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R J Shephard

Publications and source records attributed to R J Shephard.

At least 217 records · Page 12Linked to original sources
PubMed1989

Exercise in the tertiary prevention of ischemic heart disease: experimental proof.

Factors hampering experimental demonstration of the value of physical activity in decreasing the cardiac mortality rate after myocardial infarction are shown to include (1) inter-individual differences in disease severity, (2) secular changes in 'standard' therapy, (3) variations in the prescribed exercise with respect to time of initiation, frequency, intensity and duration of effort, level and duration of supervised programming, (4) incidental influences of group therapy, (5) poor compliance of test subjects and a contamination of control subjects, (6) selective referral of a low-risk sample of patients, and (7) an insufficient sample size. Because of practical difficulties in organizing a controlled trial, many early reports were based on non-randomized comparisons between programs. While such studies appeared to suggest a substantial advantage to those who were exercised, factors of patient selection cannot be ruled out. Randomized controlled trials using samples of up to 750 patients have generally shown a small (around 20%) and statistically insignificant decrease of mortality in exercised populations relative to controls. When available information from the 10-12 major trials has been combined, using various techniques of meta-analysis, the benefit from exercise has become statistically significant. The implication seems that if a patient begins and continues a program of endurance exercise, the lifespan may be increased by an average of some two years, at the cost of a considerable involvement in exercise classes. While this is a useful gain of longevity, an improved quality of life seem more important reason for advocating exercise to the post-coronary patient.

Coronary Disease↗
PubMed1989

Nutritional benefits of exercise.

Specific nutritional benefits of regular exercise include the control of obesity and its complications, the improvement of blood lipid profile, the optimization of micro-nutrient intake and the assurance of a maximum quality-adjusted life-expectancy. While epidemiologists interpret various weight for height ratios in terms of obesity, such data can be misleading, particularly in older people (where an accumulation of fat is masked by lean tissue loss). Skinfold calipers provide a more unequivocal index of the amount and distribution of subcutaneous fat. Arguments against the treatment of obesity by exercise include the large energy yield of fat, the potential for compensating changes of resting metabolism, and an inherently high "set-point" of fat stores in the obese. Exercise cannot achieve rapid fat loss, but it has several advantages over other types of treatment, including the positive nature of the prescription, the associated elevation of mood and suppression of appetite, the conservation of lean tissue, and the establishment of an improved lifestyle. Moreover, blood pressure is reduced, insulin needs are decreased in the diabetic, and favourable changes of lipid profile are observed. Total cholesterol levels are not affected by exercise if body mass is held constant, but (provided a weekly threshold of exercise is exceeded) there is an increase of HDL cholesterol, particularly HDL-2 cholesterol. The intake of vitamins and most other micronutrients is increased by a high daily energy expenditure. Frank anaemia is not common in athletes, but a low iron saturation may be an indication for dietary supplements.(ABSTRACT TRUNCATED AT 250 WORDS)

Exercise↗
PubMed1989

Sexism in CJSS.

Explore the source record for details and available documents.

Attitude↗
PubMed1989

A good article.

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Humans↗
PubMed1989

Overall intake of energy and key nutrients: data for middle-aged and older middle-class adults.

The reported 7-day dietary intake is described for 60 middle-aged and older middle-class adults aged 45-75 years. The 30 men, who apparently were mostly still moderately active (reported average energy intake for 7-day recording period 11.7 +/- 3.6 MJ/day) showed few deficiencies in the intake of key nutrients relative to standard dietary recommendations. The 30 women were relatively inactive (reported average energy intake 8.1 +/- 1.9 MJ/day). In consequence, some of them had less than an optimal intake of vitamin A, riboflavin and thiamin, while 25 of 60 subjects (17 women, 8 men) had a calcium intake of less than 800 mg/day. Calcium intake was quite closely correlated to total energy intake. Given that a low level of physical activity was apparently responsible for the failure to meet recommended dietary allowances, an increase of habitual physical activity may thus be commended as a simple approach to the optimisation of diet in the sedentary and economically comfortable older adult.

Aged↗
PubMed1988

Does suggestibility modify acute reactions to passive cigarette smoke exposure?

The influence of suggestibility on responses to passive cigarette smoke exposure was tested in a group of 24 healthy adult nonasthmatic nonsmokers and 16 asthmatic nonsmokers. Sixty-five-min exposures to air and to moderate (17 ppm carbon monoxide) and heavy (31 ppm carbon monoxide) concentrations of machine-produced cigarette smoke were carried out according to a design that permitted all six permutations of the three treatments to be equally represented. Nonasthmatic subjects exercised intermittently at an intensity inducing a respiratory ventilation of 43.6 liters/min, while asthmatic individuals were at rest, in a 14.6-m3 chamber; all viewed a bank of burning cigarettes during each exposure. Significant dose-response relationships were observed for reported symptoms, deterioration of pulmonary function, increase in nasal airflow resistance, and increase of carboxyhemoglobin levels. These findings could reflect either a pure physiological response, or an interaction between physiological and psychological responses. For asthmatics, correlations between pulmonary function responses and baseline measures of suggestibility showed 5/45 (11%) significant correlations (P less than 0.05) for both the ratio of saline diluent/air FEV1 during methacholine inhalation challenge and an index derived from the Minnesota Multiphasic Personality Inventory (MMPI), while no significant correlations were shown with the James "locus of control" test. Nonasthmatics showed 4/45 (9%) significant correlations for both the James test and the MMPI index, and 1/45 (2%) for the ratio of saline diluent/air FEV1. It is concluded that while suggestibility may augment physiological responses to passive smoking, any effect is relatively weak.

Adult↗
PubMed1988

Peak oxygen intake and hypoxia: influence of physical fitness.

Eight men and eight women each performed peak oxygen intake tests on a cycle ergometer breathing ambient air and a mixture of 12% oxygen in nitrogen (equivalent to an altitude of 4400 m) in the two experiments. Hypoxia induced an average 28% decrease of peak oxygen intake, with a somewhat smaller decrease of power output. There were also small decreases in peak heart rate, peak blood pressure, peak ventilation, and peak blood lactate concentration. The major part of the impairment in oxygen transport was due to a reduction of arterial oxygen saturation, with small contributions from the decrease in heart rate and the decrease of ventilation. Subjects in good physical condition suffered a larger decrement of oxygen transport than their more sedentary colleagues, probably due to an unfavorable ratio of peak diffusing capacity to peak cardiac output. However, in the short term, this handicap could be countered by hyperventilation, and such a tactic could probably improve athletic performance over moderate distances.

Adult↗
PubMed1988

Geriatric benefits of exercise as an adult.

Associations between habitual physical activity and health were studied by retrospective questioning of 674 retirees aged 65-90. Within the limitations of the study (a volunteer sample and a simple questionnaire index of physical activity), the data show a decrease of activity in men, but not in women, from age 50 to the retirement years. The main factors influencing disability, and therefore health-care costs, were age (disability greater in older subjects) and sex (disability greater in women than in men). ANCOVA indicated that after allowing for these two variables, there was a possible small effect of physical activity at age 50 upon subsequent disability (p less than .094), together with a significant physical activity/sex interaction (p less than .030). However, a multivariate linear regression analysis of quality-adjusted health-care costs showed no significant effect of physical activity at age 50 upon subsequent disability. Nor did those surviving to the higher quintiles of the retirement years show a higher physical activity score at age 50 than those in the lower quintiles. While further research with more precise instruments remains desirable, the present results suggest that habitual physical activity at the age of 50 has only a weak association with lower levels of current physical disability and no relationship to resultant health-care costs during the years of retirement.

Aged↗
PubMed1988

Muscle mass as a factor limiting physical work.

Maximal exercise has been performed by eight men and eight women, using four types of ergometer (2-leg, 1-leg, arm + shoulder, and arm) while breathing room air and while breathing 12% O2. Results have been related to anthropometric estimates of muscle mass in the active limbs. Although significant sex differences of O2 transfer and power output are shown, the sex-specific aerobic performance was roughly proportional to active muscle volume (both when comparing individuals on a given type of ergometer and when comparing average scores of the several types of ergometer). However, the relationship was closer for steady power output than for peak O2 intake (where the scores for arm work were boosted by the use of accessory muscles and by hyperventilation). When breathing 12% O2, the 2-leg performance was substantially reduced (an average of 28.7% for O2 transport and 19.2% for power output). This effect dropped to 9.1% for O2 transport and 12% for power output in one-leg ergometry and was negligible for arm or arm plus shoulder work. It is argued that because of difficulty in perfusing small muscles, arm work is limited largely by the intrinsic power of the active muscles, that single-leg ergometry is limited rather equally by central circulatory and muscular factors, and that two-leg ergometry is almost entirely dependent on the central circulatory transport of O2.

Adult↗
PubMed1988

Residual volume as a tool in body fat prediction.

Possible methods of estimating residual volume for the prediction of body fat have been compared in young and healthy adults, with particular reference to the potential of a rapid helium equilibration method. In the first experiment, 5 women and 5 men performed nitrogen elimination, oxygen dilution and helium equilibration tests; scores for the helium test were higher than for the other two methods, but lay between the predictions made by Bass in 1964 and by Wilmore in 1969 and the values predicted by the equation of Goldman and Becklake in 1959. However, estimates of body density and body fat, based on residual volumes obtained from the prediction equations, did not differ significantly from those obtained directly by helium equilibration. A second experiment compared the helium and the oxygen techniques in 18 men and 18 women, with similar results. A final experiment compared the simple helium equilibration procedure with vital capacity and anthropometric predictions also suited to large scale determinations of body composition. It is concluded that the rapid helium equilibration procedure provides a fast and convenient procedure for the residual volume component of a body fat estimation. However, further study of the adequacy of equilibration is needed in older subjects and in patients with chronic chest disease.

Adipose Tissue↗
PubMed1988

PAR-Q, Canadian Home Fitness Test and exercise screening alternatives.

Procedures for the preliminary screening of asymptomatic adults who wish to exercise are reviewed with particular reference to experience gained through the mass use of the physical activity readiness questionnaire (PAR-Q) and the Canadian Home Fitness Test (CHFT). It is argued that both a brief submaximal exercise test and a subsequent moderate increase of habitual activity are extremely safe tactics to recommend to a symptom-free adult. There are some useful minor modifications which could be made to the PAR-Q instrument, but its sensitivity and specificity relative to such criteria as medical examination, hypertension, CHFT completion and exercise-induced ECG abnormalities compare favourably with alternative self-administered procedures. The basic difficulty of screening an asymptomatic population (highlighted by Bayes theorem) is the high percentage of false positive and false negative test results. One remedy would be to stratify the population in terms of known cardiac risk factors and to restrict detailed pre-exercise screening to the high risk segment of the population.

Canada↗
PubMed1988

Sports medicine and the wheelchair athlete.

International competitions for the wheelchair-confined are now a major feature of the world of sport. They are helpful in improving both mood state and physiological function, while improving long term prognosis. Immediate medical problems are much as in other types of competition, but there are also specific problems (bladder infections, pressure sores, intolerance of environmental extremes, and injuries related to wheelchair use). Disability classification, based on the anatomical or functional level of a lesion, provides a reasonably fair basis for competition. Most of the functional data to date relate to strength (isometric and isokinetic) and aerobic power (measured in a wheelchair or on an arm ergometer). While the inactive patient is often severely limited, wheelchair athletes may have a greater functional capacity than sedentary normals. The principles of training for the wheelchair-confined are much as in the able-bodied, although because the arm muscles are small, much of the training response may be peripheral rather than central. The margin between an effective stimulus and overtraining is also reduced. Involvement in a training programme not only increases physiological function, but also counters depression, increasing the subject's sense of self-efficacy. Biomechanicians are now contributing increasingly to wheelchair sport, improving the design of competitive wheelchairs, improving the mechanical efficiency of participants, and helping to reduce the risks of injury. The benefits of wheelchair sport are now clearly established, and family physicians should do more to encourage the involvement of the wheelchair-confined.

Competitive Behavior↗