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1.
It has previously been shown that measurement of the critical speed is a non-invasive method of estimating the blood lactate response during exercise. However, its validity in children has yet to be demonstrated. The aims of this study were: (1) to verify if the critical speed determined in accordance with the protocol of Wakayoshi et al. is a non-invasive means of estimating the swimming speed equivalent to a blood lactate concentration of 4 mmol·l-1 in children aged 10-12 years; and (2) to establish whether standard of performance has an effect on its determination. Sixteen swimmers were divided into two groups: beginners and trained. They initially completed a protocol for determination of speed equivalent to a blood lactate concentration of 4 mmol·l-1. Later, during training sessions, maximum efforts were swum over distances of 50, 100 and 200 m for the calculation of the critical speed. The speeds equivalent to a blood lactate concentration of 4 mmol·l-1 (beginners = 0.82±0.09 m·s-1 , trained = 1.19±0.11 m·s-1; mean±s) were significantly faster than the critical speeds (beginners = 0.78±0.25·s-1 , trained = 1.08±0.04 m·s-1) in both groups. There was a high correlation between speed at a blood lactate concentration of 4 mmol·l-1 and the critical speed for the beginners (r = 0.96, P ? 0.001), but not for the trained group (r = 0.60, P > 0.05). The blood lactate concentration corresponding to the critical speed was 2.7±1.1 and 3.1±0.4 mmol·l-1 for the beginners and trained group respectively. The percent difference between speed at a blood lactate concentration of 4 mmol·l-1 and the critical speed was not significantly different between the two groups. At all distances studied, swimming performance was significantly faster in the trained group. Our results suggest that the critical speed underestimates swimming intensity corresponding to a blood lactate concentration of 4 mmol·l-1 in children aged 10-12 years and that standard of performance does not affect the determination of the critical speed. 相似文献
2.
The aim of this study was to assess the sensitivity of the lactate minimum speed test to changes in endurance fitness resulting from a 6 week training intervention. Sixteen participants (mean +/- s: age 23+/-4 years; body mass 69.7+/-9.1 kg) completed 6 weeks of endurance training. Another eight participants (age 23+/-4 years; body mass 72.7+/-12.5 kg) acted as non-training controls. Before and after the training intervention, all participants completed: (1) a standard multi-stage treadmill test for the assessment of VO2max, running speed at the lactate threshold and running speed at a reference blood lactate concentration of 3 mmol x l(-1); and (2) the lactate minimum speed test, which involved two supramaximal exercise bouts and an 8 min walking recovery period to increase blood lactate concentration before the completion of an incremental treadmill test. Additionally, a subgroup of eight participants from the training intervention completed a series of constant-speed runs for determination of running speed at the maximal lactate steady state. The test protocols were identical before and after the 6 week intervention. The control group showed no significant changes in VO2max, running speed at the lactate threshold, running speed at a blood lactate concentration of 3 mmol x l(-1) or the lactate minimum speed. In the training group, there was a significant increase in VO2max (from 47.9+/-8.4 to 52.2+/-2.7 ml x kg(-1) x min(-1)), running speed at the maximal lactate steady state (from 13.3+/-1.7 to 13.9+/-1.6 km x h(-1)), running speed at the lactate threshold (from 11.2+/-1.8 to 11.9+/-1.8 km x h(-1)) and running speed at a blood lactate concentration of 3 mmol x l(-1) (from 12.5+/-2.2 to 13.2+/-2.1 km x h(-1)) (all P < 0.05). Despite these clear improvements in aerobic fitness, there was no significant difference in lactate minimum speed after the training intervention (from 11.0+/-0.7 to 10.9+/-1.7 km x h(-1)). The results demonstrate that the lactate minimum speed, when assessed using the same exercise protocol before and after 6 weeks of aerobic exercise training, is not sensitive to changes in endurance capacity. 相似文献
3.
The aim of this study was to examine heart rate, blood lactate concentration and estimated energy expenditure during a competitive rugby league match. Seventeen well-trained rugby league players (age, 23.9 +/- 4.1 years; VO2max, 57.9 +/- 3.6 ml x kg(-1) x min(-1); height, 1.82 +/- 0.06 m; body mass, 90.2 +/- 9.6 kg; mean +/- s) participated in the study. Heart rate was recorded continuously throughout the match using Polar Vantage NV recordable heart rate monitors. Blood lactate samples (n = 102) were taken before the match, after the warm-up, at random stoppages in play, at half time and immediately after the match. Estimated energy expenditure during the match was calculated from the heart rate-VO2 relationship determined in laboratory tests. The mean team heart rate (n = 15) was not significantly different between halves (167 +/- 9 vs 165 +/- 11 beats x min(-1)). Mean match intensity was 81.1 +/- 5.8% VO2max. Mean match blood lactate concentration was 7.2 +/- 2.5 mmol x l(-1), with concentrations for the first half (8.4 +/- 1.8 mmol x l(-1)) being significantly higher than those for the second half (5.9 +/- 2.5 mmol x l(-1)) (P<0.05). Energy expenditure was approximately 7.9 MJ. These results demonstrate that semi-professional rugby league is a highly aerobic game with a considerable anaerobic component requiring high lactate tolerance. Training programmes should reflect these demands placed on players during competitive match-play. 相似文献
4.
The relationship between selected physiological variables of rowers and rowing performance as determined by a 2000 m ergometer test 总被引：6，自引：0，他引：6
The aim of this study was to establish the relationship between selected physiological variables of rowers and rowing performance as determined by a 2000 m time-trial on a Concept II Model B rowing ergometer. The participants were 13 male club standard oarsmen. Their mean (+/- s) age, body mass and height were 19.9+/-0.6 years, 73.1+/-6.6 kg and 180.5+/-4.6 cm respectively. The participants were tested on the rowing ergometer to determine their maximal oxygen uptake (VO2max), rowing economy, predicted velocity at VO2max, velocity and VO2 at the lactate threshold, and their velocity and VO2 at a blood lactate concentration of 4 mmol x l(-1). Percent body fat was estimated using the skinfold method. The velocity for the 2000 m performance test and the predicted velocities at the lactate threshold, at a blood lactate concentration of 4 mmol x l(-1) and at VO2max were 4.7+/-0.2, 3.9+/-0.2, 4.2+/-0.2 and 4.6+/-0.2 m x s(-1) respectively. A repeated-measures analysis of variance showed that the three predicted velocities were all significantly different from each other (P<0.05). The VO2max and lean body mass showed the highest correlation with the velocity for the 2000 m time-trial (r = 0.85). A stepwise multiple regression showed that VO2max was the best single predictor of the velocity for the 2000 m time-trial; a model incorporating VO2max explained 72% of the variability in 2000 m rowing performance. Our results suggest that rowers should devote time to the improvement of VO2max and lean body mass. 相似文献
5.
Plasma testosterone and cortisol responses to prolonged sculling in male competitive rowers. 总被引：5，自引：0，他引：5
In this study, we examined anabolic and catabolic hormone responses to a single endurance rowing training session in 12 male competitive single scull rowers. A work intensity eliciting a blood lactate concentration of 4 mmol(-1) was determined on a rowing ergometer during an endurance rowing training session lasting about 2 h (7891+/-761 s; distance covered 22.6+/-2.5 km; heart rate 136+/-7 beats x min(-1); intensity 77.4+/-3.8% of anaerobic threshold; mean +/- s). Venous blood samples were obtained before and after on-water rowing. Cortisol, testosterone and sex hormone binding globulin were measured and free testosterone and the free testosterone: cortisol ratio calculated. Blood lactate concentration did not change significantly during training (from 1.7+/-0.4 to 1.9+/-0.4 mmol x l(-1)); however, body mass was reduced (from 82.0+/-10.8 to 80.6+/-11.2 kg) and was related to the distance covered (r = -0.75). The concentrations of cortisol and testosterone did not change significantly during rowing or in the first 2 h of recovery. Free testosterone was reduced in the first 2 h of recovery, but no significant changes were observed in the free testosterone: cortisol ratio. Immediately after rowing, the concentrations of cortisol (r = 0.49) and free testosterone (r = -0.58) were related to the distance covered. Our findings indicate that a prolonged low-intensity training session results in a similar anabolic and catabolic hormone stimulus for trained rowers. 相似文献
6.
The aim of this study was to assess the sensitivity of the lactate minimum speed test to changes in endurance fitness resulting from a 6 week training intervention. Sixteen participants (mean +/- s :age 23 +/- 4 years;body mass 69.7 +/- 9.1 kg) completed 6 weeks of endurance training. Another eight participants (age 23 +/- 4 years; body mass 72.7 +/-12.5 kg) acted as non-training controls. Before and after the training intervention, all participants completed: (1) a standard multi-stage treadmill test for the assessment of VO 2max , running speed at the lactate threshold and running speed at a reference blood lactate concentration of 3 mmol.l -1 ; and (2) the lactate minimum speed test, which involved two supramaximal exercise bouts and an 8 min walking recovery period to increase blood lactate concentration before the completion of an incremental treadmill test. Additionally, a subgroup of eight participants from the training intervention completed a series of constant-speed runs for determination of running speed at the maximal lactate steady state. The test protocols were identical before and after the 6 week intervention. The control group showed no significant changes in VO 2max , running speed at the lactate threshold, running speed at a blood lactate concentration of 3 mmol.l -1 or the lactate minimum speed.In the training group, there was a significant increase in VO 2max (from 47.9 +/- 8.4 to 52.2 +/- 2.7 ml.kg -1 .min -1 ), running speed at the maximal lactate steady state (from 13.3 +/- 1.7 to 13.9 +/- 1.6 km.h -1 ), running speed at the lactate threshold (from 11.2 +/- 1.8 to 11.9 +/- 1.8 km.h -1 ) and running speed at a blood lactate concentration of 3 mmol.l -1 (from 12.5 +/- 2.2 to 13.2 +/- 2.1 km.h -1 ) (all P ? 0.05). Despite these clear improvements in aerobic fitness, there was no significant difference in lactate minimum speed after the training intervention (from 11.0 +/- 0.7 to 10.9 +/- 1.7 km.h -1 ). The results demonstrate that the lactate minimum speed,when assessed using the same exercise protocol before and after 6 weeks of aerobic exercise training, is not sensitive to changes in endurance capacity. 相似文献
7.
8.
The effect of active and passive recovery on repeated-sprint swimming bouts was studied in eight elite swimmers. Participants performed three trials of two sets of front crawl swims with 5 min rest between sets. Set A consisted of four 30-s bouts of high-intensity tethered swimming separated by 30 s passive rest, whereas Set B consisted of four 50-yard maximal-sprint swimming repetitions at intervals of 2 min. Recovery was active only between sets (AP trial), between sets and repetitions of Set B (AA trial) or passive throughout (PP trial). Performance during and metabolic responses after Set A were similar between trials. Blood lactate concentration after Set B was higher and blood pH was lower in the PP (18.29 +/- 1.31 mmol x l(-1) and 7.12 +/- 0.11 respectively) and AP (17.56 +/- 1.22 mmol x l(-1) and 7.14 +/- 0.11 respectively) trials compared with the AA (14.13 +/- 1.56 mmol x l(-1) and 7.23 +/- 0.10 respectively) trial (P < 0.01). Performance time during Set B was not different between trials (P > 0.05), but the decline in performance during Set B of the AP trial was less marked than in the AA or PP trials (main effect of sprints, P < 0.05). Results suggest that active recovery (60% of the 100-m pace) could be beneficial between training sets, and may compromise swimming performance between repetitions when recovery durations are short (< 2 min). 相似文献
9.
The aims of the study were to modify the training impulse (TRIMP) method of quantifying training load for use with intermittent team sports, and to examine the relationship between this modified TRIMP (TRIMP(MOD)) and changes in the physiological profile of team sport players during a competitive season. Eight male field hockey players, participating in the English Premier Division, took part in the study (mean+/-s: age 26+/-4 years, body mass 80.8+/-5.2 kg, stature 1.82+/-0.04 m). Participants performed three treadmill exercise tests at the start of the competitive season and mid-season: a submaximal test to establish the treadmill speed at a blood lactate concentration of 4 mmol . l(-1); a maximal incremental test to determine maximal oxygen uptake ([V]O(2max)) and peak running speed; and an all-out constant-load test to determine time to exhaustion. Heart rate was recorded during all training sessions and match-play, from which TRIMP(MOD) was calculated. Mean weekly TRIMP(MOD) was correlated with the change in [V]O(2max) and treadmill speed at a blood lactate concentration of 4 mmol x l(-1) from the start of to mid-season (P<0.05). The results suggest that TRIMP(MOD) is a means of quantifying training load in team sports and can be used to prescribe training for the maintenance or improvement of aerobic fitness during the competitive season. 相似文献
10.
The aims of this study were: (1) to identify the exercise intensity that corresponds to the maximal lactate steady state in adolescent endurance-trained runners; (2) to identify any differences between the sexes; and (3) to compare the maximal lactate steady state with commonly cited fixed blood lactate reference parameters. Sixteen boys and nine girls volunteered to participate in the study. They were first tested using a stepwise incremental treadmill protocol to establish the blood lactate profile and peak oxygen uptake (VO2). Running speeds corresponding to fixed whole blood lactate concentrations of 2.0, 2.5 and 4.0 mmol x l(-1) were calculated using linear interpolation. The maximal lactate steady state was determined from four separate 20-min constant-speed treadmill runs. The maximal lactate steady state was defined as the fastest running speed, to the nearest 0.5 km x h(-1), where the change in blood lactate concentration between 10 and 20 min was < 0.5 mmol x l(-1). Although the boys had to run faster than the girls to elicit the maximal lactate steady state (15.7 vs 14.3 km x h(-1), P < 0.01), once the data were expressed relative to percent peak VO2 (85 and 85%, respectively) and percent peak heart rate (92 and 94%, respectively), there were no differences between the sexes (P > 0.05). The running speed and percent peak VO2 at the maximal lactate steady state were not different to those corresponding to the fixed blood lactate concentrations of 2.0 and 2.5 mmol x l(-1) (P > 0.05), but were both lower than those at the 4.0 mmol x l(-1) concentration (P < 0.05). In conclusion, the maximal lactate steady state corresponded to a similar relative exercise intensity as that reported in adult athletes. The running speed, percent peak VO2 and percent peak heart rate at the maximal lactate steady state are approximated by the fixed blood lactate concentration of 2.5 mmol x l(-1) measured during an incremental treadmill test in boys and girls. 相似文献
11.
Nine male student games players consumed either flavoured water (0.1 g carbohydrate, Na+ 6 mmol x l(-1)), a solution containing 6.5% carbohydrate-electrolytes (6.5 g carbohydrate, Na+ 21 mmol x l(-1)) or a taste placebo (Na+ 2 mmol x l(-1)) during an intermittent shuttle test performed on three separate occasions at an ambient temperature of 30 degrees C (dry bulb). The test involved five 15-min sets of repeated cycles of walking and variable speed running, each separated by a 4-min rest (part A of the test), followed by 60 s run/60 s rest until exhaustion (part B of the test). The participants drank 6.5 ml x kg(-1) of fluid as a bolus just before exercise and thereafter 4.5 ml x kg(-1) during every exercise set and rest period (19 min). There was a trial order effect. The total distance completed by the participants was greater in trial 3 (8441 +/- 873 m) than in trial 1 (6839 +/- 512, P < 0.05). This represented a 19% improvement in exercise capacity. However, the trials were performed in a random counterbalanced order and the participants completed 8634 +/- 653 m, 7786 +/- 741 m and 7099 +/- 647 m in the flavoured water (FW), placebo (P) and carbohydrate-electrolyte (CE) trials, respectively (P = 0.08). Sprint performance was not different between the trials but was impaired over time (FW vs P vs CE: set 1, 2.41 +/- 0.02 vs 2.39 +/- 0.03 vs 2.39 +/- 0.03 s; end set, 2.46 +/- 0.03 vs 2.47 +/- 0.03 vs 2.47 +/- 0.02 s; main effect time, P < 0.01). The rate of rise in rectal temperature was greater in the carbohydrate-electrolyte trial (rise in rectal temperature/duration of trial, degrees C x h(-1); FW vs CE, P < 0.05; P vs CE, N.S.). Blood glucose concentrations were higher in the carbohydrate-electrolyte than in the other two trials (FW vs P vs CE:rest, 4.4 +/- 0.1 vs 4.3 +/- 0.1 vs 4.2 +/- 0.1 mmol x l(-1); end of exercise, 5.4 +/- 0.3 vs 6.4 +/- 0.6 vs 7.2 +/- 0.5 mmol x l(-1); main effect trial, P < 0.05; main effect time, P < 0.01). Plasma free fatty acid concentrations at the end of exercise were lower in the carbohydrate-electrolyte trial than in the other two trials (FW vs P vs CE: 0.57 +/- 0.08 vs 0.53 +/- 0.11 vs 0.29 +/- 0.04 mmol x l(-1); interaction, P < 0.01). The correlation between the rate of rise in rectal temperature (degrees C x h(-1)) and the distance completed was -0.91, -0.92 and -0.96 in the flavoured water, placebo and carbohydrate-electrolyte conditions, respectively (P < 0.01). Heart rate, blood pressure, plasma ammonia, blood lactate, plasma volume and rate of perceived exertion were not different between the three fluid trials. Although drinking the carbohydrate-electrolyte solution induced greater metabolic changes than the flavoured water and placebo solutions, it is unlikely that in these unacclimated males carbohydrate availability was a limiting factor in the performance of intermittent running in hot environmental conditions. 相似文献
12.
To develop a track version of the maximal anaerobic running test, 10 sprint runners and 12 distance runners performed the test on a treadmill and on a track. The treadmill test consisted of incremental 20-s runs with a 100-s recovery between the runs. On the track, 20-s runs were replaced by 150-m runs. To determine the blood lactate versus running velocity curve, fingertip blood samples were taken for analysis of blood lactate concentration at rest and after each run. For both the treadmill and track protocols, maximal running velocity (v max), the velocities associated with blood lactate concentrations of 10 mmol x l-1 (v10 mM) and 5 mmol x l(-1) (v5 mM), and the peak blood lactate concentration were determined. The results of both protocols were compared with the seasonal best 400-m runs for the sprint runners and seasonal best 1000-m time-trials for the distance runners. Maximal running velocity was significantly higher on the track (7.57 +/- 0.79 m x s(-1)) than on the treadmill (7.13 +/- 0.75 m x s(-1)), and sprint runners had significantly higher vmax, v10 mM, and peak blood lactate concentration than distance runners (P < 0.05). The Pearson product--moment correlation coefficients between the variables for the track and treadmill protocols were 0.96 (v max), 0.82 (v10 mM), 0.70 (v5 mM), and 0.78 (peak blood lactate concentration) (P < 0.05). In sprint runners, the velocity of the seasonal best 400-m run correlated positively with vmax in the treadmill (r = 0.90, P < 0.001) and track protocols (r = 0.92, P < 0.001). In distance runners, a positive correlation was observed between the velocity of the 1000-m time-trial and vmax in the treadmill (r = 0.70, P < 0.01) and track protocols (r = 0.63, P < 0.05). It is apparent that the results from the track protocol are related to, and in agreement with, the results of the treadmill protocol. In conclusion, the track version of the maximal anaerobic running test is a valid means of measuring different determinants of sprint running performance. 相似文献
13.
Fehrenbach E Niess AM Passek F Sorichter S Schwirtz A Berg A Dickhuth HH Northoff H 《Journal of sports sciences》2003,21(5):383-389
Haem-oxygenase-1 (HO-1) is an antioxidant stress protein that is mainly induced by reactive oxygen species, inflammatory cytokines and hyperthermia. We assessed the influence of different types of exercise on HO-1 expression in leukocytes of the peripheral blood in three groups of male participants: a short exhaustive run above the lactate steady state (n = 15), eccentric exercise (n = 12) and an intensive endurance run (half-marathon, n = 12). Blood samples were taken at rest and up to 24 h after exercise. Blood lactate concentration after exercise was 9.0 +/- 2.1, 3.8 +/- 1.6 and 5.1 +/- 2.2 mmol x l(-1) (mean +/- s) for the exhaustive run, eccentric exercise and half-marathon groups, respectively (P < 0.05). Creatine kinase concentration was highest 24 h after exercise: 133 +/- 91, 231 +/- 139 and 289 +/- 221 U x l(-1) for the exhaustive run, eccentric exercise and half-marathon groups, respectively (P < 0.05). The maximal increase in leukocyte counts after exercise was 11.5 +/- 19.2, 6.2 +/- 1.4 and 14.7 +/- 2.1 x 10(9) x l(-1). There was no change in HO-1 as a result of the short exhaustive run or the eccentric exercise, whereas the half-marathon had a significant stimulatory effect on HO-1-expression in lymphocytes, monocytes and granulocytes (P < 0.001) using flow cytometry analyses. In conclusion, eccentric exercise alone or short-term heavy exercise are not sufficient to stimulate the antioxidative stress protein HO-1 in peripheral leukocytes 相似文献
14.
Rampinini E Impellizzeri FM Castagna C Abt G Chamari K Sassi A Marcora SM 《Journal of sports sciences》2007,25(6):659-666
The aim of this study was to examine the effects of exercise type, field dimensions, and coach encouragement on the intensity and reproducibility of small-sided games. Data were collected on 20 amateur soccer players (body mass 73.1 +/- 8.6 kg, stature 1.79 +/- 0.05 m, age 24.5 +/- 4.1 years, VO(2max) 56.3 +/- 4.8 ml x kg(-1) x min(-1)). Aerobic interval training was performed during three-, four-, five- and six-a-side games on three differently sized pitches, with and without coach encouragement. Heart rate, rating of perceived exertion (RPE) on the CR10-scale, and blood lactate concentration were measured. Main effects were found for exercise type, field dimensions, and coach encouragement (P < 0.05), but there were no interactions between any of the variables (P > 0.15). During a six-a-side game on a small pitch without coach encouragement, exercise intensity was 84 +/- 5% of maximal heart rate, blood lactate concentration was 3.4 +/- 1.0 mmol x l(-1), and the RPE was 4.8. During a three-a-side game on a larger pitch with coach encouragement, exercise intensity was 91 +/- 2% of maximal heart rate, blood lactate concentration was 6.5 +/- 1.5 mmol x l(-1), and the RPE was 7.2. Typical error expressed as a coefficient of variation ranged from 2.0 to 5.4% for percent maximal heart rate, from 10.4 to 43.7% for blood lactate concentration, and from 5.5 to 31.9% for RPE. The results demonstrate that exercise intensity during small-sided soccer games can be manipulated by varying the exercise type, the field dimensions, and whether there is any coach encouragement. By using different combinations of these factors, coaches can modulate exercise intensity within the high-intensity zone and control the aerobic training stimulus. 相似文献
15.
The purpose of this study was to quantify the relationship between changes in test measures and changes in competition performance for individual elite swimmers. The 24 male and 16 female swimmers, who were monitored for 3.6 years (s = 2.5), raced in a major competition at the end of each 6-month season (3.6 competitions, s = 2.2). A 7 x 200-m incremental swimming step-test and anthropometry were conducted in up to four training phases each season. Correlations of changes in step-test and anthropometry measures between training phases and seasons with changes in competition performance between seasons were derived with repeated-measures mixed-modelling and linear regression. Changes in competition performance were best tracked by changes in test measures between taper phases. The best single predictor of competition performance was skinfolds for females (r = -0.53). The best predictor from the step-test was stroke rate at a blood lactate concentration of 4 mmol x l(-1) (females: r = 0.46; males: r = 0.41); inclusion of the second-best step-test predictor in a multiple linear regression improved the correlations (females: r = 0.52 with speed in the seventh step included; males: r = 0.58 with peak lactate concentration included). In conclusion, a combination of fitness and technique factors is important for competitive performance. The step-test is a useful adjunct in a swimmer's training preparation for tracking large changes in performance. 相似文献
16.
Acclimatization to altitude and normoxic training improve 400-m running performance at sea level 总被引：2，自引：0，他引：2
To investigate the benefits of 'living high and training low' on anaerobic performance at sea level, eight 400-m runners lived for 10 days in normobaric hypoxia in an altitude house (oxygen content = 15.8%) and trained outdoors in ambient normoxia at sea level. A maximal anaerobic running test and 400-m race were performed before and within 1 week of living in the altitude house to determine the maximum speed and the speeds at different submaximal blood lactate concentrations (3, 5, 7, 10 and 13 mmol x l(-1)) and 400-m race time. At the same time, ten 400-m runners lived and trained at sea level and were subjected to identical test procedures. Multivariate analysis of variance indicated that the altitude house group but not the sea-level group improved their 400-m race time during the experimental period (P < 0.05). The speeds at blood lactate concentrations of 5-13 mmol x l(-1) tended to increase in the altitude house group but the response was significant only at 5 and 7 mmol x l(-1) (P < 0.05). Furthermore, resting blood pH was increased in six of the eight altitude house athletes from 0.003 to 0.067 pH unit (P < 0.05). The results of this study demonstrate improved 400-m performance after 10 days of living in normobaric hypoxia and training at sea level. Furthermore, the present study provides evidence that changes in the acid-base balance and lactate metabolism might be responsible for the improvement in sprint performance. 相似文献
17.
The effect of recovery duration on running speed and stroke quality during intermittent training drills in elite tennis players 总被引：3，自引：1，他引：2
The aim of this study was to assess the effect of the recovery duration in intermittent training drills on metabolism and coordination in sport games. Ten nationally ranked male tennis players (age 25.3+/-3.7 years, height 1.83+/-0.8 m, body mass 77.8+/-7.7 kg; mean +/- sx) participated in a passing-shot drill (baseline sprint with subsequent passing shot) that aimed to improve both starting speed and stroke quality (speed and precision). Time pressure for stroke preparation was individually adjusted by a ball-machine and corresponded to 80% of maximum running speed. In two trials (T10, T15) separated by 2 weeks, the players completed 30 strokes and sprints subdivided into 6 x 5 repetitions with a 1 min rest between series. The rest between each stroke-and-sprint lasted either 10 s (T10) or 15 s (T15). The sequence of both conditions was randomized between participants. Post-exercise blood lactate concentration was significantly elevated in T10 (9.04+/-3.06 vs 5.01+/-1.35 mmol x l(-1), P < 0.01). Running time for stroke preparation (1.405+/-0.044 vs 1.376+/-0.045 s, P < 0.05) and stroke speed (106+/-12 vs 114+/-8 km x h(-1), P < 0.05) were significantly decreased in T10, while stroke precision - that is, more target hits (P < 0.1) and fewer errors (P < 0.05) - tended to be higher. We conclude that running speed and stroke quality during intermittent tennis drills are highly dependent on the duration of recovery time. Optimization of training efficacy in sport games (e.g. combined improvement of conditional and technical skills) requires skilful fine-tuning of monitoring guidelines. 相似文献
18.
Intensity of exercise recovery, blood lactate disappearance, and subsequent swimming performance 总被引：1，自引：0，他引：1
Greenwood JD Moses GE Bernardino FM Gaesser GA Weltman A 《Journal of sports sciences》2008,26(1):29-34
The aim of this study was to examine the effects of active versus passive recovery on blood lactate disappearance and subsequent maximal performance in competitive swimmers. Fourteen male swimmers from the University of Virginia swim team (mean age 20.3 years, s= 4.1; stature 1.85 m, s= 2.2; body mass 81.1 kg, s= 5.6) completed a lactate profiling session during which the speed at the lactate threshold (V(LT)), the speed at 50% of the lactate threshold (V(LT.5)), and the speed at 150% of the lactate threshold (V(LT1.5)) were determined. Participants also completed four randomly assigned experimental sessions that consisted of a 200-yard maximal-effort swim followed by 10 min of recovery (passive, V(LT.5), V(LT), V(LT1.5)) and a subsequent 200-yard maximal effort swim. All active recovery sessions resulted in greater lactate disappearance than passive recovery (P < 0.0001 for all comparisons), with the greatest lactate disappearance associated with recovery at V(LT) (P= 0.006 and 0.007 vs. V(LT.5) and V(LT1.5) respectively) [blood lactate disappearance was 2.1 mmol l(-1) (s= 2.0), 6.0 mmol l(-1) (s=2.6), 8.5 mmol l(-1) (s= 1.8), and 6.1 mmol l(-1) (s= 2.5) for passive, V(LT.5), V(LT), and V(LT1.5) respectively]. Active recovery at VLT and V(LT1.5) resulted in faster performance on time trial 2 than passive recovery (P=0.005 and 0.03 respectively); however, only active recovery at V(LT) resulted in improved performance on time trial 2 (TT2) relative to time trial 1 (TT1) [TT2- TT1: passive +1.32 s (s= 0.64), V(LT.5) +1.01 s (s= 0.53), V(LT) -1.67 s (s= 0.26), V(LT1.5) -0.07 s (s = 0.51); P < 0.0001 for V(LT)). In conclusion, active recovery at the speed associated with the lactate threshold resulted in the greatest lactate disappearance and in improved subsequent performance in all 14 swimmers. Our results suggest that coaches should consider incorporating recovery at the speed at the lactate threshold during competition and perhaps during hard training sessions. 相似文献
19.
Physiological demands of top-class soccer refereeing in relation to physical capacity: effect of intense intermittent exercise training. 总被引：1，自引：1，他引：0
To examine the activity profile and physiological demands of top-class soccer refereeing, we performed computerized time-motion analyses and measured the heart rate and blood lactate concentration of 27 referees during 43 competitive matches in the two top Danish leagues. To relate match performance to physical capacity and training, several physiological tests were performed before and after intermittent exercise training. Total distance covered was 10.07+/-0.13 km (mean +/- s(x)), of which 1.67+/-0.08 km was high-intensity running. High-intensity running and backwards running decreased (P < 0.05) in the second half. Mean heart rate was 162+/-2 beats min(-1) (85+/-1% of maximal heart rate) and the mean blood lactate concentration was 4.9+/-0.3 (range 1.7-14.0) mmol x l(-1). The amount of high-intensity running during a match was related to the Yo-Yo intermittent recovery test (r2 = 0.57; P<0.05) and the 12 min run (r2 = 0.21; P<0.05). After intermittent training (n = 8), distance covered during high-intensity running was greater (2.06+/-0.13 vs 1.69+/-0.08 km; P< 0.05) and mean heart rate was lower (159+/-1 vs 164+/-2 beats x min(-1); P< 0.05) than before training. The results of the present study demonstrate that: (1) top-class soccer referees have significant aerobic energy expenditure throughout a game and episodes of considerable anaerobic energy turnover; (2) the ability to perform high-intensity running is reduced towards the end of matches; (3) the Yo-Yo intermittent recovery test can be used to evaluate referees' match performance; and (4) intense intermittent exercise training improves referees' performance capacity during a game. 相似文献
20.
Volianitis S Dawson EA Dalsgaard M Yoshiga C Clemmesen J Secher NH Olsen N Nielsen HB 《Journal of sports sciences》2012,30(2):149-153
Reduced hepatic lactate elimination initiates blood lactate accumulation during incremental exercise. In this study, we wished to determine whether renal lactate elimination contributes to the initiation of blood lactate accumulation. The renal arterial-to-venous (a-v) lactate difference was determined in nine men during sodium lactate infusion to enhance the evaluation (0.5 mol x L(-1) at 16 ± 1 mL x min(-1); mean ± s) both at rest and during cycling exercise (heart rate 139 ± 5 beats x min(-1)). The renal release of erythropoietin was used to detect kidney tissue ischaemia. At rest, the a-v O(2) (CaO(2)-CvO(2)) and lactate concentration differences were 0.8 ± 0.2 and 0.02 ± 0.02 mmol x L(-1), respectively. During exercise, arterial lactate and CaO(2)-CvO(2) increased to 7.1 ± 1.1 and 2.6 ± 0.8 mmol x L(-1), respectively (P < 0.05), indicating a -70% reduction of renal blood flow with no significant change in the renal venous erythropoietin concentration (0.8 ± 1.4 U x L(-1)). The a-v lactate concentration difference increased to 0.5 ± 0.8 mmol x L(-1), indicating similar lactate elimination as at rest. In conclusion, a -70% reduction in renal blood flow does not provoke critical renal ischaemia, and renal lactate elimination is maintained. Thus, kidney lactate elimination is unlikely to contribute to the initial blood lactate accumulation during progressive exercise. 相似文献