Biomedical subjects

R J Shephard

Publications and source records attributed to R J Shephard.

At least 523 records · Page 29Linked to original sources

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Changes in adiposity and body mass index from late childhood to adult life in the Trois-Rivières study.

This study explored tracking of the body mass index (BMI) in a representative subgroup of subjects (95 women and 96 men) who were involved in the Trois-Rivières Growth and Development Study by testing autocorrelations between data for 10, 11, and 12 years and corresponding values at 34 years of age. Tracking of skinfold measurements (subscapular, triceps, suprailiac, and abdominal, and their sum) over the same intervals (60 women and 52 men) was also evaluated. After the age of 12 years, subjects showed a similar development of absolute values, whether they were from the experimental or the control group. Gains of the BMI and skinfold thicknesses showed expected gender differences. In particular, men showed larger gains of the BMI and abdominal skinfolds, whereas women had larger gains in the triceps skinfold. Increases in the sum of four skinfolds did not differ significantly between men and women, suggesting that the larger BMI gains in men were caused by a larger relative increase of fat-free mass in the men. Tracking coefficients for the BMI were lower in men than in women between 10, 11, 12, and 34 years (r = 0.43-0.49 vs. r = 0.64-0.70, P < 0.001). The results indicate that the body composition of participants in the Trois-Rivières Growth and Development study developed in a similar fashion whether or not their primary school instruction included additional physical education instruction. The results also suggest that prediction of adult obesity based on childhood BMI measurements is more effective in girls than in boys.

Adipose Tissue↗

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Cigarette smoke in enclosed public facilities.

A portable carbon monoxide detector (catalytic electrode) was used to record carbon monoxide concentrations in enclosed public facilities, including night clubs, bars, restaurants, stores, hospitals, and public transit vehicles. The highest concentrations of carbon monoxide were found in night clubs, where evening indoor readings averaged 13.4 ppm, which was 4.1 +/- 1.5 ppm higher than outdoor readings. In one poorly ventilated establishment, values ranged from 20 to 40 ppm, with substantial gradients around the room. Adequate ventilation and screening of restaurant employees for ischemic heart disease should prevent problems from cigarette-induced build-up of carbon monoxide. Unfortunately, much lower concentrations of other constituents of smoke cause symptoms and changes of pulmonary function in the nonsmoker. If carbon monoxide is used as an indicator of cigarette smoke accumulation, concentrations should not exceed ambient readings by more than 5 ppm.

Carbon Monoxide↗

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Brake reaction time--effects of age, sex, and carbon monoxide.

Simulated braking responses have been tested in relation to blood carboxyhemoglobin (HbCO) levels. The main determinants of percentage of HbCO in 352 subjects attending a fall fair were daily cigarette consumption and minutes since the last cigarette. In women the brake response time deteriorated from age 16 yr, but in the men there was an improvement from age 16 to the early 20s. Times at all ages were better for men than for women. Average response times and the rate of aging of the braking response were very similar in smokers and in nonsmokers. In the nonsmokers, however, response time with step function CO increments of as much as 7% HbCO. There was a suggestion of a small increase of reaction time, with an opposing decrease of leg movement time, during the first few minutes after CO exposure; nevertheless, these trends were statistically insignificant.

Adult↗

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Physiological effects of acute passive exposure to cigarette smoke.

Effects of passive inhalation of cigarette smoke at levels typically encountered in public buildings have been investigated. Twenty normal male and female nonsmokers (18 to 30 years) were each exposed for two hours on alternate days (in random order) to either room air or room air plus machine-produced cigarette smoke. Exposures were conducted in an unventilated chamber (14.6 m3). Subdivisions of lung volume, maximum expiratory flow-volume curves, single-breath nitrogen washout curves, blood carboxyhemoglobin levels, and heart rates were obtained before, during, and after exposure. A submaximal bicycle ergometer test and a symptom questionnaire were also administered after exposure. Statistical analysis revealed several significant differences between test and control days; the magnitude of the changes was small and of questionable biological significance, however, particularly when account was taken of the number of statistical comparisons made. Despite the relatively small physiological changes, subjective complaints were common-cough, and eye irritation, for example. It is concluded that in normal subjects the magnitude of physiological responses to acute exposures is minimal; thus arguments concerning effects rest on symptomatology and such other factors as the unknown risks of chronic exposure.

Adult↗

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Carbon monoxide exposure and auditory duration discrimination.

Two young adults performed an auditory duration discrimination task while sitting in an open office (i.e., without sensory isolation). The percentage of errors rose when carboxyhemoglobin (HbCO) readings of 3.2% or 4.7% were produced by a rebreathing method; there was a parallel but statistically insignificant trend at 2.0% HbCO. Analysis of the data by psychophysical measures, however, showed no significant changes of difference threshold, criterion value, or point of subjective equality. After the tape was rearranged to meet criteria of a constant interval, a balanced order of presentation, and psychological rather than physical equality of tone length, eight young adults performed the task better in an isolation booth than in an open office, scores in both situations being unaffected by increases of HbCO to greater than 8%. Further trials with five young adults compared responses before and after administration of 80 ml of CO (HbCO 4.92%); again, no effect of carbon monoxide was seen relative to control experiments. The error score of nonsmoking young adults can be increased by a level of HbCO as low as 3.2%. The likelihood of such a response, however, is markedly influenced by task difficulty, environment, and the arousal of the subjects. Furthermore, the nature of the functional disturbance remains uncertain; psychophysical measures show no significant impairment of auditory duration discrimination.

Adult↗

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Respiratory irritation from environmental tobacco smoke.

Acute physiological and chronic pathological responses of the respiratory tract to environmental tobacco smoke (ETS) are reviewed briefly. This study excludes discussion of the possible risk of lung cancer and the known impact of carbon monoxide on the fetus and adult. In some environments, the dose of particulate matter and the concentrations of irritant vapors absorbed on the ETS particles reach a level for which a physiological response may be expected, not only in the nose but also the bronchi. However, direct measurements indicate only small increases of nasal and bronchial resistance if normal subjects are exposed to maximal, likely concentrations of ETS. ETS is readily detected by the nonsmoker, but there is no strong evidence that pulmonary reactions have a psychogenic basis. The condition of approximately 20% of asthmatic patients is exacerbated by ETS exposure. Further study is needed to clarify the likelihood that adults will progress from a minor physiological response to pathological reactions, e.g., chronic obstructive lung disease. In young children (who are less able to escape from ETS), the association between exposure and an increase in respiratory disease is stronger than in adults. Exacerbation of asthma and an increase of respiratory disease are further arguments for legislation to guarantee smoke-free air to the nonsmoking public.

Asthma↗

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Population aspects of human working capacity.

Population measurements of human physical working capacity are reviewed. Problems of technique include an appropriate sample size, allowance of sampling bias, selection of an appropriate criterion of working capacity, and standardization of test methodology. The impact of constitution has been studied in terms of overall variance of data, frequencies of genetic markers, and twin sibling studies. Environmental experiments have compared similar races in different environments and vice versa. Athletes have been examined as examples of a combined genotypic and phenotypic response. Adaptations to the environment include adverse climate (extremes of heat, cold, rain and drought), hilly terrain and extreme high altitudes; an enhanced working capacity in hilly districts and circumpolar regions probably reflects vigorous daily activity. Socio-economic determinants of working capacity include nutrition, family size, chronic disease, and daily activity. Population differences in the course of growth and ageing seem to reflect differences of nutrition and daily activity. Population scientists have yet to define clearly the relative importance of phenotypic and genotypic adaptation in the development of working capacity; however, studies arising from the International Biological Programme have made valuable contributions to both test methodology and the understanding of interactions between man and his environment.

Adaptation, Physiological↗

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Body dimensions of Québecois children.

The present study examined the impact of sociocultural factors upon the body dimensions of primary school children (age 6-12 years) living within a uniquely francophone region of Québec. Data was collected prospectively on 546 students, drawn in approximately equal numbers from the two sexes and from urban and rural environments. Habitual activity was modified by allocating a half of the sample to an experimental programme that incorporated an additional five hours of required endurance activity per week into the primary school curriculum. Body dimensions at any given age were less in rural than in urban Québec, probably because of continuing socio-economic constraints. However, an increase of habitual physical activity did not modify body size. Stature was comparable with Demirjian 's Montr eal sample of francophone children, but was less than for anglophone children. Our within-sample variance suggests that socio-economic factors could explain only a part of the discrepancy. Relative to Toronto students, other dimensions such as height were affected less than standing height.

Anthropometry↗

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Age and physical work capacity.

Aging is associated with a progressive decrement in various components of physical work capacity, including aerobic power and capacity, muscular strength and endurance, and the tolerance of thermal stress. A part of the functional loss can be countered by regular physical activity, control of body mass, and avoidance of cigarette smoking. Nevertheless, athletes who continue to train regularly still show a substantial aging of both physiological function and competitive performance, reflecting a deterioration of cardiac pump function, a decrease of muscle strength, and a progressive impairment of heat tolerance. These various changes are of concern to the occupational physician, because of the rising average age of the labor force. In theory, an over-taxing of the heart and skeletal muscles might be thought to lead to a decrease of productivity, manifestations of worker fatigue such as absenteeism, accidents, and industrial disputes, and an increased susceptibility to musculoskeletal injuries, heart attacks, and strokes. However, in practice, the productivity, health, and safety of the older worker pose relatively few problems. Reasons for this paradox are discussed, and it is stressed that in general there is no longer need to push workers to their physical limits because of automation-related changes in methods of production.

Aging↗

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Kinetics of the transplanted heart. Implications for the choice of field-test exercise protocol.

PURPOSE: The transplanted heart shows a slow increase (on transient) of both heart rate (HR) and oxygen consumption (VO2) at the beginning of exercise. The hypothesis used in this study was that this would lead to unacceptably large systematic errors when field predictions of maximal oxygen intake (VO2max) were derived from cycle ergometer tests with a steep ramp function. METHODS: The subjects (27 patients who had received orthotopic heart transplants 6 months previously, and 45 age-matched control subjects) each performed a rapid progressive cycle ergometer test (increments of 16.7 Watts [W] per minute to subjective exhaustion) and a "steady-state" test (two 6-minute stages at one third and two thirds of peak power output). Time constants for HR and VO2 were determined by fitting single exponent equations to the "steady-state" data and noting the time for the difference from the plateau value to reach 36.8% of its initial value. Heart rate and VO2 also were compared between rapid progressive and "steady-state" tests at one third and two thirds of peak power output. RESULTS: At one third of peak power output (46 W in patients, 73 W in control subjects), the respective time constants (mean +/- SE [standard error]) were 60.4 +/- 6.4 and 40.5 +/- 3.0 seconds for VO2 (P < .01), and 130.0 +/- 14.3 and 67.9 +/- 10.0 seconds for HR (P < .001). At two thirds of peak power, the corresponding values were 49.2 +/- 5.5 and 34.7 +/- 2.7 seconds for VO2 (P < .05), and 147.9 +/- 13.0 and 122.2 +/- 4.8 seconds for HR (P < .10). Comparing rapid progressive and "steady-state" readings, the control subjects showed identical values for HR and VO2 at one third of peak power, but at two thirds, the rapid progressive test HR lagged behind the "steady-state" value by 8 +/- 3 beats per minute. The cardiac transplant patients showed a larger HR lag in the rapid progressive tests (109 +/- 12 vs 117 +/- 10 beats per minute, P < .05; 125 +/- 14 vs 141 +/- 14 beats per minute, P < .005). Oxygen consumption also tended to lag slightly at two thirds of peak power (118 +/- 76 mL/min, not significant). CONCLUSIONS: The rapid progressive test protocol yields acceptable field estimates of aerobic power in normal individuals, but the slow acceleration of HR after cardiac transplantation leads to unacceptably large errors if the HR from a rapid progressive test protocol is used to predict maximal oxygen intake (VO2max) in such patients.

Adult↗

PubMedDate not supplied

On the prediction of physiological and psychological responses to aerobic training in patients with stable congestive heart failure.

BACKGROUND: Physiological and psychological markers of patients with congestive heart failure (CHF) who will respond to aerobic training are needed as a guide to appropriate therapy. METHODS: Seventeen of 21 patients with stable CHF completed a 16-week supervised progressive walking program 5 times per week. Cycle ergometer determinations of peak oxygen intake and peak power output at entry and 16 weeks were supplemented by a 6-minute walk, a disease-specific Quality of Life (QOL) questionnaire, and a standard gamble. RESULTS: Peak oxygen intake increased by 2.6 +/- 1.5 mL/(kgmin) over an initial value of 15.6 mL/(kgmin), with parallel gains in peak power and the 6-minute walk. Marked improvements in QOL and standard gamble scores also developed. Initial cardiorespiratory status (heart volume, ejection fraction, oxygen pulse, and peak oxygen intake) was correlated more closely (P = 0.09 to 0.18) with delta peak oxygen intake than with delta peak power or delta walking distance. Physiological gains bore little relationship to initial psychological status. Gains in CHF Questionnaire and Standard Gamble scores were strongly associated with initial scores for these variables (dyspnea, P = .02; mastery, P = .005; standard gamble, P = .001), but could not be predicted from either initial physiological status or gains in physiological condition. CONCLUSIONS: Initial cardiorespiratory status provides little indication of which patients with CHF respond well to training. Gains in QOL score are influenced by initial scores, and seem to show a "ceiling" effect.

Aged↗

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The acceptable risk of driving after myocardial infarction: are bus drivers a special case?

BACKGROUND: Bus drivers frequently encounter difficulty in returning to their former employment after recovery from myocardial infarction. The risk that a recurrence of myocardial infarction may cause a personal-injury accident is analyzed. METHODS: The Cumulative Medical Index and Current Contents was searched systematically from 1980 to date, accepting papers irrespective of language. Relevant earlier material was drawn from the author's published reviews on bus driving and myocardial infarction and vehicle accidents. One hundred twenty-three articles were included in the database, of which 110 were used in the review. RESULTS: The risk of a personal injury accident or fatality from a sudden cardiovascular incident is calculated as the product of typical driving time per day (Td = 0.167), vehicle characteristics (V) (a low factor of 0.167 for an urban bus because of slow speed and use of reserved curb lanes), the risk of recurrence of a sudden cardiovascular incident (SCI) (.015, somewhat greater in bus drivers than in the general population), and the risk that such an incident will cause a personal-injury accident (Ac) (at 0.005, probably lower than in the general population because of low vehicle speeds and the bus driver's experience in defensive driving). CONCLUSIONS: The overall risk is 0.00002, 1 in 50,000 driver-years, is lower than accepted for passenger-car operators, and only slightly greater than for the older symptom-free adult. Bus drivers who meet the current standards of the Canadian Cardiovascular Society should be encouraged to return to their former employment.

Accidents, Traffic↗

PubMedDate not supplied

On-site evaluation of bus drivers with coronary heart disease.

BACKGROUND: Bus drivers with ischemic heart disease have been denied normal employment, although they satisfy Canadian Cardiovascular Society (CCS) Guidelines. To show the safety of their reemployment, we compared their responses when driving buses with those seen during graded exercise testing. METHODS: Twenty-two male city bus drivers, aged 48.1 +/- 5.6 years (19 had a myocardial infarction, 2 had coronary artery bypass graft, 1 had documented ischemic heart disease) were referred for work evaluation. After a CCS cardiopulmonary exercise test, they were accompanied by a physician and a therapist/technician on a normal shift. Note was kept of symptoms, signs, electrocardiogram (telemetry), blood pressure (ambulatory recording unit), and Borg rating of effort throughout. RESULTS: Average values for peak heart rate (101 +/- 12.5 versus 148.2 +/- 17.2 beats/min), peak systolic pressure (150.0 +/- 20.8 versus 198.9 +/- 25.7 mm Hg), peak rate-pressure product (15,259 +/- 3,369 versus 29,500 +/- 5,283 units), peak Borg RPE (9.9 +/- 1.4 versus 17.4 +/- 3.0 units), and peak ST-segmental depression (-0.03 +/- 0.07 versus -0.07 +/- 0.09 mV) during the shift were only about a half of average values reached during the graded stress test. Moreover, peak values were reached at the end of the shift, when carrying the loaded fare box, rather than when driving. CONCLUSIONS: Cardiovascular strain during bus driving is much less than during the CCS stress test for drivers. Using CCS methodology, the risk that a sudden cardiovascular incident will cause injury or death of others in the first year after recovery from myocardial infarction is estimated at 1 in 50,000 driver-years. Thus, those satisfying CCS requirements can return to full driving duties promptly, with minimal risk to themselves, passengers, or other road users.

Adult↗

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Risk profile and health awareness in male offspring of parents with premature coronary heart disease.

BACKGROUND: The offspring of parents who suffer from premature coronary heart disease have a significantly higher risk of early cardiac death than controls. A genetic predisposition is compounded by a commonality of environmental risk factors within families. Increasing awareness, early detection and modification of risk factors are essential components of an effective public health strategy to protect this highly vulnerable population. METHODS: The sons (n = 571) of parents with premature coronary heart disease attended the Toronto Rehabilitation Centre for a risk factor evaluation that included an interview with questionnaire, measurement of body dimensions and blood lipids, and cardiopulmonary exercise testing. A follow-up questionnaire was sent out 2 years after the evaluation. RESULTS: Despite concern about family history, 23% of subjects were smokers and 75% were inactive. Objective data confirmed a substantial prevalence of cardiac risk factors: less than optimal cardiovascular fitness (48%), overweight (34%), total cholesterol > or = 200 mg/dL (46%), high-density lipoprotein cholesterol < or = 35 mg/dL (26%), low-density lipoprotein cholesterol > or = 160 mg/dL (16%), triglycerides > or = 200 mg/dL (27%), and lipoprotein (a) > 30 mg/dL (24%). Although almost all had a family physician whom they had seen an average of 1.8 times in the past year, and 4.7 times in the previous 3 years, screening and risk factor intervention strategies were disappointing. Two-year follow-up data showed a heightened health awareness, with a greater proportion of subjects exercising and attempting to maintain an appropriate body mass. CONCLUSIONS: The male offspring of parents who have suffered a premature coronary event exhibit a substantial prevalence of modifiable risk factors. The family physician can play an essential role in promoting a healthy lifestyle through risk reduction counselling and screening.

Adult↗

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Changes in the quality of life: a major goal of cardiac rehabilitation.

BACKGROUND: Quality of life (QOL) is a major goal in the context of preventive and therapeutic cardiology. In this article, quality of life concepts are reviewed, factors limiting QOL in cardiac disease are identified, methods of measurement are explored, and clinically significant changes are defined. The changes effected by cardiac rehabilitation are considered, together with their physiological and psychological correlates. A final section suggests avenues for future research. METHODS: Relevant articles were identified by computer literature searches and review of extensive personal files. FINDINGS: In the past, there has been an excessive focus on extending the length rather than the quality of the cardiac patient's life. The overall QOL is a broad concept, influenced by personal perceptions, coping mechanisms, and environmental constraints. The ideal test instrument would be reliable, valid, and responsive to clinical change. Potential options include a Gestalt-type instrument, a disease-specific instrument, a function-specific instrument, or a detailed generic questionnaire. There have been relatively few comparisons between these potential approaches. Currently, the Standard Gamble (Gestalt-type), and Living With Heart Failure Questionnaire (disease-specific type), and the Medical Outcomes Study Short-Form 36 (SF-36) Health Survey (generic-type) are among the most popular approaches. Problems arise in distinguishing a clinically important from a statistically significant change; commonly a score change of 1 standard error of the mean is regarded as clinically important. Correlations of scores with clinical, physiological, and psychological change are sometimes weak, in part because of floor and ceiling effects. Nevertheless, potential gains in QOL provide a stronger argument for preventive and therapeutic programs than do increases in longevity. CONCLUSIONS: The current literature supports the value of QOL measurements in the management of patients with cardiac disease. However, further research is needed to determine the optimum test instrument, and the best method of interpreting resultant scores.

Aged↗

PubMedDate not supplied

Influence of exercise and life-style variables upon high density lipoprotein cholesterol after myocardial infarction.

Two groups of postcoronary patients (n = 35 and n = 27) were followed for 1 year. Group 1, recruited 2 to 3 months after infarction, showed a 9% gain of maximum oxygen intake in response to an average of 878 km of walking at speeds increasing to 6.9 km.hr-1. High density lipoprotein (HDL) cholesterol showed a statistically significant, but small, increase over the period of training. If expressed as a ratio to either low density lipoprotein or total cholesterol, the change was correlated with decreases of cigarette consumption, alcohol intake, and body mass, but was unrelated to speed or training distance. Group 2 patients trained an average of 50 to 80 km a week. In this group, HDL cholesterol correlated well with the weekly running distance, declining in those subjects who detrained, and increasing in those who intensified their training. We conclude that the dose of exercise necessary for inducing any substantial increase of HDL cholesterol is about 20 km.wk-1.

Alcohol Drinking↗

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Tests of maximum oxygen intake. A critical review.

The determinants of endurance effort vary, depending upon the extent of the muscle mass that is activated. Large muscle work, such as treadmill running, is halted by impending circulatory failure; lack of venous return may compound the basic problem of an excessive cardiac work-load. If the task calls for use of a smaller muscle mass, there is ultimately difficulty in perfusing the active muscles, and glycolysis is halted by an accumulation of acid metabolites. Simple field tests of endurance, such as Cooper's 12-minute run and the Canadian Home Fitness Test, have some value in the rapid screening of large populations, but like other submaximal tests of human performance they lack the precision needed to advise the individual. The directly measured maximum oxygen intake (VO2 max) varies with the type of exercise. The highest values are obtained during uphill treadmill running, but well trained athletes often approach these values during performance of sport-specific tasks. Limitations of methodology and wide interindividual variations of constitutional potential limit the interpretation of maximum oxygen intake data in terms of personal fitness, exercise prescription and the monitoring of training responses. The main practical value of VO2 max measurement is in the functional assessment of patients with cardiorespiratory disease, since changes are then large relative to the precision of the test.

Age Factors↗

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Physical activity and child health.

Clinicians should direct greater attention to positive health, with particular reference to the role of physical activity, in optimising the well-being of a child. Vigorous physical activity slows maturation, particularly if there is associated energy imbalance or emotional stress, but it does not greatly affect body size. Well-designed exercise programmes enhance the immediate physical, psychomotor and intellectual attainments of a child. Long term health benefits depend on a continuation of the physical activity. Internal motivation and the creation of positive attitudes are thus important. Acute illness is not prevented by vigorous exercise, but it has a favourable effect on the course of many chronic diseases. There are certain risks, including physical injury, psychological stress, and (occasionally) cardiac deaths, but in general, an exercise regimen enhances well-being, favouring the balanced development of a child.

Adolescent↗