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1.
Sue L. Hooper Laurel Traeger Mackinnon Enid M. Ginn 《European journal of applied physiology and occupational physiology》1998,78(3):258-263
The 100-m and 400-m swim time, tethered swimming forces, mood states and self-ratings of well-being of 27 competitive swimmers
were measured before and after 4 weeks of intense training and after 1 week and 2 weeks of tapering for major competition.
The swimmers were divided into three groups. Each group completed one of three taper regimes similar to those currently performed
by swimmers in preparation for competition: (a) reduced training frequency according to each athlete's daily ratings of well-being,
(b) reduced training volume, and (c) reduced training volume and intensity. Significant improvements in the Profile of Mood
States measures of tension, depression and anger (P < 0.05) were observed after 1 week of tapering, with significant improvements in total mood disturbance and fatigue (P < 0.05) and peak tethered swimming force (P < 0.01) after 2 weeks. Non-significant improvements in 100-m and 400-m swim time (P > 0.05) were observed and no significant differences were revealed among the three tapering techniques. These data highlighted
the importance of providing sufficient recovery before competition, since 1 week of reduced training was not long enough to
maximise the benefits of tapering. However, none of the three types of tapering currently used by competitive swimmers could
be shown to be more beneficial than the others.
Accepted: 9 February 1998 相似文献
2.
David V. B. James Jonathan H. Doust 《European journal of applied physiology and occupational physiology》1998,77(6):551-555
Eight male endurance runners [mean ± (SD): age 25 (6) years; height 1.79 (0.06) m; body mass 70.5 (6.0) kg; % body fat 12.5
(3.2); maximal oxygen consumption (V˙O2max 62.9 (1.7) ml · kg−1 · min−1] performed an interval training session, preceded immediately by test 1, followed after 1 h by test 2, and after 72 h by
test 3. The training session was six 800-m intervals at 1 km · h−1 below the velocity achieved at V˙O2max with 3 min of recovery between each interval. Tests 1, 2 and 3 were identical, and included collection of expired gas, measurement
of ventilatory frequency (f
v
), heart rate (f
c), rate of perceived exertion (RPE), and blood lactate concentration ([La−]B) during the final 5 min of 15 min of running at 50% of the velocity achieved at V˙O2max (50% −V˙O2max).␣Oxygen uptake (V˙O2), ventilation (V˙
E
), and respiratory exchange ratio (R) were subsequently determined from duplicate expired gas collections. Body mass and plasma volume changes were measured preceding
and immediately following the training session, and before tests 1–3. Subjects ingested water immediately following the training
session, the volume of which was determined from the loss of body mass during the session. Repeated measures analysis of variance
with multiple comparison (Tukey) was used to test differences between results. No significant differences in body mass or
plasma volume existed between the three test stages, indicating that the differences recorded for the measured parameters
could not be attributed to changes in body mass or plasma volume between tests, and that rehydration after the interval training
session was successful. A significant (P < 0.05) increase was found from test 1 to test 2 [mean (SD)] for V˙O2 [2.128 (0.147) to 2.200 (0.140) 1 · min−1], f
c [125 (17) to 132 (16) beats · min−1], and RPE [9 (2) to 11 (2)]. A significant (P < 0.05) decrease was found for submaximal R [0.89 (0.03) to 0.85 (0.04)]. These results suggest that alterations in V˙O2 during moderate-intensity, constant-velocity running do occur following heavy-intensity endurance running training, and that
this is due to factors in addition to changed substrate metabolism towards greater fat utilisation, which could explain only
31% of the increase in V˙O2.
Accepted: 8 December 1997 相似文献
3.
Daniel Courteix Philippe Obert Anne-Marie Lecoq Patrick Guenon Günter Koch 《European journal of applied physiology and occupational physiology》1997,76(3):264-269
The aim of the present study was to analyse the effect of 1 year of intensive swimming training on lung volumes, airway resistance
and on the flow-volume relationship in prepubertal girls. Five girls [9.3 (0.5) years old] performing vigorous swimming training
for 12 h a week were compared with a control group of 11 girls [9.3 (0.5) years old] who participated in various sport activities
for 2 h per week. Static lung volumes, maximal expiratory flows (MEF) at 75, 50 and 25% of vital capacity, 1-s forced expiratory
volume (FEV1.0) and airway resistance (R
aw) were measured by means of conventional body plethysmograph techniques. Prior to the training period there were no significant
differences between the two groups for any of the parameters studied. Moreover, for both groups, all parameters were within
the normal range for children of the corresponding age. After 1 year of training, vital capacity (VC), total lung capacity
(TLC) and functional residual capacity (FRC) were larger (P<0.05) in the girl swimmers than in the control group, while physical development in terms of height and weight was similar.
FEV1.0 (P<0.01), MEF25, MEF50 (P<0.05) and MEF75 as well as the ratio MEF50 / TLC (P<0.05) had increased in the girl swimmers but were unchanged in the control group. R
aw tended to be lower in the girl swimmers and higher in the control group. The results indicate that intensive swimming training
prepuberty enhances static and dynamic lung volumes and improves the conductive properties of both the large and the small
airways. As to the causative mechanism, it can be speculated that at prepuberty intensive swimming training promotes isotropic
lung growth by harmonizing the development of the airways and of alveolar lung spaces.
Accepted: 5 March 1997 相似文献
4.
Carlo Capelli Dave R. Pendergast B. Termin 《European journal of applied physiology and occupational physiology》1998,78(5):385-393
The energy cost per unit of distance (C
s, kilojoules per metre) of the front-crawl, back, breast and butterfly strokes was assessed in 20 elite swimmers. At sub-maximal
speeds (v), C
s was measured dividing steady-state oxygen consumption (V˙O2) by the speed (v, metres per second). At supra-maximal v, C
s was calculated by dividing the total metabolic energy (E, kilojoules) spent in covering 45.7, 91.4 and 182.9 m by the distance. E was obtained as: E = E
an+V˙O2max
t
p−V˙O2max(1−e−(
t
p/)), where E
an was the amount of energy (kilojoules) derived from anaerobic sources, V˙O2max litres per second was the maximal oxygen uptake, α (=20.9 kJ · l O2
−1) was the energy equivalent of O2, τ (24 s) was the time constant assumed for the attainment of V˙O2max at muscle level at the onset of exercise, and t
p (seconds) was the performance time. The lactic acid component was assumed to increase exponentially with t
p to an asymptotic value of 0.418 kJ · kg−1 of body mass for t
p ≥ 120 s. The lactic acid component of E
an was obtained from the net increase of lactate concentration after exercise (Δ[La]b) assuming that, when Δ[La]b = 1 mmol · l−1 the net amount of metabolic energy released by lactate formation was 0.069 kJ · kg−1. Over the entire range of v, front crawl was the least costly stroke. For example at 1 m · s−1, C
s amounted, on average, to 0.70, 0.84, 0.82 and 0.124 kJ · m−1 in front crawl, backstroke, butterfly and breaststroke, respectively; at 1.5 m · s−1, C
s was 1.23, 1.47, 1.55 and 1.87 kJ · m−1 in the four strokes, respectively. The C
s was a continuous function of the speed in all of the four strokes. It increased exponentially in crawl and backstroke, whereas
in butterfly C
s attained a minimum at the two lowest v to increase exponentially at higher v. The C
s in breaststroke was a linear function of the v, probably because of the considerable amount of energy spent in this stroke for accelerating the body during the pushing
phase so as to compensate for the loss of v occurring in the non-propulsive phase.
Accepted: 14 April 1998 相似文献
5.
Brian Dawson Martin Fitzsimons Simon Green Carmél Goodman Michael Carey Keith Cole 《European journal of applied physiology and occupational physiology》1998,78(2):163-169
In contrast to endurance training, little research has been carried out to investigate the effects of short (<10 s) sprint
training on performance, muscle metabolism and fibre types. Nine fit male subjects performed a mean of 16 outdoor sprint running
training sessions over 6 weeks. Distances sprinted were 30–80 m at 90–100% maximum speed and between 20 and 40 sprints were
performed in each session. Endurance (maximal oxygen consumption; V˙O2
max), sprint (10 m and 40 m times), sustained sprint (supramaximal treadmill run) and repeated sprint (6 × 40 m sprints, 24 s
recovery between each) performance tests were performed before and after training. Muscle biopsy samples (vastus lateralis)
were also taken to examine changes in metabolites, enzyme activities and fibre types. After training, significant improvements
were seen in 40 m time (P < 0.01), supramaximal treadmill run time (P < 0.05), repeated sprint performance (P < 0.05) and V˙O2
max (P < 0.01). Resting muscle concentrations of ATP and phosphocreatine did not change. Phosphorylase activity increased (P < 0.025), citrate synthase activity decreased (P < 0.01), but no significant changes were recorded in myokinase and phosphofructokinase activities. The proportion of type
II muscle fibres increased significantly (P < 0.05). These results demonstrate that 6 weeks of short sprint training can improve endurance, sprint and repeated sprint
ability in fit subjects. Increases in the proportion of type II muscle fibres are also possible with this type of training.
Accepted: 5 January 1998 相似文献
6.
The effects of short-term resistance training on endocrine function in men and women 总被引:6,自引:0,他引:6
William J. Kraemer Robert S. Staron Fredrick C. Hagerman Robert S. Hikida Andrew C. Fry Scott E. Gordon Bradley C. Nindl Lincoln A. Gothshalk Jeff S. Volek James O. Marx Robert U. Newton Keijo H?kkinen 《European journal of applied physiology and occupational physiology》1998,78(1):69-76
This investigation examined hormonal adaptations to acute resistance exercise and determined whether training adaptations
are observed within an 8-week period in untrained men and women. The protocol consisted of a 1-week pre-conditioning orientation
phase followed by 8 weeks of heavy resistance training. Three lower-limb exercises for the quadriceps femoris muscle group
(squat, leg press, knee extension) were performed twice a week (Monday and Friday) with every other Wednesday used for maximal
dynamic 1 RM strength testing. Blood samples were obtained pre-exercise (Pre-Ex), immediately post-exercise (IP), and 5 min
post-exercise (5-P) during the first week of training (T-1), after 6 weeks (T-2) and 8 weeks (T-3) of training to determine
blood concentrations of whole-blood lactate (LAC), serum total testosterone (TT), sex-hormone binding globulin (SHBG), cortisol
(CORT) and growth hormone (GH). Serum TT concentrations were significantly (P ≤ 0.05) higher for men at all time points measured. Men did not demonstrate an increase due to exercise until T-2. An increase
in pre-exercise concentrations of TT were observed both for men and women at T-2 and T-3. No differences were observed for
CORT between men and women; increases in CORT above pre-exercise values were observed for men at all training phases and at
T-2 and T-3 for women. A reduction in CORT concentrations at rest was observed both in men and women at T-3. Women demonstrated
higher pre-exercise GH values than men at all training phases; no changes with training were observed for GH concentrations.
Exercise-induced increases in GH above pre-exercise values were observed at all phases of training. Women demonstrated higher
serum concentrations of SHBG at all time points. No exercise-induced increases were observed in men over the training period
but women increased SHBG with exercise at T-3. SHBG concentrations in women were also significantly higher at T-2 and T-3
when compared to T-1 values. Increases in LAC concentrations due to exercise were observed both for men and women for all
training phases but no significant differences were observed with training. These data illustrate that untrained individuals
may exhibit early-phase endocrine adaptations during a resistance training program. These hormonal adaptations may influence
and help to mediate other adaptations in the nervous system and muscle fibers, which have been shown to be very responsive
in the early phase of strength adaptations with resistance training.
Accepted: 11 December 1997 相似文献
7.
S. Machemer-Röhnisch U. Nagel H. Machemer 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1999,185(6):517-527
We investigated the autotrophic flagellate Euglena gracilis for gravity-induced modulation of the speed of swimming as previously documented for larger protozoan cells. Methods of video-tracking
of swimming and sedimenting cells under 1 g and hypergravity up to 2 g, and computer-assisted data processing were applied. The vertical and horizontal swimming speed, and sedimentation rates
of immobilized cells, were found to be linear functions of acceleration. Accounting for sedimentation in the observed upward
and downward movements of Euglena, the active component of speed (propulsion) rose in proportion to acceleration. No saturation of gravikinesis was seen within
the g-range tested. Gravity-dependent augmentation of speed was maximal in upward swimmers and decreased continuously over horizontal
to downward swimmers. Linear extrapolations of the data to zero-g conditions suggest the absence of a threshold of gravikinesis in Euglena. Energetic considerations indicate a high sensitivity of gravitransduction near the level of Brownian molecular motion.
Accepted: 22 August 1999 相似文献
8.
Interseasonal comparison of CO2 concentrations, isotopic composition, and carbon dynamics in an Amazonian rainforest (French Guiana) 总被引:2,自引:0,他引:2
Canopy CO2 concentrations in a tropical rainforest in French Guiana were measured continuously for 5 days during the 1994 dry season
and the 1995 wet season. Carbon dioxide concentrations ([CO2]) throughout the canopy (0.02–38 m) showed a distinct daily pattern, were well-stratified and decreased with increasing height
into the canopy. During both seasons, daytime [CO2] in the upper and middle canopy decreased on average 7–10 μmol mol−1 below tropospheric baseline values measured at Barbados. Within the main part of the canopy (≥ 0.7 m), [CO2] did not differ between the wet and dry seasons. In contrast, [CO2] below 0.7 m were generally higher during the dry season, resulting in larger [CO2] gradients. Supporting this observation, soil CO2 efflux was on average higher during the dry season than during the wet season, either due to diffusive limitations and/or
to oxygen deficiency of root and microbial respiration. Soil respiration rates decreased by 40% after strong rain events,
resulting in a rapid decrease in canopy [CO2] immediately above the forest floor of about 50␣μmol mol−1. Temporal and spatial variations in [CO2]canopy were reflected in changes of δ13Ccanopy and δ18Ocanopy values. Tight relationships were observed between δ13C and δ18O of canopy CO2 during both seasons (r
2 > 0.86). The most depleted δ13Ccanopy and δ18Ocanopy values were measured immediately above the forest floor (δ13C = −16.4‰; δ18O = 39.1‰ SMOW). Gradients in the isotope ratios of CO2 between the top of the canopy and the forest floor ranged between 2.0‰ and 6.3‰ for δ13C, and between 1.0‰ and 3.5‰ for δ18O. The δ13Cleaf and calculated c
i/c
a of foliage at three different positions were similar for the dry and wet seasons indicating that the canopy maintained a
constant ratio of photosynthesis to stomatal conductance. About 20% of the differences in δ13Cleaf within the canopy was accounted for by source air effects, the remaining 80% must be due to changes in c
i/c
a. Plotting 1/[CO2] vs. the corresponding δ13C ratios resulted in very tight, linear relationships (r
2 = 0.99), with no significant differences between the two seasons, suggesting negligible seasonal variability in turbulent
mixing relative to ecosystem gas exchange. The intercepts of these relationships that should be indicative of the δ13C of respired sources were close to the measured δ13C of soil respired CO2 and to the δ13C of litter and soil organic matter. Estimates of carbon isotope discrimination of the entire ecosystem, Δe, were calculated as 20.3‰ during the dry season and as 20.5‰ during the wet season.
Received: 3 March 1996 / Accepted: 19 October 1996 相似文献
9.
Mode of depolymerisation of hemicellulose by various mannanases and xylanases in relation to their ability to bleach softwood pulp 总被引:2,自引:0,他引:2
G. M. Gübitz D. Haltrich B. Latal W. Steiner 《Applied microbiology and biotechnology》1997,47(6):658-662
Endo-mannanases and endo-xylanases cleave different heteromannans and xylans yielding mainly dimers and trimers of the corresponding
sugars as end-products. However, in the early stages of hydrolysis, four purified mannanases and four xylanases from fungal
and bacterial origin, examined in this study, showed a different pattern of released oligomers (determined up to the pentamers).
Furthermore, some of these enzymes showed a preference for cleaving the polysaccharides in the middle of the chain while others
acted more at the end. When the increase in the specific fluidity of mannan and xylan solutions per reducing sugar released
(K
v) was measured against the bleaching effect of the enzymes on softwood kraft pulp, a correlation was found. A xylanase from
Penicillium simplicissimum (K
v = 0.15 l mPa−1s−1g−1) and a mannanase from Sclerotium rolfsii (K
v = 0.12 l mPa−1s−1g−1) applied in a O(QX)P bleaching sequence (O = oxygen delignification, X = treatment with hemicellulolytic enzymes, Q = chelation
of metals, P = treatment with hydrogen peroxide in alkaline solution) gave a high brightness increase of 3.0% and 1.9% ISO
respectively. A less significant brightness increase was obtained with enzymes showing lower K
v values, such as a xylanase from Schizophyllum commune (Kv = 0.051 l mPa−1s−1g−1, 0.2% ISO) and a bacterial mannanase (K
v = 0.061 l mPa−1s−1g−1,0.5% ISO).
Received: 19 December 1996 / Received revision: 20 February 1997 / Accepted: 22 February 1997 相似文献
10.
S. Grant W. Davidson T. Aitchison J. Wilson 《European journal of applied physiology and occupational physiology》1998,78(4):324-332
The aim of this study was to compare the exercise intensity and rating of perceived exertion (RPE) of a high-impact (HIP)
and a low-impact (LIP) university aerobic dance session. Ten women [mean (SD) age 22.9 (2.6) years] took part in the study.
An incremental treadmill test was performed by each subject to determine maximum oxygen consumption (V˙O2
max
) and maximum heart rate (HR
max
). The measured V˙O2
max
[mean (SD)] was 49.0 (7.5) ml · kg−1 · min−1. The subjects were randomly assigned to LIP and HIP sessions (i.e. five of the subjects participated in the HIP session first,
and the other five participated in the LIP session first). In a laboratory, heart rate, oxygen uptake and RPE were measured
throughout each session for each subject. Expired air was collected continuously throughout the sessions using Douglas bags
(ten bags over a 30-min period). The sessions consisted of 20 min of aerobic exercise (bags 1–7) followed by 5 min of local
muscular endurance exercise (bags 8 and 9) and 5 min of flexibility exercises (bag 10). The mean intensity of the aerobic
section of the LIP and HIP sessions was 51.6% and 64.7% V˙O2
max
, respectively. Ninety-five percent confidence intervals for the average difference between the HIP and LIP sessions demonstrate
that the %V˙O2
max
was between 12% and 14% higher for the HIP session. The mean %HR
max
for the LIP and HIP sessions was 71.4% and 76.7%, respectively, with the %HR
max
in the HIP session being between 5.4% and 7.2% higher on average than that of the LIP session. On average, the RPE for the
aerobic section of the HIP session (12.1) was consistently higher than that of the LIP session (11.1). HIP activity has the
potential to maintain/improve the aerobic fitness of its participants. According to the literature, the exercise intensity
elicited by LIP activity may have a limited training effect for the population utilised in this study, and for some individuals
may result in detraining. Conversely, LIP activities may be an appropriate mode of exercise for overweight and unfit individuals.
Accepted: 5 January 1998 相似文献
11.
Edith Filaire Pascale Duché Gérard Lac 《European journal of applied physiology and occupational physiology》1998,78(5):466-471
This study was designed to investigate in the saliva the influence in female athletes of handball or volleyball training on
concentrations of cortisol [C], dehydroepiandrosterone [DHEA], and on the [DHEA]:[C] ratio over 16 weeks of training. Data
were compared to those of sedentary women. Saliva samples were collected upon waking after an overnight fast during the 1st
week (W1) of the training programme and in the 16th week (W16). The training programme increased the resting concentrations of saliva [DHEA] in all the sportswomen. In contrast, a decrease
of [DHEA] was noted in the sedentary group (W16 < W1; P < 0.05). In none of the women did the [C] at rest change significantly during the study. Between W1 and W16, the [DHEA]:[C] ratio increased by more than 30% in all the sportswomen. In addition, the athletes with the highest performance
levels and greatest amount of training had the lowest [DHEA]:[C] ratio. Negative linear relationships between the amount of
training and the [DHEA]:[C] ratio were found both at W1 (r = −0.53 P < 0.001), and W16 (r=−0.73 P < 0.001), suggesting that the latter could be used as an indicator of the training status of sportswomen.
Accepted: 12 May 1998 相似文献
12.
Short duration repeated maximal efforts are often used in swimming training to improve lactate tolerance, which gives swimmers the ability to maintain a high work rate for a longer period of time. The aim of the study was to examine the kinematics of swimming and its relation to the changes in blood acid-base status and potassium level. Seven collegiate swimmers, with at least 6 years of training experience, volunteered to participate in the study. The test consisted of 8 x 25 m front crawl performed with maximum effort. The rest period between repetitions was set to five seconds. Blood samples were taken from the fingertip at rest, after warm-up and in the 3rd minute after completion of the test. The swimming was recorded with a video recorder, for later analysis of time, velocity and technique (stroke index). Based on the swimming velocity results, the obtained curve can be divided into rapid decrease of velocity and relatively stable velocities. The breaking point of repetition in swimming velocity was assumed as the swimming velocity threshold and it was highly correlated with the decrease of the blood acid-base status (pH r=0.82, BE r=0.87, HCO3
- r=0.76; p<0.05 in all cases). There was no correlation between stroke index or fatigue index and blood acid-base status. Analysis of the swimming speed in the 8 x 25 m test seems to be helpful in evaluation of lactate tolerance (anaerobic capacity) in collegiate swimmers. 相似文献
13.
K. P. Hebbar R. D. Lumsden S. M. Poch J. A. Lewis 《Applied microbiology and biotechnology》1997,48(6):714-719
Conditions for optimizing spore production, especially chlamydospores, by host-specific mycoherbicidal strains of Fusarium oxysporum causing vascular wilts in coca (Erythroxylum coca) and poppy (Papaver somniferum) were studied in 2.5-1 fermentors. The fermentor dissolved oxygen and pH had significant effects on the growth characteristics
of F. oxysporum strains. The effect of the fungal strain, however was not significant for most of the variables studied except for chlamydospore
formation. After 14 days of fermentation, the spore types produced were microconidia and chlamydospores, with very little
production of macroconidia. While the total viable counts were significantly higher under high than under low dissolved O2, the chlamydospore counts were significantly higher under low than under high dissolved O2. The percentage of chlamydospores obtained, as a proportion of total viable was significantly higher when the fermentor pH
was increased, than when it was not. Scaling-up the liquid fermentation to 20 l, yielded log10
c = 6.8 (where c = chlamydospores ml−1) after 14 days' fermentation, with biomass viable counts of log10
v∼8.0 (where v = viable counts g−1 air-dried biomass). A single-step liquid fermentation reported in this study increased chlamydospore yields and reduced the
time required for their production with techniques currently available from 5 weeks to less than 2 weeks.
Received: 24 April 1997 / Received revision: 6 August 1997 / Accepted: 29 August 1997 相似文献
14.
Wilson RS James RS Johnston IA 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(2):117-124
Among amphibians, the ability to compensate for the effects of temperature on the locomotor system by thermal acclimation
has only been reported in larvae of a single species of anuran. All other analyses have examined predominantly terrestrial
adult life stages of amphibians and found no evidence of thermal acclimatory capacity. We examined the ability of both tadpoles
and adults of the fully aquatic amphibian Xenopus laevis to acclimate their locomotor system to different temperatures. Tadpoles were acclimated to either 12 °C or 30 °C for 4 weeks
and their burst swimming performance was assessed at four temperatures between 5 °C and 30 °C. Adult X. laevis were acclimated to either 10 °C or 25 °C for 6 weeks and their burst swimming performance and isolated muscle performance
was determined at six temperatures between 5 °C and 30 °C. Maximum swimming performance of cold-acclimated X. laevis tadpoles was greater at cool temperatures and lower at the highest temperature in comparison with the warm-acclimated animals.
At the test temperature of 12 °C, maximum swimming velocity of tadpoles acclimated to 12 °C was 38% higher than the 30 °C-acclimation
group, while at 30 °C, maximum swimming velocity of the 30 °C-acclimation group was 41% faster than the 12 °C-acclimation
group. Maximum swimming performance of adult X. laevis acclimated to 10 °C was also higher at the lower temperatures than the 25 °C acclimated animals, but there was no difference
between the treatment groups at higher temperatures. When tested at 10 °C, maximum swimming velocity of the 10 °C-acclimation
group was 67% faster than the 25 °C group. Isolated gastrocnemius muscle fibres from adult X. laevis acclimated to 10 °C produced higher relative tetanic tensions and decreased relaxation times at 10 °C in comparison with
animals acclimated to 25 °C. This is only the second species of amphibian, and the first adult life stage, reported to have
the capacity to thermally acclimate locomotor performance.
Accepted: 28 October 1999 相似文献
15.
M. Sandsund M. Sue-Chu J. Helgerud R. E. Reinertsen L. Bjermer 《European journal of applied physiology and occupational 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
16.
M. Faina V. Billat R. Squadrone M. De Angelis J. P. Koralsztein A. Dal Monte 《European journal of applied physiology and occupational physiology》1997,76(1):13-20
Using 23 elite male athletes (8 cyclists, 7 kayakists, and 8 swimmers), the contribution of the anaerobic energy system to
the time to exhaustion (t
lim) at the minimal exercise intensity (speed or power) at which maximal oxygen uptake (V˙O2
max) occurs (I
V˙O2
max) was assessed by analysing the relationship between the t
lim and the accumulated oxygen deficit (AOD). After 10-min warming up at 60% of V˙O2
max, the exercise intensity was increased so that each subject reached his I
V˙O2max
in 30 s and then continued at that level until he was exhausted. Pre-tests included a continuous incremental test with 2 min
steps for determining the I
V˙O2max
and a series of 5-min submaximal intensities to collect the data that would allow the estimation of the energy expenditure
at I
V˙O2max
. The AOD for the t
lim exercise was calculated as the difference between the above estimation and the accumulated oxygen uptake. The mean percentage
value of energy expenditure covered by anaerobic metabolism was 15.2 [(SD 6)%, range 8.9–24.1] with significant differences
between swimmers and kayakists (16.8% vs 11.5%, P≤0.05) and cyclists and kayakists (16.4% vs 11.5%, P≤0.05). Absolute AOD values ranged from 26.4 ml · kg−1 to 83.6 ml · kg−1 with a mean value of 45.9 (SD 18) ml · kg−1. Considering all the subjects, the t
lim was found to have a positive and significant correlation with AOD (r = 0.62, P≤0.05), and a negative and significant correlation with V˙O2
max (r = −0.46, P≤0.05). The data would suggest that the contribution of anaerobic processes during exercise performed at I
V˙O2max
should not be ignored when t
lim is used as a supplementary parameter to evaluate specific adaptation of athletes.
Accepted: 17 December 1996 相似文献
17.
Timothy J. Carroll Peter J. Abernethy Peter A. Logan Margaret Barber Michael T. McEniery 《European journal of applied physiology and occupational physiology》1998,78(3):270-275
Seventeen subjects performed resistance training of the leg extensor and flexor muscle groups two (2/wk) or three (3/wk)
times per week. Changes in the relative myosin heavy chain (MHC) isoform contents (I, IIa and IIx) of the vastus lateralis
and isometric, isokinetic and squat-lift one-repetition maximum (1RM) strength were compared between conditions after both
a common training period (6 weeks) and number of training sessions (18). After 6 weeks and 18 sessions (9 weeks for the 2/wk
group), increments in 1RM strength for the 3/wk and 2/wk groups were similar [effect size (ES) differences ≈0.3, 3/wk > 2/wk],
whereas the 2/wk group presented greater isokinetic (ES differences = 0.3–1.2) and isometric (ES differences ≈0.7) strength
increases than the 3/wk condition. A significant (P < 0.05) increase in MHC IIa percentage was evident for the 2/wk group after 18 sessions. Both training groups exhibited a
trend towards a reduction in the relative MHC IIx and an increase in MHC IIa contents (ES range = 0.5–1.24). However, correlations
between changes in the strength and MHC profiles were weak (r
2: 0.0–0.5). Thus, isometric and isokinetic strength responses to variations in training frequency differed from 1RM strength
responses, and changes in strength were not strongly related to alterations in relative MHC content.
Accepted: 19 March 1998 相似文献
18.
Schmid J Speakman JR 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(8):633-641
We aimed to investigate the pattern of utilisation of torpor and its impact on energy budgets in free-living grey mouse lemurs
(Microcebus murinus), a small nocturnal primate endemic to Madagascar. We measured daily energy expenditure (DEE) and water turnover using doubly
labelled water, and we used temperature-sensitive radio collars to measure skin temperature (T
sk) and home range. Our results showed that male and female mouse lemurs in the wild enter torpor spontaneously over a wide
range of ambient temperatures (T
a) during the dry season, but not during the rainy season. Mouse lemurs remained torpid between 1.7–8.9 h with a daily mean
of 3.4 h, and their T
sk s fell to a minimum of 18.8 °C. Mean home ranges of mouse lemurs which remained normothermic were similar in the rainy and
dry season. During the dry season, the mean home range of mouse lemurs showing daily torpor was significantly smaller than
that of animals remaining normothermic. The DEE of M. murinus remaining normothermic in the rainy season (122 ± 65.4 kJ day−1) was about the same of that of normothermic mouse lemurs in the dry season (115.5 ± 27.3 kJ day−1). During the dry season, the mean DEE of M. murinus that utilised daily torpor was 103.4 ± 32.7 kJ day−1 which is not significantly different from the mean DEE of animals remaining normothermic. We found that the DEE of mouse
lemurs using daily torpor was significantly correlated with the mean temperature difference between T
sk and T
a (r
2=0.37) and with torpor bout length (r
2
=0.46), while none of these factors explained significant amounts of variation in the DEE of the mouse lemurs remaining normothermic.
The mean water flux rate of mouse lemurs using daily torpor (13.0 ± 4.1 ml day−1) was significantly lower than that of mouse lemurs remaining normothermic (19.4 ± 3.8 ml day−1), suggesting the lemurs conserve water by entering torpor. Thus, this first study on the energy budget of free-ranging M. murinus demonstrates that torpor may not only reflect its impact on the daily energy demands, but involve wider adaptive implications
such as water requirements.
Accepted: 29 August 2000 相似文献
19.
Thermal acclimation of locomotor performance in tadpoles of the frog Limnodynastes peronii 总被引:3,自引:0,他引:3
R. S. Wilson C. E. Franklin 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(6):445-451
Previous analyses of thermal acclimation of locomotor performance in amphibians have only examined the adult life history
stage and indicate that the locomotor system is unable to undergo acclimatory changes to temperature. In this study, we examined
the ability of tadpoles of the striped marsh frog (Limnodynastes peronii) to acclimate their locomotor system by exposing them to either 10 °C or 24 °C for 6 weeks and testing their burst swimming
performance at 10, 24, and 34 °C. At the test temperature of 10 °C, maximum velocity (Umax) of the 10 °C-acclimated tadpoles was 47% greater and maximum acceleration (Amax) 53% greater than the 24 °C-acclimated animals. At 24 °C, Umax was 16% greater in the 10 °C-acclimation group, while there was no significant difference in Amax or the time taken to reach Umax (T-Umax). At 34 °C, there was no difference between the acclimation groups in either Umax or Amax, however T-Umax was 36% faster in the 24 °C-acclimation group. This is the first study to report an amphibian (larva or adult) possessing
the capacity to compensate for cool temperatures by thermal acclimation of locomotor performance. To determine whether acclimation
period affected the magnitude of the acclimatory response, we also acclimated tadpoles of L. peronii to 10 °C for 8 months and compared their swimming performance with tadpoles acclimated to 10 °C for 6 weeks. At the test
temperatures of 24 °C and 34 °C, Umax and Amax were significantly slower in the tadpoles acclimated to 10 °C for 8 months. At 10 °C, T-Umax was 40% faster in the 8-month group, while there were no differences in either Umax or Amax. Although locomotor performance was enhanced at 10 °C by a longer acclimation period, this was at the expense of performance
at higher temperatures.
Accepted: 25 June 1999 相似文献
20.
Sandström ME Siegler JC Lovell RJ Madden LA McNaughton L 《Cell stress & chaperones》2008,13(2):169-175
The purpose of this study was to investigate the alterations in serum heat shock protein (Hsp) 70 levels during a 15-consecutive-day
intermittent heat–exercise protocol in a 29-year-old male ultra marathon runner. Heat acclimation, for the purpose of physical
activities in elevated ambient temperatures, has numerous physiological benefits including mechanisms such as improved cardiac
output, increased plasma volume and a decreased core temperature (T
c). In addition to the central adaptations, the role of Hsp during heat acclimation has received an increasing amount of attention.
The acclimation protocol applied was designed to correspond with the athlete’s tapering period for the 2007 Marathon Des Sables.
The subject (VO2max = 50.7 ml·kg−1·min−1, peak power output [PPO] = 376 W) cycled daily for 90 min at a workload corresponding to 50% of VO2max in a temperature-controlled room (average WBGT = 31.9 ± 0.9°C). Venous blood was sampled before and after each session
for measurement of serum osmolality and serum Hsp70. In addition, T
c, heart rate (HR) and power output (PO) was measured throughout the 90 min to ensure that heat acclimation was achieved during
the 15-day period. The results show that the subject was successfully heat acclimated as seen by the lowered HR at rest and
during exercise, decreased resting and exercising T
c and an increased PO. The heat exercise resulted in an initial increase in Hsp70 concentrations, known as thermotolerance,
and the increase in Hsp70 after exercise was inversely correlated to the resting values of Hsp70 (Spearman’s rank correlation = −0.81,
p < 0.01). Furthermore, the 15-day heat–exercise protocol also increased the basal levels of Hsp70, a response different from
that of thermotolerance. This is, as far as we are aware, the first report showing Hsp70 levels during consecutive days of
intermittent heat exposure giving rise to heat acclimation. In conclusion, a relatively longer heat acclimation protocol is
suggested to obtain maximum benefit of heat acclimation inclusive of both cellular and systemic adaptations. 相似文献