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1.
Effect of exercise on the mitochondrial DNA content of peripheral blood in healthy women 总被引:1,自引:0,他引:1
Lim S Kim SK Park KS Kim SY Cho BY Yim MJ Lee HK 《European journal of applied physiology》2000,82(5-6):407-412
Exercise decreases insulin resistance and increases maximal exercise capacity as estimated from maximal oxygen uptake (V˙O2max). Recent reports have demonstrated that the mitochondrial DNA (mtDNA) content of blood is correlated with V˙O2max in healthy subjects (mean age 31 years) and is inversely correlated with insulin resistance parameters. The aim of this study
was to determine the effect of regular exercise on the mtDNA content in the peripheral blood of 16 healthy young women of
mean age 24.8 (SD 6.2) years and 14 healthy older women of mean age 66.7 (SD 5.8) years. The exercise programme lasted for
10 weeks and consisted of three sessions a week, each of 1 h and aiming to attain 60%–80% of V˙O2max. The mtDNA content of peripheral blood was measured by competitive polymerase chain reaction. The V˙O2max had significantly increased following the exercise programme [from 33.1 (SD 3.4) to 35.2 (SD 3.4) ml · kg−1 · min−1 in the young and from 24.3 (SD 5.3) to 30.3 (SD 7.3) ml · kg−1 · min−1 in the older women, both P < 0.05]. Exercise decreased systolic blood pressure, and concentrations of triglyceride, low density lipoprotein-cholesterol
(LDL-C), glucose and insulin in the blood of the young and of total cholesterol, LDL-C and glucose in that of the older women.
High density lipoprotein-cholesterol (HDL-C) in the young women was increased by exercise. The mtDNA content significantly
increased following the exercise programme in both groups [from 27.1 (SD 17.9) to 52.7 (SD 44.6) amol · 5 ng−1 genomic DNA in the young and from 15.3 (SD 10.2) to 32.1 (SD 30.0) amol · 5 ng−1 genomic DNA in the older women, both P < 0.05]. There was a significant positive correlation between the change in mtDNA content and the change in V˙O2max (r=0.74 in the young and r=0.71 in the older women, both P < 0.01). In conclusion, 10 weeks of moderate intensity, regular exercise increased the mtDNA content in peripheral blood
and decreased insulin resistance parameters. This data suggests that increase in the mtDNA content may be associated with
increased insulin sensitivity.
Accepted: 15 April 2000 相似文献
2.
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
3.
M. J. Tipton G. M. Franks G. S. Meneilly I. B. Mekjavic 《European journal of applied physiology》1997,76(1):103-108
It is generally assumed that exercise and shivering are analogous processes with regard to substrate utilisation and that,
as a consequence, exercise can be used as a model for shivering. In the present study, substrate utilisation during exercise
and shivering at the same oxygen consumption (V˙O2) were compared. Following an overnight fast, eight male subjects undertook a 2-h immersion in cold water, designed to evoke
three different intensities of shivering. At least 1 week later they undertook a 2-h period of bicycle ergometry during which
the exercise intensity was varied to match the V˙O2 recorded during shivering. During both activities hepatic glucose output (HGO), the rate of glucose utilisation (Rd), blood
glucose, plasma insulin, free fatty acid (FFA) and beta-hydroxybutyrate (B-HBA) concentrations were measured. The V˙O2 measured during the different levels of shivering averaged 0.49 l · min−1 (level 1: low), 0.6 l · min−1 (level 2: low-moderate), and 0.9 l · min−1 (level 3: moderate), and corresponded closely to the levels measured during exercise. HGO and Rd were greater (P < 0.05) during exercise than during shivering at the same V˙O2 (9.5% and 14.7%, respectively). The average (SD) HGO during level 3 exercise was 3.0 (0.91) mg · kg−1 . min−1 compared to 2.76 (1.0) mg · kg−1 . min−1 during shivering. The values for Rd were 3.06 (0.98) mg · kg−1 · min−1 during level 3 exercise and 2.68 (0.82) mg · kg−1 · min−1 during shivering. Blood glucose levels did not differ between conditions, averaging 5.4 (0.3) mmol . l−1 over all levels of shivering and 5.2 (0.3) mmol · l−1 during exercise. Plasma FFA and B-HBA were higher (P < 0.01) during shivering than during corresponding exercise (12.3% and 33.3%, respectively). FFA averaged 0.61 (0.2) mmol · l−1 over all levels of shivering and 0.47 (0.16) mmol · l−1 during exercise. The figures for B-HBA were 0.44 (0.13) mmol · l−1 during all levels of shivering and 0.32 (0.1) mmol · l−1 during exercise. Plasma insulin was higher (P < 0.05) during level 2 and 3 shivering compared to corresponding exercise; at these levels the average value for plasma insulin
was 95.9 (21.9) pmol · l−1 during shivering and 80.6 (16.1) pmol · l−1 during exercise. On the basis of the present findings it is concluded that, with regard to substrate utilisation, shivering
and exercise of up to 2 h duration should not be regarded as analogous processes.
Accepted: 12 February 1997 相似文献
4.
Basal metabolic rate is scaled to body mass to the power of 0.73, and we evaluated whether a similar scaling applies when
the O2 transport capacity of the body is challenged during maximal exercise (i.e. at maximal O2 uptake, V˙O
2max). The allometric relationship between V˙O
2max and body mass (y=a · x
b, where y is V˙O
2max and x is body mass) was developed for 967 athletes representing 25 different sports, with up to 157 participants in each sport.
With an increasing number of observations, the exponent approached 0.73, while for ventilation the exponent was only 0.55.
By using the 0.73 exponent for V˙O
2max, the highest value [mean (SD)] for the males was obtained for the runners and cyclists [234 (16) ml · kg−0.73 · min−1], and for the females the highest value was found for the runners [189 (14) ml · kg−0.73 · min−1]. For the females, aerobic power was about 80% of the value achieved by the males. Scaling may help both in understanding
variation in aerobic power and in defining the physiological limitations of work capacity.
Accepted: 3 November 2000 相似文献
5.
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
6.
Jean-Claude Chatard Chantal Boutet Claire Tourny Sylvie Garcia Sophie Berthouze Charles-Yannick Guézennec 《European journal of applied physiology》1997,77(1-2):157-163
The nutritional status of elderly sportsmen has not been reported on, neither has the nutritional balance nor the precise
relationship between nutritional status and physical fitness been detailed for this population. Thus, group of 18 sportsmen
[age 63 (SD 4.5) years] was monitored by weighing their food during a 6-day period. Macro nutrient, mineral and vitamin content
was derived from tables. Daily energy expenditure (DEE) and sport activity (DSA) were quantified over a 7-day period using
a questionnaire. Physical fitness was assessed by maximal oxygen uptake (V˙O2max) measurements. The DEE was 11 429 (SD 1890) kJ · day−1. The DSA corresponded to 38% of DEE and V˙O2max to 35.9 (SD 6.1) ml · min−1 · kg−1. When compared with French recommended dietary allowances (RDA) intakes were higher for energy (+24%), macro nutrients, and
most minerals and vitamins. Despite high energy intakes, some subjects had mineral and vitamin deficits. Energy intakes were
significantly related to intakes of magnesium, phosphorus, iron, vitamins B2, B6, C and to V˙O2max, but not to age. Stepwise regressions indicated that vitamin C intake was the only determinant to have a relationship with
V˙O2max. Thus, most elderly sportsmen had higher nutritional status than RDA, although some had mineral and vitamin deficits. It
is therefore suggested that elderly sportsmen should be encouraged to consume food with higher mineral and vitamin contents.
Accepted: 17 June 1997 相似文献
7.
Gas exchange responses to continuous incremental cycle ergometry exercise in primary pulmonary hypertension in humans 总被引:1,自引:0,他引:1
Riley MS Pórszász J Engelen MP Brundage BH Wasserman K 《European journal of applied physiology》2000,83(1):63-70
In patients suffering from primary pulmonary hypertension (PPH), a raised pulmonary vascular resistance may limit the ability
to increase pulmonary blood flow as work rate increases. We hypothesised that oxygen uptake (V˙O2) may not rise appropriately with increasing work rate during incremental cardiopulmonary exercise tests. Nine PPH patients
and nine normal subjects performed symptom-limited maximal continuous incremental cycle ergometry exercise. Mean peak V˙O2 [1.00 (SD 0.22) compared to 2.58 (SD 0.64) l · min−1] and mean V˙O2 at lactic acidosis threshold [LAT, 0.73 (SD 0.17) compared to 1.46 (SD 0.21 · l) ml · min−1] were much lower in patients than in normal subjects (both P < 0.01, two-way ANOVA with Tukey test). The mean rate of change of V˙O2 with increasing work rate above the LAT [5.9 (SD 2.1) compared to 9.4 (SD 1.3) ml · min−1 · W−1, P < 0.01)] was also much lower in patients than in normal subjects [apparent δ efficiency 60.3 (SD 38.8)% in patients compared
to 31.0 (SD 4.9)% in normal subjects]. The patients displayed lower mean values of end-tidal partial pressure of carbon dioxide
than the normal subjects at peak exercise [29.7 (SD 6.8) compared to 42.4 (SD 5.8) mmHg, P < 0.01] and mean oxyhaemoglobin saturation [89.1 (SD 4.1) compared to 93.6 (SD 1.8)%, P < 0.05]. Mean ventilatory equivalents for CO2 [49.3 (SD 11.4) compared to 35.0 (SD 7.3), P < 0.05] and O2 [44.2 (SD 10.7) compared to 29.9 (SD 5.1), P < 0.05] were greater in patients than normal subjects. The sub-normal slopes for the V˙O2-work-rate relationship above the LAT indicated severe impairment of the circulatory response to exercise in patients with
PPH. The ventilatory abnormalities in PPH suggested that the lung had become an inefficient gas exchange organ because of
impaired perfusion of the ventilated lung.
Accepted: 17 April 2000 相似文献
8.
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
9.
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
10.
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
11.
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
12.
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
13.
Changes in blood lactate and respiratory gas exchange measures in sports with discontinuous load profiles 总被引:2,自引:0,他引:2
Smekal G von Duvillard SP Pokan R Tschan H Baron R Hofmann P Wonisch M Bachl N 《European journal of applied physiology》2003,89(5):489-495
This study compares two different sport events (orienteering = OTC; tennis = TEC) with discontinuous load profiles and different
activity/recovery patterns by means of blood lactate (LA), heart rate (HR), and respiratory gas exchange measures (RGME) determined
via a portable respiratory system. During the TEC, 20 tennis-ranked male subjects [age: 26.0 (3.7) years; height: 181.0 (5.7) cm;
weight: 73.2 (6.8) kg; maximal oxygen consumption (V˙O2max): 57.3 (5.1) ml·kg−1·min−1] played ten matches of 50 min. During the OTC, 11 male members of the Austrian National Team [age: 23.5 (3.9) years; height:
183.6 (6.8) cm; weight: 72.4 (3.9) kg; V˙O2max: 67.9 (3.8) ml·kg−1·min−1] performed a simulated OTC (six sections; average length: 10.090 m). In both studies data from the maximal treadmill tests
(TT) were used as reference values for the comparison of energy expenditure of OTC and TEC. During TEC, the average V˙O2 was considerably lower [29.1 (5.6) ml·kg−1·min−1] or 51.1 (10.9)% of VO2max and 64.8.0 (13.3)% of V˙O2 determined at the individual anaerobic threshold (IAT) on the TT. The short high-intensity periods (activity/recovery = 1/6)
did not result in higher LA levels [average LA of games: 2.07 (0.9) mmol·l−1]. The highest average V˙O2 value for a whole game was 47.8 ml·kg−1·min−1 and may provide a reference for energy demands required to sustain high-intensity periods of tennis predominately via aerobic
mechanism of energy delivery. During OTC, we found an average V˙O2 of 56.4 (4.5) ml·kg−1·min−1 or 83.0 (3.8)% of V˙O2max and 94.6 (5.2)% of V˙O2 at IAT. In contrast to TEC, LA were relatively high [5.16 (1.5) mmol·l−1) although the average V˙O2 was significantly lower than V˙O2 at IAT. Our data suggest that portable RGEM provides valuable information concerning the energy expenditure in sports that
cannot be interpreted from LA or HR measures alone. Portable RGEM systems provide valuable assessment of under- or over-estimation
of requirements of sports and assist in the optimization and interpretation of training in athletes.
Electronic Publication 相似文献
14.
M. Sandsund M. Sue-Chu J. Helgerud R. E. Reinertsen L. Bjermer 《European journal of applied physiology》1998,77(4):297-304
The effects of whole-body exposure to ambient temperatures of −15°C and 23°C on selected performance-related physiological
variables were investigated in elite nonasthmatic cross-country skiers. At an ambient temperature of −15°C we also studied
the effects of the selective β2-adrenergic agonist Salbutamol (0.4 mg × 3) which was administered 10 min before the exercise test. Eight male cross-country
skiers with known maximal oxygen uptakes (V˙O2
max
) of more than 70 ml · kg−1 · min−1 participated in the study. Oxygen uptake (V˙O2), heart rate (f
c), blood lactate concentration ([La−]b) and time to exhaustion were measured during controlled submaximal and maximal running on a treadmill in a climatic chamber.
Lung function measured as forced expiratory volume in 1 s (FEV1) was recorded immediately before the warm-up period and at the conclusion of the exercise protocol. Submaximal V˙O2 and [La−]b at the two highest submaximal exercise intensities were significantly higher at −15°C than at 23°C. Time to exhaustion was
significantly shorter in the cold environment. However, no differences in V˙O2
max
or f
c were observed. Our results would suggest that exercise stress is higher at submaximal exercise intensities in a cold environment
and support the contention that aerobic capacity is not altered by cold exposure. Furthermore, we found that after Salbutamol
inhalation FEV1 was significantly higher than after placebo administration. However, the inhaled β2-agonist Salbutamol did not influence submaximal and maximal V˙O2, f
c, [La−]b or time to exhaustion in the elite, nonasthmatic cross-country skiers we studied. Thus, these results did not demonstrate
any ergogenic effect of the β2-agonist used.
Accepted: 18 August 1997 相似文献
15.
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
16.
In this study, we compared the biomechanical and physiological responses of healthy men and women during bilateral load carriage
while they walked on a treadmill at their self-selected velocity. Eleven men mean (SD) maximal oxygen uptake, [V˙O2
max
= 56.0 (7.1) ml · kg−1 · min−1] and 11 women [V˙O2
max = 44.6 (7.6) ml · kg−1 · min−1] carried 15-kg and 20-kg loads in random order using a custom-designed load-carriage device. The load supported by each hand
was measured by placing strain gauges in each handle of the device. The load supported by the body was calculated as the difference
between the load carried and that supported by each hand. Physiological measurements were recorded using standard procedures,
and cardiac output was measured by carbon dioxide rebreathing while standing, walking, and during load carriage. Three-way
analysis of variance (gender by load by test phase) indicated no significant (P > 0.05) three-way interaction, implying that the overall trend in these responses was similar in men and women. A-priori
Scheffe multiple comparisons revealed the following significant (P < 0.05) gender differences during load carriage: (1) women supported a lower proportion of the load with the hands and transferred
a greater amount to the body by resting the load against the chest, (2) the oxygen uptake increased by a greater amount in
the women compared with men and exceeded the ventilatory threshold during the 20-kg walk in women, and (3) the cardiovascular
stress, as indicated by the percentage of maximal heart rate and rate pressure product (product of heart rate and systolic
blood pressure), was significantly higher in women compared with men during both of the load-carriage walks. These observations
suggest that when carrying absolute loads of 15 kg and 20 kg, women are more susceptible to fatigue and are at a greater risk
of cardiovascular complications than men.
Accepted: 18 June 1999 相似文献
17.
C. J. Gore S. C. Little A. G. Hahn G. C. Scroop K. I. Norton P. C. Bourdon S. M. Woolford J. D. Buckley T. Stanef D. P. Campbell D. B. Watson D. L. Emonson 《European journal of applied physiology》1997,75(2):136-143
This study examined the effect of mild hypobaria (MH) on the peak oxygen consumption (O2peak) and performance of ten trained male athletes [ (SEM); O2peak = 72.4 (2.2) ml · kg−1 · min−1] and ten trained female athletes [O2peak = 60.8 (2.1) ml · kg−1 · min−1]. Subjects performed 5-min maximal work tests on a cycle ergometer within a hypobaric chamber at both normobaria (N, 99.33
kPa) and at MH (92.66 kPa), using a counter-balanced design. MH was equivalent to 580 m altitude. O2peak at MH decreased significantly compared with N in both men [− 5.9 (0.9)%] and women [− 3.7 (1.0)%]. Performance (total kJ)
at MH was also reduced significantly in men [− 3.6 (0.8)%] and women [− 3.8 (1.2)%]. Arterial oxyhaemoglobin saturation (SaO2) at O2peak was significantly lower at MH compared with N in both men [90.1 (0.6)% versus 92.0 (0.6)%] and women [89.7 (3.1)% versus
92.1 (3.0)%]. While SaO2 at O2peak was not different between men and women, it was concluded that relative, rather than absolute, O2peak may be a more appropriate predictor of exercise-induced hypoxaemia. For men and women, it was calculated that 67–76% of the
decrease in O2peak could be accounted for by a decrease in O2 delivery, which indicates that reduced O2 tension at mild altitude (580 m) leads to impairment of exercise performance in a maximal work bout lasting ≈ 5 min.
Accepted: 30 July 1996 相似文献
18.
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
19.
Simulated moderate altitude elevates serum erythropoietin but does not increase reticulocyte production in well-trained runners 总被引:7,自引:0,他引:7
Ashenden MJ Gore CJ Dobson GP Boston TT Parisotto R Emslie KR Trout GJ Hahn AG 《European journal of applied physiology》2000,81(5):428-435
The purpose of this study was to investigate whether the modest increases in serum erythropoietin (sEpo) experienced after
brief sojourns at simulated altitude are sufficient to stimulate reticulocyte production. Six well-trained middle-distance
runners (HIGH, mean maximum oxygen uptake, V˙O2max = 70.2 ml · kg−1 · min−1) spent 8–11 h per night for 5 nights in a nitrogen house that simulated an altitude of 2650 m. Five squad members (CONTROL,
mean V˙O2max = 68.9 ml · kg−1 · min−1) undertook the same training, which was conducted under near-sea-level conditions (600 m altitude), and slept in dormitory-style
accommodation also at 600 m altitude. For both groups, this 5-night protocol was undertaken on three occasions, with a 3-night
interim between successive exposures. Venous blood samples were measured for sEpo after 1 and 5 nights of hypoxia on each
occasion. The percentage of reticulocytes was measured, along with a range of reticulocyte parameters that are sensitive to
changes in erythropoiesis. Mean serum erythropoietin levels increased significantly (P < 0.01) above baseline values [mean (SD) 7.9 (2.4) mU · ml−1] in the HIGH group after the 1st night [11.8 (1.9) mU · ml−1, 57%], and were also higher on the 5th night [10.7 (2.2) mU · ml−1, 42%] compared with the CONTROL group, whose erythropoietin levels did not change. After athletes spent 3 nights at near
sea level, the change in sEpo during subsequent hypoxic exposures was markedly attenuated (13% and −4% change during the second
exposure; 26% and 14% change during the third exposure; 1st and 5th nights of each block, respectively). The increase in sEpo
was insufficient to stimulate reticulocyte production at any time point. We conclude that when daily training loads are controlled,
the modest increases in sEpo known to occur following brief exposure to a simulated altitude of 2650 m are insufficient to
stimulate reticulocyte production.
Accepted: 7 October 1999 相似文献
20.
Perini R Milesi S Fisher NM Pendergast DR Veicsteinas A 《European journal of applied physiology》2000,82(1-2):8-15
It has been proposed that cardiac control is altered in the elderly. Power spectral analysis of heart rate variability (HRV)
was performed on 12 male and 11 female elderly subjects (mean age 74 years) while at rest in supine and sitting positions,
and at steady states during 5 min of exercise (35–95% peak oxygen consumption, V˙O2peak). There were no differences in power, measured as a percentage of the total of the high frequency peak (HF, centred at about
0.25 Hz; 13% in males vs 12% in females), low frequency peak (LF, centred at 0.09 Hz; 25% in males and 22% in females), and
very low frequency component (VLF, at 0.03 Hz; 66% in males and 69% in females) between body positions at rest. There was
no difference in spectral power between male and female subjects. Total power decreased as a function of oxygen consumption
during exercise, LF% did not change up to about 14 ml · kg−1 · min−1 (40% and 80% V˙O2peak in males and females, respectively), then decreased towards minimal values in both genders. HF% power and central frequency
increased linearly with metabolic demand, reaching higher values in male subjects than in female subjects at V˙O2peak, while VLF% remained unchanged. Thus, the power spectra components of HRV did not reflect the changes in autonomic activity
that occur at increasing exercise intensities, confirming previous findings in young subjects, and indicated similar responses
in both genders.
Accepted: 30 November 1999 相似文献