血液氧自由基、血乳酸、主观用力感觉、心率与运动强度相关性的研究

为探索抗氧化运动强度与监控指标的确定,采用CR2000RC氧自由基生化分析仪、LT 1710血乳酸测定仪、Borg(15、10)主观用力感觉等级量表、心率监测系统对受试者(n=9)从事300、600、900、1200、1500KPM/min不同强度踏车(Monark839E)运动(每级负荷运动5min)时血液氧自由基、血乳酸、主观用力感觉、心率的变化进行测定,并对其进行了相关性分析。结果表明:心率、RPE(15、10)与运动强度(KPM/min)之间呈现高度线性相关,r=0 959、0 923、0 918;血液氧自由基浓度与运动强度、心率、RPE之间的相关性较低,但其变化趋势类似于血乳酸的变化,低强度时(≤900KPM/min)虽运动强度增加但血液氧自由基浓度保持不变,当运动强度超过900KPM/min时,血液氧自由基浓度随运动强度增加而增加;RPE10与血乳酸之间的相关程度高于RPE15、心率、运动强度与血乳酸的相关程度。认为心率、RPE(15、10)可作为监控抗氧化运动强度的理想指标;血液氧自由基浓度不能作为运动强度的监控指标;从抗氧化运动角度而言,健身运动的强度应以血乳酸4mM、心率130beats/min、RPE15值11、RPE10值3左右为宜。     

Caffeine lowers perceptual response and increases power output during high-intensity cycling

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.     

Perceptual and cognitive responses during exercise: Relationships with metamotivational state and dominance

Abstract

In this study, we examined ratings of perceived exertion (RPE) and attentional focus during exercise in relation to telic and paratelic metamotivational dominance and state. Thirty regular exercisers (11 females, 19 males), of whom 10 were telic dominant (mean Paratelic Dominance Scale score=6.2±2.9), 10 paratelic dominant (mean PDS score=23.8±1.4), and 10 non-dominant (mean PDS score=15.4±0.7) completed two exercise trials. In the first trial, the participants completed a maximal ramped exercise test on a motorized treadmill to determine their gas exchange threshold (the speed at which determined exercise intensity of the subsequent trial). Throughout the second trial (a 30-min treadmill run), the participants reported their metamotivational state, RPE, and attentional focus (associative or dissociative) at 5-min intervals. Heart rate was recorded at 3, 8, 13, 18, 23, and 28 min and expired air was analysed for oxygen consumption (VO₂) between 1–3, 6–8, 11–13, 16–18, 21–23, and 26–28 min. There was no main effect of dominance or dominance×time interaction on any variables (P >0.05). Oxygen consumption did not differ between states but RPE was higher in the telic than paratelic state at 25 and 30 min (t ₂₈=2.87, P <0.05; t _26.77=3.88, P <0.05, respectively). Attentional focus was more associative in the telic than paratelic state at 20, 25, and 30 min (t ₂₈=? 3.73, P <0.05; t ₂₈=? 4.85, P <0.01; t ₂₈=? 5.15, P <0.05, respectively) and heart rate was higher at 23 min in the telic state (t ₂₇=3.40, P <0.05). During the latter stages of exercise, the telic metamotivational state, not dominance, was related to a more associative attentional focus and higher RPE. Our results support the use of reversal theory (Apter, 2001) to understand perceptual and cognitive responses during aerobic exercise, but an experimental design in which state is manipulated is needed to examine the effects of metamotivational dominance and state on perceptual and cognitive responses.     

Comparison of treadmill and over-ground Nordic walking

Abstract

The purpose of this study was to compare the physiological responses of Nordic walking on a specially designed treadmill and Nordic walking on a level over-ground surface. Thirteen participants completed three 1-h Nordic walking training sessions. Following the training sessions, each participant performed two 1600-m over-ground Nordic walking trials at a self-selected pace. Each participant then completed two 1600-m Nordic walking treadmill trials on a Hammer Nordic Walking XTR Treadmill®, at the mean walking speed of their two over-ground Nordic walking trials. Breath-by-breath analysis of oxygen uptake ([Vdot]O₂) and heart rate was performed during each trial. Caloric expenditure was calculated using the [Vdot]O₂. Rating of perceived exertion (RPE) was assessed at the end of each trial. We found no significant differences in physiological variables collected during the two over-ground Nordic walking trials or the two treadmill Nordic walking trials. Mean walking speed was 106.96±11.49 m · min^?1. Mean heart rate during treadmill walking (99±13 beats · min^?1) was 22% lower than that during the over-ground condition (126±17 beats · min^?1). Mean [Vdot]O₂ and mean caloric expenditure were also lower during treadmill walking (15.18±3.81 ml · min^?1 · kg^?1, 0.08±0.02 kcal · min^?1 · kg^?1) than over-ground walking (24.16±4.89 ml · min^?1 · kg^?1, 0.12±0.02 kcal · min^?1 · kg^?1). Analysis of variance demonstrated that all variables were significantly higher during over-ground Nordic walking (P<0.001). A Mann-Whitney U-test demonstrated that the RPE for over-ground Nordic walking was greater than that for treadmill Nordic walking (P=0.02). Thus over-ground Nordic walking created a greater physiological stress than treadmill Nordic walking performed at the same speed and distance. The reason for this difference may have been the relatively narrow walking and poling decks on the treadmill, which made it difficult for the participants to place their poles correctly and maintain a consistent walking pattern. This would decrease the contribution of the arm muscles to overall oxygen consumption. In conclusion, the Hammer Nordic Walking XTR Treadmill® does not replicate the physiological stress of over-ground Nordic walking. Increasing the width of the decks could eliminate the discrepancy.     

丙酮酸或丙酮酸-肉碱补充对定量负荷运动时脂肪动用和RPE的影响

本研究通过观察定量负待运动前后血液中自由脂肪酸、血糖和乳酸水平的变化及运动中RQ和RPE的变化，研究丙酮改补充对机体有氧运动时脂肪动用和主观感觉疲劳的影响及肉碱对此的作用，探讨丙酮酸—肉碱复合剂的应用价值。结果：与安慰剂组相比，2试验组的FFA水平较高；除定量负荷运动30mi时外，丙酮酸组在安静时，定量负荷运动15min时的RQ较低，复合剂组在各种条件下的RQ均较低，2试验组运动中RPE较低，均有显著性意义。结论：丙酮酸补充能促进有氧运动中脂肪的动员，但对有氧运动中脂肪利用的影响不大；复合剂能同时促进有氧运动中脂肪的动员和利用；丙酮酸和复合剂能改善有氧运动时的主观感觉疲劳状态；复合剂对体重控制有一定的应用价值。     

Systematic review of the acute and chronic effects of high-intensity interval training on executive function across the lifespan

ABSTRACT

Research regarding the effects of high-intensity interval training (HIIT) on executive function has grown exponentially in recent years. However, there has been no comprehensive review of the current state of literature. Therefore, the aim of this systematic review is to summarize previous research regarding the acute and chronic effects of HIIT on executive function across the lifespan and highlight future research directions. The results indicated that acute bouts of HIIT has a positive effect on inhibition in children/adolescents and adults, and further that chronic HIIT benefits inhibition and working memory in children. More research employing chronic interventions, focusing on middle-aged and older adults, and examining the effects on the working memory and cognitive flexibility domains of executive function are needed. Future research should also focus on a) the use of stronger research designs, b) the effects of HIIT dosage/modality, c) consideration of individual differences, d) possible underlying mechanisms, and e) examining the feasibility of translating HIIT to real-word settings.     

Repeated sprint ability in young basketball players: one vs. two changes of direction (Part 2)

The aim of this study was to compare the training effects based on repeated sprint ability (RSA) (with one change of direction) with an intensive repeated sprint ability (IRSA) (with two changes of direction) on jump performance and aerobic fitness. Eighteen male basketball players were assigned to repeated sprint ability and intensive repeated sprint ability training groups (RSAG and IRSAG). RSA, IRSA, squat jump (SJ), countermovement jump (CMJ) and Yo-Yo intermittent recovery level 1 test were assessed before and after four training weeks. The RSA and IRSA trainings consisted of three sets of six sprints (first two weeks) and eight sprints (second two weeks) with 4-min sets recovery and 20-s of sprints recovery. Four weeks of training led to an overall improvement in most of the measures of RSA, but little evidence of any differences between the two training modes. Jump performance was enhanced: CMJ of 7.5% (P < 0.0001) and 3.1% (P = 0.016) in IRSAG and RSAG respectively. While SJ improved of 5.3% (P = 0.003) for IRSAG and 3.4% (P = 0.095) for RSAG. Conversely the Yo-Yo distance increased 21% (P = 0.301) and 34% (P = 0.017) in IRSAG and RSAG respectively. Therefore, short-term repeated sprint training with one/two changes of direction promotes improvements in both RSA and IRSA respectively but the better increase on jump performance shown a few changes on sprint and endurance performances.     

大运动量训练时自由式摔跤运动员应激激素变化的探讨

观察了大运动量训练期8名自由式摔跤运动员应激激素、焦虑水平及主观强度感的变化。研究过程中,每周安排11次大运动量训练,共进行2次实验,每次3个取样点(运动前、即刻和次日晨)。结果显示,两次取样时期次日晨ACTH水平较运动后即刻明显降低;C水平在第二次取样运动后即刻水平和次日晨水平明显高于运动前的,并且该时期运动后即刻C水平也明显高于第一次取样时期运动后即刻水平;E水平在第二次取样运动后即刻水平明显高于第一次取样运动后即刻的,且次日晨该激素水平也明显高于第一次取样次日晨的;血浆β-END水平在第二次取样运动后即刻水平明显高于运动前,也高于第一次取样运动后即刻,第二次取样次日晨该激素水平均低于运动前和运动后即刻水平,同时低于第一次取样次日晨的;血清NE水平变化与β-END水平变化类似;而RPE等级和焦虑水平在两次测试中呈现出运动后即刻水平高于运动前和次日晨的趋势,但不明显;RPE等级与诸多应激激素之间存在着弱相关关系。这预示着,在运动员身体机能评定工作中欲采用简单易行的显示身体机能的外部指标来表现不易测到的内部变化还需努力。     

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.     

Senior men’s pacing profiles at the IAAF World Cross Country Championships

Abstract

The aim of this study was to describe pacing profiles used by senior men competing in the World Cross Country Championships. Lap times were collated for 1273 competitors across 10 races. Each individual’s lap times were expressed as a percentage of the eventual winner’s lap times, and athletes were grouped according to finishing position. Most athletes started the race by following the pace set by the leaders but slowed relative to the winner with each successive lap. The gold medallists were faster than the other medallists only after the final lap (P < 0.001). Most athletes who dropped out (61%) had completed the first lap within 105% of the winner’s lap time. The medallists used a strategy of running close to the front from an early stage, but did not separate themselves from other top 15 finishers until halfway, with the eventual medal positions decided even closer to the finish. Athletes finishing further down had positive pacing profiles relative to the winner, possibly because of early fatigue caused by a relatively quick first lap. Athletes should note that a patient approach during the early stages can benefit not only the mass field but also those who aim to win a medal.     

Blood flow restriction reduces time to muscular failure

Abstract

Exercise to failure results in similar muscle protein synthesis responses, independent of intensity. However, low-intensity exercise likely requires more repetitions and individuals with injuries may be incapable of sustaining the mechanical stress to reach failure. The aim of this study was to determine if knee wraps provide a stimulus to decrease time to failure. Twenty healthy individuals participated in a randomized crossover study consisting of three trials. The first trial was used to determine one-repetition maximum (1-RM) on leg extension. Participants were then assigned to a blood flow restriction or control group. After trial 2, participants crossed over to the opposite trial. Knee wraps were placed around the upper thigh of each leg during blood flow restriction. Leg extensions were completed at 30% 1-RM until failure. A rating of perceived exertion was taken after exercise and whole blood samples were taken before, after, and 3 min after exercise for the determination of lactate. Repetitions until failure and total work were significantly lower with practical blood flow restriction compared with the control trial. Metabolic stress as measured by whole blood lactate was higher immediately after muscular failure in the control compared with the blood flow restriction trial, but not so 3 min after exercise. There were no differences in ratings of perceived exertion. In conclusion, knee wraps provide a stimulus for blood flow restriction allowing failure to occur sooner with similar metabolic stress after reperfusion. However, similar perceptual responses despite the lower workload with blood flow restriction may limit its application to the highly motivated.     

短时间力竭运动血清生长激素水平与血糖和血乳酸浓度相关性研究

测定了男性大学生短时间力竭运动前后不同时刻血清GH、BG和LA的浓度。结果显示:短时间力竭运动后即刻BG浓度显著高于运动前安静值(P<0 01);运动后30min、运动后60min时BG浓度与安静值无显著性差异,运动后BG浓度呈恢复趋势;运动后即刻、运动后30min时血液LA水平显著高于运动前安静值(P<0 01),运动后60min时LA水平高于运动前安静值(P<0 05),呈恢复趋势;短时间力竭运动后血液LA浓度的变化与GH浓度的变化呈显著正相关(r=0 83,P<0 01)。研究认为,剧烈运动后血液LA水平与GH水平所表现出的相关性有可能是两者与运动强度的相关,安静时低BG所引起的GH分泌增多取决于中枢对BG代谢的利用性,而非血液BG水平。