The influence of sensory cues on the perception of exertion during exercise and central regulation of exercise performance.

The perception of effort during exercise and its relationship to fatigue is still not well understood. Although several scales have been developed to quantify exertion Borg's 15-point ratings of perceived exertion (RPE) scale has been adopted as a valid and reliable instrument for evaluating whole body exertion during exercise. However, Borg's category-ratio scale is useful in quantifying sensations of exertion related to those variables that rise exponentially with increases in exercise intensity. Previous research has examined the extent to which afferent feedback arising from cardiopulmonary and peripheral variables mediates the perception of exertion. However, the literature has not identified a single variable that consistently explains exertion ratings. It is concluded that effort perception involves the integration of multiple afferent signals from a variety of perceptual cues. In a process defined as teleoanticipation, the changes in perceived exertion that result from these afferent signals may allow exercise performance to be precisely regulated such that a task can be completed within the biomechanical and metabolic limits of the body. The accuracy with which individuals can regulate exercise intensity based upon RPE values, the decrease in muscle recruitment (central drive) that occurs before fatigue, and the extent to which perceived exertion and heart rate can be altered with hypnosis and biofeedback training all provide evidence for the existence of such a regulatory system. Future research is needed to precisely quantify the extent to which efferent feedforward commands and afferent feedback determine pacing strategies such that an exercise event can be completed without irreversible tissue damage.     

The role of self-talk in the awareness of physiological state and physical performance

Different studies have suggested that the majority of self-talk during exercise is either positive or neutral in character. The majority of 'thoughts' during low-intensity exercise have been described as being dissociative conversational chatter. However, with increasing exercise intensity, there is a greater percentage of associative and motivational thoughts, which includes thoughts about feeling and affect, body monitoring, command, instruction and pace monitoring. It has been suggested that self-talk is necessary for creating a time 'wedge' between the activity described by the self-talk, and the self-talk itself. The information redundancy created by this time-wedge allows the capacity for reflection about what is occurring, and self-awareness of the part played by the individual themselves in the activity being performed. Self-talk may be a discussion between a singular 'I' and a singular 'me', or may be a multi-party dialogue. There are anatomical correlates to self-talk, with neural activity in a number of brain areas related to the occurrence of both overt and subvocal self-talk, particularly in Broca's region in the left frontal cortex, and Wernicke's region in the left posterior superior temporal cortex. Whether specific training of self-talk can improve performance is controversial, although recent studies have suggested that task-specific self-talk appears to have a beneficial effect on physical performance. Further studies are required to assess the ability of physical or mental training to modify self-talk in a beneficial and permanent manner, and whether these changes affect an individual's exercise performance and sense of self.     

Effects of light physical exercise on sleep regulation in rats

PURPOSE: Acute physical exercise is known to enhance slow-wave sleep (SWS) and reduce paradoxical sleep (PS) in humans. In this study, we examined the effects of moderate physical exercise on sleep in rats. METHOD: Young adult Wistar rats underwent a 4-h baseline electroencephalographic (EEG) recording session. The following day, they were induced to walk (0.8 m x min(-1)) or run (4 m x min(-1)) for 45 min in a rota-rod treadmill. Active control rats (ACR) were placed on the locked rota-rod for 45 min, whereas passive control rats (PCR) remained in their home cages. They were then left free to sleep for 4 h during which EEG activity was recorded. Rectal temperature (Tre) was monitored before and after exercise in ACR, walking and running rats (WR and RR, respectively) and at 45 min intervals in PCR. RESULTS: WR were able to walk for 45 min consecutively whereas in RR performances differed. Posttraining Tre was unchanged in ACR, PCR, and WR and resulted about 1.8 degrees C above baseline in RR. In both WR and RR after exercise i) length of SWS and PS, ii) intensity of SWS (spectral power density in 1-4 Hz range), and iii) propensity for falling asleep were enhanced. Interestingly, there was a more conspicuous increment in PS than SWS. In ACR and PCR there were no changes in sleep. CONCLUSIONS: Due to the complexity of sleep regulation, the interaction of several factors might underlie the observed increment in SWS and PS. Nevertheless, it is interesting that light physical exercise favors sleep and above all a harmonic enhancement of both sleep phases.     

Effort regulation in rowing races depends on performance level and exercise mode

This study investigated the influence of performance level and exercise mode on the rowers’ pacing strategies. On-water and indoor split times and placements (every 500-m) were obtained from individual 2000-m performances set at the elite, national and sub-elite competitive levels. The data was sorted into indoor (n = 580) and on-water exercises (n = 507). Indoor and on-water strategies statistically differed, whatever the competition level (p < 0.001). Analysis of absolute and normalised velocities demonstrated higher and steadier paces in elite races compared to national and sub-elite races (p < 0.001). On water, intermediate placements highlighted the great influence of taking the front of the race particularly at the elite level (at the elite level 78% of the winners were first at the middle of the race and 100% were in the first three). A “parabolic-shaped” profile could describe all races but performance level and exercise mode may alter this effort regulation to even (elite races) or positive paces (national and sub-elite indoor races). The even paces reported as the optimal strategy were not observed in lower performance levels probably because of rowers’ inability to combine higher physiological effort and technical requirements of on-water rowing. Training exercise may account for these paces differences, according to the athletes’ competitive level and to exercise mode.     

Effects of montelukast on physical performance and exercise economy in adult asthmatics with exercise-induced bronchoconstriction

Leukotriene antagonists are effective in the treatment of exercise-induced bronchoconstriction. Montelukast is a specific cysteinyl-leukotriene receptor1 antagonist without known effects on the pulmonary vessels, which in theory should be advantageous with respect to gas exchange. In addition to lung function, we investigated the effects of montelukast on parameters of gas exchange and physical performance in 16 asthmatics with exercise-induced bronchoconstriction in a double-blind cross-over placebo-controlled study. Subjects were tested at an ambient temperature of -15 degrees C with a tread mill exercise protocol consisting of consecutive workloads of 80% V'O(2max) (6 min), rest (4 min), 60% V'O(2max) (6 min) and step increments of exercise until exhaustion. Montelukast reduced the maximum post-exercise fall in FEV1 (P < 0.01), improved the running time to exhaustion in 11 of 16 test subjects (one unchanged) (P = 0.03), and reduced the Borg score at exhaustion (P = 0.03) and the breathing frequency after 3 min at 60% V'O(2max) (P = 0.03). V'(O2), V'CO(2), minute ventilation, ventilatory equivalents, respiratory exchange ratio, heart rate and oxygen pulse were not significantly different after montelukast and placebo. We conclude that montelukast has a beneficial effect on physical performance in most adults with exercise-induced asthma without any observed effect on gas-exchange parameters.     

From catastrophe to complexity: a novel model of integrative central neural regulation of effort and fatigue during exercise in humans

It is a popular belief that exercise performance is limited by metabolic changes in the exercising muscles, so called peripheral fatigue. Exercise terminates when there is a catastrophic failure of homoeostasis in the exercising muscles. A revolutionary theory is presented that proposes that exercise performance is regulated by the central nervous system specifically to ensure that catastrophic physiological failure does not occur during normal exercise in humans.     

Prediction of physical fitness and physical activity level in adulthood by physical performance and physical activity in adolescence - An 18-year follow-up study

Barnekow-Bergkvist M, Hedberg G, Janlert U, Jansson E. Prediction of physical fitness and physical activity level in adulthood by physical performance and physical activity in adolescence - An 18-year follow-up study. The aim of the study was to investigate relationships between physical fitness and self-reported physical activity in adulthood and to what extent the level of physical fitness and leisure-time physical activity in adulthood can be explained by anthropometric measures, physical performance, physical activity, attitudes to sports activities and socio-demographic characteristics at the age of 16. A group of 157 men and 121 women was tested at the ages of 16 and 34 by means of questionnaires and fitness tests. Physically active men and women had higher estimated VO_{2 max} and performed better in curl ups and bench press than those who were inactive. Performance in physical tests, height, weight and physical activity at the age of 16 contributed best to explain adult physical performance and physical activity. The magnitude of explanation varied between 10% (9-min run test) and 56% (bench press test); it was in general lower in the men than in the women. The various fitness tests and physical activity were explained by different predictors and the predictors also differed between men and women. The findings about attitudes to sports and socio-demographic factors at a young age that influence adult physical activity habits and fitness are very complex and further research is required to identify specific inactivity risks.     

下体负压联合体育锻炼对运动耐力及体能的影响

目的：研究制定适合疗养期间高性能战斗机飞行员进行专项下体负压和体能训练方案。方法：24名健康男性随机分为3组。体育锻炼组连续2周进行力量锻炼;下体负压锻炼组利用倾斜床进行下体负压锻炼。联合锻炼组每天以上述两种不同的锻炼方式进行复合锻炼。锻炼前后进行运动耐力及体能测试。结果：体育锻炼联合下体负压锻炼组锻炼10d后PWC170／kg、最大耗氧量显著提高,肌肉爆发力及静肌力指标较锻炼前显著提高（P〈0．05）;单纯体育锻炼组平板卧推、负重蹲起、30m冲刺跑、15m蛙跳成绩较锻炼前显著提高（P〈0．05）,单纯下体负压组仅平板卧推及15m蛙跳成绩较锻炼前显著提高（P〈0．05）。结论：体育锻炼联合下体负压锻炼10d后可明显提高受试者运动耐力及下肢、腰腹肌肉爆发力及静肌力。     

The effect of breathing an ambient low-density, hyperoxic gas on the perceived effort of breathing and maximal performance of exercise in well-trained athletes

Background

The role of the perception of breathing effort in the regulation of performance of maximal exercise remains unclear.

Aims

To determine whether the perceived effort of ventilation is altered through substituting a less dense gas for normal ambient air and whether this substitution affects performance of maximal incremental exercise in trained athletes.

Methods

Eight highly trained cyclists (mean SD) maximal oxygen consumption (VO₂max) = 69.9 (7.9) (mlO₂/kg/min) performed two randomised maximal tests in a hyperbaric chamber breathing ambient air composed of either 35% O₂/65% N₂ (nitrox) or 35% O₂/65% He (heliox). A ramp protocol was used in which power output was incremented at 0.5 W/s. The trials were separated by at least 48 h. The perceived effort of breathing was obtained via Borg Category Ratio Scales at 3‐min intervals and at fatigue. Oxygen consumption (VO₂) and minute ventilation (V_E) were monitored continuously.

Results

Breathing heliox did not change the sensation of dyspnoea: there were no differences between trials for the Borg scales at any time point. Exercise performance was not different between the nitrox and heliox trials (peak power output = 451 (58) and 453 (56) W), nor was VO₂max (4.96 (0.61) and 4.88 (0.65) l/min) or maximal V_E (157 (24) and 163 (22) l/min). Between‐trial variability in peak power output was less than either VO₂max or maximal V_E.

Conclusion

Breathing a less dense gas does not improve maximal performance of exercise or reduce the perception of breathing effort in highly trained athletes, although an attenuated submaximal tidal volume and V_E with a concomitant reduction in VO₂ suggests an improved gas exchange and reduced O₂ cost of ventilation when breathing heliox.Sensations of respiratory discomfort are consciously monitored during exercise,¹ and, at higher workloads, sensations of dyspnoea are closely related to perceived exertion.^2,3 This evidence indicates a potential role for afferent sensory feedback of ventilatory exertion from the respiratory muscles in regulating maximum performance of exercise in humans.⁴ However, the role of perceived respiratory effort in the regulation of maximal performance of exercise remains unclear.⁵Perception of respiratory effort can be manipulated by altering the work of breathing. This effect has traditionally been achieved by either using a pressure‐assisted ventilation (PAV) device, in which a demand valve senses pressure changes at the nose and mouth and reactively assists the breathing,^6,7 or altering the properties of the inspired air so that it is less dense than normal air and therefore reduces the work required to move the air in and out of the lungs.^8,9,10A serious limitation to the PAV method is the potential to disrupt the normal breathing pattern of the subjects, as the novelty of the task requires subjects to “train” to breathe on the apparatus before undergoing testing.⁷ A further limitation is the delayed response time of the demand valve to pressure changes at the mouth.⁷ The result is that the PAV method can only be used effectively during steady‐state exercise and therefore cannot assess the role of ventilatory work or its associated sensations as a factor limiting progressive maximal exercise to exhaustion. Studies have produced mixed results regarding the effects of unloading the work of the respiratory muscles on exercise capacity possibly as a result of these limitations.^6,7By contrast, the performance benefits of breathing a less dense gas have produced more consistent results.^8,10,11,12 However, the increased breathing resistance imposed by the external gas delivery and collection systems used in these studies creates a potential difficulty in differentiating between the effects of the lighter gas on the anatomical respiratory tree and on the external respiratory tubing.^13,14 Furthermore, altering the properties of the inspired air may result in altered ventilatory dynamics. Although some researchers^15,16 have suggested that a less dense carrier gas might increase the alveolar–arterial partial pressure of oxygen (pO₂) gradient, thereby reducing arterial blood oxygen saturation, Nemery et al¹⁷ reported that the physical properties of the inspired gas do not affect ventilatory dynamics. Indeed, more recent studies have found that breathing a helium–oxygen mix improved arterial saturation.^9,18 Therefore, it seems that breathing a less dense gas during high‐intensity exercise may improve alveolar ventilation or the alveolar–arterial O₂ difference or both, thereby enhancing the oxygen content of arterial blood.^5,19To fully elucidate any potential role for the perceived effort of breathing in regulating maximal exercise, the confounding effects of breathing a gas less dense than air need to be considered. Conducting a trial on the performance of exercise in an environment in which “lighter” air is substituted for the ambient air will negate the need for external breathing apparatus, and hence the confounding effects of unloading the added respiratory resistance caused by such an apparatus. Furthermore, any ergogenic benefits derived from improved pulmonary dynamics can be minimised by increasing the fraction of oxygen in the inspired air.¹⁹Young et al²⁰ showed that physically active subjects are able to differentially assess feelings of effort pertaining to the respiratory and cardiovascular systems. Therefore, we aimed to investigate the perceptual and performance effects of breathing a low‐density, hyperoxic gas during a graded maximal exercise test to exhaustion in a young, physically fit population. We hypothesised that breathing a less dense gas would attenuate the perceived effort of breathing and improve incremental exercise time to exhaustion.     

Cognitive, psychomotor, and physical performance in cold air after cooling by exercise in cold water

INTRODUCTION: This study evaluated performance after lowering core temperature at different rates while local tissues were either cooled (lower body) or not cooled (upper body). METHODS: There were 10 men who volunteered to perform up to 8 cold water immersions (CWI) at combinations of 2 water temperatures (10 degrees C and 15 degrees C), 2 depths [waist (W), chest (C)], and 2 walking speeds (0.44 or 0.88 m x s(-1)) until their core temperature fell to 35.5 degrees C, stabilized above that temperature, or they requested to stop. They also completed a control trial (120 min rest in 19 degrees C air). Immediately following each CWI and control, cognitive and physical performance tests were performed in cold air (10 degrees C; CAE). RESULTS: Overall, the CWI protocol lowered rectal temperature by 0.3-1.0 degrees C. Mean skin temperature was approximately 26 degrees C and finger temperature was approximately 15 degrees C during CAE. No statistical differences were observed across trials for any cognitive test. On the physical performance tests, step test performance was degraded approximately 12% on CWI trials compared with control, but there were no differences in manual dexterity, hand grip strength, marksmanship, or pull-ups. CONCLUSIONS: These results indicate that cognitive performance can be maintained despite mild hypothermia, and that physical performance is related to local tissue temperature, not a moderately reduced core temperature.     

Study of the type of physical effort exerted by competition in Supercross]

The authors draw up a tentative account of the physiological load a pilot bears during a Supercross event. Examination of heart frequency and blood lactate concentration curves during a series of races shows that this sport is not only highly stressful, but demands by the same token a muscular effort which has to be taken into account. Muscular work is of the mixed type, both aerobic and anaerobic, the share of the latter being of moderate importance, as it depends mainly on the technical proficiency of the driver.     

From catastrophe to complexity: a novel model of integrative central neural regulation of effort and fatigue during exercise in humans: summary and conclusions

It is hypothesised that physical activity is controlled by a central governor in the brain and that the human body functions as a complex system during exercise. Using feed forward control in response to afferent feedback from different physiological systems, the extent of skeletal muscle recruitment is controlled as part of a continuously altering pacing strategy, with the sensation of fatigue being the conscious interpretation of these homoeostatic, central governor control mechanisms.     

Autonomic regulation of the association between exercise and diabetes

The inverse association between physical activity and diabetes is attributable to a number of biologically plausible mechanisms. We hypothesize that physical activity-induced improvements in autonomic function are one mechanism by which higher levels of activity are inversely associated with diabetes development. Evidence in support of our hypothesis is derived from a combination of observational studies and clinical trials.     

Biological underpinnings of mood and the role of physical exercise

Physical movement is suggested to the common population by numerous medical institutions, because it is a significant instrument for improving public health. On the other hand, physical movement can also be harmful, particularly when performed in a very extreme mode. Different biological and psychological indicators have been used to optimize competitive readiness. On the psychological part, mood states have been revealed to be susceptible to modifications in physical exercise. On the biological side, technical advances have been made by the introduction of non invasive assessment of biomarkers. This article reviews the research on the Profile of Mood States effects associated with sport and exercise (occasional and intense) and biological markers. The series of studies reveals relations between biological markers and mood states, and sustains the conclusion that hormonal responses indicate physiological processes that produce and are affected by psychological processes.     

Erythrocytic system under the influence of physical exercise and training

It is obvious that physical performance, endurance capacity and resistance to fatigue in humans are dependent upon many different factors. One factor, the oxygen carrying capacity of blood, seems to be of particular importance. This factor is mainly determined by haemoglobin concentration, number of circulating erythrocytes and the efficiency of their functions. A single bout of physical effort and, even more, repeated exercise may change the morphological indices of blood and influence the erythropoietic processes in the bone marrow. That is why there is so great an interest now attached to the effects of physical exercise on the erythrocytic system. Although in recent years many papers have been published on the subjects their findings pertaining to the effects of single bouts of exercise and systematic training on the erythrocytic system are often contradictory. The haematological parameters in some top-class athletes, particularly those performing in endurance disciplines are lowered at rest. Anaemia has been described in sportsmen, even among the members of Olympic teams. This type of anaemia has been called 'sports anaemia', 'athletes' anaemia' or 'postexercise anaemia' in order to emphasise its character. Among many possible causes which may bring about the development of sports anaemia the most commonly recognised are: postexercise plasma expansion, intensified haemolysis during physical efforts, iron deficiency, losses of erythrocytes by the way of bleeding into the digestive and urinary systems and also some disturbances in erythropoiesis. However, there is evidence of the intensification of erythropoiesis by many factors occurring during physical exercise.     

Morning resistance exercise and cricket-specific repeated sprinting each improve indices of afternoon physical and cognitive performance in professional male cricketers

ObjectivesTo compare two modes (general and cricket-specific) of morning priming exercise on afternoon physical and cognitive performance, and subjective readiness to perform in professional male cricketers.DesignRandomised, crossover, counterbalanced.MethodsOn three occasions, 16 professional men's cricketers completed afternoon tests of countermovement jump height, cricket-specific sprint performance (running between the wickets, two runs), cognitive function (Stroop test, time taken), and subjective readiness to perform. Control (CON; passive rest), lower-body resistance exercise priming (LIFT; trap bar deadlifts, 6 × 4 repetitions up to 85% of one repetition maximum), or cricket-specific running priming (RUN; 6 × 35.36 m sprints including a 180° change of direction) interventions were implemented 5.5 h before testing.ResultsAfternoon sprint times were faster in RUN (?0.04 s, p = 0.013) and LIFT (?0.07 s, p < 0.001) versus CON, and faster in LIFT than RUN (?0.03 s, p = 0.032). Jump height (+1.1 cm, p = 0.021) and cognitive function (?3.83 s, p = 0.003) were greater in LIFT than CON, whilst RUN outperformed CON for cognition (?2.52 s, p = 0.023). Although perceived readiness was not influenced by trial (p > 0.05), players reported favourable responses on the “aggression” subscale in LIFT relative to CON (+1 arbitrary unit, p = 0.022).ConclusionsBoth general (lower-body resistance exercise) and cricket-specific (simulated running between wickets) morning priming are effective match-day strategies to improve afternoon markers of physical and cognitive performance in professional men's cricketers. Practitioners may thus be afforded flexibility in situations where resistance exercise is not feasible on the morning of a match.