共查询到20条相似文献,搜索用时 31 毫秒
1.
Several studies investigating the effect of caffeine on immune function following exercise have used one large bolus dose
of caffeine. However, this does not model typical caffeine consumption. Therefore, the purpose of this study was to investigate
whether small repeated doses of caffeine ingested throughout the day would elicit a similar response as one large bolus dose
ingested 1 h prior to exercise on antigen-stimulated NK cell CD69 expression following strenuous intermittent exercise. In
a randomized cross-over design, 15 healthy males completed six 15 min blocks of intermittent running consisting of maximal
sprinting interspersed with less intense running and walking. Participants had ingested either 0 (PLA), 2 mg kg−1 body mass (BM) caffeine on three separate occasions during the day (3× CAF) or one dose of 6 (1× CAF) mg kg−1 BM caffeine, 1 h before exercise. At 1-h post-exercise, the number of antigen-stimulated CD3−CD56+ cells expressing CD69 was lower on 1× CAF compared with PLA [P < 0.05; PLA: 42.0 (34.0) × 106 cells L−1, 1× CAF: 26.2 (25.0) × 106 cells L−1], with values on 1× CAF at this time point remaining close to pre-supplement. 1× CAF tended to attenuate the exercise-induced
increase in geometric mean fluorescence intensity of CD69 expression on antigen-stimulated CD3−CD56+ cells 1-h post-exercise [P = 0.055; PLA: 141 (28)%, 1× CAF: 119 (20)%]. These findings suggest that although one large bolus dose of caffeine attenuated
the exercise-induced increase in antigen-stimulated NK cell CD69 expression 1 h following strenuous intermittent exercise,
this attenuation at no point fell below pre-supplement values and caffeine does not appear to depress NK cell CD69 expression. 相似文献
2.
Michael J. Simmonds Clare L. Minahan Surendran Sabapathy 《European journal of applied physiology》2010,109(2):287-295
The purpose of this study was to determine if improved supramaximal exercise performance in trained cyclists following caffeine
ingestion was associated with enhanced O2 uptake (
[(V)\dot]\textO2 \dot{V}{\text{O}}_{2} kinetics), increased anaerobic energy provision (accumulated O2—AO2—deficit), or a reduction in the accumulation of metabolites (for example, K+) associated with muscular fatigue. Six highly trained male cyclists (
[(V)\dot]\textO2 \dot{V}{\text{O}}_{2} peak 68 ± 8 mL kg−1 min−1) performed supramaximal (120%
[(V)\dot]\textO2 \dot{V}{\text{O}}_{2} peak) exercise bouts to exhaustion on an electronically braked cycle ergometer, following double-blind and randomized ingestion
of caffeine/placebo (5 mg kg−1). Time to exhaustion (TE),
[(V)\dot]\textO2 \dot{V}{\text{O}}_{2} kinetics, AO2 deficit, blood lactate (La−), plasma potassium (K+), caffeine and paraxanthine concentrations were measured. Caffeine ingestion elicited significant increases in TE (14.8%,
p < 0.01) and AO2 deficit (6.5%, p < 0.05). In contrast, no changes were observed in AO2 deficit at isotime,
[(V)\dot]\textO2 \dot{V}{\text{O}}_{2} kinetics, blood [La−] at exhaustion or peak [K+] following caffeine ingestion. However, [K+] was significantly reduced (13.4%, p < 0.01) during warm-up cycling immediately prior to the onset of the supramaximal bout for the caffeine trials, compared
with placebo. It appears that caffeine ingestion is beneficial to supramaximal cycling performance in highly trained men.
The reduced plasma [K+] during submaximal warm-up cycling may prolong the time taken to reach critical [K+] at exhaustion, thus delaying fatigue. Considering caffeine ingestion did not change
[(V)\dot]\textO2 \dot{V}{\text{O}}_{2} kinetics or isotime AO2 deficit, increases in absolute AO2 deficit may be a consequence of prolonged TE, rather than causal. 相似文献
3.
Marwood S Roche D Garrard M Unnithan VB 《European journal of applied physiology》2011,111(11):2775-2784
Previous studies have demonstrated faster pulmonary oxygen uptake (
[(V)\dot]\textO2 \dot{V}{\text{O}}_{2} ) kinetics in the trained state during the transition to and from moderate-intensity exercise in adults. Whilst a similar
effect of training status has previously been observed during the on-transition in adolescents, whether this is also observed
during recovery from exercise is presently unknown. The aim of the present study was therefore to examine
[(V)\dot]\textO2 \dot{V}{\text{O}}_{2} kinetics in trained and untrained male adolescents during recovery from moderate-intensity exercise. 15 trained (15 ± 0.8 years,
[(V)\dot]\textO2max \dot{V}{\text{O}}_{2\max} 54.9 ± 6.4 mL kg−1 min−1) and 8 untrained (15 ± 0.5 years,
[(V)\dot]\textO2max \dot{V}{\text{O}}_{2\max } 44.0 ± 4.6 mL kg−1 min−1) male adolescents performed two 6-min exercise off-transitions to 10 W from a preceding “baseline” of exercise at a workload
equivalent to 80% lactate threshold;
[(V)\dot]\textO2 \dot{V}{\text{O}}_{2} (breath-by-breath) and muscle deoxyhaemoglobin (near-infrared spectroscopy) were measured continuously. The time constant
of the fundamental phase of
[(V)\dot]\textO2 \dot{V}{\text{O}}_{2} off-kinetics was not different between trained and untrained (trained 27.8 ± 5.9 s vs. untrained 28.9 ± 7.6 s, P = 0.71). However, the time constant (trained 17.0 ± 7.5 s vs. untrained 32 ± 11 s, P < 0.01) and mean response time (trained 24.2 ± 9.2 s vs. untrained 34 ± 13 s, P = 0.05) of muscle deoxyhaemoglobin off-kinetics was faster in the trained subjects compared to the untrained subjects.
[(V)\dot]\textO2 \dot{V}{\text{O}}_{2} kinetics was unaffected by training status; the faster muscle deoxyhaemoglobin kinetics in the trained subjects thus indicates
slower blood flow kinetics during recovery from exercise compared to the untrained subjects. 相似文献
4.
Tumilty L Davison G Beckmann M Thatcher R 《European journal of applied physiology》2011,111(12):2941-2950
Increased brain dopamine availability improves prolonged exercise tolerance in the heat. It is unclear whether supplementing
the amino-acid precursor of dopamine increases exercise capacity in the heat. Eight healthy male volunteers [mean age 32 ± 11
(SD) years; body mass 75.3 ± 8.1 kg; peak oxygen uptake ([(V)\dot]O2peak \dot{V}O_{{2peak}} ) 3.5 ± 0.3 L min−1] performed two exercise trials separated by at least 7 days in a randomised, crossover design. Subjects consumed 500 mL of
a flavoured sugar-free drink (PLA), or the same drink with 150 mg kg body mass−1 tyrosine (TYR) in a double-blind manner 1 h before cycling to exhaustion at a constant exercise intensity equivalent to 68 ± 5%
[(V)\dot]O2peak \dot{V}O_{{2peak}} in 30°C and 60% relative humidity. Pre-exercise plasma tyrosine:large neutral amino acids increased 2.9-fold in TYR (P < 0.01), while there was no change in PLA (P > 0.05). Subjects cycled longer in TYR compared to PLA (80.3 ± 19.7 min vs. 69.2 ± 14.0 min; P < 0.01). Core temperature, mean weighted skin temperature, heart rate, ratings of perceived exertion and thermal sensation
were similar in TYR and PLA during exercise and at exhaustion (P > 0.05) despite longer exercise time in TYR. The results show that acute tyrosine supplementation is associated with increased
endurance capacity in the heat in moderately trained subjects. The results also suggest for the first time that the availability
of tyrosine, a nutritional dopamine precursor, can influence the ability to subjectively tolerate prolonged submaximal constant-load
exercise in the heat. 相似文献
5.
Jesse G. Greiner Miriam E. Clegg Michael L. Walsh Matthew D. White 《European journal of applied physiology》2010,109(1):109-115
Hyperthermia potentiates the influence of CO2 on pulmonary ventilation (
[(V)\dot]\textE \dot{V}_{\text{E}} ). It remains to be resolved how skin and core temperatures contribute to the elevated exercise ventilation response to CO2. This study was conducted to assess the influences of mean skin temperature (
[`(T)]\textSK \overline{T}_{\text{SK}} ) and end-tidal PCO2 (PETCO2) on
[(V)\dot]\textE \dot{V}_{\text{E}} during submaximal exercise with a normothermic esophageal temperature (T
ES). Five males and three females who were 1.76 ± 0.11 m tall (mean ± SD), 75.8 ± 15.6 kg in weight and 22.0 ± 2.2 years of
age performed three 1 h exercise trials in a climatic chamber with the relative humidity (RH) held at 31.5 ± 9.5% and the
ambient temperature (T
AMB) maintained at one of 25, 30, or 35°C. In each trial, the volunteer breathed eucapnic air for 5 min during a rest period
and subsequently cycle ergometer exercised at 50 W until T
ES stabilized at ~37.1 ± 0.4°C. Once T
ES stabilized in each trial, the volunteer breathed hypercapnic air twice for ~5 min with PETCO2 elevated by approximately +4 or +7.5 mmHg. The significantly (P < 0.05) different increases of PETCO2 of +4.20 ± 0.49 and +7.40 ± 0.51 mmHg gave proportionately larger increases in
[(V)\dot]\textE \dot{V}_{\text{E}} of 10.9 ± 3.6 and 15.2 ± 3.6 L min−1 (P = 0.001). This hypercapnia-induced hyperventilation was uninfluenced by varying the
[`(T)]\textSK \overline{T}_{\text{SK}} to three significantly different levels (P < 0.001) of 33.2 ± 1.2°C, to 34.5 ± 0.8°C to 36.4 ± 0.5°C. In conclusion, the results support that skin temperature between
~33 and ~36°C has neither effect on pulmonary ventilation nor on hypercapnia-induced hyperventilation during a light exercise
with a normothermic core temperature. 相似文献
6.
Davis JK Bishop PA Zhang Y Matt Green J Casaru C Orrick KD Curtner-Smith M Richardson MT Schumacker RE 《European journal of applied physiology》2012,112(2):725-734
This study examined heat stress, heart rate (HR), fluid balance, micro-environment temperature and humidity with Islamic athletic
clothing (IC) compared to traditional soccer uniform (SC). Ratings of perceived exertion (RPE), session RPE (S-RPE), comfort,
and cooling response were also examined. Female volunteers (N = 8) completed a treadmill
[(V)\dot]\textO2\textpeak \dot{V}{\text{O}}_{{2{\text{peak}}}} test and then, in a randomized, counter-balanced order, two intermittent running bouts (45 min total) in a hot environment
(30.0°C WBGT) in IC and SC. Thereafter, participants sat for 40 min in the hot ambient environment. Repeated measures ANOVA
revealed significantly greater micro-environment temperature (p = 0.02) (IC 33.3 ± 3.2°C, SC 32.0 ± 2.8°C) and humidity (p = 0.04) (IC 48.4 ± 8.1%, SC 42.9 ± 7.9%) in IC during the exercise trial but no difference in the 40-min recovery period
for micro-environment temperature (p = 0.25) or humidity (p = 0.18). No significant difference (p > 0.05) was shown for core temperature (T
rec) (IC 38.3 ± 0.4°C, SC 38.2 ± 0.4°C), HR (IC l54 ± 28 beats min−1, SC 151 ± 26 beats min−1) or RPE (IC 4.7 ± 2.1, SC 3.8 ± 1.7) during the exercise trial or recovery period. Results from a paired t test revealed a significantly greater (p < 0.05) S-RPE (IC 5.8 ± 1.2, SC 4.3 ± 1.9), sweat loss (IC 1.4 ± 0.4 L h−1, SC 1.2 ± 0.4 L h−1) and greater discomfort during the exercise and recovery period for the IC. IC clothing appears to have no detrimental effects
on heat storage or heat strain during exercise or recovery. 相似文献
7.
Clarke ND Maclaren DP Reilly T Drust B 《European journal of applied physiology》2011,111(7):1447-1455
Ingestion of carbohydrate and reducing core body temperature pre-exercise, either separately or combined, may have ergogenic
effects during prolonged intermittent exercise in hot conditions. The aim of this investigation was to examine the effect
of carbohydrate ingestion and pre-cooling on the physiological responses to soccer-specific intermittent exercise and the
impact on subsequent high-intensity exercise performance in the heat. Twelve male soccer players performed a soccer-specific
intermittent protocol for 90 min in the heat (30.5°C and 42.2% r.h.) on four occasions. On two occasions, the participants underwent a pre-cooling manoeuvre. During these sessions either a
carbohydrate–electrolyte solution (CHOc) or a placebo was consumed at (PLAc). During the remaining sessions either the carbohydrate–electrolyte
solution (CHO) or placebo (PLA) was consumed. At 15-min intervals throughout the protocol participants performed a mental
concentration test. Following the soccer-specific protocol participants performed a self-chosen pace test and a test of high-intensity
exercise capacity. The period of pre-cooling significantly reduced core temperature, muscle temperature and thermal sensation
(P < 0.05). Self-chosen pace was greater with CHOc (12.5 ± 0.5 km h−1) compared with CHO (11.3 ± 0.4 km h−1), PLA (11.3 ± 0.4 km h−1) and PLAc (11.6 ± 0.5 km h−1) (P < 0.05). High-intensity exercise capacity was improved with CHOc and CHO when compared with PLA (CHOc; 79.8 ± 7 s, CHO; 72.1 ± 5 s,
PLAc; 70.1 ± 8 s, PLA; 57.1 ± 5 s; P < 0.05). Mental concentration during the protocol was also enhanced during CHOc compared with PLA (P < 0.05). These results suggest pre-cooling in conjunction with the ingestion of carbohydrate during exercise enhances exercise
capacity and helps maintain mental performance during intermittent exercise in hot conditions. 相似文献
8.
No previous studies have investigated the effect of lower body compression garments (CG) on running performance in the heat.
This study tested the hypothesis that CG would negatively affect running performance in the heat by comparing CG and non-CG
conditions for running performance and physiological responses in hot and cold conditions. Ten male recreational runners (29.0 ± 10.0
years,
[(V)\dot]\textO 2 \dot{V}{\text{O}}_{ 2} max: 58.7 ± 2.7 ml kg−1 min−1) performed four treadmill tests consisting of 20-min running at first ventilatory threshold followed by a run to exhaustion
at
[(V)\dot]\textO 2 \dot{V}{\text{O}}_{ 2} max velocity in four conditions: 10°C with CG, 10°C without CG, 32°C with CG, and 32°C without CG (randomised, counterbalanced
order). Time to exhaustion (TTE), skin and rectal temperature,
[(V)\dot]\textO 2 \dot{V}{\text{O}}_{ 2} , heart rate and rating of perceived exertion (RPE) were compared between CG and non-CG conditions at each environmental temperature.
TTE was not significantly different between the CG and non-CG conditions at 10°C (158 ± 74 vs. 148 ± 73 s) and 32°C (115 ± 40
vs. 97 ± 33 s); however, there was a small (0.15) and moderate effect size (0.48), respectively, suggestive of an improvement
in TTE with CG. Lower limb skin temperature was 1.5°C higher at 10°C with CG (P < 0.05), but no significant differences in other physiological variables, including rectal temperature, were observed between
garment conditions. Interestingly, RPE was lower (P < 0.05) during submaximal running at 32°C with CG (13.8 ± 2.0) compared with non-CG (14.5 ± 2.7). It was concluded that CG
had no adverse effects on running performance in hot conditions. 相似文献
9.
Induction and decay of short-term heat acclimation 总被引:1,自引:0,他引:1
Andrew T. Garrett Niels G. Goosens Nancy G. Rehrer Mark J. Patterson James D. Cotter 《European journal of applied physiology》2009,107(6):659-670
The purpose of this work was to investigate adaptation and decay from short-term (5-day) heat acclimation (STHA). Ten moderately
trained males (mean ± SD age 28 ± 7 years; body mass 74.6 ± 4.4 kg;
[(V)\dot]\textO 2\textpeak \dot{V}_{{{\text{O}}_{ 2{\text{peak}}} }} 4.26 ± 0.37 l min−1) underwent heat acclimation (Acc) for 90-min on 5-days consecutively (T
a = 39.5°C, 60% RH), under controlled hyperthermia (rectal temperature 38.5°C). Participants completed a heat stress test (HST)
1 week before acclimation (Acc), then on the 2nd and 8th day (1 week) following Acc (T
a = 35°C, 60% RH). Seven participants completed HSTs 2 and 3 weeks after Acc. HST consisted of 90-min cycling at 40% peak power
output before an incremental performance test. Rectal temperature at rest (37.1 ± 0.4°C) was not lowered by Acc (95% CI −0.3
to 0.2°C), after 90-min exercise (38.6 ± 0.5°C) it reduced 0.3°C (−0.5 to −0.1°C) and remained at this level 1 week later
(−0.5 to −0.1°C), but not two (0.1°C −0.4 to 0.5°C; n = 7) or 3 weeks. Similarly, heart rate after 90-min exercise (146 ± 21 b min−1) was reduced (−13: −6 to −20 b min−1) and remained at this level after 1 week (−13: −6 to −20 b min−1) but not two (−9: 6 to −23 b min−1; n = 7) or 3 weeks. Performance (746 s) increased 106 s: 59 to 152 s after Acc and remained higher after one (76 s: 31 to 122)
but not two (15 s: −88 to 142 s; n = 7) or 3 weeks. Therefore, STHA (5-day) induced adaptations permitting increased heat loss and this persisted 1 week but
not 2 weeks following Acc. 相似文献
10.
Eileen Y. Robertson Philo U. Saunders David B. Pyne Christopher J. Gore Judith M. Anson 《European journal of applied physiology》2010,110(2):379-387
Elite athletes often undertake altitude training to improve sea-level athletic performance, yet the optimal methodology has
not been established. A combined approach of live high/train low plus train high (LH/TL+TH) may provide an additional training
stimulus to enhance performance gains. Seventeen male and female middle-distance runners with maximal aerobic power
( [(V)\dot]\textO2 max ) \left( {\dot{V}{\text{O}}_{{2{ \max }}} } \right) of 65.5 ± 7.3 mL kg−1 min−1 (mean ± SD) trained on a treadmill in normobaric hypoxia for 3 weeks (2,200 m, 4 week−1). During this period, the train high (TH) group (n = 9) resided near sea-level (~600 m) while the LH/TL+TH group (n = 8) stayed in normobaric hypoxia (3,000 m) for 14 hours day−1. Changes in 3-km time trial performance and physiological measures including
[(V)\dot]\textO2 max , \dot{V}{\text{O}}_{{2{ \max }}} , running economy and haemoglobin mass (Hbmass) were assessed. The LH/TL+TH group substantially improved
[(V)\dot]\textO2 max \dot{V}{\text{O}}_{{2{ \max }}} (4.8%; ±2.8%, mean; ±90% CL), Hbmass (3.6%; ±2.4%) and 3-km time trial performance (−1.1%; ±1.0%) immediately post-altitude. There was no substantial improvement
in time trial performance 2 weeks later. The TH group substantially improved
[(V)\dot]\textO2 max \dot{V}{\text{O}}_{{2{ \max }}} (2.2%; ±1.8%), but had only trivial changes in Hbmass and 3-km time-trial performance. Compared with TH, combined LH/TL+TH substantially improved
[(V)\dot]\textO2 max \dot{V}{\text{O}}_{{2{ \max }}} (2.6%; ±3.2%), Hbmass (4.3%; ±3.2%), and time trial performance (−0.9%; ±1.4%) immediately post-altitude. LH/TL+TH elicited greater enhancements
in physiological capacities compared with TH, however, the transfer of benefits to time-trial performance was more variable. 相似文献
11.
Michail E. Keramidas Bojan Musizza Stylianos N. Kounalakis Igor B. Mekjavic 《European journal of applied physiology》2010,109(1):133-140
Cold-induced vasodilatation (CIVD) is a cyclical increase in finger temperature that has been suggested to provide cryoprotective
function during cold exposures. Physical fitness has been suggested as a potential factor that could affect CIVD response,
possibly via central (increased cardiac output, decreased sympathetic nerve activity) and/or peripheral (increased microcirculation)
cardiovascular and neural adaptations to exercise training. Therefore, the purpose of this study was to investigate the effect
of endurance exercise training on the CIVD response. Eighteen healthy males trained 1 h d−1 on a cycle ergometer at 50% of peak power output, 5 days week−1 for 4-weeks. Pre, Mid, Post, and 10 days after the cessation of training and on separate days, subjects performed an incremental
exercise test to exhaustion
(\mathop V · \textO2\textpeak ), (\mathop V\limits^{ \cdot }\!\! {\text{O}}_{{2{\text{peak}}}} ), and a 30-min hand immersion in 8°C water to examine their CIVD response. The exercise-training regimen significantly increased
\mathop V ·\textO2\textpeak \mathop V\limits^{ \cdot }\!\!{\text{O}}_{{2{\text{peak}}}} (Pre: 46.0 ± 5.9, Mid: 52.5 ± 5.7, Post: 52.1 ± 6.2, After: 52.6 ± 7.6 ml kg−1 min−1; P < 0.001). There was a significant increase in average finger skin temperature (Pre: 11.9 ± 2.4, After: 13.5 ± 2.5°C; P < 0.05), the number of waves (Pre: 1.1 ± 1.0, After: 1.7 ± 1.1; P < 0.001) and the thermal sensation (Pre: 1.7 ± 0.9, After: 2.5 ± 1.4; P < 0.001), after training. In conclusion, the aforementioned endurance exercise training significantly improved the finger
CIVD response during cold-water hand immersion. 相似文献
12.
This study investigated the possible influence of oral caffeine administration on endogenous glucose production and energy
substrate metabolism during prolonged endurance exercise. Twelve trained endurance athletes [seven male, five female; peak
oxygen consumption (
) = 65.5 ml·kg–1·min–1] performed 60 min of cycle ergometry at 65%
twice, once after oral caffeine administration (6 mg·kg–1) (CAF) and once following consumption of a placebo (PLA). CAF and PLA were administered in a randomized double-blind manner
75 min prior to exercise. Plasma glucose kinetics were determined with a primed-continuous infusion of [6,6-2H]glucose. No differences in oxygen consumption (
), and carbon dioxide production (
) were observed between CAF and PLA, at rest or during exercise. Blood glucose concentrations were similar between the two
conditions at rest and also during exercise. Exercise did lead to an increase in serum free fatty acid (FFA) concentrations
for both conditions; however, no differences were observed between CAF and PLA. Both the plasma glucose rate of appearance
(
) and disappearance (
) increased at the onset of exercise (P<0.05), but were not affected by CAF, as compared to PLA. CAF did lead to a higher plasma lactate concentration during exercise
(P<0.05). It was concluded that an acute oral dose of caffeine does not influence plasma glucose kinetics or energy substrate
oxidation during prolonged exercise in trained endurance athletes. However, CAF did lead to elevated plasma lactate concentrations.
The exact mechanism of the increase in plasma lactate concentrations remains to be determined.
Electronic Publication 相似文献
13.
Osamu Nagayama Akira Koike Takeya Suzuki Masayo Hoshimoto-Iwamoto Hitoshi Sawada Tadanori Aizawa 《The journal of physiological sciences : JPS》2010,60(2):137-142
The overshoot in oxygen uptake ([(V)\dot] \dot{\rm{V}} O2 overshoot) during recovery from maximal exercise is thought to reflect an overshoot in cardiac output. We investigated whether
this phenomenon is related to cardiopulmonary function during exercise in cardiac patients. A total of 201 consecutive patients
with previous myocardial infarction underwent cardiopulmonary exercise testing (CPX). An apparent [(V)\dot] \dot{\rm{V}} O2 overshoot during the recovery from CPX (6.5 ± 8.1% increase relative to the peak [(V)\dot] \dot{\rm{V}} O2) was observed in ten patients. A comparison of patients with the [(V)\dot] \dot{\rm{V}} O2 overshoot to those without the [(V)\dot] \dot{\rm{V}} O2 overshoot revealed that the former had a significantly lower left ventricular ejection fraction (40.1 ± 19.1 vs. 55. 2 ±
14.9%, respectively, p = 0.002) and larger left ventricular diastolic and systolic dimensions. Patients with the [(V)\dot] \dot{\rm{V}} O2 overshoot also had a significantly lower peak [(V)\dot] \dot{\rm{V}} O2 (13.1 ± 6.1 vs. 18.1 ± 4.5 ml/min/kg, p < 0.001), lower Δ[(V)\dot] \dot{\rm{V}} O2/ΔWR (work rate) (6.6 ± 3.8 vs. 9.5 ± 1.7 mL/min/W, p < 0.0001), and a higher [(V)\dot] \dot{\rm{V}} E (minute ventilation)/[(V)\dot] \dot{\rm{V}} CO2 (carbon dioxide output) slope (45.0 ± 18.6 vs. 32.6 ± 6.6, p < 0.0001) than those without the overshoot. A [(V)\dot] \dot{\rm{V}} O2 overshoot during recovery from maximal exercise was found in 5% of patients with previous myocardial infarction. This condition,
which suggests a transient mismatch between cardiac contractility and afterload reduction, was found to be related to impaired
cardiopulmonary function during exercise. 相似文献
14.
The objective of the study is to examine the impact of accurate and inaccurate ‘split-time’ feedback upon a 10-mile time trial
(TT) performance and to quantify power output into a practically meaningful unit of variation. Seven well-trained cyclists
completed four randomised bouts of a 10-mile TT on a SRM™ cycle ergometer. TTs were performed with (1) accurate performance
feedback, (2) without performance feedback, (3) and (4) false negative and false positive ‘split-time’ feedback showing performance
5% slower or 5% faster than actual performance. There were no significant differences in completion time, average power output,
heart rate or blood lactate between the four feedback conditions. There were significantly lower (p < 0.001) average
[(V)\dot]\textO2 \dot{V}{\text{O}}_{2} (ml min−1) and
[(V)\dot]\textE \dot{V}{\text{E}} (l min−1) scores in the false positive (3,485 ± 596; 119 ± 33) and accurate (3,471 ± 513; 117 ± 22) feedback conditions compared to
the false negative (3,753 ± 410; 127 ± 27) and blind (3,772 ± 378; 124 ± 21) feedback conditions. Cyclists spent a greater
amount of time in a ‘20 watt zone’ 10 W either side of average power in the negative feedback condition (fastest) than the
accurate feedback (slowest) condition (39.3 vs. 32.2%, p < 0.05). There were no significant differences in the 10-mile TT performance time between accurate and inaccurate feedback
conditions, despite significantly lower average
[(V)\dot]\textO2 \dot{V}{\text{O}}_{2} and
[(V)\dot]\textE \dot{V}{\text{E}} scores in the false positive and accurate feedback conditions. Additionally, cycling with a small variation in power output
(10 W either side of average power) produced the fastest TT. Further psycho-physiological research should examine the mechanism(s)
why lower
[(V)\dot]\textO2 \dot{V}{\text{O}}_{2} and
[(V)\dot]\textE \dot{V}{\text{E}} scores are observed when cycling in a false positive or accurate feedback condition compared to a false negative or blind
feedback condition. 相似文献
15.
Ricardo Mora-Rodriguez Juan Del Coso Nassim Hamouti Emma Estevez Juan F. Ortega 《European journal of applied physiology》2010,109(5):973-981
To determine if the increases in rectal temperature (T
REC) during exercise in the heat at a given percent of
[(V)\dot]O2 \textpeak \dot{V}\hbox{O}_{{2\,{\text{peak}}}} depend on a subject’s aerobic fitness level. On three occasions, 10 endurance-trained (Tr) and 10 untrained (UTr) subjects
([(V)\dot]O2 peak \dot{V}\hbox{O}_{2\,{\rm peak}} : 60 ± 6 vs. 44 ± 3 mL kg−1 min−1, P < 0.05) cycled in a hot-dry environment (36 ± 1°C; 25 ± 2% humidity, airflow 2.5 m s−1) at three workloads (40, 60, and 80% [(V)\dot]O2 peak \dot{V}\hbox{O}_{2\,{\rm peak}} ). At the same percent of [(V)\dot]O2 peak \dot{V}\hbox{O}_{2\,{\rm peak}} , on average, Tr had 28 ± 5% higher heat production but also higher skin blood flow (29 ± 3%) and sweat rate (20 ± 7%; P = 0.07) and lower skin temperature (0.5°C; P < 0.05). Pre-exercise T
REC was lower in the Tr subjects (37.4 ± 0.2 vs. 37.6 ± 0.2; P < 0.05) but similar to the UTr at the end of 40 and 60% [(V)\dot]O2 peak \dot{V}\hbox{O}_{2\,{\rm peak}} trials. Thus, exercise T
REC increased more in the Tr group than in the UTr group (0.6 ± 0.1 vs. 0.3 ± 0.1°C at 40% [(V)\dot]O2 peak \dot{V}\hbox{O}_{2\,{\rm peak}} and 1.0 ± 0.1 vs. 0.6 ± 0.3°C at 60% [(V)\dot]O2 peak \dot{V}\hbox{O}_{2\,{\rm peak}} ; P < 0.05). At 80% [(V)\dot]O2 peak \dot{V}\hbox{O}_{2\,{\rm peak}} not only the increase in T
REC (1.7 ± 0.1 vs. 1.3 ± 0.3°C) but also the final T
REC was larger in Tr than in UTr subjects (39.15 ± 0.1 vs. 38.85 ± 0.1°C; P < 0.05). During exercise in the heat at the same relative intensity, aerobically trained individuals have a larger rise in
T
REC than do the untrained ones which renders them more hyperthermic after high-intensity exercise. 相似文献
16.
Sweat sodium concentration during exercise in the heat in aerobically trained and untrained humans 总被引:1,自引:0,他引:1
Hamouti N Del Coso J Ortega JF Mora-Rodriguez R 《European journal of applied physiology》2011,111(11):2873-2881
The purpose of this study was to determine whether sweat sodium concentration ([Na+]sweat) during exercise in the heat differs between aerobically trained and untrained individuals. On three occasions, ten endurance-trained
(Tr) and ten untrained (UTr) subjects (
[(V)\dot]\textO2\textpeak \dot{V}{\text{O}}_{{2{\text{peak}}}} = 4.0 ± 0.8 vs. 3.4 ± 0.7 L min−1, respectively; P < 0.05) cycled in a hot-ventilated environment (36 ± 1°C; 25 ± 2% humidity, airflow 2.5 m s−1) at three workloads (i.e., 40, 60, and 80%
[(V)\dot]\textO2\textpeak \dot{V}{\text{O}}_{{2{\text{peak}}}} ). Whole-body (SRWB) and back sweat rates (SRBACK) were measured. At the conclusion of the study, Na+ in sweat and blood samples was analyzed to calculate Na+ secretion and reabsorption rates. SRWB and SRBACK were highly correlated in Tr and UTr (r = 0.74 and 0.79, respectively; P < 0.0001). In both groups, SRBACK increased with the increases in exercise intensity (P < 0.05). Likewise, [Na+]sweat increased with the exercise intensity in both groups (P < 0.05) and it tended to be higher in Tr than in UTr at 60 and 80%
[(V)\dot]\textO2\textpeak \dot{V}{\text{O}}_{{2{\text{peak}}}} (~22 mmol L−1 higher; P = 0.06). However, when normalized for SRBACK, [Na+]sweat was not different between groups. In both groups, Na+ secretion and reabsorption rates increased with the increases in SRBACK (P < 0.05). However, Na+ reabsorption rate was lower in the Tr than in the UTr (mean slope = 48 vs. 82 ηmol cm−2 min−1; P = 0.03). In conclusion, using a cross-sectional study design, our data suggest that aerobic fitness level does not reduce
sweat Na+ secretion or enhance Na+ reabsorption during prolonged exercise in the heat that induced high sweat rates. 相似文献
17.
B. Nielsen Søren Strange Niels Juel Christensen Jørgen Warberg Bengt Saltin 《Pflügers Archiv : European journal of physiology》1997,434(1):49-56
Acute and repeated exposure for 8–13 consecutive days to exercise in humid heat was studied. Twelve fit subjects exercised
at 150 W [45% of maximum O2 uptake (V.O2,max)] in ambient conditions of 35°C and 87% relative humidity which resulted in exhaustion after 45 min. Average core temperature
reached 39.9 ± 0.1°C, mean skin temperature (T–
sk) was 37.9 ± 0.1°C and heart rate (HR) 152 ± 6 beats min–1 at this stage. No effect of the increasing core temperature was seen on cardiac output and leg blood flow (LBF) during acute
heat stress. LBF was 5.2 ± 0.3 l min–1 at 10 min and 5.3 ± 0.4 l min–1 at exhaustion (n = 6). After acclimation the subjects reached exhaustion after 52 min with a core temperature of 39.9 ± 0.1°C, T–
sk 37.7 ± 0.2°C, HR 146 ± 4 beats min–1. Acclimation induced physiological adaptations, as shown by an increased resting plasma volume (3918 ± 168 to 4256 ± 270
ml), the lower exercise heart rate at exhaustion, a 26% increase in sweating rate, lower sweat sodium concentration and a
6% reduction in exercise V.O2. Neither in acute exposure nor after acclimation did the rise of core temperature to near 40°C affect metabolism and substrate
utilization. The physiological adaptations were similar to those induced by dry heat acclimation. However, in humid heat the
effect of acclimation on performance was small due to physical limitations for evaporative heat loss.
Received: 3 July 1996 / Received after revision: 26 September 1996 / Accepted: 7 January 1997 相似文献
18.
Reis JF Alves FB Bruno PM Vleck V Millet GP 《European journal of applied physiology》2012,112(5):1689-1697
This study aimed to characterise both the
[(V)\dot]\textO2 \dot{V}{\text{O}}_{2} kinetics within constant heavy-intensity swimming exercise, and to assess the relationships between
[(V)\dot]\textO2 \dot{V}{\text{O}}_{2} kinetics and other parameters of aerobic fitness, in well-trained swimmers. On separate days, 21 male swimmers completed:
(1) an incremental swimming test to determine their maximal oxygen uptake
([(V)\dot]\textO2max ) (\dot{V}{\text{O}}_{2\max } ) , first ventilatory threshold (VT), and the velocity associated with
[(V)\dot]\textO2max \dot{V}{\text{O}}_{2\max }
(v[(V)\dot]\textO2max ) (v\dot{V}{\text{O}}_{2\max } ) and (2) two square-wave transitions from rest to heavy-intensity exercise, to determine their
[(V)\dot]\textO2 \dot{V}{\text{O}}_{2} kinetics. All the tests involved breath-by-breath analysis of freestyle swimming using a swimming snorkel.
[(V)\dot]\textO2 \dot{V}{\text{O}}_{2} kinetics was modelled with two exponential functions. The mean values for the incremental test were 56.0 ± 6.0 ml min−1 kg−1, 1.45 ± 0.08 m s−1; and 42.1 ± 5.7 ml min−1 kg−1 for
[(V)\dot]\textO2max \dot{V}{\text{O}}_{2\max } ,
v[(V)\dot]\textO2max v\dot{V}{\text{O}}_{2\max } and VT, respectively. For the square-wave transition, the time constant of the primary phase (τp) averaged 17.3 ± 5.4 s and the relevant slow component (A′sc) averaged 4.8 ± 2.9 ml min−1 kg−1 [representing 8.9% of the end-exercise
[(V)\dot]\textO2 \dot{V}{\text{O}}_{2} (%A′sc)]. τp was correlated with
v[(V)\dot]\textO2max v\dot{V}{\text{O}}_{2\max } (r = −0.55, P = 0.01), but not with either
[(V)\dot]\textO 2 \textmax \dot{V}{\text{O}}_{{ 2 {\text{max}}}} (r = 0.05, ns) or VT (r = 0.14, ns). The %A′sc did not correlate with either
[(V)\dot]\textO 2 \textmax \dot{V}{\text{O}}_{{ 2 {\text{max}}}} (r = −0.14, ns) or
v[(V)\dot]\textO2max v\dot{V}{\text{O}}_{2\max } (r = 0.06, ns), but was inversely related with VT (r = −0.61, P < 0.01). This study was the first to describe the
[(V)\dot]\textO2 \dot{V}{\text{O}}_{2} kinetics in heavy-intensity swimming using specific swimming exercise and appropriate methods. As has been demonstrated in
cycling, faster
[(V)\dot]\textO2 \dot{V}{\text{O}}_{2} kinetics allow higher aerobic power outputs to be attained. The slow component seems to be reduced in swimmers with higher
ventilatory thresholds. 相似文献
19.
Effect of exercise-induced muscle damage on ventilatory and perceived exertion responses to moderate and severe intensity cycle exercise 总被引:2,自引:1,他引:1
Rosemary C. Davies Ann V. Rowlands Roger G. Eston 《European journal of applied physiology》2009,107(1):11-19
This study examined the effect of exercise-induced muscle damage (EIMD) on ventilatory and perceived exertion responses to
cycle exercise. Ten healthy, physically active men cycled for 6 min at moderate intensity and to exhaustion at severe intensity
before and 48 h after eccentric exercise (100 squats with a load corresponding to 70% of body mass). Changes in ventilation
and ratings of perceived exertion (RPE) were calculated for each individual and expressed against time (moderate and severe
exercise) and as a percentage of time to exhaustion (severe exercise). Ventilation increased during moderate exercise at 48 h
(
[(V)\dot]\textE \dot{V}_{\text{E}} ; 34.5 ± 5.0 to 36.3 ± 3.8 l min−1, P < 0.05) but increases in RPE were not significant. During severe exercise at 48 h, time to exhaustion (TTE) was reduced and
[(V)\dot]\textE \dot{V}_{\text{E}} (87.1 ± 14.1 to 93.8 ± 11.7 l min−1) and RPE (15.5 ± 1.3 to 16.1 ± 1.4) were elevated (P < 0.05). When expressed as a percentage of TTE, the differences in ventilation and RPE values disappeared. Findings indicate
that the augmented ventilatory response to cycle exercise following EIMD may be an important cue in informing effort perception
during high-intensity exercise but not during moderate-intensity exercise. 相似文献
20.
We have previously demonstrated that provision of a cold fluid (4°C) during exercise in the heat increases fluid intake and
improves exercise capacity when compared to a control fluid (19°C). The present study investigated whether these positive
effects could simply be replicated with a cooling agent, menthol. Nine healthy, non-acclimatised males (25 ± 7 years; [(V)\dot] \dot{V} O2max: 54 ± 5 ml kg−1 min−1) cycled to exhaustion at 65% of their peak aerobic power output at 34°C, swilling 25 ml of either an l(−)-menthol (0.01%) or orange-flavoured placebo solution every 10 min, whilst water was available ad libitum; all fluids were
kept at 19°C. Eight out of nine subjects cycled for longer whilst swilling with menthol and this resulted in a 9 ± 12% improvement
in endurance capacity. Rectal temperatures rose by 1.7°C during exercise with the same time course in both conditions, whilst
skin temperature remained largely unchanged. Swilling with menthol resulted in hyperventilation by 8 ± 10 L min−1 and reduced central (cardiopulmonary) ratings of perceived exertion by 15 ± 14%. No differences between trials were observed
for heart rate, oxygen uptake or carbon dioxide production, blood concentrations of glucose or lactate, sweat rate or volume
of water ingested. We conclude that a change in the sensation of oropharyngeal temperature during exercise in the heat significantly
affects endurance capacity, ventilation and the (central) sense of effort. 相似文献