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[Tropomyosin metabolism in muscles and its blood levels during physical exertion].

Physical exercise induces phasic changes in the tropomyosin content and metabolism in muscles and its concentration in blood. The intensive catabolic processes (decrease of 14C-leicin inclusion and time of half-life) of muscle tropomyosin and its appearance in blood were shown 2-24 hours after the exercise. Intensive anabolic processes of muscle tropomyosin were found at the late period of rest (72-144 h). These results reveal the biochemical mechanism of muscle adaptation to physical exercise. Data on the tropomyosin content in blood permit recommending tropomyosin for development of the diagnostic test of functional condition of the skeletal muscle.

Animals↗
PubMed1977

[Evaluation of tolerance of prolonged physical work as a function of the degree of endurance. I. Useflness of various tests determining physical endurance and the physiological cost of long-term physical exertion].

The physical capacity was determined in 23 men (aged from 19 to 27) using the following set of tests: Astrand and Ryhming's test, PWC170, PWC130, LPI, Crampton's test. The 70 min effort on the bicycle ergometer was considered as the model of prolonged work and the following parameters were accepted as standards of physiological cost of work; oxygen consumption, mechanical efficiency, heart rate during the work, stroke volume and cardiac output as well as the sum of systoles during recovery. The results of the correlation analysis point out that, at a given work intensity. the heart rate depends on results of PWC170 test and the systoles sum during recovery on the results of Crampton's tests. The capacity determined with used tests had no effect on the remaining indices of the cost of physical work.

Adult↗
PubMed1994

[Stress factors in acute myocardial infarct: the role of physical exertion and unusual life events].

OBJECTIVE: It is controversial whether the onset of myocardial infarction is a "random" event or whether there are triggering factors of the disease. Previous reports on possible triggers were based on case studies or inadequately controlled studies. The TRIMM study (Triggers and Mechanisms of Myocardial Infarction) was designed to determine the influence of physical activity and other external factors on the acute risk of myocardial infarction. METHODS: At Klinikum Steglitz, Berlin, all consecutive patients with myocardial infarction were included. In the Augsburg area, all patients with myocardial infarction in a prospectively defined cohort (n = 330,000) were registered by monitoring 26 hospitals. Information on the circumstances and possible triggers of the disease was obtained by standardized interviews. The control group was matched for age, sex, precinct, and time of a control event. The statistical analysis included a case-control comparison of patients with control subjects and a case-crossover comparison comparing the average exposure to a possible trigger with the time of the last exposure prior to the onset of disease. RESULTS: From January 1989 to December 1991, 1194 patients (74% men, 61 +/- 9 years) were enrolled 13 +/- 6 days after myocardial infarction. During the initial three hours after awakening, the occurrence of myocardial infarction was almost threefold compared to other times of day. A multivariate analysis yielded a twofold risk of myocardial infarction during physical exertion, statistically independently of time of day. 7.1% of patients had engaged in exertional physical activity at onset of the event, as opposed to 3.9% of control subjects. The case-crossover analysis demonstrated a relative risk of 2.1 (1.6-3.1) of exertional physical activity within 1 hour prior to myocardial infarction. Patients whose average frequency of physical exertion was < 4 versus > or = to 4 times per week had relative risks of 6.9 versus 1.3 (p < 0.01). Unusual life events within 24 hours and 24 hours to 4 weeks prior to the event occurred with similar frequencies and control subjects. CONCLUSIONS: Physical exertion appears to increase the acute risk of myocardial infarction in patients with coronary heart disease, particularly in untrained individuals. Unusual life events, however, are of less importance for the acute risk of disease. These findings are important for further investigation of triggering mechanisms of myocardial infarction and for improving preventive strategies.

Adult↗
PubMed2002

[Acute cardiovascular complications of vigorous physical exertion by untrained persons].

Physical exertion has paradoxical effects: regular physical activity offers protection against cardiovascular diseases, but, on the other hand, it has been shown that strenuous exercise can provoke coronary heart disease and sudden death. The risks of vigorous exertion apply particularly to untrained individuals and persons with a sedentary lifestyle. Physical exertion can cause a myocardial infarction or sudden death in people who were considered perfectly healthy before this event. In most cases, the mechanism of this is probably a rupture at the site of a vulnerable atherosclerotic plaque, with local activation of coagulation. Disturbances in cardiac rhythm may also be a cause of these complications.

Coronary Disease↗
PubMed1993

Triggering of acute myocardial infarction by heavy physical exertion. Protection against triggering by regular exertion. Determinants of Myocardial Infarction Onset Study Investigators.

BACKGROUND: Despite anecdotal evidence suggesting that heavy physical exertion can trigger the onset of acute myocardial infarction, there have been no controlled studies of the risk of myocardial infarction during and after heavy exertion, the length of time between heavy exertion and the onset of symptoms (induction time), and whether the risk can be modified by regular physical exertion. To address these questions, we collected data from patients with confirmed myocardial infarction on their activities one hour before the onset of myocardial infarction and during control periods. METHODS: Interviews with 1228 patients conducted an average of four days after myocardial infarction provided data on their usual annual frequency of physical activity and the time, type, and intensity of physical exertion in the 26 hours before the onset of myocardial infarction. We compared the observed frequency of heavy exertion (6 or more metabolic equivalents) with the expected values using two types of self-matched analyses based on a new case-crossover study design. The low frequency of heavy exertion during the control periods was validated by data from a population-based control group of 218 subjects. RESULTS: Of the patients, 4.4 percent reported heavy exertion within one hour before the onset of myocardial infarction. The estimated relative risk of myocardial infarction in the hour after heavy physical exertion, as compared with less strenuous physical exertion or none, was 5.9 (95 percent confidence interval, 4.6 to 7.7), Among people who usually exercised less than one, one to two, three to four, or five or more times per week, the respective relative risks were 107 (95 percent confidence interval, 67 to 171), 19.4 (9.9 to 38.1), 8.6 (3.6 to 20.5), and 2.4 (1.5 to 3.7). Thus, increasing levels of habitual physical activity were associated with progressively lower relative risks. The induction time from heavy exertion to the onset of myocardial infarction was less than one hour, and symptoms usually began during the activity. CONCLUSIONS: Heavy physical exertion can trigger the onset of acute myocardial infarction, particularly in people who are habitually sedentary. Improved understanding of the mechanisms by which heavy physical exertion triggers the onset of myocardial infarction and the manner in which regular exertion protects against it would facilitate the design of new preventive approaches.

Adult↗
PubMed1996

Self-reported physical exertion in geriatric care. A risk indicator for low back symptoms?

STUDY DESIGN: The study group consisted of 131 female nursing aides who took part in an intervention program with physical training or education. Assessments were performed before the intervention program and after 6 months. At follow-up evaluation, 91 nursing aides remained in the study. OBJECTIVES: To examine if perceived physical exertion was a risk indicator for low back symptoms, and to examine the relationship between perceived physical exertion, aerobic capacity, back endurance, psychological demands, and job control. SUMMARY OF BACKGROUND DATA: Perceived physical exertion frequently is assessed in epidemiologic studies concerning low back symptoms. More information about the relationship between perceived exertion, other potential risk indicators, and symptoms may provide opportunities for effective prevention of symptoms. METHODS: Assessments were obtained by questionnaires and physical capacity tests. RESULTS: The nursing aides who reported high physical exertion and were 45 years of age or older were at greater risk in the follow-up period for reporting new symptoms, continued symptoms with the same intensity, or more intense symptoms from the low back (rate ratio, 3.01; 95% confidence interval, 1.1-8.2). The exposure variable correlated most strongly (r = 0.4) with perceived physical exertion was psychological demands. CONCLUSIONS: The results indicated being aged 45 years or older, combined with high perceived physical exertion, was a risk indicator for low back symptoms. A relationship between perceived physical exertion and psychological demands was observed, but there was no influence of physical capacity on perceived physical exertion.

Adult↗
PubMed1975

The importance of adrenal glands in the improved adaptation of trained animals to physical exertion.

The importance of adrenal glands in the adaptation of rats to physical exertion was studied. Exercise training, significantly increased the working ability and prevented the water accumulation in myocardial cells during acute exertion. The latter shift was characteristic of untrained animals. However, adrenalectomy abolished the benefical effect of training on working ability and myocardial adaptation to exertion. The results obtained supported the view that the effect of training is partly mediated through the improved adrenocortical function while adrenal hormones, by regulating the heart metabolism and function, significantly influenced the adaptation of rats to physical exertion.

Adaptation, Physiological↗
PubMed2001

Do psychosocial strain and physical exertion predict onset of low-back pain among nursing aides?

OBJECTIVES: The aim of this study was to investigate psychosocial factors and physical exertion at work in relation to the onset of low-back pain. METHODS: The study was carried out as a case-crossover investigation of nursing aides caring for the elderly. Cases were identified among 157 nursing aides over a period of 2 years. Psychosocial factors, physical exertion, and low-back pain were reported daily in diary questionnaires over three consecutive days at work, repeated in six periods of 3 days. For each subject, case observations were identified as pain onset from one day to the next and matched with reference observations with no pain onset from the same person. Prospective data collection allowed analyses to be conducted with and without a lag in time between exposure and pain onset. RESULTS: The results of the analyses with time lag (longitudinal) did not support the hypothesis that psychosocial and physical strain from 1 day of work predicts pain onset the following day. However, physical exertion, stress, and, to some extent, time pressure were associated with pain on the day of onset. CONCLUSION: The effect period, if any, of exposure to physical exertion, stress, and time pressure on the onset of acute low-back pain is considered to be less than 24 hours.

Adolescent↗
PubMed1995

Evaluation of physical exertion by statistical analysis of worker's heart rate at log skidding.

Results of investigation into the physical exertion of the log skidding workers: tractor driver, winch operator and choker are presented. The investigation consisted of laboratory and field measurements and included measurements of the heart rate and assessment of the work effect, the work time structure, and the worker's physical exertion and energy consumption. According to the average rate during daily work, the physical exertion of the tractor driver and winch operator was classified as low exertion (75-95 min-1), whereas that of the choker was established as medium exertion (96-115 min-1). Energy consumption was calculated for the daily working time of 262 minutes, according to field measurements and for normal eight-hour work. According to field measurement values the tractor driver's and winch operator's work was categorized as light work (1.23-2.51 MJ) and that of the choker as heavy work (2.52-6.30 MJ). According to the values for eight-hour work, the tractor driver's and the winch operator's jobs were classified as heavy work (2.52-6.30 MJ/8 h) and the choker's job as the heaviest (6.31-10.47 MJ/8 h).

Energy Metabolism↗
PubMed1990

Work-related physical exertion and risk of preterm, low birthweight delivery.

Although many women work during pregnancy, the effect of maternal job experience on pregnancy outcome is controversial. We investigated whether work-related physical exertion increases a woman's risk of delivering a preterm, low birthweight infant. We studied 773 employed, pregnant women included in the National Longitudinal Survey of Labor Market Experience, Youth Cohort (NLSY), a nationally representative sample of young adults. Data concerning work status, job title during pregnancy, and other factors affecting the outcome of pregnancy were obtained from the NLSY. Assessment of physical exertion was based on job title, using an established catalogue of occupational characteristics. Women in jobs characterised by high physical exertion experienced a higher rate of preterm, low birthweight delivery, defined as maternal report of delivery more than 3 weeks early and birthweight under 2,500 g (adjusted RR = 5.1, 95% CI = 1.5, 17.7). These findings support a policy of limiting work-related physical exertion during pregnancy.

Adolescent↗
PubMed2003

Triggers of subarachnoid hemorrhage: role of physical exertion, smoking, and alcohol in the Australasian Cooperative Research on Subarachnoid Hemorrhage Study (ACROSS).

BACKGROUND AND PURPOSE: Unaccustomed strenuous physical exertion can trigger myocardial infarction, but little is known about the mechanisms precipitating subarachnoid hemorrhage (SAH). METHODS: We identified all cases of first-ever SAH among the combined populations (2.8 million) of 4 urban centers in Australia and New Zealand. Information on the type, time, and intensity of exposures in the 26 hours before the onset of SAH was ascertained by structured interviews. We used the case-crossover technique to assess the risk of SAH associated with transient exposures of moderate to extreme physical exertion, heavy cigarette smoking, and binge alcohol consumption. RESULTS: We registered 432 first-ever cases of SAH (62% women; mean age, 56.5 years). A definite time of onset of SAH was established for 393 patients (91%), and information on the levels of physical activity in the preceding 26 hours was obtained in 338 (78%). Of these patients, 19% engaged in moderate to extreme exertion (>or=5 metabolic equivalents) in the 2 hours before SAH, which was associated with a tripling in the risk of SAH (odds ratio [OR], 2.7; 95% CI, 1.6 to 4.6). There was no evidence of any association between heavy cigarette smoking or binge drinking and risk of SAH in the subsequent 2 hours (OR, 1.1; 95% CI, 0.4 to 3.7; and OR, 0.41; 95% CI, - infinity to 5.3). Habitual exercise did not appear to alter the risk of SAH associated with moderate to extreme exertion. CONCLUSIONS: Moderate to extreme physical exertion tripled the risk of SAH, but there was no association between transient heavy smoking or binge drinking and risk of SAH. These data suggest that heavy physical activity may trigger SAH.

Adult↗