Individualized Accelerometer Activity Cut-Points for the Measurement of Relative Physical Activity Intensity Levels     

Erreka Gil-Rey  Sara Maldonado-Martín  Esteban M. Gorostiaga 《Research quarterly for exercise and sport》2013,84(3):327-335

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Combined metabolic gas analyser and dGPS analysis of performance in cross-country skiing     

Peter Larsson  Karin Henriksson-Larsén 《Journal of sports sciences》2013,31(8):861-870

The purpose of this study was to provide a more detailed analysis of performance in cross-country skiing by combining findings from a differential global positioning system (dGPS), metabolic gas measurements, speed in different sections of a ski-course and treadmill threshold data. Ten male skiers participated in a freestyle skiing field test (5.6?km), which was performed with dGPS and metabolic gas measurements. A treadmill running threshold test was also performed and the following parameters were derived: anaerobic threshold, threshold of decompensated metabolic acidosis, respiratory exchange ratio = 1, onset of blood lactate accumulation and peak oxygen uptake ([Vdot]O_2peak). The combined dGPS and metabolic gas measurements made detailed analysis of performance possible. The strongest correlations between the treadmill data and final skiing field test time were for [Vdot]O_2peak (l?·?min^?1), respiratory exchange ratio = 1 (l?·?min^?1) and onset of blood lactate accumulation (l?·?min^?1) (r = ?0.644 to ??0.750). However, all treadmill test data displayed stronger associations with speed in different stretches of the course than with final time, which stresses the value of a detailed analysis of performance in cross-country skiing. Mean oxygen uptake ([Vdot]O₂) in a particular stretch in relation to speed in the same stretch displayed its strongest correlation coefficients in most stretches when [Vdot]O₂ was presented in units litres per minute, rather than when [Vdot]O₂ was normalized to body mass (ml?·?kg^?1?·?min^?1 and ml?·?min^?1?·?kg^?2/3). This suggests that heavy cross-country skiers have an advantage over their lighter counterparts. In one steep uphill stretch, however, [Vdot]O₂ (ml?·?min^?1?·?kg^?2/3) displayed the strongest association with speed, suggesting that in steep uphill sections light skiers could have an advantage over heavier skiers.  相似文献   

Enzyme activity and myoglobin concentration in rat myocardium and skeletal muscles after passive intermittent simulated altitude exposure     

Santi Esteva  Pere Panisello  Joan Ramon Torrella  Teresa Pagés 《Journal of sports sciences》2013,31(6):633-640

Abstract

We studied the effect of intermittent hypobaric hypoxia exposure on lactate dehydrogenase and citrate synthase activities, together with myoglobin content, of rat myocardium, tibialis anterior, and diaphragm muscles. The intermittent hypoxia exposure programme consisted of daily 4-h sessions in a hypobaric chamber (5000 m) over a period of 22 days. Samples were taken at the end of the programme, and 20 and 40 days later, and compared with those of control animals. In myocardium, lactate dehydrogenase activity was significantly depressed in animals 20 days post-exposure (314.6 ± 15.3 IU · g^?1) compared with control animals (400 ± 14.3 IU · g^?1), while citrate synthase activity and myoglobin concentration showed a significant stepwise increase from control animals (88.2 ± 3.6 IU · g^?1 and 4.38 ± 0.13 μm · mg^?1) to animals 20 days (104.7 ± 3.7 IU · g^?1 and 5.01 ± 0.17 μm · mg^?1) and 40 days post-exposure (108.8 ± 6.5 IU · g^?1 and 5.11 ± 0.22 μm · mg^?1). In contrast, no differences were found in diaphragm and tibialis anterior muscles. Our results show that intermittent hypobaric hypoxia exposure increased the oxidative character of myocardium even 20 days after the hypoxic stimulus has ceased, and that this effect lasts for more than 40 days for citrate synthase activity and myoglobin concentration. These findings support our previous results on skeletal and cardiac muscle capillarization after passive intermittent simulated altitude exposure, thus providing morphofunctional and biochemical evidence for increased cardiac aerobic efficiency.  相似文献   

Field and laboratory correlates of performance in competitive cross-country mountain bikers     

Louise Prins  Elmarie Terblanche 《Journal of sports sciences》2013,31(8):927-935

Abstract

We designed a laboratory test with variable fixed intensities to simulate cross-country mountain biking and compared this to more commonly used laboratory tests and mountain bike performance. Eight competitive male mountain bikers participated in a cross-country race and subsequently did six performance tests: an individual outdoor time trial on the same course as the race and five laboratory tests. The laboratory tests were as follows: an incremental cycle test to fatigue to determine peak power output; a 26-min variable fixed-intensity protocol using an electronically braked ergometer followed immediately by a 1-km time trial using the cyclist's own bike on an electronically braked roller ergometer; two 52-min variable fixed-intensity protocols each followed by a 1-km time trial; and a 1-km time trial done on its own. Outdoor competition time and outdoor time trial time correlated significantly (r = 0.79, P < 0.05). Both outdoor tests correlated better with peak power output relative to body mass (both r = ?0.83, P < 0.05) than absolute peak power output (outdoor competition: r = ?0.65; outdoor time trial: r = ?0.66; non-significant). Outdoor performance times did not correlate with the laboratory tests. We conclude that cross-country mountain biking is similar to uphill or hilly road cycling. Further research is required to design sport-specific tests to determine the remaining unexplained variance in performance.  相似文献   

Cardiorespiratory responses to exercises of equal relative intensity distributed between the upper and lower body     

S. Aunola  H. Rusko 《Journal of sports sciences》2013,31(4):309-323

Abstract

The aim of this study was to compare the ‘anaerobic threshold’ (AnT) of subjects determined during a continuous 2‐min incremental exercise test until exhaustion and the ‘maximal lactate steady‐state’ (BLaSs_max) determined during prolonged exercise at constant loads corresponding to the subjects’ AnT and/or 5–25% above and below it. Seventeen subjects performed an incremental exercise test and 1–5 prolonged exercise tests on a cycle ergometer until exhaustion at intervals of 1 week, and work rates, oxygen uptake (VO₂) values and brachial venous blood lactate (BLa) levels were measured. It was proposed that when exercising at a constant workload below AnT, BLa would fall after having reached its peak; at the level of AnT, BLa reaches maximal steady‐state (BLaSs_max); and above AnT, BLa increases continuously. Altogether, in 34 of 45 tests with a constant workload between 80 and 125% AnT, BLa values were as expected. In those cases in which BLaSs_max was reached, BLa increased on average by 3.8 mM from resting levels. This increase was 2.0 mM greater than that seen between resting levels and AnT during incremental exercise. There was no correlation between BLa values at BLaSs_max and at AnT, both when expressed as an increase in BLa (ABLa) and absolute BLa concentration. Altogether, 81% of the variation in BLa concentration at BLaSs_max could be explained by the subjects’ age, the percentage of slow‐twitch fibres and BLa levels at rest. The AnT and BLaSs_max did not differ significantly, and these values were correlated (r = 0.83). Together, AnT and age accounted for 85% of the variation seen in BLaSs_max. The BLaSs_max did not correlate with AnT when fixed at a BLa concentration of 4 mM (AnT_4mM). The three hypotheses tested in this study were confirmed, and the present results demonstrate that AnT correlates with BLaSs_max. The few exceptions to anticipated BLa kinetics were small in magnitude and could be explained by physiological variations.  相似文献   

Caffeine supplementation does not affect match activities and fatigue resistance during match play in young football players     

Svein Arne Pettersen  Peter Krustrup  Mads Bendiksen  Morten Bredsgaard Randers  Joao Brito  Jens Bangsbo 《Journal of sports sciences》2014,32(20):1958-1965

Abstract

The study examined the effect of caffeine supplementation on match activities and development of fatigue during a football match. In a randomised, double-blind cross-over design, two experimental football games separated by 7 days were organised between the junior teams of two professional football clubs (17.6 ± 1.1 years (±s), 71.7 ± 6.9 kg, 13.9% ± 5.0% body fat). The players ingested either a capsule of 6 mg · kg^?1 b.w. caffeine or placebo (dextrose) 65 min prior to the matches. Match activities were assessed using the ZXY match analysis system, and a Yo-Yo intermittent recovery test–level 2 (Yo-Yo IR2) was conducted immediately post-game. Heart rate was monitored throughout the game, and blood samples were obtained at baseline, half-time and after the game. There were no differences between caffeine and placebo regarding total distance covered (10,062 ± 916 vs 9854 ± 901 m), high-intensity running (557 ± 178 vs 642 ± 240 m), sprinting distance (109 ± 58 vs 112 ± 69 m) or acceleration counts (123 ± 31 vs 126 ± 24). In both trials, players displayed lower (P < 0.05) values in total distance and acceleration counts in the last 15 min compared to all other 15-min periods of the matches. Post-game Yo-Yo IR2 performance was not different between game trials (caffeine: 829 ± 322 m; placebo 819 ± 289 m). In conclusion, oral caffeine administration does not appear to have an ergogenic effect in young football players during match play.  相似文献   

健身跑运动对中年人血脂异常者血脂、身体成分的影响   总被引：2，自引：0，他引：2  

郑健荣 《北京体育大学学报》2009,(7)

目的:观察乳酸阈下强度健身跑运动对中年血脂异常患者血脂和身体成分的影响。方法:90名(男45名,女45名)中年血脂异常患者随机分成低强度组(L组)、中等强组(M组)和对照组(C组)三组。L组和M组分别参加8周乳酸阈下强度健身跑运动。结果:8周运动干预后,L组和M组血脂指标均有改善,而且8周运动后M组TG、LDL-c/HDL-c的降低量明显高于L组(p<0.05)。同时体脂百分比、体重及体重指数较运动前明显降低(p<0.01)。C组血脂指标8周前后,除LDL-c水平明显增高外(p<0.05),其余无显著改变;身体成分各指标8周前后亦无显著行差异。运动干预后,体脂百分比的降低与TG、HDL-c与LDL-c/HDL-c密切相关性(p<0.05)。结论:8周乳酸阈下强度健身跑运动对中年血脂异常患者的血脂、身体成分有良好的改善作用,但对于血脂与体脂百分比改变的相关性有待于进一步的研究。  相似文献   

American Association for Health,Physical Education,and Recreation     

Matthew J. Barnes  Jeremy Fraser  Karl Coley  Blake G. Perry 《Research quarterly for exercise and sport》2013,84(4):504-510

ABSTRACT

Purpose: The purpose of this study was to identify whether post-resistance exercise (REx) blood flow restriction (BFR) can elicit a similar acute training stimulus to that offered by either heavy REx or traditional low-load BFR REx. Method: Ten men completed trials with 30% one-repetition maximum (1RM) for 5 sets of 15 repetitions without BFR (30%), with BFR during exercise (30% RD), and with postexercise BFR (30% RP) and at 75% 1RM for 3 sets of 10 repetitions. Lactate and cortisol were measured before and up to 60 min after exercise. Thigh circumference, ratings of perceived exertion (RPE), and pain were measured before and after exercise. Surface electromyography was measured during exercise. Results: All conditions had a large effect (effect size [ES] > 0.8) on lactate, with the largest effects observed with the 75% condition; no differences were observed between the 30% conditions. All conditions had a moderate effect (ES > 0.25 ≤ 0.4) on increasing thigh circumference. This effect was maintained (ES = 0.35) with the application of BFR after REx (30% RP). Change in RPE, from the first to last set, was significantly greater with 30% RD compared with other conditions (all p < .05). Electromyography amplitude was higher and percentage change was greater for the 75% condition compared with the other conditions (both p < .05). Conclusions: The application of BFR immediately post-REx altered several of the responses associated with REx that is aimed at inducing muscular hypertrophy. Additionally, these changes occurred with less pain and perceived exertion suggesting that this form of REx may offer an alternative, tolerable method of REx.  相似文献   

Movement pattern and physiological response in recreational small-sided football – effect of number of players with a fixed pitch size     

Morten B. Randers  Christina Ørntoft  Marie Hagman  Jens J. Nielsen  Peter Krustrup 《Journal of sports sciences》2018,36(13):1549-1556

Recreational soccer is an effective health-promoting activity, but it is unclear how different game formats influence internal and external load. Thus, to be able to advise how to maximise the outcome of recreational football, we examined movement pattern and physiological response in 11 untrained men (32.6 ± 6.7 yrs, 23.3 ± 4.9 fat%, 43.4 ± 5.3 ml·min^?1·kg^?1) during three football sessions comprising 4 × 12 min of 3v3, 5v5 or 7v7 with a constant pitch size of 20 × 40 m. Movement pattern, heart rate (HR), blood lactate and RPE were measured during and after the 12-min periods. Greater (P < 0.05) total distance and high-speed distance was covered during 3v3 than 5v5 (14 and 30%) and 7v7 (15 and 75%). Mean HR was higher in 3v3 (85.7 ± 5.7%HRmax) and 5v5 (84.2 ± 5.1%HRmax) than in 7v7 (80.7 ± 4.6%HRmax, P < 0.05) and percentage time >90%HR was higher in 3v3 (43 ± 18%, P < 0.05) than in 5v5 (28 ± 21%) and 7v7 (18 ± 14%). Blood lactate was higher in 3v3 (7.4 ± 2.7 mmol·l^?1) than in 7v7 (4.5 ± 2.2 mmol·l^?1, P < 0.001) but not in 5v5 (6.1 ± 2.1 mmol·l^?1, P = 0.061). RPE was higher in 3v3 (6.7 ± 2.3, P < 0.01) than in 5v5 (5.2 ± 2.2) and 7v7 (4.3 ± 2.3). In conclusion, higher external and internal load was found with fewer players, when the pitch size is fixed.  相似文献   

人参皂苷Rg1对β淀粉样肽诱导原代培养胎鼠皮质神经元损伤的保护作用   总被引：1，自引：0，他引：1  

郑丽华  吴仲敏  杨世晓 《台州学院学报》2009,31(6):59-64

研究人参皂苷Rgl对β淀粉样肽诱导原代培养胎鼠皮质神经元损伤的保护作用。利用乳酸脱氢酶（LDH）测定试剂盒检测胎鼠皮质神经元培养液中LDH活力,并用四甲基偶氮唑蓝（MTT）比色法测定神经元存活率,观察人参皂苷Rg1对β淀粉样肽诱导原代培养胎鼠皮质神经元损伤的保护作用。结果显示：终浓度为5μmol／L、10μmol／L、15μmol／L的β淀粉样肽作用于皮质神经元48h后,培养液中LDH活力增高,神经细胞存活率下降,与不作任何处理的空白对照组比较,15μmol／L的β淀粉样肽组有显著性差异（P〈0．01）;经人参皂苷Rg1（20βLmol／L）预处理24h再加入15μmol／Lβ淀粉样肽作用48h,LDH活力下降,神经细胞的存活率升高,与仅加入15μLmol／Lβ淀粉样肽的损伤组比较差异显著（P〈0．01）。分析表明：人参皂苷Rg1能拮抗β淀粉样肽诱导的神经细胞损伤,对β淀粉样肽引起的神经细胞毒性有一定的保护作用。  相似文献