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PubMed2005

Anatomical and mechanical changes following repetitive eccentric exertions.

BACKGROUND: Submaximal eccentric exertions occur occupationally when rapidly rising tool-generated forces exceed the operator's capacity to react against them. The purpose of this study was to investigate the effects of short duration repetitive submaximal eccentric forearm exertions at levels comparable to industrial power hand tool use on dynamic mechanical properties (stiffness, effective mass and damping) and on forearm edema. METHODS: This study investigated changes following short term repetitive submaximal eccentric exertions comparable to occupational levels. Eight male participants exercised eccentrically for 30 min at 50% of isometric maximum voluntary contraction forearm supination in a posture and loading similar to power hand tool use in the workplace. Dynamic mechanical properties (stiffness, effective mass and damping) of the upper limb were measured before, immediately following, and daily for three days after the activity. An MRI scan to assess edema was also performed for five of the participants before, on day one and day three following the activity. FINDINGS: Mechanical stiffness decreased 51% (P < 0.05) and effective mass decreased 43% (P = 0.052) immediately following eccentric exercise. Average isometric strength also decreased 42% immediately following exercise (P < 0.01) and pain persisted for two days. The recovery of static strength however was not correlated with changes in mechanical stiffness (r = 0.56) or effective mass (r = 0.30). The exercised arms had a 360% increase (P < 0.01) in supinator-extensor T(2) relaxation time difference, a quantifiable measure of edema, one day after exercise while the non-exercised arms had no significant changes. INTERPRETATION: Changes in both T(2) relaxation time, indicative of edema, and forearm mechanical properties, were observed following short duration submaximal repetitive exercise. If similar changes in dynamic mechanical properties of the upper extremity occur following repetitive submaximal eccentric activity in the workplace, they could negatively impact the ability of the arm to react to rapid forceful loading during repetitive industrial work activities and increase mechanical loading of the upper limb.

Adaptation, Physiological↗
PubMed2006

The effect of gait speed and gender on perceived exertion, muscle activity, joint motion of lower extremity, ground reaction force and heart rate during normal walking.

This study aims to investigate the effect of speed and gender on subjective perceived exertion, muscle activity, joint motion of lower extremity, vertical ground reaction force and heart rate during barefoot walking. Thirty healthy young adults, 15 females and 15 males, participated in this study. The Borg CR-10 scale was applied to evaluate the perceived exertion of whole body and 10 local areas. Objective measurements included electromyography (EMG), joint motion, vertical ground reaction force (VGRF) and heart rate. The results indicate that walking speed had significant influence on perceived exertion of whole body, as well as the buttock, rear thigh, front thigh and rear shank areas (p<0.05). Increased walking speed caused significant increase in the muscle activities of lumbar erector spinae, biceps femoris, and medial gastrocnemius, lumbar motion, as well as the vertical ground reaction force in the loading response and mid-stance phases. For gender effect, females showed significantly higher tibialis anterior muscle activity, ankle motion, vertical ground reaction force and average heart rate than males. Some systematic relations among the physiological, kinematics, kinetics and psychophysical responses were found for interpreting gait performance.

Adult↗
PubMed1998

Exertional dyspnea in heart failure: a symptom unrelated to pulmonary function at rest or during exercise. Duke University Clinical Cardiology Studies (DUCCS) Exercise Group.

BACKGROUND: Exertional dyspnea is a common symptom in patients with heart failure, and the mechanisms responsible for the symptom are unknown. The purpose of this study was to identify factors responsible for the symptom of exertional dyspnea in patients with heart failure. METHODS: Resting pulmonary-function tests and maximal cardiopulmonary exercise tests were performed in 71 patients with New York Heart Association functional class II-IV symptoms (mean ejection fraction 30.6%; mean age, 68 years). RESULTS: The severity of dyspnea at peak exercise, which patients rated as 3 to 10 on a 1 to 10 severity scale, did not correlate with rest or exercise hemodynamic, spirometric, or metabolic variables, including peak oxygen uptake (VO2), minute ventilation (Ve), and respiratory rate, or with derived variables including Ve/VO2, Ve/VCO2, and the dyspnea index (Ve/maximum voluntary ventilation). Additionally, these variables did not differ between patients who reported limitation of exercise by dyspnea and those who were limited by fatigue. CONCLUSIONS: The symptom of exertional dyspnea in patients with heart failure is not determined by abnormalities in ventilatory function or demand.

Aged↗
PubMed2003

Perceived and measured levels of exertion of patients with chronic back pain exercising in a hydrotherapy pool.

OBJECTIVE: To investigate the efficacy of using ratings of perceived exertion (RPEs) to regulate exercise intensity for patients with chronic back pain while they undergo hydrotherapy. DESIGN: Experimental study. SETTING: Hydrotherapy pool in the United Kingdom. PARTICIPANTS: Twenty-six patients (16 women, 10 men) with chronic low back pain of more than 12 months in duration. All were referred for hydrotherapy after attending a back pain triage clinic. INTERVENTIONS: Not applicable. Main outcome measures Borg Ratings of Perceived Exertion Scale; heart rate expressed as a percentage of age-predicted maximum heart rate, computed from readings using heart rate monitors; Oswestry Disability Questionnaire; and pain score from a visual analog scale. RESULTS: At workloads below 55% of age-predicted maximum heart rate, great variability was found in the relation between RPE and exercise intensity. However, for workloads between 55% and 85% of age-predicted maximum heart rate, RPE had a strong correlation with relative exercise intensity during hydrotherapy. CONCLUSIONS: At workloads sufficient to induce an aerobic training response, and yet be safe for patients with chronic back pain, RPE was an accurate predictor of exercise intensity. At lower intensities, back and leg pain may exert a mediating influence. Further investigation is needed to determine the exact relation between back pain, exercise type, and RPE at low exercise intensities.

Adult↗
PubMed1986

The effect of isoprenaline and physical exertion to exhaustion on the mechanism of glucocorticoid action in the rat heart.

The effect of ATP and factors known to alter cellular ATP level on the properties of cytosolic glucocorticoid receptor of the heart were investigated. We measured the number of binding sites, binding affinity, receptor transformation and nuclear binding. Experiments performed on the cardiac cytosol of adrenalectomized rats labeled with hormone in vitro showed that both isoprenaline treatment and physical exertion to exhaustion decreased the number of triamcinolone acetonide binding sites, but had no significant effect on the binding affinity. Although ATP had an activating effect on the cytosolic steroid-receptor complexes, the results of phase partitioning and DEAE-cellulose chromatography indicated that neither isoprenaline nor exertion to exhaustion had any apparent effect on the equilibrium between the activated and unactivated forms of complexes. The amount of translocated complexes was dependent on the cytosolic receptor concentration. Experiments performed on the heart cytosol labeled with the hormone in vivo, showed that exertion to exhaustion changed the equilibrium between activated and unactivated complexes in favour of the latter form and at the same time decreased the amount of complexes bound to the nuclei and chromatin. It is not clear whether these changes reflect alterations in receptor activation and its accumulation in the nuclei, or whether they are connected with the release of the nuclear receptor due to the decrease in receptor affinity to chromatin or some other nuclear component. Speculatively, the data suggest that glucocorticoid action in heart cells may depend on the ability of cells to maintain a certain level of ATP.

Adenosine Triphosphate↗
PubMed2001

A spectrum of exertional headaches.

Headaches that have an explosive onset with exercise, including sexual activity, generally are benign in origin. A subarachnoid hemorrhage, a mass lesion in the brain, or an anomaly of the posterior fossa must be considered, however. The mechanisms that produce sexually induced or cough headaches of abrupt onset are unknown. It is known, however, that a rapid increase in intrathoracic pressure suddenly reduces right atrial pressure and presumably decreases venous sinus drainage from the brain. This situation results in a transient increase in intracranial pressure. Jaw pain that occurs with chewing often is considered to be TMJ dysfunction when arthritic in quality and if subluxations of the jaw can be shown on the physical examination. Giant cell arteritis and common or external carotid artery occlusive disease should be considered when the pain is ischemic in quality. An anginal equivalent is another possibility. Headaches that worsen with vigorous exercise are commonly migrainous. When their onset is apoplectic with exertion (particularly exertion against a closed glottis), the most likely diagnoses are increased intracranial pressure, a posterior fossa abnormality, or benign exertional headaches. Most cardiac induced headaches, but not all, are of a more gradual onset. If there are significant risk factors for coronary artery disease, an exercise stress test is appropriate. A therapeutic trial of nitroglycerin may help to establish a diagnosis if it improves the headache. Using antimigraine drugs as a diagnostic test is inappropriate because triptans and ergots are contraindicated in the presence of coronary artery disease, and a positive response is not diagnostic of migraine.

Adult↗
PubMed1995

Myoplasmic Ca2+ concentration during exertional rhabdomyolysis.

Exertional rhabdomyolysis can destroy muscle but the pathophysiology is unknown. Using intracellular selective microelectrodes, we found that intracellular Ca2+ concentration ([Ca2+]i) was 1.27 (0.17) mumol/L (median and interquartile range) in skeletal-muscle biopsy specimens from patients with exertional rhabdomyolysis compared with 0.12 (0.01) mumol/L in controls. 3 days treatment with dantrolene, a drug that inhibits Ca2+ release from the sarcoplasmic reticulum, decreased [Ca2+]i to 0.22 (0.05) mumol/L and accelerated patients' recovery. This study demonstrated that exertional rhabdomyolysis is associated with elevated [Ca2+]i, and that dantrolene has a beneficial effect in this syndrome.

Adult↗
PubMed1988

Exertional heat stroke and acute renal failure in a young woman.

Strenuous exercise leading to heat stroke is known to cause rhabdomyolysis and acute renal failure in men, but there are no reports of this environmental illness in otherwise healthy women. We report the first case of heat and exercise induced acute renal failure in a young nonacclimated adult female following intense exertion in the Grand Canyon. This individual displayed the typical clinical features of exertional heat stroke including hyperpyrexia, CNS disturbance, rhabdomyolysis, oligoanuric acute renal failure, and disseminated intravascular coagulopathy. The pathophysiology is discussed as well as sexual differences in response to heat and exercise. The specific factors that may have predisposed this young woman to heat stroke from exertion are identified.

Acclimatization↗
PubMed1998

Catecholamine and cortisol responses of horses to incremental exertion.

The responses of the plasma concentrations of catecholamines and cortisol in horses to varied relative intensities of exertion were examined. The plasma concentrations of cortisol, epinephrine and norepinephrine increased significantly (p < 0.05) with exertion. The plasma cortisol concentrations at relative work intensities of 48.3% +/- 1.4%, 82.3% +/- 2.0% and 99.6% +/- 0.4% of VO2max were 114%, 124%, and 126%, respectively, of those at rest, whereas the plasma epinephrine concentrations were 239%, 772% and 3483%, and the norepinephrine concentrations were 138%, 255%, and 1121% of the values at rest. There was a significant (p < 0.0001) relationship between the plasma epinephrine and norepinephrine concentrations. The blood lactate concentration and the plasma epinephrine and norepinephrine concentrations were significantly (p < 0.0001) related, as were the relative work intensity (%VO2max) and the plasma epinephrine and norepinephrine concentrations. The relationships between the plasma cortisol concentration and work intensity or blood lactate concentration were not significant (p > 0.05). This study demonstrates a relationship between work intensity and indicators of adrenal medullary and sympathetic activity during brief exertion in horses.

Adrenal Medulla↗
PubMed2002

Concordance between rating of perceived exertion and function in persons with chronic, disabling back pain.

Rating of perceived exertion (RPE), or the Borg scale, has been shown to be positively associated with physiologic effort in individuals undergoing cardiovascular assessment. This study examined the correlations between cardiovascular performance, psychosocial factors, and the RPE scale among 50 persons with chronic pain undergoing multidisciplinary assessment. The results indicated a significant negative association between fitness outcome measures (maximum VO2 and endurance on bicycle), psychosocial measures, and age. With a mean maximum heart rate achieved on the exercise bicycle of 79.2% (SD = 8.3), there was no significant association between the highest rating of perceived exertion on the exercise bicycle test and percent of maximum heart rate. Percent of maximum heart rate was significantly related to self-reported pain and disability as well as age. These findings suggest that perceived exertion in this population is not highly correlated with physiologic effort, as other factors such as pain may influence effort ratings.

Adult↗
PubMed1993

Static force exertion in postures with different degrees of freedom.

In assessing human force exertion, the use of standardized postures can lead to the inaccurate prediction of the forces and postures which occur in everyday life. Therefore force data obtained using postures freely chosen by subjects themselves may be considered more relevant. A standardized posture, however, is considered to yield more reliable data. The question arose whether it would be possible to combine the two in some way, calling the result a 'functional posture'. Research was necessary to determine a way of operationalizing these functional postures, and to test their reproducibility. First, a method is proposed to describe functional postures through explorative research. This includes the fixation of members that transfer force to the outside world, while the rest of the body is allowed to move freely. The results of further research show that the exerted force is reproducible in free, functional, and standardized postures. The difference in average force, though, is considerable and significant. The conclusion is that force exertion in free posture is most suitable for design research.

Adult↗
PubMed1995

Psychophysical frequency and sustained exertion at varying wrist postures for a drilling task.

Two laboratory experiments were conducted; first, to utilize the psychophysical approach (method of adjustment) to establish maximum acceptable frequency (MAF) for a sheet metal drilling task and, second, to examine the effect of sustained, static exertion upon objective and subjective measures under similar task conditions. In both experiments, the wrist posture (flexation, ulnar deviation) required by the task was varied. Twelve healthy females served as subjects. Results show that the psychophysically adjusted task frequency was significantly lower when wrist deviation was required, particularly flexion. MAF for one-third (25 degrees) and two-thirds (50 degrees) flexion were 88% and 73%, respectively, of those selected in the neutral posture. Furthermore, these results were supported by trends in grip strength, heart rate, blood pressure, EMG and perceived exertion. Results from the sustained exertion trials revealed that significant increases in physiological parameters occurred during 3-minute sessions and that this trend was exasperated with deviated wrist posture, particularly flexion. Considering results of both experiments, it was concluded that while the neutral wrist posture may be preferred for a drilling operation, task frequency should be reduced for deviated postures when redesign is not feasible and it is further recommended that deviation be limited to one-third maximum flexion (25 degrees) and two-thirds maximum ulnar deviation (30 degrees). It is also suggested that the psychophysical approach may be utilized to establish 'acceptable' parameters for other industrial tasks involving upper extremity stress, particularly in the current absence of more objective biomechanical and/or physiological criteria for reducing the risk of exposure to cumulative trauma disorders.

Adult↗
PubMed1989

Effects of a verbal and visual feedback system on running technique, perceived exertion and running economy in female novice runners.

The purpose of this study was to determine the effects of a verbal and visual feedback system on running technique, ratings of perceived exertion (RPE), and running economy. Twenty-two female novice runners were randomly assigned to experimental (n = 11) and control (n = 11) groups. The experimental subjects received verbal and visual feedback concerning their running technique prior to and during each training run. Training involved 15 20-min treadmill running sessions over a 5-week period. The control group adhered to the same training routine but did not receive feedback concerning their running technique. High-speed (100 Hz) photography was used to collect biomechanical data. A submaximal oxygen consumption test and Borg's RPE scale were used to collect data concerning running economy and perceived exertion, respectively. Statistical analysis using ANCOVA revealed that the proposed feedback system had a significant (P less than 0.01) effect on the experimental group's running technique by affecting the following desired changes relative to the control group: greater relative stride lengths, shorter support time, greater ankle dorsiflexion during support and greater knee flexion during support and non-support. There were no significant differences between the groups in submaximal VO2 or RPE. The results of this study suggest that verbal and visual feedback are effective means of eliciting modifications in running style in female novice runners. The link between modifications in running style and improvements in running economy and perceived exertion remains unclear.

Adolescent↗
PubMed1991

Perceived exertion and physiological economy of competition walking, ordinary walking and running.

Four competition walkers performed competition walking, ordinary walking and running on a treadmill on two different occasions. During the two walking modes, the subjects performed maximal tests. During running, the session was terminated at a heart rate of 150 beats min-1 or an exertion rating--for either chest or leg--of 5 or higher. The tests commenced at 2.5 km h-1 and the velocity was increased by 2.5 km h-1 every 4 min. Measures of chest exertion and breathlessness, leg exertion, heart rate and blood lactate were taken every 4 min just prior to the velocity changes. The measured psychological and physiological variables were described by monotonously accelerating power functions with exponents around 2 for the perceptual variables at both walking modes. The heart rate growth for competition walking accelerated according to a function with an exponent of 1.7, which is lower than that for ordinary walking (2.0), but higher than that for running which is linear. No significant difference was found between maximal oxygen uptake when competition walking and running were compared. A second test was carried out so as to confirm the cross-over point for the heart rate curves in the two walking modes. The cross-over point for the two walking curves were determined to be at 8.6 km h-1.

Adolescent↗
PubMed2003

Evaluation of cardio-respiratory fitness and perceived exertion for patients with depressive and anxiety disorders: a study on reliability.

PURPOSE: The implementation of a physical reconditioning programme for patients with depressive and/or anxiety disorders requires a thorough evaluation of the physical fitness and the perceived exertion during exercise. This implies the use of reliable and clinically useful instruments. The present study examined the reliability of the Franz ergocycle test, as measure for cardio-respiratory fitness, and the Borg Category Ratio 10 Scale, as measure for subject-perceived exertion. METHOD: Sixty-eight hospitalized patients performed test and re-test of the Franz ergocycle test and the Borg CR 10 Scale with a between interval of 1 week. RESULTS: The Physical Work Capacity 130 and the Physical Work Capacity 150, determined by the Franz ergocycle test, had a proper to good test-re-test reliability (r ranged from 0.74 to 0.90). The Borg Category Ratio 10 Scale had a moderate reliability (r ranged from 0.42 to 0.82). CONCLUSIONS: The Franz ergocycle test seems to be a reasonable reliable instrument for measuring physical work capacity of these patients. Possible explanations for the simply moderate reliability of the Borg Category Ratio 10 Scale could be the low level of physical activity prior to hospitalization, and the depressive and anxiety symptoms that might influence the perceived exertion.

Adult↗
PubMed2006

Effect of physical exertion on the biological monitoring of exposure of various solvents following exposure by inhalation in human volunteers: I. Toluene.

Physical exertion (work load) has been recognized as one of several factors that can influence the kinetics of xenobiotics within the human body. This study was undertaken to evaluate the impact of physical exertion on two exposure indicators of toluene (TOL) in human volunteers exposed under controlled conditions in an inhalation chamber. A group of four volunteers (one woman, three men) were exposed to TOL (50 ppm) according to the following scenarios involving several periods during which volunteers were asked to perform either aerobic (AERO), muscular (MUSC), or both (AERO/MUSC) types of physical exercise (exercise bicycle, treadmills, pulleys). The target intensities (W) for each exercising period of 30 min--interspaced with 15 min at rest--were the following: REST, 50 W AERO (time-weighted average intensity [TWAI]: 46 watts); 50 W AERO/MUSC (TWAI: 38 watts) and 100 W AERO (TWAI: 71 watts) for 7 hours and 50 W MUSC for 3 hours (TWAI: 29 watts). Alveolar air and urine samples were collected at different time intervals before, during, and after exposure for the measurement of unchanged TOL in expired air (TOL-A) and urinary o-cresol (o-CR). Overall, the results showed that TOL-A measured during and after all scenarios involving physical activities were higher (approximately 1.4-2.0 fold) compared with exposures at rest. All scenarios involving physical exertion also resulted in increased end-of-exposure urinary o-CR (mean +/- SD): 0.9 +/- 0.1 mg/L (REST) vs. 2.0 +/- 0.1 mg/L (TWAI 46 watts). However, exposure at a TWAI of 71 watts did not further increase o-CR excretion (1.7 +/- 0.2 mg/L). This study confirms the significant effect of work load on TOL kinetics and showed that o-CR excretion increased proportionally with work load expressed as TWAI or with the estimated mean pulmonary ventilation during the period of exposure. This study also shows that exposure to TOL (50 ppm) involving a work load of around 50 W (light intensity) or lower is likely to produce urinary o-CR values that clearly exceed the current biological exposure index value for TOL.

Adult↗
PubMed1976

A study of inflatable cuffs on endotracheal tubes. Pressures exerted on the trachea.

A simple method of measuring the pressure exerted by the cuff of an endotracheal tube on the trachea is described and has been used to measure the pressures exerted by 16 commercially available cuffs on the wall of a model trachea. The Shiley, Portex soft-seal, Kamen-Wilkinson (Bivona Fome) tubes had the lowest tracheal wall pressures. Using this method in vivo the changes in tracheal wall pressure exerted by a low-pressure cuff during percussion and vibration physiotherapy, and when the patient "fights the ventilator", were recorded.

Humans↗
PubMed1997

Catecholamines contribute to exertional dyspnoea and to the ventilatory response to exercise in normal humans.

BACKGROUND: Exogenous catecholamine administration in humans stimulates ventilation. The present study was designed to investigate whether increased endogenous catecholamine release influences objective measures of ventilation and subjective measures of breathlessness in normal subjects. METHODS: Yohimbine, a pre-synaptic alpha 2 adrenoceptor antagonist, or placebo was administered to 10 normal male subjects in a double-blind cross-over fashion. Ventilation and metabolic gas exchange were measured during steady state exercise at 60% of previously determined maximal oxygen consumption. Venous lactate and noradrenaline were measured during exercise. Subjects' sensation of breathlessness and fatigue were recorded using visual analogue scales. RESULTS: Plasma noradrenaline was higher following yohimbine administration (at 6 min exercise; 4.58 +/- 0.56 nmol.l-1 vs 8.74 +/- 1.53; P < 0.05). Oxygen consumption was unchanged, but ventilation was greater throughout exercise following yohimbine. The sensation of exertion was greater following yohimbine, and at any given level of ventilation, the sensation of exertion was greater. CONCLUSIONS: Yohimbine administration causes increased noradrenaline release. This is associated with an increased ventilatory response and an increase in the sensation of exertion during steady state exercise. An increase in circulating noradrenaline might be a mechanism for both increased ventilation and pathological conditions of breathlessness such as chronic heart failure.

Adrenergic alpha-Antagonists↗