and the slower V˙O2 τ with arm exercise are consistent with a greater recruitment of metabolically inefficient type II muscle fibres during arm
cranking than during leg cycling.
Electronic Publication 相似文献
20.
John Sproule 《European journal of applied physiology》1998,77(6):536-542
This study investigated the effects on running economy (RE) of ingesting either no fluid or an electrolyte solution with
or without 6% carbohydrate (counterbalanced design) during 60-min running bouts at 80% maximal oxygen consumption (V˙O2max). Tests were undertaken in either a thermoneutral (22–23°C; 56–62% relative humidity, RH) or a hot and humid natural environment
(Singapore: 25–35°C; 66–77% RH). The subjects were 15 young adult male Singaporeans [V˙O2max = 55.5 (4.4 SD) ml kg−1 min−1]. The RE was measured at 3 m s−1 [65 (6)% V˙O2max] before (RE1) and after each prolonged run (RE2). Fluids were administered every 2 min, at an individual rate determined
from prior tests, to maintain body mass (group mean = 17.4 ml min−1). The V˙O2 during RE2 was higher (P < 0.05) than that during the RE1 test for all treatments, with no differences between treatments (ANOVA). The mean increase
in V˙O2 from RE1 to RE2 ranged from 3.4 to 4.7 ml kg−1 min−1 across treatments. In conclusion, the deterioration in RE at 3 m s−1 (65% V˙O2max) after 60 min of running at 80% V˙O2max appears to occur independently of whether fluid is ingested and regardless of whether the fluid contains carbohydrates or
electrolytes, in both a thermoneutral and in a hot, humid environment.
Accepted: 30 October 1997 相似文献