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At least 145 records · Page 8Linked to original sources
PubMed2001

Assessing the effect of exercise training in men with heart failure; comparison of maximal, submaximal and endurance exercise protocols.

AIMS: No consensus exists regarding the most appropriate exercise testing protocol for patients with congestive heart failure. This study describes the effect of exercise training on performance using three different protocols (maximal, submaximal and endurance testing) in patients with heart failure. METHODS AND RESULTS: Thirty men (mean age 67+/-8 years) with congestive heart failure in NYHA class III (mean ejection fraction 32+/-5%) were evaluated prior to and following exercise training. A maximal exercise cycle test with gas exchange measurements, a submaximal 6 min walk test and an endurance treadmill test with blood lactate sampling were used to evaluate exercise capacity after 12 weeks of exercise training. There was a 44.6% (P<0.001) increase in work performed during the maximal cycle test, with no significant increase in peak VO(2). The distance covered by the submaximal 6 min walk test increased by 8.1% (P<0.001). Lactate measured as area under the curve during the matched work intensity treadmill endurance test was reduced by 19.5% (P<0.005). CONCLUSION: We demonstrated a significant improvement in maximal, submaximal and endurance exercise capacity following 12 weeks of exercise training in patients with congestive heart failure. Endurance tests may be more sensitive and appropriate when assessing the efficacy of intervention in this population. Specifically, demonstration of reduced lactate production at matched work intensities suggests more efficient work and decreased dependence on anaerobic metabolism following training. Although maximal cycle tests are commonly used in clinical work, submaximal and endurance testing might be preferable for evaluating new treatment regimens in this population as they are easy to perform, are reproducible, and reflect daily tasks better than the maximal cycle test in this population.

Aged↗
PubMed1986

Renal responses to bicycle exercise in trained athletes: influence of exercise intensity.

The effects of exercise on renal function were studied in 11 male bicyclists, using a bicycle ergometer. At a work intensity of 100/150 W, bicycle exercise for 1 h was associated with a significant increase in urine volume, endogenous creatinine clearance, and renal sodium and potassium excretion. In contrast, exercise of the same duration at a work intensity of 150/200 W produced no significant changes in the above variables. Exercise intensity seems to influence renal responses, presumably through a differential effect on renal blood flow.

Adolescent↗
PubMed1979

Perception of effort during constant work to self-imposed exhaustion.

The purpose of this study was to describe the pattern of change in effort sense and the value of this pattern in predicting work end-point at relatively high work intensity (80% VO2 max). The patterns of change of various physiological functions were also observed. Two modes of work (walking and running) were compared to ascertain generalizability of results. 26 healthy male volunteers served as subjects. Time to exhaustion (ET) did not differ between walking and running. As work continued during both tasks, significant increases of VE, VE/VO2, VE/VCO2 and HR and a significant decrease of ETCO2 were observed; while VO2 and R remained fairly constant. VO2 and VE during the run were about 5% greater than during the walk; there were no differences in other measures. Ratings of perceived exertion (RPE) from the Borg Scale were identical for both conditions, increasing in a near linear fashion from a value of 12.9 at 25% of total work time to 18.9 at exhaustion. Ratings obtained at 25 and 50% ET were extrapolated to time of exhaustion; the point of intercept corresponded to ratings of perceived exertion for maximal work. At exhaustion, subjects rated perception of respiratory exertion for the walk as less than that for the run; perception of leg exertion was not different for the two conditions. Plasma lactate, epinephrine and norepinephrine concentrations following exercise did not differ between the two conditions. The findings for the walking experiment were essentially replicated in a second investigation involving another 28 subjects. It is concluded that, with the exception of VO2 and some ventilatory parameters, walking and running at the same relative work intensity resulted in comparable perceptual and physiological responses. Psychophysical judgments made early during work were reasonably accurate predictors of exhaustion time.

Adult↗
PubMed1978

Transient O2 uptake response at the onset of exercise.

One purpose of this study was to determine whether the half time of the oxygen consumption (VO2) response at the onset of exercise varies with work intensity. Fifteen subjects performed 5 min of bicycle ergometer exercise across a range of relative work loads with VO2 determined continuously via computer analysis. The results revealed that the half time of the VO2 response increased as work intensity increased. Our second purpose was to determine whether VO2 response kinetics are dependent on the maximum oxygen uptake (VO2max) of the subject. When VO2 response kinetics were compared at equal absolute work loads for a highly trained (n = 8, mean VO2max = 70.2 ml/kg.min) and an untrained (n = 7, mean VO2max = 49.7 ml/kg.min) group, the highly trained group had a more rapid VO2 response (P less than 0.05). The same tendency was evident at equal relative work loads but the differences were not significant. The more rapid adaptation of the highly trained subjects at absolute work loads may be caused by the enzymatic and circulatory adaptations which result from endurance training. The more rapid adjustment of VO2 at the onset of exercise may explain the slower phosphagen and glycogen depletion found in highly trained subjects following short-term work at equal absolute loads.

Adult↗
PubMed1992

[Health status and prevention of disorders in people performing intensive visual work].

Electronic industry workers, whose work involves visual strain were examined. The work appeared to be characterized by a plenty of unfavourable factors: high visual and emotional intensity, considerable strain of the locomotor apparatus in supporting a fixed sitting posture. The micromountain workers were exposed to poor ionized and ozonized air conditions combined with high bacterial contamination and lack of the UV rays in the air. Examinees showed markedly changed health and functional status of the main body systems. A complex of hygienic, prophylactic, physiological, technological and medical measures yielded remarkable results. Working conditions of electron industry workers are to be regulated.

Adult↗
PubMed1984

Oxygen consumption and hemodynamic responses during graded treadmill exercise in the dog.

A description is given of a technique that provides a relatively simple means by which O2 consumption and hemodynamic variables can be measured in exercising dogs. We used a multistage submaximal treadmill test to study the responses of 10 foxhounds to dynamic exercise. They were also studied during maximal treadmill exercise. O2 consumption increased from 16.3 +/- 1.7 ml O2 X min-1 X kg-1 at rest to 92.9 +/- 9.7 ml O2 X min-1 X kg-1 at a work load of 6.4 km/h, 20% grade and to 111.9 +/- 9.6 ml O2 X min-1 X kg-1 during maximal exercise. Cardiac output (CO) increased from 6.11 +/- 0.45 l/min at rest to 16.91 +/- 1.46 and 17.66 +/- 0.60 l/min at 6.4 km/h, 20% grade and maximal exercise, respectively. Arteriovenous O2 difference increased from 5.8 +/- 0.3 vol% at rest to 12.0 +/- 0.4 and 13.2 +/- 0.7 vol% at 6.4 km/h, 20% grade and maximal exercise, respectively. Heart rate (HR) increased from 116 +/- 7 beats/min at rest to 250 +/- 8 beats/min at 6.4 km/h, 20% grade and to 278 +/- 6 beats/min during maximal exercise. O2 uptake, CO, and arteriovenous O2 difference increased with the onset of exercise, appeared to level at lower work intensities (6.4 km/h, 4 and 8% grade), and increased significantly at each of the higher work intensities (6.4 km/h, 12, 16, and 20% grade). Additionally, we observed linear relationships between O2 consumption and HR (HR = 1.35 X VO2 + 120.5; r = 0.87; P less than 0.001) and between O2 consumption and CO (CO = 5.91 X VO2 + 216.6; r = 0.96; P less than 0.001). Further, the linear relationship between O2 consumption and CO demonstrated in the present study is similar to that observed in humans.

Animals↗
PubMed1978

Decreased VO2 consumption during exercise with elicitation of the relaxation response.

Oxygen consumption is usually considered to be predictable and unalterable at a fixed work intensity. The relaxation response is hypothesized to be an integrated hypothalamic response which results in generalized decreased sympathetic nervous system activity. One physiologic manifestation of the relaxation response is decreased oxygen consumption. The possibility that the elicitation of the relaxation response could decrease oxygen consumption at a fixed work intensity was investigated. Oxygen consumption was decreased 4 percent (p less than 0.05) in eight subjects working at a fixed intensity when the relaxation response was simultaneously elicited.

Female↗
PubMed1992

Acid-base regulation during exercise and recovery in humans.

Arterial pH, PCO2, standard bicarbonate, lactate, and ventilation were measured with a high sampling density during rest, exercise, and recovery in normal subjects performing upright cycle ergometer exercise. Three 6-min constant-work exercise tests (moderate, heavy, and very heavy) were performed by each subject. We found a small respiratory acidosis during the moderate-intensity exercise and an early respiratory acidosis followed by a metabolic acidosis for the heavy- and very-heavy-intensity exercise. During recovery, arterial pH rapidly returned to the preexercise value for the moderate-intensity work. However, arterial pH decreased further during the first 2 min of recovery for the heavy- and very-heavy-intensity work, before a slower return toward the resting values. We conclude that arterial acidosis is the consistent arterial pH reaction for moderate-, heavy-, and very-heavy-intensity cycle ergometer exercise in humans and that this acidosis is blunted but not eliminated by the ventilatory response. During recovery, the return to resting arterial pH and PCO2 and standard bicarbonate appears to be determined by the rate of lactate decline.

Acid-Base Equilibrium↗
PubMed2004

Effect of high-intensity submaximal work, with or without rest, on subsequent VO2max.

PURPOSE: In practice, tests of maximal oxygen uptake (.VO2max) are often preceded by a lactate profile, a highly intense but submaximal exercise bout. The .VO2max response to preceding high-intensity submaximal exercise, with or without a rest period, has not been determined. If .VO2max is limited after a lactate profile, exercise-induced hypoxemia (EIH) may explain the deficit. The purposes of this study were to: 1) examine the effects of high-intensity submaximal exercise, with or without rest, on subsequent .VO2max; and 2) evaluate the role of EIH in causing any observed changes. METHODS: Ten healthy, well-trained, male cross-country skiers (age = 20.5 +/- 4.7 yr, height = 181.6 +/- 6.0 cm, mass = 72.1 +/- 5.7 kg) completed three exercise trials: an incremental run to fatigue (MAX), MAX preceded by a high-intensity submaximal run (lactate profile) and a 20-min rest period (discontinuous protocol [DC]), and MAX preceded by a high-intensity submaximal exercise run with no rest (continuous protocol [C]). .VO2max, minute ventilation, and arterial oxygen saturation were measured throughout, and diffusion capacity was evaluated 2 min postexercise. RESULTS No significant between trial differences were observed, although the difference between .VO2max determined during the MAX trial (62.7 +/- 6.7 mL.kg-1.min-1) and during the DC trial (58.3 +/- 4.4 mL.kg-1.min-1) approached significance (P = 0.059). DC .VO2max responses could be separated into two groups: five responders whose .VO2max suffered during the DC trial (decreased >7.5% from MAX) and five nonresponders, whose .VO2max was unaffected by preceding submaximal exercise and a rest period. Responders showed greater aerobic capacity during the MAX trial. CONCLUSION: .VO2max is significantly reduced in approximately 50% of cross-country skiers when a maximal exercise test is preceded by high-intensity submaximal exercise and a 20 min rest period; the role of EIH in causing these reductions is unclear.

Adaptation, Physiological↗
PubMed1981

Plasma volume, osmolality, vasopressin, and renin activity during graded exercise in man.

Plasma volume (PV), renin activity (PRA), and osmotic (Osm), sodium (Na+), and arginine vasopressin (AVP) concentrations were measured in venous blood samples taken before and after three levels of cycle ergometer exercise (100, 175, and 225 W) in 15 young male volunteers. Plasma volume and solute concentrations changed significantly (P less than 0.05, denoted by *) with work intensity. The % delta PV was -3.7%* at 100 W, -8.8%* at 175 W, and -12.4%* at 225 W. Plasma Na+ concentration, Osm, and AVP increase were curvilinear with graded exercise and were significant only when work intensity exceeded 40% VO2max. PRA increase was linear and significant at all work levels. The % delta PV was significantly correlated with delta Osm (r = 0.99*) and delta Na+ (r = 0.89*) but had low correlations with delta AVP (r = 0.22, NS) and delta PRA (r = 0.12, NS). However, delta AVP was significantly correlated with delta Na+ (r = 0.86*) and delta Osm (r = 0.83*), whereas delta PRA had low correlations with delta Na+ (r = 0.33, NS), delta Osm (r = 0.29, NS), and delta AVP (r = 0.43, NS). The data support the hypothesis that a) with exercise, AVP release is a primary factor for fluid and electrolyte regulation as it is highly correlated with the plasma hyperosmolality produced by a net hypotonic plasma efflux; b) an exercise intensity greater than 40% VO2max is required to change plasma osmolality and, thus, stimulate significant AVP release; and c) the stimulation of the renin-angiotensin system is a more general stress response, which responds to increasing sympathetic nervous activity.

Adult↗
PubMed1977

[Utilization and restitution of energy sources during muscular activity under steady-state metabolic conditions].

During muscular activity at steady state of metabolism both the carbohydrate and the free fatty acids are utilized as energy sources. Kreatine phosphate expense, carbohydrate mobilization, and intensity of glycolysis during the same work are in positive correlation with the work intensity, while fatty acids mobilization is in negative correlation. Intensity of restoration of energy sources is in positive correlation with the intensity of work and the energy source expense, while being in negative correlation with steady state level of metabolism. In trained organism, both the steady state level of metabolism during muscular activity and intensity of restitution during recovery period are greater than in untrained organism.

Adenylyl Cyclases↗
PubMed1999

Sweat production and localisation of carbonic anhydrase in the equine sweat gland during exercise at two ambient temperatures.

The aim of this investigation was to study sweat production during exercise at 2 ambient temperatures (20 degrees C and 35 degrees C) and the concurrent localisation of carbonic anhydrase (CA) in the sweat gland. Horses develop alkalosis during prolonged exercise and the sweat contains HCO3-. Carbonic anhydrase is therefore of interest since it catalyses the reaction CO2 + H2O<-->HCO3- + H+. Four standardbred trotters performed an exercise test. Skin biopsies were taken from the neck, and sweat rate, blood and skin temperatures were measured. There was a close relationship between sweat rate, temperatures and work intensity at 20 degrees C. Temperatures and sweat rate were higher at 35 degrees C and did not fall when the work intensity dropped. A significant decrease in the sweat gland cell area was found after exercise at 35 degrees C with an accompanying decrease of vesicles. Strong CA activity was present at the luminal cell membrane and weaker basolaterally. The staining intensity increased after exercise. We suggest that CA might be of importance for counteracting the alkalosis developed after exercise by delivering HCO3- for generation of the alkaline pH in sweat.

Animals↗
PubMedDate not supplied

[Systems analysis of activities of the intensive care and resuscitation department at a multidisciplinary hospital. II. Intensity of work and quality indicators].

The second part of the research is devoted to problems of the personnel labor load, to maintenance of reanimation asepsis, to analysis of the complications of intensive care, the causes and outcomes of these complications. A total system approach allows, as the authors believe, an objective assessment of the prerequisites of complications in expert evaluations.

Asepsis↗
PubMed1990

[Validity of daily energy expenditure estimated by calorie counter combined with accelerometer].

To estimate a reasonable and convenient method for the assessment of daily energy expenditure in workers, the validity of a calorie counter combined with an accelerometer (Kenz Calorie Counter) was tested during treadmill exercise. Ten male and female students each volunteered for exercise on a treadmill at different running speeds: 9 speeds at 2 to 10 km/h each for male subjects: 8 speeds at 2 to 9 km/h each for female subjects. Energy expenditure measured with respiratory gas analysis was compared with that estimated by the calorie counter outfitted on the waist of the subjects. For running speed slower than 9 km/h, the work intensity reading on the calorie counter increased in direct proportion to the speed of the treadmill. The correlation between running speed and the work intensity reading of the calorie counter was linear up to 8 km/h (y = 0.95 x -0.2, r = 0.96, P less than 0.001). A linear relationship during treadmill exercise (at a speed of less than 9 km/h) was also established between energy consumption measured by respiratory gas analysis and that estimated from the calorie counter (y = 1.00 x + 11.7, r = 0.94, P less than 0.001). Thus, we validated the usefulness of the calorie counter for the assessment of energy expenditure during daily physical activities.

Acceleration↗
PubMed2004

Changes in job stress, musculoskeletal symptoms, and complaints of unfavorable working conditions among nurses after the adoption of a computerized order communication system.

OBJECTIVES: Order communication system (OCS) is a real-time computerized hospital information system that supports communication of orders from the ward users to the service departments. The adoption of an OCS may profoundly alter the service patterns of healthcare workers. As a result, job stress, musculoskeletal symptoms, and complaints of unfavorable working conditions can be expected to increase. This study investigated changes in job stress, musculoskeletal symptoms, and complaints of unfavorable working conditions among nurses after an OCS had been adopted and whether adoption of the system affected the changes. METHODS: A group of nurses employed in a university hospital in Korea was surveyed 1 month before and 3 months after the OCS had been adopted. We used Karasek's job contents questionnaire (JCQ) to evaluate job stress. The cumulative trauma disorder (CTD) questionnaire was used to assess the presence of musculoskeletal symptoms. The presence of unfavorable working conditions was also assessed. Next, we evaluated whether non-work factors (such as demographic factors and life events) had influence on job stress, musculoskeletal symptoms, and complaints of unfavorable working conditions after adoption of the OCS. RESULTS: One hundred thirty nurses from the hospital (51.2%) responded to both surveys. Several JCQ scales were notably altered after OCS adoption; psychological job demand was significantly decreased (P < 0.01), although subjective assessment for hazardous conditions was significantly increased (P < 0.01). There was a significant increase in back complaints (P < 0.05). There was considerable decrease in the number of nurses who complained of 'increase in work intensity' (P < 0.05), 'increase of staying time to deal with remaining duties' (P < 0.05), and 'abrupt change of duties' (P < 0.01). According to the analysis for the associations between non-work factors and significantly changed variables, only two non-work factors, 'tenure' and 'conflicts with friend(s)', showed statistical significance with complaints of 'increase in work intensity' (P < 0.05) CONCLUSIONS. This study suggests that a newly adopted computerized system might have provoked changes in job stress, musculoskeletal symptoms, and the complaints of unfavorable working conditions. It was found that, despite the overall favorable changes, complaints of hazardous conditions and back symptoms increased.

Adult↗
PubMed1986

Increases in factor VIII complex and fibrinolytic activity are dependent on exercise intensity.

Components of the factor VIII complex increase and activation of the fibrinolytic system occur during exercise. The relation between the duration and intensity of exercise and the relative changes in the VIII complex and fibrinolytic system have not been previously examined. Five healthy male subjects were exercised with three protocols: a graded progressive exercise test to exhaustion on a cycle ergometer with 50-W increments every 4 min, steady-state exercise, 15 min at 5 and 125 W each, and an acute 30-s maximal exercise test on a cycle ergometer. Venous blood samples were drawn at base line, during the last 30 s of each power output in the graded exercise, at 5-min intervals for the steady-state exercise, and for up to 1 h after completion of exercise in all three protocols. At the maximum exercise intensities, increases in plasma lactate concentration ([La]), O2 uptake, and [H+] were observed. Components of the VIII complex [VIII procoagulant, VIII procoagulant antigen, VIII-related antigen (VIIIR:Ag), VIII ristocetin cofactor activity] abruptly rose at only the highest work intensities, whereas the whole blood clot lysis time began to gradually shorten much earlier at low work intensities. There were no qualitative changes in the factor VIIIR:Ag on crossed immunoelectrophoresis nor was there evidence of thrombin generation as determined by fibrinopeptide A generation. We conclude that during exercise the changes observed in the coagulation and fibrinolytic systems are related to the intensity of the exercise, which is reflected by increases in plasma [La] and [H+], and that the fibrinolytic system is activated before the changes in the VIII complex are observed.

Adult↗