Physiological comparison of intensity-controlled,isocaloric intermittent and continuous exercise†

VO2 fluctuations are argued to be an important mechanism underpinning chronic adaptations following interval training. We compared the effect of exercise modality, continuous vs. intermittent realized at a same intensity, on electrical muscular activity, muscular oxygenation and on whole body oxygen uptake. Twelve participants (24?±?5 years; VO2peak: 43?±?6?mL·?min^?1·kg^?1) performed (i) an incremental test to exhaustion to determine peak work rate (WR_peak); two randomized isocaloric exercises at 70%WRpeak; (ii) 1 bout of 30 min; (iii) 30 bouts of 1?min work intercepted with 1?min passive recovery. For electromyography, only the CON exercise showed change for the vastus lateralis root-mean-square (+6.4?±?5.1%, P?P?vs. 2.32?±?1.21?mM, respectively, for the CON and INT, P?vs. 356?±?301?sec, respectively, for the CON and INT, P?相似文献   

Better Economy on Indoor Track Compared to Treadmill Running With 1% Inclination

ABSTRACT

Purpose: The purpose of this study was to investigate the differences in metabolic responses between the track and the treadmill (1% inclination) running. The latter is recommended for use in laboratory settings to mimic outdoor running. Method: Seventeen male endurance athletes (mean 25.8, s = 3.8 years) performed 4-min running bouts on an indoor track and the treadmill. Results: At all speeds (11, 13, and 15 km·h^?1) athletes showed better economy on the track running compared to the treadmill expressed as oxygen (7.9%, 5.2%, and 2.8%) and caloric (7.0%, 5.3%, and 2.6%) unit cost. Rating of perceived exertion was evaluated substantially higher at all speeds on the treadmill (F(1,16) = 31.45, p < .001, η²_p = .663) compared to running on the track. Participants presented lower heart rate (F(1,16) = 13.74, p = .002, η²_p = .462) on the track at the speed of 11 and 13 km·h^?1 compared to the treadmill, but not at 15 km·h^?1 (p = .021). Conclusions: We conclude that constant inclination (i.e.. 1%) during the treadmill test might not be suitable to reproduce comparable effort to running on the track; rather, there is an optimal treadmill inclination for different intensities to reproduce similar effort compared to the track running.     

Hydration kinetics and 10-km outdoor running performance following 75% versus 150% between bout fluid replacement

Abstract

Current American College of Sports Medicine (ACSM) guidelines recommend replacing 150% of sweat losses between training bouts separated by ≤12 hours, but little evidence exists concerning the implications of this strategy for runners. Participants (n = 13) in this study replaced 75% (1637 ± 372 mL) or 150% (3099 ± 850 mL) of sweat losses following an outdoor evening run (～75 minutes; Wet-bulb-globe temperature (WBGT) = ～27°C) and consumed a standardised evening meal and breakfast before completing an outdoor (WBGT = ～23°C) 10-km time-trial the following morning. Urine was collected between runs and urine specific gravity (USG) was assessed pre-run. Significant differences were found in pre-run body mass (75% = 69.6 ± 9.2; 150% = 70.1 ± 9.3 kg; P = 0.02) and USG (75% = 1.026 ± 0.005; 150% = 1.014 ± 0.007; P < 0.001). Heart rate during 10-km run (168 ± 14 versus 168 ± 12 beats min^?1) and post-run intestinal temperature (39.08 ± 0.52 versus 39.00 ± 0.70 °C) did not differ for 75% and 150%, respectively, despite an ～3% performance improvement (75% = 47.28 ± 6.64; 150% = 45.93 ± 6.04 minutes; P = 0.001) due to a faster pace in the second half of the run with 150% replacement. Session rate of perceived exertion (RPE) was lower (P = 0.02) during 150% (7.5 ± 1.3) versus 75% (8.4 ± 0.9). Reluctant drinkers potentially hinder training quality between evening and morning runs in the heat, but copious urine production and difficulty in consuming recommended fluid volumes suggest fluid replacement <150% may be more ideal.     

肌组织对耐力性运动适应能力的生理学分析

在耐力性运动中,有氧代谢是机体能量供应的1种主要方式,肌组织对有氧训练的适应能力是通过训练中肌肉的主动性运动而获取的。这些适应能力依靠运动训练的持续性而存在或发展;随运动训练的停止而减弱或消退。本文就肌纤维的类型、线粒体的含量、毛细血管的分布、血流量等方面分析了耐力性运动中肌组织在有氧代谢过程中所产生的适应性变化的机制以及运动强度和持续时间等外界因素对这种生理变化过程的影响。     

The effect of cold ambient temperatures on climbing-specific finger flexor performance

Different ambient temperatures are known to affect muscular performance based on the type of contraction. The effect of cold (10°C) and thermoneutral (TN) (24°C) ambient temperatures on finger flexor performance was examined in 12 rock climbers. After 30?min of seated rest in the designated temperature condition, participants completed maximal voluntary contractions (MVC) on a climbing-specific finger flexor assessment device equipped with a crimp grip hold. Participants then completed an intermittent fatiguing task until failure. The fatiguing task consisted of 10-s contractions at 40% MVC followed by a 3-s of rest. MVC recovery was assessed immediately, 5, 10, and 15?min post-task failure. Estimated muscle temperature and subjective thermal ratings were significantly lower throughout testing in the cold condition (P?<?.001). Finger flexor MVC strength was similar between conditions at baseline and throughout recovery. Time to task failure was significantly longer (364?±?135 vs. 251?±?97 s, P?=?.003) and force time integral was greater (53,715?±?19,988 vs. 40,243?±?15,360?Ns, P?=?.001) during the cold condition. No significant differences were found between conditions for force variability or electromyography (EMG) at the start and end of the fatiguing task. However, the rate of increase in EMG for the TN condition was significantly faster (P?=?.03). These results suggest important implications for researchers when examining climbing performance, especially in outdoor settings where temperatures may vary from day to day. Inconsistencies in testing temperatures might significantly affect muscular endurance.     

The influence of hip mobility and quadriceps fatigue on sagittal spinal posture and muscle activation in rugby scrum performance

Rugby Union scrumming puts the spine under a high degree of loading. The aim of the current study was to determine how sagittal hip range of motion and quadriceps fatigue influence force output, spinal posture, and activation of the trunk and quadriceps muscles in rugby scrumming. Measures of sagittal hip flexion/extension range of motion were collected from 16 male varsity and club first XV level participants. Sagittal spine motion (electromagnetic motion capture), trunk and quadriceps activation (electromyography), and applied horizontal compressive force (force plate) were measured during individual machine scrumming. Participants performed a 5-trial scrum block involving 5?s of contact with 1–2?min recovery between each trial. They then performed a fatiguing protocol (wall sit to failure) and immediately returned to the scrum machine to perform another five trials. Though there was no significant influence of fatigue on the horizontal compressive force applied during contact (P?=?.83), there was a 52% increase in cervical flexion (P?P?P?相似文献   

Glucose–fructose ingestion and exercise performance: The gastrointestinal tract and beyond

Carbohydrate ingestion can improve endurance exercise performance. In the past two decades, research has repeatedly reported the performance benefits of formulations comprising both glucose and fructose (GLUFRU) over those based on glucose (GLU). This has been usually related to additive effects of these two monosaccharides on the gastrointestinal tract whereby intestinal carbohydrate absorption is enhanced and discomfort limited. This is only a partial explanation, since glucose and fructose are also metabolized through different pathways after being absorbed from the gut. In contrast to glucose that is readily used by every body cell type, fructose is specifically targeted to the liver where it is mainly converted into glucose and lactate. The ingestion of GLUFRU may thereby profoundly alter hepatic function ultimately raising both glucose and lactate fluxes. During exercise, this particular profile of circulating carbohydrate may induce a spectrum of effects on muscle metabolism possibly resulting in an improved performance. Compared to GLU alone, GLUFRU ingestion could also induce several non-metabolic effects which are so far largely unexplored. Through its metabolite lactate, fructose may act on central fatigue and/or alter metabolic regulation. Future research could further define the effects of GLUFRU over other exercise modalities and different athletic populations, using several of the hypotheses discussed in this review.     

Circulatory effects of fluid loss and fluid intake during exercise

Abstract

Cardiorespiratory responses to two levels of exercise (133 and 200 W) on a bicycle ergometer were measured in nine subjects before and after a 1‐h outdoor run of 12.8 km completed in ambient temperatures of 20–25° C. After the run, the subjects showed a mean weight loss of 1.49 kg; the laboratory exercises produced higher mean levels of O2 consumption than before the run (1.91 and 2.66 1 min‐1 compared with 1.80 and 2.46 1 min‐1) and higher mean heart rates (141 and 158 beats min‐1 compared with 115 and 140 beats min‐1); and lower levels of stroke volume (83 and 85 ml compared with 109 and 101 ml) and of cardiac output (11.6 and 13.3 1 min‐1 compared with 12.6 and 14.1 1 min‐1). Five subjects were studied in a similar way on a second occasion when they consumed 1.25 1 of a dextrose‐electrolyte solution during the first 45 min of the outdoor run. Differences in the exercise variables measured before and after the outdoor run were now small or insignificant. It is postulated that in the first study uncompensated loss of body water reduced plasma volume and cardiac filling, thus reducing stroke volume and cardiac output. Such changes jeopardize body temperature regulation during exercise.     

口服支链氨基酸对小鼠耐力的影响

实验组小鼠每天额外供给支链氨基酸２５ｍｇ,对照组每天额外供给葡萄２５ｍｇ。４天后发现,运动后试验组和对照组血清乳酸水平分别为２．７５ｍｍｏＬ／Ｌ和３．８９ｍｍｏＬ／Ｌ,差异非常显著,Ｐ＜０．０１。力竭运动试验游泳时间延长,乳酸水平下降,表明支链氨基酸可增强实验动物的运动能力,延缓运动性疲劳的出现。     

略谈运动性疲劳的成因

运动性疲劳是由于机体本身所引起的,是由于肌肉活动达到一定程度,身体所表现出的必然现象。近年来,国内外学者对运动性疲劳产生的原因做了大量的研究。本文采用文献资料和面访等方法对国内外学者有关运动性疲劳产生机制的学说进行分析,旨在提高对运动性疲劳的认识,以便科学有效地指导运动训练。     

旱莲草提取物抗疲劳作用研究

目的:研究旱莲草提取物的抗疲劳作用;方法:给药组以8 g·kg-1·d-1旱莲草煎液灌胃给药,1次/d.测定小鼠血清SOD、LA、LDH,血红蛋白,血糖和肝、肌糖原等指标.结果:旱莲草提取物使小鼠血清SOD和LDH的活性和Hb和肝、肌糖原含量升高,LA含量降低;结论:旱莲草提取物具有抗疲劳作用而提高机体的运动能力,可作为抗疲劳功能食品进行开发和研究.     

运动重塑大脑海马:来自神经科学的研究证据与发展展望

运动可以重塑大脑海马的结构与功能,改善情绪、增强记忆,对促进个体心理健康及成功老化具有重要意义。从动物学视角看,运动重塑海马结构主要包括运动促进海马神经发生和运动对海马神经元凋亡的双重影响两方面;运动重塑海马功能则集中在运动可以调节海马突触长时程增强效应方面。从人类影像学视角切入,运动重塑海马结构聚焦于运动对海马体积的影响;运动重塑海马功能则涉及运动影响海马激活水平、血流灌注水平及海马与其他脑区的功能连接三个方面。不同运动形式、不同运动剂量对海马作用效果存在差异,其机制涉及脑可塑性假说、脑源性神经营养因子假说和神经递质假说。未来研究可进一步关注海马可塑性与早期应激事件、儿童青少年学习与教育、情绪健康、老年期认知功能以及临床康复领域的关联。研究路径与布局需继续优化实验设计、革新研究技术手段、推进多学科交叉融合,从人毕生发展的角度深入探索运动促进海马健康的认知神经机制,开发运动干预海马相关神经系统疾病的运动处方,从而推进健康关口前移,发挥运动是良医的功效。     

蛋白质组学及其技术在运动人体科学中的研究

蛋白质组学是继基因组学后的重要研究方向之一,它对于分析样本间差异蛋白图谱,揭示运动训练对机体的内在影响,寻找有意义的蛋白标志物有重要作用。对蛋白质组学数据来源、主要技术及其在运动人体科学中的应用研究进行了综述,以期进一步促进蛋白质组学研究在体育科学中的发展。     

不适当运动致心脏损害1例

报告一男运动员不适当运动致心脏损害。心电图显示心律失常 ,经停训及药物治疗 ,离队2年后复查仍有频发性室性早搏。     

辅酶NADH对运动疲劳小鼠心肌细胞损伤的保护作用

目的:探讨辅酶还原型烟酰胺腺嘌呤二核苷酸(reduced nicotinamide adenine dinucleotide,NADH)对运动疲劳所致小鼠心肌细胞损伤的保护作用及机制.方法:选取32只雄性昆明小鼠,随机分成4组:对照组、运动疲劳组、NADH正常对照处理组和运动疲劳NADH预处理组.采用反复力竭递增负荷跑台运动建立小鼠运动疲劳模型;分组处理后测定心肌组织超氧化物岐化酶(SOD)活性和丙二醛(MDA)含量;Rodamine123荧光染色后流式细胞仪检测细胞内线粒体膜电位的变化;Annexin Ⅴ/PI双染流式细胞仪检测细胞凋亡率和坏死率.结果:NADH预处理组心肌组织超氧化物岐化酶(SOD)活性和丙二醛(MDA)含量较运动损伤组明显改善,细胞内线粒体膜电位增高,细胞凋亡率和坏死率降低.结论:NADH可减少运动疲劳所致氧化应激引起的心肌细胞损伤,可通过提高细胞线粒体功能起到保护的作用.