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1.
Four groups of male subjects participated in anaerobic testing on a Repco EX10 cycle ergometer to determine the effectiveness of sodium bicarbonate (0.3 g kg-1 body mass) as an ergogenic aid during exercise of 10, 30, 120 and 240 s duration. Blood was collected 90 min prior to ingestion of sodium bicarbonate (NaHCO3), after ingestion of NaHCO3 and immediately post-exercise from a heated (43-46 degrees C) fingertip and analysed immediately post-collection for pH, base excess, bicarbonate and lactate. The total work undertaken (kJ) and peak power achieved during the tests were also obtained via a Repco Work Monitor Unit. Blood bicarbonate levels were again increased above the control and placebo conditions (P < 0.001) and blood lactate levels were also increased following the bicarbonate trials. The pH levels fell significantly (P < 0.05) below the control and placebo conditions in all trials. The results indicate that NaHCO3 at this dosage has no ergogenic benefit for work of either 10 or 30 s duration, even though blood bicarbonate levels were significantly increased (P < 0.05) following ingestion of NaHCO3. For work periods of 120 and 240 s, performance was significantly increased (P < 0.05) above the control and placebo conditions following NaHCO3 ingestion.  相似文献   

2.
Bicarbonate ingestion: effects of dosage on 60 s cycle ergometry.   总被引：3，自引：0，他引：3  
Nine healthy male subjects who were all participating in athletic events volunteered to take part in this study, the aim of which was to determine whether there are specific dosages of sodium bicarbonate (HCO3-) that are useful as an ergogenic aid as far as anaerobic performance times are concerned. A control, placebo (CaCO3 500 mg kg-1) and five dosages of bicarbonate (100, 200, 300, 400 and 500 mg kg-1) were used. The anaerobic test consisted of pedalling a Repco Exertech cycle ergometer for 1 min during which total work (kJ) and peak power (W) were measured. The subjects completed more work in the 200 (P < 0.05), 300, 400 and 500 mg kg-1 (P < 0.005) trials with most work being undertaken in the 300 mg kg-1 trial (41.9 kJ min-1). Peak power was not significantly different from the control until the 300 mg kg-1 dose, and there were no further changes from this with increasing doses of HCO3-. The highest level of peak power achieved was 1295 +/- 72.8 W at the 300 mg kg-1 dosage. Blood pH indicated that after ingestion of all but the 100 mg kg-1 dose, a state of alkalosis was achieved (P < 0.005), and this was also indicated by changes in base excess. Bicarbonate levels increased post-ingestion in all but the 100 mg kg-1 dose, with these changes reflecting the changes that occurred in the work output. Blood lactate (BLa) levels increased post-exercise (P < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

3.
Abstract

This study examined the effects of combined glucose and sodium bicarbonate ingestion prior to intermittent exercise. Ninemales (mean ± s age 25.4 ± 6.6 years, body mass 78.8 ± 12.0 kg, maximal oxygen uptake ([Vdot]O2max) 47.0 ± 7ml · kg · min?1) undertook 4 × 45 min intermittent cycling trials including 15 × 10 s sprints one hour after ingesting placebo (PLA), glucose (CHO), sodium bicarbonate (NaHCO3) or a combined CHO and NaHCO3 solution (COMB). Post ingestion blood pH (7.45 ± 0.03, 7.46 ± 0.03, 7.32 ± 0.05, 7.32 ± 0.01) and bicarbonate (30.3 ± 2.1, 30.7 ± 1.8, 24.2 ± 1.2, 24.0 ± 1.8 mmol · l?1) were greater for NaHCO3 and COMB when compared to PLA and CHO, remaining elevated throughout exercise (main effect for trial; P < 0.05). Blood lactate concentration was greatest throughout exercise for NaHCO3 and COMB (main effect for trial; P < 0.05). Blood glucose concentration was greatest 15 min post-ingestion for CHO followed by COMB, NaHCO3 and PLA (7.13 ± 0.60, 5.58 ± 0.75, 4.51 ± 0.56, 4.46 ± 0.59 mmol · l?1, respectively; P < 0.05). Gastrointestinal distress was lower during COMB compared to NaHCO3 at 15 min post-ingestion (P < 0.05). No differences were observed for sprint performance between trials (P = 1.00). The results of this study suggest that a combined CHO and NaHCO3 beverage reduced gastrointestinal distress and CHO availability but did not improve performance. Although there was no effect on performance an investigation of the effects in more highly trained individuals may be warranted.  相似文献   

4.
Eight trained male cyclists who competed regularly in track races, were studied under control, alkalotic (NaHCO3) and placebo (CaCO3) conditions in a laboratory setting to study the effect of orally induced metabolic alkalosis on 60 s anaerobic work and power output on a bicycle ergometer. Basal, pre- and post-exercise blood samples in the three conditions were analysed for pH, pCO2, pO2, bicarbonate, base excess and lactate. All blood gas measurements were within normal limits at basal levels. There were significant differences in the amount of work produced, and in the maximal power output produced by the cyclists in the experimental condition when compared to the control and placebo conditions (P less than 0.01). The post-exercise pH decreased in all three conditions (P less than 0.05) and post-exercise pCO2 increased significantly in the alkalosis trial (P less than 0.01). In the alkalotic condition, the pre-exercise base excess and HCO3- levels were both higher (P less than 0.05) than the basal levels, suggesting that the bicarbonate ingestion had a significant increase in the buffering ability of the blood. Post-exercise lactate levels were significantly higher (P less than 0.05) after the alkalotic trial when compared to the other two conditions, immediately post-exercise and for the next 3 min. Post-exercise lactate levels were higher than basal or pre-exercise levels (P less than 0.001). This was true immediately post-exercise and for the next 5 min. The results of this study suggest that NaHCO3 is an effective ergogenic aid when used for typically anaerobic exercise as used in this experiment. We feel that this ergogenic property is probably due to the accelerated efflux of H+ ions from the muscle tissue due to increased extracellular bicarbonate buffering.  相似文献   

5.
In order to determine the influence of two artificially induced alkalotic states on the ability to perform maximal exercise, six male subjects (mean age, 22.0 years; mean height, 176.8 cm; mean weight, 69.1 kg; mean VO2 max, 3.83 1 min‐1) were studied during three experimental trials. The subjects performed six 60‐s cycling bouts, at a work rate corresponding to 125% VO2 max, with 60 s recovery between work bouts; these regimes were performed 1 h after the ingestion of a solution containing either: I, placebo; II, NaHCO3 in a dosage of 0.15 g per kg body weight; or III, NaHCO3 0.30 g per kg body weight. The sixth work bout was continued until the pedal velocity dropped below 50 rev min‐1. Total work done for the entire work period was calculated. Blood samples were taken from a forearm vein prior to the exercise bouts for analysis of pH and HCO3. The results showed a significant pre‐exercise difference in pH and HCO3 for all conditions (P<0.01). In conditions where artificial alkalosis had been achieved prior to exercise there was significant increase in the work produced: I, 121.6 kJ; II, 133.1 kJ; III, 133.5 kJ (P<0.05). The time to fatigue in the sixth bout was also significantly increased: I, 74.7 s; II, 111.0 s; III, 106.0 s (P<0.05). There were no significant differences between conditions II and III. Thus augmentation of the bicarbonate reserves has a significant positive effect on the energy metabolism in interval‐type exercise, leading to an increase in the work done and in the time to fatigue. However, an increasing level of alkalosis had no additional benefit, suggesting that maximum contribution to buffering capacity had been achieved at the lower dose.  相似文献   

6.
Purpose: To investigate the effect of sodium bicarbonate (NaHCO3) on performance and estimated energy system contribution during simulated taekwondo combat. Methods: Nine taekwondo athletes completed two experimental sessions separated by at least 48?h. Athletes consumed 300?mg/kg body mass of NaHCO3 or placebo (CaCO3) 90?min before the combat simulation (three rounds of 2 min separated by 1 min passive recovery), in a double-blind, randomized, repeated-measures crossover design. All simulated combat was filmed to quantify the time spent fighting in each round. Lactate concentration [La?] and rating of perceived exertion (RPE) were measured before and after each round, whereas heart rate (HR) and the estimated contribution of the oxidative (WOXI), ATP (adenosine triphosphate)-phosphocreatine (PCr) (WPCR), and glycolytic (W[ La? ]) systems were calculated during the combat simulation. Results: [La?] increased significantly after NaHCO3 ingestion, when compared with the placebo condition (+14%, P?=?0.04, d?=?3.70). NaHCO3 ingestion resulted in greater estimated glycolytic energy contribution in the first round when compared with the placebo condition (+31%, P?=?0.01, d?=?3.48). Total attack time was significantly greater after NaHCO3 when compared with placebo (+13%, P?=?0.05, d?=?1.15). WOXI, WPCR, VO2, HR and RPE were not different between conditions (P?>?0.05). Conclusion: NaHCO3 ingestion was able to increase the contribution of glycolytic metabolism and, therefore, improve performance during simulated taekwondo combat.  相似文献   

7.
Abstract

Ten healthy, non-cycling trained males (age: 21.2 ± 2.2 years, body mass: 75.9 ± 13.4 kg, height: 178 ± 6 cm, [Vdot]O2PEAK: 46 ± 10 ml · kg?1 · min?1) performed a graded incremental exercise test, two familiarisation trials and six experimental trials. Experimental trials consisted of cycling to volitional exhaustion at 100%, 110% and 120% WPEAK, 60 min after ingesting either 0.3 g · kg?1 body mass sodium bicarbonate (NaHCO3) or 0.1 g · kg?1 body mass sodium chloride (placebo). NaHCO3 ingestion increased cycling capacity by 17% at 100% WPEAK (327 vs. 383 s; P = 0.02) although not at 110% WPEAK (249 vs. 254 s; P = 0.66) or 120% WPEAK (170 vs. 175 s; P = 0.60; placebo and NaHCO3 respectively). Heart rate (P = 0.02), blood lactate (P = 0.001), pH (P < 0.001), [HCO3 ?], (P < 0.001), and base excess (P < 0.001) were greater in all NaHCO3 trials. NaHCO3 attenuated localised ratings of perceived exertion (RPEL) to a greater extent than placebo only at 100% WPEAK (P < 0.02). Ratings of abdominal discomfort and gut fullness were mild but higher for NaHCO3. NaHCO3 ingestion significantly improves continuous constant load cycling at 100% WPEAK due to, in part, attenuation of RPEL.  相似文献   

8.
Effect of induced alkalosis on swimming time trials.   总被引：1，自引：0，他引：1  
Previous studies have shown that sodium bicarbonate ingestion prior to exercise may improve performance during repeated (interval) bouts. To examine the practical implications of such findings, seven collegiate swimmers participated in simulated swim competitions of multiple events following sodium bicarbonate (B) ingestion, placebo (P) ingestion and control (C--no ingestion) treatments. Each swimmer reported to the laboratory 1 h prior to the simulated competitions (72 h apart) and was randomly assigned to one of the three experimental treatments. Competition consisted of one relay (100 yards; 91.4 m) and two individual (200 yards; 182.8 m) swimming events with 20 min rest between events. Analysis of variance (ANOVA) with repeated measures revealed no significant differences in performance times as a result of the three treatments (P greater than 0.05). The results suggest that sodium bicarbonate ingestion prior to swim competition consisting of significant rest intervals between events is not an ergogenic procedure.  相似文献   

9.
The aim of this study was to investigate the effect of pre-induced inspiratory muscle fatigue (IMF) on race-paced swimming and acid-base status. Twenty-one collegiate swimmers performed two discontinuous 400-m race-paced swims on separate days, with (IMF trial) and without (control trial) pre-induced IMF. Swimming characteristics, inspiratory and expiratory mouth pressures, and blood parameters were recorded. IMF and expiratory muscle fatigue (P < 0.05) were evident after both trials and swimming time was slower (P < 0.05) from 150-m following IMF inducement. Pre-induced IMF increased pH before the swim (P < 0.01) and reduced bicarbonate (P < 0.05) and the pressure of carbon dioxide (PCO2) (P < 0.05). pH (P < 0.05), bicarbonate (P < 0.01) and PCO2 (P < 0.05) were lower during swimming in the IMF trial. Blood lactate was similar before both trials (P > 0.05) but was higher (P < 0.01) in the IMF trial after swimming. Pre-induced IMF induced respiratory alkalosis, reduced bicarbonate buffering capacity and slowed swimming speed. Pre-induced and propulsion-induced IMF reflected metabolic acidosis arising from dual role breathing and propulsion muscle fatigue.  相似文献   

10.
The aim of this study was to determine the effects of caffeine ingestion on a ‘preloaded’ protocol that involved cycling for 2?min at a constant rate of 100% maximal power output immediately followed by a 1-min ‘all-out’ effort. Eleven male cyclists completed a ramp test to measure maximal power output. On two other occasions, the participants ingested caffeine (5?mg?·?kg?1) or placebo in a randomized, double-blind procedure. All tests were conducted on the participants' own bicycles using a Kingcycle? test rig. Ratings of perceived exertion (RPE; 6–20 Borg scale) were lower in the caffeine trial by approximately 1 RPE point at 30, 60 and 120?s during the constant rate phase of the preloaded test (P?<0.05). The mean power output during the all-out effort was increased following caffeine ingestion compared with placebo (794±164 vs 750±163?W; P?=?0.05). Blood lactate concentration 4, 5 and 6?min after exercise was also significantly higher by approximately 1?mmol?·?l?1 in the caffeine trial (P?<0.05). These results suggest that high-intensity cycling performance can be increased following moderate caffeine ingestion and that this improvement may be related to a reduction in RPE and an elevation in blood lactate concentration.  相似文献   

11.
The aim of this study was to investigate the effects of sodium bicarbonate (NaHCO3) on 4 km cycling time trial (TT) performance when individualised to a predetermined time to peak blood bicarbonate (HCO3?). Eleven male trained cyclists volunteered for this study (height 1.82 ± 0.80 m, body mass (BM) 86.4 ± 12.9 kg, age 32 ± 9 years, peak power output (PPO) 382 ± 22 W). Two trials were initially conducted to identify time to peak HCO3? following both 0.2 g.kg?1 BM (SBC2) and 0.3 g.kg?1 BM (SBC3) NaHCO3. Thereafter, on three separate occasions using a randomised, double-blind, crossover design, participants completed a 4 km TT following ingestion of either SBC2, SBC3, or a taste-matched placebo (PLA) containing 0.07 g.kg?1 BM sodium chloride (NaCl) at the predetermined individual time to peak HCO3?. Both SBC2 (?8.3 ± 3.5 s; p < 0.001, d = 0.64) and SBC3 (?8.6 ± 5.4 s; p = 0.003, d = 0.66) reduced the time to complete the 4 km TT, with no difference between SBC conditions (mean difference = 0.2 ± 0.2 s; p = 0.87, d = 0.02). These findings suggest trained cyclists may benefit from individualising NaHCO3 ingestion to time to peak HCO3? to enhance 4 km TT performance.  相似文献   

12.
The aim of this study was to perform a systematic review and meta-analysis on the acute and chronic effects of sodium bicarbonate (NaHCO3) ingestion on Wingate performance. Following a search through PubMed, Scopus and Web of Science, 9 studies were found meeting inclusion criteria (6 acute and 3 chronic). Random-effects meta-analysis of standardized mean difference (SMD) for peak and mean power was performed. Study quality was assessed using the QualSyst. Results of the meta-analysis showed that acute ingestion of NaHCO3 did not improve Wingate test peak (weighted average effect size Hedges’s g = 0.02, 95%CI: – 0.19 to 0.23, P = 0.87) or mean power (weighted average effect size Hedges’s g = 0.15, 95%CI: ?0.06 to 0.36, P = 0.92). However, chronic ingestion of NaHCO3 improved Wingate test peak (weighted average effect size Hedges’s g = 1.21, 95%CI: 0.83 to 1.42, P = 0.001) and mean power (weighted average effect size Hedges’s g = 1.26, 95%CI: 0.96 to 1.56, P = 0.001). Quality assessment of selected articles was classified as strong. This meta-analysis provides evidence that chronic, but not acute, ingestion of NaHCO3 increases both Wingate test peak and mean power.  相似文献   

13.
The aim of this study was to determine the effects of caffeine ingestion on a 'preloaded' protocol that involved cycling for 2 min at a constant rate of 100% maximal power output immediately followed by a 1-min 'all-out' effort. Eleven male cyclists completed a ramp test to measure maximal power output. On two other occasions, the participants ingested caffeine (5 mg. kg(-1)) or placebo in a randomized, double-blind procedure. All tests were conducted on the participants' own bicycles using a Kingcycle test rig. Ratings of perceived exertion (RPE; 6-20 Borg scale) were lower in the caffeine trial by approximately 1 RPE point at 30, 60 and 120 s during the constant rate phase of the preloaded test (P <0.05). The mean power output during the all-out effort was increased following caffeine ingestion compared with placebo (794+/-164 vs 750+/-163 W; P=0.05). Blood lactate concentration 4, 5 and 6 min after exercise was also significantly higher by approximately 1 mmol. l(-1) in the caffeine trial (P <0.05). These results suggest that high-intensity cycling performance can be increased following moderate caffeine ingestion and that this improvement may be related to a reduction in RPE and an elevation in blood lactate concentration.  相似文献   

14.
Abstract

The effects of carbohydrate (CHO) ingestion during sports which require high levels of motor and cognitive skill, such as squash, have produced conflicting results. This study aimed to explore the effect of CHO ingestion on squash skill following short duration exercise simulating the demands of squash play. Sixteen male squash players of a high standard were recruited. Following a VO2max test, and familiarisation trial, subjects completed two further trials assessing skill pre- and post-exercise designed to simulate the demands of squash play. A squash skill test assessed accuracy of the forehand and backhand straight drives. Exercise consisted of 20 minutes of shuttle running at 82(±5)% HRmax, and 9 minutes of ghosting at 94(±4)% HRmax. Capillary blood samples (20 µl) were taken at five intervals for measurement of glucose and lactate. Cognitive function was measured with choice visual and auditory reaction time (RT) tests pre- and post-exercise, as was forearm wrist flexor MVC and fatigue profile. CHO drink (6.4% CHO) or matched placebo (PL) were administered after the initial skill test (500 ml), after the shuttle running (250 ml), and after the ghosting (250 ml) in a double blind crossover design. There was no overall effect of CHO ingestion on skill maintenance (p=0.10) however, significantly fewer balls landed outside the scoring zone (p=0.03) on the CHO ingestion trial. There was no change of visual RT pre- to post-exercise on PL (+0.01±0.03s), but a significant improvement (?0.07±0.05s) was observed in the CHO trial. Auditory RT improved pre- to post-exercise during both trials. MVC and fatigue profile of the wrist flexors was not different between trials but showed a force decrement pre- to post-exercise (p<0.05). A significant difference in blood glucose was observed between trials (p<0.01) but blood lactate response during both trials was similar. These results lend some support to a beneficial effect of CHO ingestion on skill during game sports.  相似文献   

15.
We have previously shown that single‐leg training results in improved endurance for exercise with the untrained leg (UTL) as well as for exercise with the trained leg (TL). The purpose of this study was to see whether the improved endurance of the untrained leg could be explained on the basis of changes in muscle metabolism. Exercise time to exhaustion at 80% of maximum oxygen uptake (VO2 max) was determined for each leg separately, pre‐ and post‐training. Muscle metabolite concentrations were measured pre‐ and post‐training in biopsy samples obtained immediately before this endurance test and at the pre‐training point of exhaustion (END1). After six weeks of single‐leg training endurance time was increased for both the UTL and the TL (UTL 34.0+16.4 min vs 97.9±26.3 min, P<0.01; TL 28.3 + 10.1 min vs 169.0 + 32.6 min, P < 0.01). No changes in muscle metabolite concentrations were found in resting muscle. Training increased muscle ATP (P <0.05) and glycogen (P <0.01) concentrations and decreased muscle lactate concentration (P<0.05) in the TL at END1. No significant changes in muscle metabolite concentrations were found for the UTL. The improved endurance of the contralateral limb after single‐leg training could not be explained on the basis of changes in muscle metabolism.  相似文献   

16.
This study investigated the effects of two separate doses of sodium bicarbonate (NaHCO3) on 4 km time trial (TT) cycling performance and post-exercise acid base balance recovery in hypoxia. Fourteen club-level cyclists completed four cycling TT’s, followed by a 40 min passive recovery in normobaric hypoxic conditions (FiO2 = 14.5%) following one of either: two doses of NaHCO3 (0.2 g.kg?1 BM; SBC2, or 0.3 g.kg?1 BM; SBC3), a taste-matched placebo (0.07 g.kg?1 BM sodium chloride; PLA), or a control trial in a double-blind, randomized, repeated-measures and crossover design study. Compared to PLA, TT performance was improved following SBC2 (p = 0.04, g = 0.16, very likely beneficial), but was improved to a greater extent following SBC3 (p = 0.01, g = 0.24, very likely beneficial). Furthermore, a likely benefit of ingesting SBC3 over SBC2 was observed (p = 0.13, g = 0.10), although there was a large inter-individual variation. Both SBC treatments achieved full recovery within 40 min, which was not observed in either PLA or CON following the TT. In conclusion, NaHCO3 improves 4 km TT performance and acid base balance recovery in acute moderate hypoxic conditions, however the optimal dose warrants an individual approach.  相似文献   

17.
Abstract

This study investigated the effects of acute caffeine ingestion following short-term creatine supplementation on an incremental cycling to exhaustion task. Twelve active males performed the task under three conditions: baseline condition (BASE, no ergogenic aid), creatine plus caffeine condition (CRE + CAF), and creatine with placebo condition (CRE + PLA). Following the establishment of BASE condition, participants were administered CRE + CAF (0.3 g·kg?1·day?1 of creatine for 5 days followed by 6 mg·kg?1 of caffeine 1 h prior to testing) and CRE + PLA (0.3 g·kg?1·day?1 of creatine for 5 days followed by 6 mg·kg?1 of placebo 1 h prior to testing) in a double-blind, randomized crossover and counterbalancing protocol. No significant differences were observed in relative maximal oxygen consumption ([Vdot]O2max) (51.7±5.5, 52.8±4.9 and 51.3±5.6 ml·kg?1·min?1 for BASE, CRE + CAF and CRE + PLA, respectively; P>0.05) and absolute [Vdot]O2max (3.6±0.4, 3.7±0.4 and 3.5±0.5 l·min?1 for BASE, CRE + CAF and CRE + PLA, respectively; P>0.05). Blood samples indicated significantly higher blood lactate and glucose concentrations in the CRE + CAF among those in the BASE or CRE + PLA condition during the test (P<0.05). The time to exhaustion on a cycling ergometer was significantly longer for CRE + CAF (1087.2±123.9 s) compared with BASE (1009.2±86.0 s) or CRE + PLA (1040.3±96.1 s). This study indicated that a single dose of caffeine following short-term creatine supplementation did not hinder the creatine–caffeine interaction. In fact, it lengthened the time to exhaustion during an incremental maximum exercise test. However, this regime might lead to the accumulation of lactate in the blood.  相似文献   

18.
Abstract

The aim of this study was to determine if inducing metabolic alkalosis would alter neuromuscular control after 50 min of standardized submaximal cycling. Eight trained male cyclists (mean age 32 years, s = 7; [Vdot]O2max 62 ml · kg?1 · min?1, s = 8) ingested capsules containing either CaCO3 (placebo) or NaHCO3 (0.3 g · kg?1 body mass) in eight doses over 2 h on two separate occasions, commencing 3 h before exercise. Participants performed three maximal isometric voluntary contractions (MVC) of the knee extensors while determining the central activation ratio by superimposing electrical stimulation both pre-ingestion and post-exercise, followed by a 50-s sustained maximal contraction in which force, EMG amplitude, and muscle fibre conduction velocity were assessed. Plasma pH, blood base excess, and plasma HCO3 were higher (P < 0.01) during the NaHCO3 trial. After cycling, muscle fibre conduction velocity was higher (P < 0.05) during the 50-s sustained maximal contraction with NaHCO3 than with placebo (5.1 m · s?1, s = 0.4 vs. 4.2 m · s?1, s = 0.4) while the EMG amplitude remained the same. Force decline rate was less (P < 0.05) during alkalosis-sustained maximal contraction and no differences were shown in central activation ratio. These data indicate that induced metabolic alkalosis can increase muscle fibre conduction velocity following prolonged submaximal cycling.  相似文献   

19.

This study examined the influence of water ingestion on endurance capacity during submaximal treadmill running. Four men and four women with a mean (± S.E.) age of 21.4 ± 0.7 years, height of 169 + 2 cm, body mass of 63.1 ± 2.9 kg and VO 2 max of 51.1 ± 1.8 ml kg?1 min?1, performed two randomly assigned treadmill runs at 70% VO 2 max to exhaustion. No fluid was ingested during one trial (NF‐trial), whereas a single water bolus of 3.0 ml kg?1 body mass was ingested immediately pre‐exercise and serial feedings of 2.0 ml kg?1 body mass were ingested every 15 min during exercise in a fluid replacement trial (FR‐trial). Run time for the NF‐trial was 77.7 ± 7.7 min, compared to 103 ± 12.4 min for the FR‐trial (P<0.01). Body mass (corrected for water ingestion) decreased by 2.0 ± 0.2% in the NF‐trial and 2.7 ± 0.2% in the FR‐trial (P<0.01), while plasma volume decreased by 1.1 ± 1.1% and 3.5 ± 1.1% in the two trials respectively (N.S.). However, these apparent differences in circulatory volume were not associated with differences in rectal temperature. Respiratory exchange ratios indicated increased carbohydrate metabolism (73% vs 64% of total energy expenditure) and suppressed fat metabolism after 75 min of exercise in the NF‐trial compared with the FR‐trial (NF‐trial, 0.90 ± 0.01; FR‐trial, 0.86 ± 0.03; P<0.01). Blood glucose concentrations were similar in both trials, while blood lactate concentrations were higher in the NF‐trial at the end of exercise (4.83 ± 0.34 vs 4.18 ± 0.38 mM; P<0.05). In summary, water ingestion during prolonged running improved endurance capacity.  相似文献   

20.
The purpose of this study was to examine CHO ingestion on a cognitive task using a field-simulated time-trial (TT) under hypoxia in well-trained triathletes. Ten male triathletes (age: 22.1 ± 1.1 years; VO2max: 59.4 ± 1.4 ml/kg/min) participated in this double-blind/crossover/counter-balanced design study. Participants completed 3 TT trials: 1) normoxic placebo (NPLA; FiO2 = 20.9%), 2) hypoxic placebo (HPLA; FiO2 = 16.3%), and 3) hypoxic CHO (HCHO; 6% CHO provided as 2 ml/kg/15 min; FiO2 = 16.3%). During the TT, physiological responses (SpO2, HR, RPE, and blood glucose/lactate), cognitive performance, and cerebral haemodynamics were measured. Hypoxia reduced TT performance by ~3.5–4% (p < 0.05), but CHO did not affect TT performance under hypoxia. For the cognitive task, CHO slightly preserved exercise-induced cognitive reaction speed but did not affect response accuracy during hypoxic exercise. However, CHO did not preserve the decreased Hb-Diff (cerebral blood flow, CBF) and increased HHb in the prefrontal lobe (p < 0.05) during hypoxic exercise, and CHO failed to preserve hypoxia-suppressed prefrontal CBF and tissue oxygen saturation. In conclusion, the present study demonstrates that CHO is effective in sustaining reaction speed for a cognitive task but not promoting TT performance during hypoxic exercise, which would be important for strategy-/decision-making when athletes compete at moderate high-altitude.  相似文献   

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