The effects of work:rest duration on physiological and perceptual responses during intermittent exercise and performance

Abstract

In this study, we examined the effects of different work:rest durations during 20 min intermittent treadmill running and subsequent performance. Nine males (mean age 25.8 years, s = 6.8; body mass 73.9 kg, s = 8.8; stature 1.75 m, s = 0.05; [Vdot]O_2max 55.5 ml · kg^?1 · min^?1, s = 5.8) undertook repeated sprints at 120% of the speed at which [Vdot]O_2max was attained interspersed with passive recovery. The work:rest ratio was constant (1:1.5) with trials involving either short (6:9 s) or long (24:36 s) work:rest exercise protocols (total exercise time 8 min). Each trial was followed by a performance run to volitional exhaustion at the same running speed. Testing order was randomized and counterbalanced. Heart rate, oxygen consumption, respiratory exchange ratio, and blood glucose were similar between trials (P > 0.05). Blood lactate concentration was greater during the long than the short exercise protocol (P < 0.05), whereas blood pH was lower during the long than the short exercise protocol (7.28, s = 0.11 and 7.30, s = 0.03 at 20 min, respectively; P < 0.05). Perceptions of effort were greater throughout exercise for the long than the short exercise protocol (16.6, s = 1.4 and 15.1, s = 1.6 at 20 min, respectively; P < 0.05) and correlated with blood lactate (r = 0.43) and bicarbonate concentrations (r = ?0.59; P < 0.05). Although blood lactate concentration at 20 min was related to performance time (r = ?0.56; P < 0.05), no differences were observed between trials for time to exhaustion (short exercise protocol: 95.8 s, s = 30.0; long exercise protocol: 92.0 s, s = 37.1) or physiological responses at exhaustion (P > 0.05). Our results demonstrate that 20 min of intermittent exercise involving a long work:rest duration elicits greater metabolic and perceptual strain than intermittent exercise undertaken with a short work:rest duration but does not affect subsequent run time to exhaustion.     

The Reliability of the [Vdot]O2-HR Relation during Graded Treadmill Exercise in Prepubertal Boys and Adult Men

Abstract

When subjects make simultaneous aiming movements of the upper limbs over different distances, assimilation effects are shown; the shorter distance limb overshoots when paired with a longer distance limb. However, it is not known whether assimilation effects are due to variations in distance per se or to variations in target location. To separate the possible influences of distance and location, 60 subjects made rapid bimanual aiming movements in one of four conditions. The two different-distance groups made a 20° movement in the left hand and a 60° movement in the right hand to either the same or different target locations. The comparison groups moved 20° in each limb. Somewhat surprisingly, spatial assimilations were greater when moving different distances to the same, rather than different, target locations, which suggests interlimb differences in distance mediate assimilation effects rather than target location. Temporal assimilations were greater when distance and location were varied, but the assimilations were not related to interlimb differences in velocity, as predicted by Marteniuk and MacKenzie (1980).     

Rain influences the physiological and metabolic responses to exercise in hot conditions

Outdoor exercise often proceeds in rainy conditions. However, the cooling effects of rain on human physiological responses have not been systematically studied in hot conditions. The present study determined physiological and metabolic responses using a climatic chamber that can precisely simulate hot, rainy conditions. Eleven healthy men ran on a treadmill at an intensity of 70% VO_2max for 30 min in the climatic chamber at an ambient temperature of 33°C in the presence (RAIN) or absence (CON) of 30 mm · h^?1 of precipitation and a headwind equal to the running velocity of 3.15 ± 0.19 m · s^?1. Oesophageal temperature, mean skin temperature, heart rate, rating of perceived exertion, blood parameters, volume of expired air and sweat loss were measured. Oesophageal and mean skin temperatures were significantly lower from 5 to 30 min, and heart rate was significantly lower from 20 to 30 min in RAIN than in CON (P < 0.05 for all). Plasma lactate and epinephrine concentrations (30 min) and sweat loss were significantly lower (P < 0.05) in RAIN compared with CON. Rain appears to influence physiological and metabolic responses to exercise in heat such that heat-induced strain might be reduced.     

广东省优秀女子跆拳道运动员实战的心率与血乳酸变化研究

为研究跆拳道实战对优秀女子跆拳道运动员机体能量代谢特点的影响,以8名参加与越南队实战的广东省优秀女子跆拳道运动员为研究对象,在实战前、实战中、实战后对心率和血乳酸进行测定,结果显示:实战、实战后的心率和血乳酸均明显高于实战前(p＜0.01),实战后3min的心率明显低于第3回合(p＜0.01),实战后3min的血乳酸低于第3回合即刻,不存在显著差异(p＞0.05),实战后3min、5min的心率和乳酸均不存在显著差异性(p＞0.05).提示跆拳道项目比赛强度大,无氧代谢能力对跆拳道项目起着重要作用;体能训练时,应该注重高强度的无氧训练以及高、低强度交替的间歇性有氧训练.     

Physiological intensity profile,exercise load and performance predictors of a 65-km mountain ultra-marathon

The aims of the study were to describe the physiological profile of a 65-km (4000-m cumulative elevation gain) running mountain ultra-marathon (MUM) and to identify predictors of MUM performance. Twenty-three amateur trail-runners performed anthropometric evaluations and an uphill graded exercise test (GXT) for VO_2max, ventilatory thresholds (VTs), power outputs (PMax, PVTs) and heart rate response (HRmax, HR@VTs). Heart rate (HR) was monitored during the race and intensity was expressed as: Zone I (VT2) for exercise load calculation (training impulse, TRIMP). Mean race intensity was 77.1%±4.4% of HRmax distributed as: 85.7%±19.4% Zone I, 13.9%±18.6% Zone II, 0.4%±0.9% Zone III. Exercise load was 766±110 TRIMP units. Race time (11.8±1.6h) was negatively correlated with VO_2max (r = ?0.66, P <0.001) and PMax (r = ?0.73, P <0.001), resulting these variables determinant in predicting MUM performance, whereas exercise thresholds did not improve performance prediction. Laboratory variables explained only 59% of race time variance, underlining the multi-factorial character of MUM performance. Our results support the idea that VT1 represents a boundary of tolerable intensity in this kind of events, where exercise load is extremely high. This information can be helpful in identifying optimal pacing strategies to complete such extremely demanding MUMs.     

低温环境下不同强度运动对糖脂代谢相关激素的影响

目的:研究低温环境下不同强度运动对糖脂代谢相关激素变化的影响,旨在为冰上项目运动者的训练监控提供一定的指导意义。方法:选取10名北京体育大学田径专项男生为研究对象,在室内温度为12℃的条件下静息、65%VO_2max和80%VO_2max强度跑台各运动20min,每次运动前后均采集血液进行相关指标的测试,每两次测试时间间隔不少于1周。结果:与静息前相比,静息20 min后血清胰岛素(Ins)水平、胰高血糖素(PG)水平、Ins/PG均有显著降低,脂联素(ADPN)水平显著升高;与65%VO_2max强度运动前相比,运动后PG水平显著降低;与80%VO2max强度运动前相比,运动后Ins水平、Ins/PG比值显著降低,PG水平显著升高。与静息后相比,65%VO_2max强度运动后血清去甲肾上腺素(NE)、PG、瘦素(LP)水平显著降低,Ins/PG、多巴胺(DA)水平显著升高,80%VO_2max强度运动后血清NE、LP水平显著降低,DA水平显著升高;与65%VO_2max强度运动后相比,80%VO2max强度运动后血清肾上腺素(Ad)、NE水平显著上升,DA、Ins、LP水平显著降低。结论:低温环境可使Ins和Ins/PG下降,ADPN升高,且以中等强度运动后血清FFA显著升高,建议在低温环境下以中等强度运动更有利于脂肪的分解。     

The Physiologic Response of Exercising in the Water and on Land with and without the X1000 Walk 'N Tone Exercise Belt

Abstract

Study of the physiological effects of exercise that decreases lower joint impact is needed. Participants (N = 18) were exposed to either land or water exercise that included or did not include wearing a belt. Physiological variables of caloric expenditure, net oxygen cost, net oxygen pulse, and heart rate were assessed A 2 × 2 (Environment × Belt) analysis of variance (ANOVA) revealed a significant environment main effect for net oxygen cost and caloric expenditure. Water actually decreased the energy cost of the exercise. A 2 × 2 × 4 (Environment x Belt x Time) ANOVA revealed a significant environment main effect for net oxygen cost and caloric expenditure. Specifically, land heart rates increased over time, whereas water heart rates did not.     

不同间歇期短距离快速跑的生理生化负荷强度评价研究

目的：选择我国16～17岁的少年足球运动员作为研究对象，观察心率和血乳酸在短距离快速跑训练中的变化，并对训练的质量和效果进行评价研究，旨在进一步揭示特定年龄段的运动员生理、生化负荷强度水平，并提出适宜的负荷强度安排。方法：测定跑动过程中不同时相段的时间；对不同间歇期心率进行现场采集；测定运动前、运动过程中和恢复阶段的血乳酸。采用SPSS统计软件包进行数据处理。内容：测定运动员30mxl5次跑(两种不同间歇，30s和60s)，比较跑动时间及相关的生理生化指标变化。结论：足球运动员宜在较短的间歇中具备不断的快速冲刺跑能力，30mR30s的练习方式能够体现这一特点，但须在跑的次数安排上做出适当调整。     

Relative Endurance and Physiological Responses: A Study of Individual Differences in Prepubescent Boys and Adult Men

Abstract

The reliability of individual differences in relative endurance performance and physiological response was studied in prepubescent boys (N = 21) and adult men (N = 21). Subjects were tested twice (test and retest) on a relative endurance test consisting of pedalling a bicycle ergometer for 8 minutes duration at a high initial work-rate. The work-rate averaged 103% ± 1.0% VO₂ max (mean ± S.E.) for the children and 105% ± 1.1% VO₂ max for the adults, p > .05. Except for minute 3, children and adults had similar patterns for consistency of relative endurance performance (RPM). However, in comparison to adults, children had smaller individual difference variation for both VO₂ and HR (p > .05). On the average, children had a greater proportion of total variability in VO₂ (34% vs. 17%) and HR (49% vs. 13%) due to intra-individual variability in comparison to true individual differences. Children-adult differences were attributed to maturity differences.     

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。     

Physiological and metabolic responses of wheelchair athletes in different racing classes to prolonged exercise

The aims of this study were to examine and compare selected physiological and metabolic responses of wheelchair athletes in two paraplegic racing classes [T3: n?=?8 (lesion levels T1–T7; paraplegics); T4: n?=?9 (lesion levels below T7; paraplegics)] to prolonged exercise. In addition, we describe the responses of three tetraplegic athletes [T2: n?=?3 (lesion levels C6/C7: tetraplegics)]. Twenty athletes completed 90?min of exercise at 75% [Vdot]O_2peak on a motorized treadmill adapted for wheelchairs. The mean (±s) heart rates of the T3 and T4 racing classes were 165±2 and 172±6 beats?·?min^?1, respectively. For the T4 racing class, heart rate gradually increased during the test (P?<0.05), whereas for the T3 racing class, heart rate reached a plateau after an initial increase. The mean heart rate of the tetraplegics was 114±3 beats?·?min^?1. The T3 and T4 classes exhibited similar respiratory exchange ratios, plasma lactate and glucose concentrations throughout the test. For both the T3 and T4 racing class, free fatty acid, glycerol, ammonia, urea and potassium concentrations had increased from resting values by the end of the test (P?<0.05). In conclusion, the results of this study suggest that endurance-trained wheelchair athletes are able to maintain velocities equivalent to the same relative exercise intensity (75% [Vdot]O_2peak) for prolonged periods irrespective of lesion level.     

Comparing the effects of low and high load resistance exercise to failure on adaptive responses to resistance exercise in young women

The aim of this study was to compare the effect of 6 weeks of resistance training to volitional failure at low (30% 1 repetition maximum (RM)) or high (80%1RM) loads on gains in muscle size and strength in young women. Thirteen women (age: 29.7 ± 4.7years; height 166.7 ± 6.4cm; weight 64.2 ± 12.2kg) completed 2 training sessions per week for 6 weeks and muscle strength (1RM), muscle thickness (ultrasound) were measured before and after training. Training comprised 1 set to volitional failure of unilateral leg extensions and bicep curls with each limb randomly assigned to train at either 80% 1RM or 30% 1RM. Increases in muscle thickness [arms: 6.81 ± 3.15% (30% 1RM), 5.90 ± 3.13% (80% 1RM) and legs: 9.37 ± 5.61% (30% 1RM), 9.13 ± 7.9% (80% 1RM)] and strength [arms: 15.4 ± 12.2% (30% 1RM), 18.26 ± 12.2% (80% 1RM) and legs: 25.30 ± 18.4 (30% 1RM), 27.20 ± 14.5 (80% 1RM)] were not different between loads. When resistance exercise is performed to volitional failure gains in muscle size and strength are independent of load in young women.     

Validity and reliability of rating perceived exertion in women with fibromyalgia: exertion-pain discrimination

The present study aimed (1) to assess the validity and reliability of the Borg category-ratio (CR-10) scale for monitoring exercise intensity in women with fibromyalgia (FM) and (2) to examine whether women with FM can discriminate between perceived exertion and exercise-induced pain. Thirty-three women with FM performed two incremental treadmill tests (1 week separated). Heart rate, oxygen uptake, minute ventilation and respiratory quotient were measured. The ratings of perceived exertion (RPE: CR-10 scale) and exercise-induced pain were obtained at each workload. The Spearman’s correlation of RPE with the physiological responses ranged from 0.69 to 0.79. The regression models explained ~50% of the variability of the studied physiological responses. We found “perfect acceptable” agreement in 69% of the observations. Weighted Kappa was 0.66 (95% confidence interval [CI]: 0.59–0.72). There were differences between RPE and pain at workloads 3 (1.50; 95%CI: 0.85–2.16), 4 (2.10; 95%CI: 1.23–2.96), 5 (3.40; 95%CI: 1.29–5.51) and 6 (3.97; 95%CI: 1.61–6.33). The main findings of the present study suggest that the Borg CR-10 scale is valid and moderately reliable for monitoring exercise intensity in women with FM, and these patients were able to discriminate between exertion and exercise-induced pain.     

The Dual-Mode Theory of affective responses to exercise in metatheoretical context: I. Initial impetus,basic postulates,and philosophical framework

The exercise psychology literature is replete with assertions that ‘exercise makes people feel better’. However, this appears to be inconsistent with the high prevalence of physical inactivity and drop-out rates. Recent empirical findings, based on a new methodological platform, have demonstrated that the exercise-affect relationship is complex, exhibiting both a dose-response pattern and substantial inter-individual variability. The Dual-Mode Theory was developed to (a) bridge mind-focused and body-focused approaches for explaining the exercise-affect relationship, (b) provide a fit to extant data by accounting for patterns of dose-response and inter-individual variability, and (c) be consistent with information from exercise physiology and emerging evidence on the neural basis of affect. Investigations based on the Dual-Mode Theory could inform the ongoing debate on the role of somatic influences in generating affective responses and guide interventions designed to improve the affective responses of exercisers. A selective review of phenomenological accounts that served as the philosophical basis of the theory supports the thesis that affect has a dual basis, being driven by cognition in many circumstances but by direct somatic cues when homeostasis is challenged.     

The effects of substrate and fluid provision on thermoregulatory and metabolic responses to prolonged exercise in a hot environment

A high ambient temperature reduces the capacity to perform prolonged exercise. Total carbohydrate oxidation is less, and thus glycogen depletion is not limiting. Fluid ingestion in the heat should, therefore, focus on maintenance of hydration status rather than on substrate provision. Six healthy males cycled to exhaustion at 60% of maximum oxygen consumption (VO 2max ) with no drink, ingestion of a 15% carbohydrate-electrolyte drink (1.45 - 0.29 litres) or ingestion of a 2% carbohydrate-electrolyte drink (3.12 - 0.47 litres). The ambient temperature was 30.2 - 0.6°C (mean - s ), with a relative humidity of 71 - 1% and an air speed of approximately 0.7 m.s -1 on all trials. Weighted mean skin temperature, rectal temperature and heart rate were recorded and venous samples drawn for determination of plasma volume changes, blood metabolites, serum electrolytes and osmolality. Expired gas was collected to estimate rates of fuel oxidation. Exercise capacity was significantly ( P ? 0.05) different in all trials. The median (range) time to exhaustion was 70.9 min (39.4-97.4 min) in the no-drink trial, 84.0 min (62.7-145 min) in the 15% carbohydrate trial and 118 min (82.6-168 min) in the 2% carbohydrate trial. The 15% carbohydrate drink resulted in significantly ( P ? 0.05) elevated blood glucose and total carbohydrate oxidation compared with the no-drink trial. The 2% carbohydrate drink restored plasma volume to pre-exercise values by the end of exercise. No differences were observed in other thermoregulatory or cardiorespiratory responses between trials. These results suggest that fluid replacement with a large volume of a dilute carbohydrate drink is beneficial during exercise in the heat, but the precise mechanisms for the improved exercise capacity are unclear.     

Effects of strengthening and stretching exercise programmes on kinematics and kinetics of running in older adults: a randomised controlled trial

The aim of this study was to investigate the effects of strengthening and stretching exercises on running kinematics and kinetics in older runners. One hundred and five runners (55–75 years) were randomly assigned to either a strengthening (n = 36), flexibility (n = 34) or control (n = 35) group. Running kinematics and kinetics were obtained using an eight-camera system and an instrumented treadmill before and after the eight-week exercise protocol. Measures of strength and flexibility were also obtained using a dynamometer and inclinometer/goniometer. A time effect was observed for the excursion angles of the ankle sagittal (P = 0.004, d = 0.17) and thorax/pelvis transverse (P < 0.001, d = 0.20) plane. Similarly, a time effect was observed for knee transverse plane impulse (P = 0.013, d = 0.26) and ground reaction force propulsion (P = 0.042, d = ?0.15). A time effect for hip adduction (P = 0.006, d = 0.69), ankle dorsiflexion (P = 0.002, d = 0.47) and hip internal rotation (P = 0.048, d = 0.30) flexibility, and hip extensor (P = 0.001, d = ?0.48) and ankle plantar flexor (P = 0.01, d = 0.39) strength were also observed. However, these changes were irrespective of exercise group. The results of the present study indicate that an eight-week stretching or strengthening protocol, compared to controls, was not effective in altering age-related running biomechanics despite changes in ankle and trunk kinematics, knee kinetics and ground reaction forces along with alterations in muscle strength and flexibility were observed over time.     

Effect of body composition on redox homeostasis at rest and in response to exercise: The case of underfat women

Underfat individuals have been neglected as a malnourished population in terms of redox homeostasis. The aim of the present study was to evaluate the effect of body composition on redox homeostasis at rest and in response to exercise. Underfat, lean and overfat women, classified according to their BMI and body fat percentage, participated in the study and were subjected to an acute session of eccentric exercise. With regard to muscle function and damage, a significant group × time interaction was found for range of motion (P < .01), isometric peak torque at 90° (P < .01), delayed onset muscle soreness (P < .01) and creatine kinase (P < .05), with the lean group generally exhibiting faster recovery compared to the underfat and overfat groups. With regard to redox homeostasis, a significant group × time interaction was found for F₂-isoprostanes, protein carbonyls and glutathione (P < .01 for all biomarkers), with the underfat and overfat groups exhibiting increased resting oxidative stress levels and lower exercise-induced reactive species production . In conclusively, our data underline the importance of normal body composition for redox homeostasis, since underfat and overfat women demonstrate a similar pattern of redox disturbances both at rest and in response to exercise.