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Biomedical subjects

R J Shephard

Publications and source records attributed to R J Shephard.

At least 181 records · Page 10Linked to original sources
PubMed1991

Handgrip dynamometry, Cybex measurements and lean mass as markers of the ageing of muscle function.

Isometric handgrip force, isokinetic knee flexion and extension torque, and anthropometric data were obtained on 67 older men and women (ranging in age from 45 to 75 years, mean 59.7 years). Hydrostatic and skinfold estimates of lean body mass were quite closely correlated with each other in this sample (r = 0.93). Handgrip force, isokinetic knee flexion and extension torque, and lean mass all decreased by 6-8% per decade over the age span examined, although in the men the loss was most marked in terms of handgrip and lean mass, whereas in the women the loss of torque in the knee muscles was dominant. Because of these differences, the handgrip data were only weakly correlated with the isokinetic strength measurements (r = 0.22), and the isokinetic data were more strongly related to lean body mass and body mass. The optimum equation for a field prediction of isokinetic strength in this age group (a combination of age, sex, age-sex interaction and lean body mass) has an error approaching 25%, with a multiple r2 of 0.37, and a standard error of the estimate (s.e.e.) of 24.5%. It is concluded that handgrip data and slow isokinetic torque measurements evaluate relatively independent aspects of the ageing of muscular function.

Aged↗
PubMed1991

Occupational demand and human rights. Public safety officers and cardiorespiratory fitness.

The issue of discrimination in physically demanding employment, such as police, firefighters, prison guards and military personnel, is contentious. In terms of oxygen transport, the 'action limit' (calling for personnel selection or task redesign) is a steady oxygen consumption of 0.7 L/min, while the maximum permissible limit is 2.1 L/min. Note is taken of the commonly expressed belief that public safety duties are physically demanding, calling for personnel with an aerobic power of at least 3 L/min, or 42 to 45 ml/kg/min. The actual demands of such work can be assessed on small samples by physiological measurements (using heart rate or oxygen consumption meters), but the periods sampled may not be typical of a normal day. A Gestalt can also be formed as to the heaviness of a given job, or a detailed task analysis can be performed; most such analyses of public safety work list distance running and other aerobic activities infrequently. An arbitrary requirement of 'above average fitness' is no longer accepted by courts, but a further approach is to examine the characteristics of those currently meeting the demands of public safety jobs satisfactorily. Young men commonly satisfy the 3 L/min standard, but this is not usually the case for women or older men; in the case of female employees, it also seems unreasonable that they should be expected to satisfy the same standards as men, since a lower body mass reduces the energy cost of most of the tasks that they must perform. A second criterion sometimes applied to physically demanding work (a low vulnerability to heart attacks) is examined critically. It is concluded that the chances that a symptom-free public safety officer will develop a heart attack during a critical solo mission are so low that cardiac risk should not be a condition of employment. Arbitrary age- and sex-related employment criteria are plainly discriminatory, since some women and 65-year-old men have higher levels of physical fitness than the average young man of 25 years. Neither laboratory nor field tests offer a satisfactory means of distinguishing such individuals, and the only equitable basis of selecting personnel for physically demanding work seems a probationary period of employment.

Cardiovascular Diseases↗
PubMed1991

Fuel for exercise.

Explore the source record for details and available documents.

Energy Metabolism↗
PubMed1991

Gains of cardiorespiratory fitness with arm-crank training in spinally disabled men.

Cardiorespiratory responses to four patterns of arm-crank training (thrice weekly sessions at 50 or 70% of peak oxygen intake, 20 or 40 min per session) were examined over 8, 16, and 24 weeks in 24 initially inactive subjects with paraplegia. Training was associated with a significant increment of the peak oxygen intake during arm-crank tests except in control subjects and those combining a low intensity (50% of peak) with short-duration training (20-min sessions). There were associated increases in cardiac stroke volume, as assessed by a carbon dioxide rebreathing technique during submaximal exercise. It is suggested that the performance of inactive wheelchair users is limited by a pooling of blood in paralysed regions, with a reduction of cardiac preloading; nevertheless, substantial gains of performance are possible through prolonged arm-crank exercise of moderate intensity.

Adolescent↗
PubMed1991

Responses to acute exercise and training after cardiac transplantation: a review.

Cardiac transplant patients now survive for several years, and the quality of life after recovery from the immediate operation is of increasing interest. The acute response to exercise depends mainly upon an increase of venous return (acting through the Frank-Starling mechanism) and slower chronotropic and inotropic responses to circulating catecholamines. At rest, there is some increase of heart rate and blood pressure, with a low normal cardiac output. During submaximal exercise the stroke volume is greater than normal, but the cardiac output is somewhat reduced, leading to a widening of arteriovenous oxygen difference. Peak heart rate, peak stroke volume, and peak cardiac output are all substantially reduced in the immediate postoperative period. Poor ventricular performance reflects in part an increase of afterloading associated with lean tissue loss. Endurance training restores lean tissue, with associated and probably causally related gains of cardiac function and peak oxygen transport. Exercise prescription after transplantation is commonly regulated by walking distance and pace, ventilatory and blood pressure responses, and ratings of perceived exertion, monitoring for episodes of infection and transplant rejection. There are psychological disturbances immediately following surgery, but again training appears to help ameliorate the mood state. Heterotopic transplants (in which donor and recipient hearts are conserved) generally yield a less satisfactory result than the standard orthotopic procedure. The ventilatory response to exercise is greater for a heart-lung transplant than for a cardiac transplant, but overall functional responses seem similar for the two types of patients. Patients tolerate exercise quite well after cardiac transplantation, and progressive endurance training is a helpful component of treatment in such individuals.

Exercise↗
PubMed1991

Physical activity and the immune system.

Methods of examining immune function include a charting of susceptibility to infections, differential blood counts or lymphocyte counts, and measures of cell proliferation and immunoglobulin synthesis in response to external mitogens. The reported acute response to exercise is transient and quite variable, depending upon the type of exercise, the immunological methodology used, the intensity of effort relative to the fitness of the individual, and the timing of observation. A leucocytosis, a granulocytosis, a small lymphocytosis, and a decrease in the proportion of T to B cells reflect mainly changes of blood volume, demargination, and migration of cells. Lymphocyte subsets show a decreased helper/suppressor cell ratio and an increase of natural killer cells. Because of the lymphocytosis, mitogens induce an increased overall cell proliferation, but proliferation for a given number of cells is decreased. Prolonged exercise leads to a decrease of serum and salivary immunoglobulin levels. Soluble factors such as interleukin-1 and interferon are increased by a bout of exercise. Cross-sectional comparisons and training experiments suggest that under resting conditions well-conditioned individuals show some lymphocytosis, increased natural killer cell activity, higher levels of interleukin-1, and possibly an enhanced reaction to mitogens. Moderate training does not greatly change exercise responses at a given fraction of maximal effort. Excessive training suppresses immune function, but the changes are small, variable, and thus difficult to relate to overtraining. Moreover, because of their transient nature, they have only a limited influence upon the risks of infection or cancer.

Exercise↗
PubMed1991

Measurements of fitness. The Canadian experience.

The history of fitness assessment in Canada is reviewed briefly, with an emphasis upon geographic and socio-cultural factors that have influenced the Canadian approach to this issue. The current policy continues to be a three-tiered system of testing: self-assessment, paramedical testing and detailed medical evaluation. At the intermediate level (large-scale representative population sampling), the emphasis is upon a combination of physical activity questionnaires and simple test procedures that can be applied by a paramedical professional in the subject's home. Observations include height, weight, blood pressure, skinfold readings, simple tests of muscular force and endurance, a stepping test of aerobic performance and the sit and reach test of flexibility. Possible modifications to sampling, questionnaires and fitness test procedures are discussed in the context of the 1981 and 1988 Canada Fitness Surveys.

Canada↗
PubMed1991

Benefits of sport and physical activity for the disabled: implications for the individual and for society.

An increase of physical activity is commonly recommended to those with physical disability, but it is necessary to distinguish competitive sport from fitness programmes, remedial gymnastics and active recreation. Potential benefits of enhanced activity are reviewed. Likely psychological gains include an improvement of mood-state, with a reduction of anxiety and depression, an increase of self-esteem and feelings of greater self-efficacy. Sociological gains include new experiences, new friendships, and a countering of stigmatization. Perceived health is improved, and in a more long-term perspective there is a reduced risk of many chronic diseases. Finally, there is a greater likelihood of employment, with less absenteeism and enhanced productivity. Both the health and the industrial benefits have a potential to yield cost savings that could make an important contribution toward the expense of suitably adapted physical activity programmes. It is concluded that the physically disabled should be encouraged to engage in physical activity, although further large-scale longitudinal studies are needed to determine the optimal type of programme for such individuals.

Persons with Disabilities↗
PubMed1991

Right-branch bundle block in circumpolar Inuit.

The prevalence of right-branch bundle block (RBBB) has been examined in the Inuit residents of Igloolik (69 degrees 40'N, Canadian N.W.T.) over a twenty-year period. Original reports of a very high prevalence of RBBB probably reflected a selective testing of patients with chronic respiratory disease by visiting physicians. Cases of RBBB are certainly seen somewhat more frequently than in a southern community, but the majority of subjects show no more than a slight notching of the R wave of the electrocardiogram, with no appreciable broadening of the QRS complex. While a few of the more marked cases of RBBB may be attributable to chronic respiratory disease, the majority are associated with high normal values for both lung function and predicted maximal oxygen intake. The probable cause is thus a ventricular hypertrophy due to the vigorous physical activity demanded by life in a northern community rather than chronic respiratory disease. The physical demands of life in Igloolik have diminished over the past two decades, and an apparent increase in the prevalence of RBBB over this period is probably due mainly to a great awareness+ of the condition by those reading the electrocardiograms.

Adolescent↗