游泳运动员运动应激损伤评价实验研究

通过血液、尿液标本的监控,对游泳运动员进行运动应激损伤评价的实验研究。方法：在安静状态、大负荷训练后2h内、次日晨,采集游泳队运动员的血、尿标本,进行相关指标的测试,并进行统计分析。结果：大负荷训练后,运动员出现应激反应,BU、CK、LDH等生化指标升高明显;RBC、Hb、HCT等指标降低,WBC显著升高,且主要是N的升高;尿液PRO、KET等出现弱阳性,次日晨有部分指标未完全恢复至安静水平。结论：血液BU、CK、LDH、RBC、Hb、HCT、WBC、N及尿液PRO、KET等指标,对游泳运动员的应激损伤评价具有参考价值。     

Constitutions,Institutions, and Games

We provide a new wrinkle to the Argument from Unfair Advantage, a rather popular one in the ethics of doping in sports discussions. But we add a new argument that we believe places the moral burden on those who favor doping in sports. We also defend our position against some important concerns that might be raised against it. In the end, we argue that for the time being, doping in sports ought to be banned until it can be demonstrated that our concerns can be satisfied.     

Accumulating short bouts of running reduces resting blood pressure in young normotensive/pre-hypertensive men

Abstract

In this study, we compared the effects of accumulated and continuous running on resting arterial blood pressure. Ten normotensive/pre-hypertensive men, aged 25.0 ± 4.2 years (mean ± s), participated in three 2-day trials at least one week apart in a randomized, repeated-measures design. On Day 1, participants rested (control) or ran at 70% of maximum oxygen uptake in either ten 3-min bouts (30 min rest between bouts) or one continuous 30-min bout. On Day 2, participants rested throughout the day. Blood pressure was measured at hourly intervals throughout Days 1 and 2. Mean resting systolic blood pressure on Day 2 was 6% lower during the accumulated and continuous running trials compared with the control trial (110 ± 6 vs. 110 ± 8 vs. 117 ± 6 mmHg respectively; P < 0.05), but there were no differences in resting diastolic blood pressure among the three trials (70 ± 7 vs. 69 ± 6 vs. 70 ± 5 mmHg respectively). These findings demonstrate that accumulating 30 min of running throughout the day in short bouts is as effective as 30 min of continuous running for reducing resting systolic blood pressure on the next day in young normotensive/pre-hyptertensive men.     

A novel method for the performance of isometric exercise in the home

There is a paucity of research on devices suitable for home-based isometric exercise. Our aim was to compare cardiovascular responses to isometric exercise using novel and established methods. Ten individuals (age 34.0?±?8.5 years, mass 68.2?±?10.4?kg, height 1.72?±?0.09?m; mean?±?s) performed three different isometric exercise protocols with 48?h between each. Each protocol involved four repeated exercise bouts of 2?min at 30% maximum voluntary contraction force using alternate legs (transducer), alternate arms (transducer), or alternate arms (novel device). Systolic blood pressure, diastolic blood pressure, mean arterial blood pressure and heart rate were measured every 30?s. The highest (peak) values during each 2?min bout of exercise were recorded (peak systolic blood pressure, peak diastolic blood pressure, peak mean arterial blood pressure and peak heart rate). At the end of each 2?min exercise bout, the participants rated their perceived discomfort using Borg's CR-10 scale. There was a statistically significant difference in peak systolic blood pressure between isometric arm flexion using the force transducer and the novel device [158.1?±?10.8 vs. 149.1?±?13.9?mmHg (mean?±?s); P = 0.02]. Further analysis showed that peak systolic blood pressure was on average 9?mmHg higher using the force transducer with limits of agreement of –?15.97 to 33.97?mmHg. Analysis of the peak diastolic blood pressure, peak mean arterial blood pressure, peak heart rate and CR-10 data revealed no statistically significant differences between the three protocols. These results suggest that this novel, home-based method elicited similar cardiovascular responses during isometric exercise to those of established laboratory-based methods. However, the lower peak systolic blood pressure using the modified scales warrants further investigation before this method is used widely in the home.     

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

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.     

Effects of rest interval during high-repetition resistance training on strength,aerobic fitness,and repeated-sprint ability

Abstract

The effect of altering the rest period on adaptations to high-repetition resistance training is not well known. Eighteen active females were matched according to leg strength and repeated-sprint ability and randomly allocated to one of two groups. One group performed resistance training with 20-s rest intervals between sets, while the other group employed 80-s rest intervals between sets. Both groups performed the same total training volume and load. Each group trained 3 days a week for 5 weeks [15- to 20-repetition maximum (RM), 2 – 5 sets]. Repeated-sprint ability (5×6-s maximal cycle sprints), 3-RM leg press strength, and anthropometry were determined before and after each training programme. There was a greater improvement in repeated-sprint ability after training with 20-s rest intervals (12.5%) than after training with 80-s rest intervals (5.4%) (P = 0.030). In contrast, there were greater improvements in strength after training with 80-s rest intervals (45.9%) than after training with 20-s rest intervals (19.6%) (P = 0.010). There were no changes in anthropometry for either group following training. These results suggest that when training volume and load are matched, despite a smaller increase in strength, 5 weeks of training with short rest periods results in greater improvements in repeated-sprint ability than the same training with long rest periods.     

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

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.     

Factors associated with physical activity referral completion and health outcomes

Abstract

Participant socio-demographic characteristics and referral reason were investigated in relation to completion and health outcomes in a Primary Care Physical Activity Referral Scheme using a prospective population-based longitudinal design. Participants (n = 1735) were recruited over a 2-year period. A three-stage binary logistic regression analysis identified the factors associated with the outcomes of completion (model 1), body mass reduction (model 2) and blood pressure reduction (model 3). Participant's age, gender, ethnicity, occupation and referral reason were the independent variables for model 1, with the variables of completion added in model 2 and completion and body mass reduction added in model 3. Logistic regression analysis revealed that increasing age is associated with the likelihood of completion (Odds Ratio, OR = 1.019; Confidence Interval, CI = 1.008–1.030; P = 0.001). Participants with a pulmonary condition are less likely to complete (OR = 0.546; CI = 0.346–0.860; P < 0.01) compared to those referred for cardiovascular conditions. For ethnicity, in comparison to the white category, patients in the mixed category are significantly more likely to achieve a reduction in body mass (OR = 3.991; CI = 1.191–13.373; P < 0.05). Those who complete are more likely to achieve a reduction in body mass (OR = 3.541; CI = 2.721–4.608; P < 0.001). When compared to the unemployed category, the skilled manual category had an increased likelihood of achieving a reduction in blood pressure (OR = 1.875; CI = 1.044–3.227; P < 0.05). Participants who completed also demonstrated an increased likelihood of a reduction in blood pressure (OR = 1.680; CI = 1.250–2.003; P < 0.001). Furthermore, those participants who achieved a reduction in body mass had an increased likelihood of achieving a reduction in blood pressure (OR = 1.292; CI = 1.008–1.641; P < 0.05). Completion is associated with health outcomes of reduced body mass and blood pressure.     

The influence of 2 weeks of low-volume high-intensity interval training on health outcomes in adolescent boys

Abstract

The present study aimed to establish whether 2 weeks of high-intensity interval training would have a beneficial effect on aerobic fitness, fat oxidation, blood pressure and body mass index (BMI) in healthy adolescent boys. Ten adolescent boys (15.1 ± 0.3 years, 1.3 ± 0.2 years post-estimated peak height velocity) completed six sessions of Wingate-style high-intensity interval training over a 2-week period. The first session consisted of four sprints with training progressed to seven sprints in the final session. High-intensity interval training had a beneficial effect on maximal O₂ uptake (mean change, ±90% confidence intervals: 0.19 L · min^?1, ±0.19, respectively), on the O₂ uptake at the gas exchange threshold (0.09 L · min^?1, ±0.13) and on the O₂ cost of sub-maximal exercise (–0.04 L · min^?1, ±0.04). A beneficial effect on the contribution of lipid (0.06 g · min^?1, ±0.06) and carbohydrate (–0.23 g · min^?1, ±0.14) oxidation was observed during sub-maximal exercise, but not for the maximal rate of fat oxidation (0.04 g · min^?1, ±0.08). Systolic blood pressure (1 mmHg, ±4) and BMI (0.1 kg · m², ±0.1) were not altered following training. These data demonstrate that meaningful changes in health outcomes are possible in healthy adolescent boys after just six sessions of high-intensity interval training over a 2-week period.     

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

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.