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1.
Isabelle Sendowski Gustave Savourey Yves Besnard Jacques Bittel 《European journal of applied physiology》1997,75(6):471-477
To study the physiological responses induced by immersing in cold water various areas of the upper limb, 20 subjects immersed either the index finger (T1), hand (T2) or forearm and hand (T3) for 30?min in 5°C water followed by a 15-min recovery period. Skin temperature of the index finger, skin blood flow (Qsk) measured by laser Doppler flowmetry, as well as heart rate (HR) and mean arterial blood pressure (¯BPa) were all monitored during the test. Cutaneous vascular conductance (CVC) was calculated as Qsk?/?¯BPa. Cold induced vasodilatation (CIVD) indices were calculated from index finger skin temperature and CVC time courses. The results showed that no differences in temperature, CVC or cardiovascular changes were observed between T2 and T3. During T1, CIVD appeared earlier compared to T2 and T3 [5.90 (SEM 0.32) min in T1 vs 7.95 (SEM 0.86) min in T2 and 9.26 (SEM 0.78) min in T3, P?0.01]. The HR was unchanged in T1 whereas it increased significantly at the beginning of T2 and T3 [+13 (SEM 2) beats?·?min?1 in T2 and +15 (SEM 3) beats?·?min?1 in T3, P?0.01] and then decreased at the end of the immersion [?12 (SEM 3) beats?·?min?1 in T2, and ?15 (SEM 3) beats?·?min?1 in T3, P?0.01]. Moreover, ¯BPaincreased at the beginning of T1 but was lower than in T2 and T3 [+9.3 (SEM 2.5) mmHg in T1, P?0.05;? +20.6 (SEM 2.6) mmHg and 26.5 (SEM 2.8) mmHg in T2 and T3, respectively, P?0.01]. The rewarming during recovery was faster and higher in T1 compared to T2 and T3. These results showed that general and local physiological responses observed during an upper limb cold water test differed according to the area immersed. Index finger cooling led to earlier and faster CIVD without significant cardiovascular changes, whereas hand or forearm immersion led to a delayed and slower CIVD with a bradycardia at the end of the test. 相似文献
2.
The present study aimed at investigating the spatial variability of skin temperature (T
sk) measured at various points on the hand during convective and cold contact exposure. A group of 8 subjects participated in a study of convective cooling of the hand (60 min) and 20 subjects to contact cooling of the finger pad (5 min). Experiments were carried out in a small climatic chamber into which the hand was inserted. For convective cold exposure,T
sk was measured at seven points on the palmar surface of the fingers of the left hand, one on the palmar surface and one on the dorsal surface of the hand. The air temperature inside the mini-chamber was 0, 4, 10 and 16°C. With the contact cold exposure, the subjects touched at constant pressures an aluminium cube cooled to temperatures of –7, 0 and 7°C in the same mini-chamber. ContactT
sk was measured on the finger pad of the index finger of the left hand. TheT
sk of the proximal phalanx of the index finger (on both palm and back sides), and of the middle phalanx of the little finger was also measured. The variation ofT
sk between the proximal and the distal phalanx of the index finger was between 1.5 to 10°C during the convective cold exposure to an air temperature of 0°C. Considerable gradients persisted between the hand and fingers (from 2 to 17°C at 0°C air temperature) and between the phalanges of the finger (from 0.5 to 11.4°C at 0°C air temperature). The onset of cold induced vasodilatation (CIVD) on different fingers varied from about 5 to 15 min and it did not always appear in every finger. For contact cold exposure, whenT
sk on the contact skin cooled down to nearly 0°C, the temperature at the area close to the contact skin could still be 30°C. Some cases of CIVD were observed in the contact skin area, but not on other measuring points of the same finger. These results indicated that local thermal stimuli were the main determinents of CIVD. Representative hand skin temperature may require five or more measuring points. Our results strongly emphasised a need to consider the large spatial and individual variations in the prediction and modelling of extremity cooling. 相似文献
3.
The purpose of this study was to examine the cardiovascular responses at the onset of passive leg cycle exercise (PLCE) in
paraplegics with spinal cord injury (PSCI) to investigate the increase in venous return from the paralyzed lower limbs during
PLCE. Six male PSCI having lesions at levels ranging from T8 to L1 and five male able-bodied subjects (ABS) participated in
this study. The subjects performed PLCE at pedalling frequencies of 40 rpm for 6 min. Cardiac output (Q˙
c), stroke volume (SV) and heart rate (f
c) were measured before and during PLCE. In the steady state (4th and 5th min) of PLCE, both PSCI and ABS showed a significant
increase in Q˙
c. At the onset of PLCE, however, clear differences in the cardiovascular response were found between PSCI and ABS. The ABS
showed a rapid and marked increase in f
c and consequently Q˙
c within 20 s of the onset of PLCE. On the other hand, in PSCI, the Q˙
c increased more slowly, compared with that in ABS, because of a smaller increase in f
c and a delayed increase in SV. The observed delay in the increases of Q˙
c and SV at the onset of PLCE in PSCI was presumably due to the absence of afferent reflexes from the lower limbs, and to the
additional time needed for venous return to arrive at the heart from the passively moved muscles.
Accepted: 23 September 1999 相似文献
4.
Charloux A Lonsdorfer-Wolf E Richard R Lampert E Oswald-Mammosser M Mettauer B Geny B Lonsdorfer J 《European journal of applied physiology》2000,82(4):313-320
The objectives of this study were to evaluate the reliability and accuracy of a new impedance cardiograph device, the Physio
Flow, at rest and during a steady-state dynamic leg exercise (work intensity ranging from 10 to 50 W) performed in the supine
position. We compared cardiac output determined simultaneously by two methods, the Physio Flow (Q˙
cPF) and the direct Fick (Q˙
cFick) methods. Forty patients referred for right cardiac catheterisation, 14 with sleep apnoea syndrome and 26 with chronic obstructive
pulmonary disease, took part in this study. The subjects' oxygen consumption values ranged from 0.14 to 1.19 l · min−1. The mean difference between the two methods (Q˙
cFick−Q˙
cPF) was 0.04 l · min−1 at rest and 0.29 l · min−1 during exercise. The limits of agreement, defined as mean difference ± 2SD, were −1.34, +1.41 l · min−1 at rest and −2.34, +2.92 l · min−1 during exercise. The difference between the two methods exceeded 20% in only 2.5% of the cases at rest, and 9.3% of the cases
during exercise. Thoracic hyperinflation did not alter Q˙
cPF. We conclude that the Physio Flow provides a clinically acceptable and non-invasive evaluation of cardiac output under these
conditions. This new impedance cardiograph device deserves further study using other populations and situations.
Accepted: 3 April 2000 相似文献
5.
Seven healthy men performed steady-state dynamic leg exercise at 50 W in supine and upright postures, before (control) and
repeatedly after 42 days of strict head-down tilt (HDT) (−6°) bedrest. Steady-state heart rate (f
c), mean arterial blood pressure, cardiac output (Q˙
c), and stroke volume (SV) were recorded. The following data changed significantly from control values. The f
c was elevated in both postures at least until 12 days, but not at 32 days after bedrest. Immediately after HDT, SV and Q˙
c were decreased by 25 (SEM 3)% and 19 (SEM 3)% in supine, and by 33 (SEM 5)% and 20 (SEM 3)% in upright postures, respectively.
Within 2 days there was a partial recovery of SV in the upright but not in the supine posture. The SV and Q˙
c during supine exercise remained significantly decreased for at least a month. Submaximal oxygen uptake did not change after
HDT. We concluded that the cardiovascular response to exercise after prolonged bedrest was impaired for so long that it suggested
that structural cardiac changes had developed during the HDT period.
Accepted: 6 June 2000 相似文献
6.
Takahashi T Okada A Saitoh T Hayano J Miyamoto Y 《European journal of applied physiology》2000,81(3):233-239
Cardiovascular responses were examined in seven healthy male subjects during 10 min of recovery in the upright or supine
position following 5 min of upright cycle exercise at 80% peak oxygen uptake. An initial rapid decrease in heart rate (f
c) during the early phase of recovery followed by much slower decrease was observed for both the upright and supine positions.
The average f
c at the 10th min of recovery was significantly lower (P < 0.05) in the supine position than in the upright position, while they were both significantly greater than the corresponding
pre-exercise levels (each P < 0.05). Accordingly, the amplitude of the high frequency (HF) component of R-R interval variability (by spectrum analysis)
in both positions was reduced with a decrease in mean R-R interval, the relationship being expressed by a regression line
– mean R-R interval = 0.006 × HF amplitude + 0.570 (r = 0.905, n = 28, P < 0.001). These results would suggest that the slower reduction in f
c following the initial rapid reduction in both positions is partly attributable to a retardation in the restoration of the
activity of the cardiac parasympathetic nervous system. Post-exercise upright stroke volume (SV, by impedance cardiography)
decreased gradually to just below the pre-exercise level, whereas post-exercise supine SV increased markedly to a level similar
to that at rest before exercise. The resultant cardiac output (Q˙
c) and the total peripheral vascular resistance (TPR) in the upright and supine positions returned gradually to their respective
pre-exercise levels in the corresponding positions. At the 10th min of recovery, both average SV and Q˙
c were significantly greater (each P < 0.005) in the supine than in the upright position, while average TPR was significantly lower (P < 0.05) in the supine than in the upright position. In contrast, immediately after exercise, mean blood pressure dropped
markedly in both the supine and upright positions, and their levels at the 10th min of recovery were similar. Therefore we
concluded that arterial blood pressure is maintained relatively constant through various compensatory mechanisms associated
with f
c, SV, Q˙
c, and TPR during rest and recovery in different body positions.
Accepted: 4 September 1999 相似文献
7.
Herault S Fomina G Alferova I Kotovskaya A Poliakov V Arbeille P 《European journal of applied physiology》2000,81(5):384-390
The objectives of this investigation were to study the effects of thigh cuffs (bracelets) on cardiovascular adaptation and
deconditioning in 0 g. The cardiovascular parameters of six cosmonauts were measured by echocardiography, Doppler, and plethysmography, during
three 6-month MIR spaceflights. Measurements were made at rest during preflight (−30 days), inflight (1, 3–4, and 5–5.5 months)
without cuffs (morning) and after 5 h with cuffs, and during postflight (+3 and +7 days). Lower-body negative pressure (LBNP)
measurements were performed 1 day after each resting session. Inflight values of left ventricle end-diastolic volume and stroke
volume measured without the thigh cuffs (−8 to −24% and −10 to −16%, respectively, both P < 0.05) were lower than corresponding preflight values. The jugular and femoral vein cross-sectional areas (A
jv and A
fv, respectively) were enlarged (A
jv: by 23–30%, P < 0.001; A
fv: by 33–70% P < 0.01). The renal and femoral vascular resistances (R
ra and R
fa, respectively) decreased (R
ra: by −15 to −16%, P < 0.01; R
fa: by −5 to −11%, P < 0.01). Inflight, the thigh cuffs reduced the A
jv (by −12 to −20%, P < 0.02), but enlarged the A
fv (A
fv: by 9–20%, P < 0.02) and increased the vascular resistance (R
ra: by 8–13%, P < 0.05; R
fa: by 10–16%, P < 0.01) compared to corresponding inflight, without-cuffs values. During LBNP (−45 mmHg, where 1 mmHg=133.3 N/m2), R
fa and the ratio between cerebral and femoral blood flow (Q˙
ca/Q˙
fa) increased less inflight and postflight (+25% for R
fa and +30% for Q˙
ca/Q˙
fa) than during preflight (60% for R
fa and 75% for Q˙
ca/Q˙
fa, P < 0.01). This reduced vasoconstrictive response and less efficient flow redistribution toward the brain was associated with
orthostatic intolerance during postflight stand tests in all of the cosmonauts. The calf circumference increased less inflight
and postflight (6% P < 0.05) than preflight (9% P < 0.05). The vascular response to LBNP remained similarly altered throughout the flight. The thigh cuffs compensated partially
for the cardiovascular changes induced by exposure to 0 g, but did not interfere with 0 g deconditioning.
Accepted: 5 November 1999 相似文献
8.
Yoshimitsu Inoue Manabu Shibasaki Kozo Hirata Tsutomu Araki 《European journal of applied physiology》1998,79(1):17-23
To examine the mechanisms and regional differences in the age-related decrement of skin blood flow, 11 young (age 20–25 years)
and 10 older (age 64–76 years) men were exposed to a mild heat stress by immersing their feet and lower legs in water at 42°C
for 60 min, while they were sitting in near thermoneutral conditions [25°C and 45% relative humidity (rh)]. During the equilibrium
period (25°C and 45% rh) before the heat test, no group differences were observed in rectal (T
re) and mean skin (T
sk) temperatures or mean arterial pressure (MAP). During passive heating, T
sk was significantly lower in the older men 20 min after commencing exposure (P < 0.001), although there were similar increases in T
re in both groups. Exposure time and age did not affect MAP. The local sweating rate (m˙
sw) and the percentage change in skin blood flow by laser Doppler flowmetry (%LDF) relative to baseline values on the chest,
back, forearm and thigh were significantly lower in the older men (P < 0.001), especially on the thigh. After starting the heat exposure, three temporal phases were observed in the relationship
between %LDF and m˙
sw at most sites in each subject. In phase A, %LDF increased but with no increase in m˙
sw. In phase B, m˙
sw increased but with no secondary increase in %LDF. Finally, in phase C, there were proportional increases in %LDF and m˙
sw. The increase in %LDF in phase A was significantly lower on the forearm and thigh (P < 0.05) for the older men, but not on the chest and back. In phase C, the slopes of the regression lines between %LDF and
m˙
sw were lower for the older men on the back (P < 0.03), forearm (P = 0.08) and thigh (P < 0.03), but not on the chest. These results would suggest that the age-related decrement in skin blood flow in response
to passive heating may be due in part to a smaller release of vasoconstrictor tone and to less active vasodilatation once
sweating begins. Regional differences exist in the impaired vasoconstriction and active vasodilatation systems.
Accepted: 29 May 1998 相似文献
9.
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
10.
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
11.
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
12.
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
13.
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
14.
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
15.
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
16.
John G. Morris Mary E. Nevill Clyde Williams 《European journal of applied physiology》2000,81(1-2):84-92
Eight female games players (GP) and eight female endurance athletes (EA) ran intermittently at high-intensity and for prolonged
periods in hot (30°C) and moderate (16°C) ambient temperatures. The subjects performed a two-part (A, B) test based on repeated
20-m shuttle runs. Part A comprised 60 m of walking, a maximal 15-m sprint, 60 m of cruising (90% maximal oxygen uptake, V˙O2max) and 60 m of jogging (45% V˙O2max) repeated for 75 min with a 3-min rest every 15 min. Part B involved an exercise and rest pattern of 60-s running at 100%
V˙O2max and 60-s rest which was continued until fatigue. Although the GP and EA did not respond differently in terms of distances
completed, performance was 25 (SEM 4)% less (main effect trial, P < 0.01) in the hot (HT) compared with the moderate trial (MT). Sprints of 15 m took longer to complete in the heat (main
effect, trial, P < 0.01), and sprint performance declined during HT but not MT (interaction, trial × time, P < 0.01). A very high correlation was found between the rate of rise in rectal temperature in HT and the distance completed
[GP, r =−0.94, P < 0.01; EA (n = 7), r = −0.93, P < 0.01]. Blood lactate [La− ]b and plasma ammonia [NH3]p1 concentrations were higher for GP than EA, but were similar in HT and MT [La− ]b, HT: GP vs EA, 8.0 (SEM 0.9) vs 4.9 (SEM 1.1) mmol · l−1; MT: GP vs EA, 8.0 (SEM 1.3) vs 4.4 (SEM 1.2) mmol · l−1; interaction, group × time, P < 0.01; [NH3]p1, HT: GP vs EA, 70.1 (SEM 12.7) vs 43.2 (SEM 6.1) mmol · l−1; MT: GP vs EA, 76.8 (SEM 8.8) vs 32.5 (SEM 3.8) μmol · l−1; interaction, group × time, P < 0.01. Ad libitum water consumption was higher in HT [HT: GP vs EA, 18.9 (SEM 2.9) vs 13.5 (SEM 1.7) ml · kg−1 · h−1; MT: GP vs EA, 12.7 (SEM 3.7) vs 8.5 (SEM 1.5) ml · kg−1 · h−1; main effect, group, n.s.; main effect, trial, P < 0.01]. These results would suggest that elevated body temperature is probably the key factor limiting performance of prolonged,
intermittent, high-intensity running when the ambient temperature is high, but not because of its effect on the metabolic
responses to exercise.
Accepted: 19 July 1999 相似文献
17.
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
18.
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
19.
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
20.
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