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Biomedical subjects

R J Shephard

Publications and source records attributed to R J Shephard.

At least 109 records · Page 6Linked to original sources
PubMed1995

Heavy exercise, nutrition and immune function: is there a connection?

Exercise participation can modulate interactions between nutritional status and immune function in at least three ways. Athletes and health conscious exercisers may occasionally adopt an unusual diet: megadoses of vitamins, large quantities of protein, carbohydrate or polyunsaturated fat, specific amino acid supplements, or an overall energy deficit. Prolonged exercise may also deplete glycogen reserves, leading to competition between the muscles and immune cells for key amino acids. Finally, an increased intake of antioxidants may protect the active person against an augmented production of reactive species associated with increased tissue metabolism and minor muscle injuries. Despite many potential mechanisms for a disturbance of immune function, most changes in nutritional status are short-lived, and there is little evidence that resistance to infection is reduced, with the possible exceptions of ultraendurance events, chronic overtraining and drastic attempts to reduce body mass.

Animals↗
PubMed1995

Personal health benefits of Masters athletics competition.

Questionnaires (750 respondents, 44.4% response rate) examined the long-term health value of endurance exercise training in older age-classed competitors ('Masters Athletes', 551 men and 199 women) over a 7-year period (1985-1992). The majority had initially completed maximal exercise tests. The weekly time devoted to training, competition and exercise-related travel was 10 to 30 h, and the annual expenditure on clothing, equipment and entrance fees was typically in the range Canadian $500-1500. Despite their age (mean(s.d.) 58(10), current range 40-81 years), only 1.4% reported sustaining a non-fatal heart attack and 0.6% had required bypass surgery over the 7-year interval. The majority (90%) were very interested in good health; 76% considered themselves as less vulnerable to viral illnesses than their peers, and 68% regarded their quality of life as much better than that of their sedentary friends. The majority of former smokers had stopped smoking before they began training, but 37% indicated that exercise had helped them in smoking withdrawal. In keeping with their health-conscious attitude, 59% had regular medical check-ups, and 86% obeyed legislation requiring use of a seat-belt when driving. In contrast with many older people, 88% slept well or very well. Slightly over half of the sample (57%) had sustained some injury which had limited their training for one or more weeks over the 7-year study. Although participation in Masters competition appears to carry considerable health benefits, gains may in part reflect an overall healthy lifestyle.

Adult↗
PubMed1995

Cancer, immune function, and physical activity.

Despite the problems of interpreting epidemiological studies and the difficulty in developing appropriate animal models, there is growing evidence that moderate habitual physical activity can protect against certain types of neoplasm, particularly tumors of the colon and the female reproductive tract. Exercise programs also appear to have a beneficial influence on clinical course, at least in the early stages of the disease. Recent demonstration of exercise-induced changes in the activity of macrophages, natural killer cells, lymphokine activated killer cells, neutrophils, and regulating cytokines suggest that immuno-modulation may contribute to the protective value of exercise. Depression of immune function, such as in HIV infection and in old age, is associated with an enhanced susceptibility to tumors; but the sites of tumorigenesis in HIV infection are not those that gain protection from physical activity. Further research is thus needed before it can be asserted that favorable exercise-induced changes in immune function have a material influence on the risks posed by various types of cancer.

Aged↗
PubMed1995

Using an extracurricular physical activity program to enhance social skills.

The value of an individually supervised physical activity program with a strong social skills component was examined for 45 students with learning disabilities (34 boys, 11 girls; mean age = 9.4 +/- 1.1 years). Subjects were randomly divided into an experimental group of 23 students who received two 90-minute exercise sessions for each of 10 weeks, and a control group of 22 students who received equal individualized attention through extra academic instruction. Scores for the Bruininks-Oseretsky test of motor proficiency, teacher ratings of social behavior, and self-perceptions of academic and nonacademic competence showed strong effects of time, but no substantial time x treatment interaction. Time effects on social behaviors persisted 3 months following treatment, suggesting that they reflected extra attention, rather than an expectancy, or halo, effect. There would seem to be merit in further exploring the value of extra attention, which here was provided to students with learning disabilities by volunteers with limited formal training.

Child↗
PubMed1995

Exercise programmes in the treatment of children with learning disabilities.

Learning disability is characterised by a discrepancy between achievement and assessed intellectual ability. Children with this problem commonly (but not invariably) show impaired motor proficiency, as assessed by such instruments as the Bruininks-Oseretsky Test of motor proficiency. It has been hypothesised that poor motor performance and/or poor social skills lead to exclusion from games, creating a vicious cycle of decreasing participation, decreasing competence, a deterioration of self-worth and increasing social maladjustment. Attempts to break the vicious cycle with programmes designed to enhance motor proficiency have been uniformly unsuccessful. There is limited experimental evidence to support the view that structured physical activity programmes with an embedded social skills training component can be an effective method of enhancing both actual motor ability and self-perception of physical and academic competence. However, a controlled comparison with small-group, academic instruction has shown that, from the educational perspective, a physical activity-based intervention is no more effective than other forms of special attention. The main argument for delivering social skills training through a physical activity programme lies not in a unique impact upon learning disability, but rather in terms of the other well-established long term health benefits of exercise.

Adolescent↗
PubMed1995

Spinal cord injury, exercise and quality of life.

The ultimate goal of comprehensive rehabilitation in individuals with spinal cord injury (SCI) has shifted over time from an extension of their life expectancy to attainment of an optimal level of independent living and quality of life. After World War II, the important influence of sport and exercise upon the course of rehabilitation following SCI was recognised. Nonetheless, 5 decades later, there remains a lack of understanding of how an exercise programme can contribute to an improvement of quality of life among individuals with SCI. In future, attention should be directed toward avoidance of secondary impairments, disabilities and handicaps. The World Health Organization model of disablement provides a suitable framework for addressing this issue. The most common benefits of exercise are biological in nature. They target a reduction in secondary impairments (loss of cardiorespiratory, and muscular function, metabolic alterations and systemic dysfunctions). This in turn could minimise the development of disabilities and the appearance of such handicaps as loss of mobility, physical dependence and poor social integration. A lack of physical fitness for specific tasks can be a serious obstacle to autonomy following SCI. In a very short period of time, physical deconditioning can significantly decrease quality of life in individuals with SCI, ultimately placing them in a state of complete dependency. Quality of life is closely associated with independent living and, increasingly, it is a key outcome when measuring the success of rehabilitation. Consequently, research designs that examine the impact of exercise upon individuals with disabilities should not only include objective outcome measures, but also subjective measures relating to life-satisfaction and quality of life.

Activities of Daily Living↗
PubMed1995

Growth patterns of Canadian Inuit children. A longitudinal study.

A longitudinal study has examined the growth of height, sitting height, body mass and triceps skinfolds in a sample of Inuit (281 boys and 266 girls) attending the Igloolik school between the years 1981 and 1989. Heights were around the 10th percentile of U.S. norms for 1970. A peak height velocity of 9.2 +/- 2.3 cm/year was reached by girls at 11.3 +/- 0.7 years, and in boys the peak rate of 8.6 +/- 3.7 cm/year was seen at 13.5 +/- 0.8 years. Sitting heights were also low relative to urban norms. Body mass approached the 50th percentile of U.S. norms, giving a large mass for height ratio at all ages. Triceps thicknesses for the girls were around the 10th percentile of urban norms, and in the boys began around the 25th percentile, but dropped steadily to the 5-10th percentile. No significant differences of growth patterns were seen between cohorts formed from students born in the years 1970/72, 1973/74 and 1975/76. However, comparison with earlier cross-sectional surveys in the same community showed a secular trend to greater stature and greater skinfold readings as the community had become acculturated to such features of modern living as mechanized transport and television. There were no systematic differences of growth rates between the summer and the winter seasons, and nutrition was good throughout. We thus conclude that the short stature has an inherited basis. Attention is drawn to the problem of interpreting curves of growth and weight for height in populations with an unusual body build.

Adolescent↗
PubMed1995

Body fat distribution and other cardiac risk factors among circumpolar Inuit and nGanasan.

Secular trends in skinfold thicknesses and body fat distribution were examined in the adult Inuit of Igloolik, N.W.T. through surveys conducted in 1969/70, 1979/80 and 1989/93. Findings were compared with the nGanasan population of Volochanka (Taimir peninsula, Siberia), who were examined in 1992/3. The skinfold readings of the Inuit have increased over the two decades of observation. Currently, the young male Inuit and nGanasan remain relatively thin, but older Inuit men and the women of both populations are now quite obese relative to subjects from Southern Canada. The male Inuit have also developed a centripetal, coronary-prone pattern of fat distribution, with subscapular/triceps skinfold ratios that now exceed averages for southern Canada. The majority of both Inuit and nGanasan are current smokers and many fail to meet minimal standards of aerobic performance. Plasma cholesterol levels are still not very high, but a substantial proportion of the nGanasan are affected by hypertension; their source of animal protein is reindeer meat rather than the marine mammals eaten in Igloolik. Alcohol consumption is also higher in Volochanka than in Igloolik. Action is needed to control smoking, reduce body fat content and increase physical activity if circumpolar populations are not to experience an epidemic of cardiovascular disease.

Aged↗
PubMed1995

Plasma fatty acid profiles of Canadian Inuit and Siberian Ganasan.

Cross-sectional data from 86 male and 59 female coastal Inuit of Igloolik (69 degrees 40'N, 81 degrees W) showed a steep age-related increase in the percentage of plasma n-3 fatty acids, with parallel trends in 20:5 and 22:6 but not 18:3 n-3 fatty acid concentrations. Omega-7 + 9 (p < .001) and omega-9 fatty acid concentrations (P < .001 in M, .008 in F) also decreased with age. A tundra-based Siberian indigenous population (30 male and 11 female nGanasan) had similar percentages of n-3 and n-6 fatty acids to the young Inuit, with little age-related change in either measure. Correlation matrices for the Inuit men showed quite strong negative associations of n-3 fatty acid percentages with total triglycerides (r = .34, p < .001) and phosphatidylcholine/free cholesterol ratio (r = -.36, p < .001). In the Inuit women, n-3 percentages were strongly related to phosphatidylcholine/free cholesterol ratio (r = -.60, p < .001), but not to triglyceride readings. The phosphatidylcholine/free cholesterol ratio was also correlated with n-6 percentages (r = -.55, p < .001). In the nGanasan men, triglyceride levels were correlated with n-6 (r = -.35, p < .050), but the size of the female sample was insufficient to establish useful correlations. The present data suggest that as the younger coastal Inuit are abandoning their traditional country foods, plasma levels of n-3 fall. Reasons why n-3 fatty acid levels are negatively related to the plasma phosphatidyl choline/free cholesterol ratio merit further investigation.

Adult↗
PubMed1995

Exercise and cancer: linkages with obesity?

A growing number of well-controlled studies suggest that both hard physical work and an active leisure can reduce the overall incidence of cancer. Benefit is demonstrated most clearly for colonic tumors. Here, benefit persists after control of the data for body mass index, and a likely mechanism is the speeding of colonic transit. Occasional reports suggest protection against tumors of the breast, reproductive tract, and other body organs. In some of these latter sites, potential mechanisms of protection include a suppression of sex hormone secretion, and a reduction of body fat depots, where androgens are converted to toxic estrogen derivatives; vigorous athletic participation may well modulate hormone output, but a reduction of body fat is a more likely explanation of any benefit from moderate physical activity.

Animals↗
PubMed1995

Modernization of lifestyle, body fat content and body fat distribution: a comparison of Igloolik Inuit and Volochanka nGanasan.

OBJECTIVE: To compare two circumpolar populations at different stages in adoption of a modern lifestyle with respect to body fat content, fat distribution, blood lipids and blood pressures. DESIGN: Cross-sectional comparison between Inuit and nGanasan. SUBJECTS: 141 male and 107 female Inuit (aged 17-49 years) living in the modern settlement of Igloolik (69 degrees 40'N, 81 degrees W) and 38 male and 39 female nGanasan living a more traditional lifestyle in Volochanka (71 degrees N, 94 degrees E). MEASUREMENT: Triceps, subscapular and suprailiac skinfold thicknesses, chest and waist circumferences, blood pressures, plasma total cholesterol, plasma HDL-cholesterol and triglyceride concentrations. RESULTS: Igloolik Inuit now have similar subcutaneous fat readings to their urban counterparts, average values increasing with age from 10 to 16 mm in males, and from 15 to 29 mm in females. In Volochanka, the men retain low readings (6-8 mm), but the women (13-25 mm) almost match their Inuit counterparts. Individual skinfolds, chest and waist circumferences all show substantial correlations with blood pressure (nGanasan > Inuit). The subscapular/triceps ratio is also high (Igloolik, 1.55 to 1.74 in men, 1.06 to 1.15 in women; Volochanka, 1.45 to 1.70 in men and 1.20 to 1.70 in women), but this ratio is only weakly correlated with plasma lipids and blood pressures. CONCLUSIONS: Internal fat deposition may reduce correlations between skinfolds and other cardiac risk factors. Nevertheless, the Inuit have accumulated fat in adopting a modern, sedentary lifestyle, with adverse implications for their future health.

Adolescent↗
PubMed1995

Relationship between perceptions of physical activity and health-related fitness.

OBJECTIVE: To assess perceptions of fitness, intensity and frequency of habitual physical activity as predictors of cardiovascular function, metabolic health and obesity. DESIGN: Cross-sectional correlational, with covariance adjustment of data for age and socio-economic status. SETTING: An urban community of some 250,000 people. PARTICIPANTS: Convenience sample of healthy but relatively sedentary subjects, 172 males and 178 females aged 14-68 years. MEASURES: Self-reports of perceived fitness, habitual activity, intensity and frequency of exercise; standard laboratory tests of cardiovascular function (resting heart rate, PWC 150/kg, systolic and diastolic blood pressure), metabolic health (blood glucose, total cholesterol, HDL-cholesterol, triglycerides and uric acid), obesity (body mass index, skinfolds, hydrostatic body fat, and abdominal circumferences) and socio-economic status (education, job classification and income). RESULTS: In men, the strongest associations of fitness markers were with peer comparisons of fitness and activity. In women, such comparisons also yielded significant positive associations, but the most consistent relationships of fitness were with Godin questionnaire ratings of sweat-inducing and frequent heavy activity. Perceptions of intense activity were associated more with cardiovascular than with metabolic health. Perceptions of frequent activity (peer activity ratings, occupational walking, and the number of activities reported) were associated with control of body fat, and to a lesser extent with cardiovascular function, but were unrelated to markers of metabolic health. CONCLUSION: Perceptions of personal fitness, intensity and frequency of habitual activity are all associated with markers of health-related fitness after allowance for effects of gender, age and socio-economic status. The public should thus be encouraged to pursue activity that they perceive as frequent, intense and improving their fitness.

Adolescent↗
PubMed1994

Physiological consequences of acculturation: a 20-year study of fitness in an Inuit community.

Surveys in 1969/1970, 1979/1980, and 1989/1990 assessed physical fitness among adult Inuit living in Igloolik, Northwest Territories, Canada, during a period of rapid acculturation to a sedentary lifestyle. MANOVA for age, cohort, and age-cohort effects indicated significant trends to greater skinfold readings [male (M) and female (F)] and body mass (F only), a lower handgrip and knee extension force (M and F), and lower step test predictions of aerobic power (M and F) in the more recent cohorts, with no change of forced vital capacity, 1-s forced expiratory volume, or hemoglobin level. By 1989/1990, continuing hunters tended to have thicker skinfolds than other villagers, and showed no advantage of aerobic power. The average fitness of the sample when tested in 1989/1990 was comparable with that of sedentary populations in Southern Canada, but a minority of villagers who now practiced regular sport had conserved the high levels of fitness that were observed in 1969/1970. We conclude that the fitness of this community appears to have deteriorated markedly as it has become more sedentary, and we thus recommend that health authorities develop methods of promoting an active lifestyle that are culturally appropriate to the populations of circumpolar settlements.

Acculturation↗
PubMed1994

Effects of training and acclimation on heat tolerance in exercising men wearing protective clothing.

This study examined the effectiveness of endurance training and heat acclimation in reducing the physiological strain imposed by exercising in the heat while wearing protective clothing. Seven young men underwent 8 weeks of physical training [60-80% maximal aerobic power (VO2max) for 30-45 min.day-1, 3-4 days.week-1 at < 25 degrees C] followed by 6 days of heat acclimation (45-55% VO2max for 60 min.day-1 at 40 degrees C, 30% relative humidity). Nine other young men underwent corresponding periods of control observation and heat acclimation. Before and after each treatment, subjects completed a treadmill walk (4.8 km.h-1, 2% grade) in a climatic chamber (40 degrees C, 30% relative humidity), wearing in turn normal combat clothing or clothing protecting against nuclear, biological, and chemical (NBC) agents. Criteria for halting this test were: (1) a rectal temperature (T(re)) of 39.3 degrees C; (2) a heart rate (fc) > or = 95% of the subject's observed maximum, maintained for 3 min; (3) unwillingness of the subject to continue; (4) the elapse of 120 min. The training regimen increased mean VO2max by 16% and mean plasma volume by 8%. When tested in normal combat clothing, the rates of increase in T(re) and fc were slower after training. However, when wearing NBC protective clothing, the only significant change induced by training was a higher mean skin temperature (Tsk) in the early part of the test. Heat acclimation increased the mean plasma volume of untrained subjects by 8%, but their VO2max remained unchanged. When tested in normal combat clothing, acclimation decreased their mean values of T(re), Tsk, fc, and metabolic rate. When wearing NBC protective clothing, the only significant decrease after acclimation was in overall T(re). In trained subjects, heat acclimation induced no further improvement in any physiological variable when wearing normal combat clothing, but reduced overall T(re) and Tsk when wearing NBC protective clothing. Training- or acclimation-induced increases of sweat secretion (an average increment of 0.14-0.23 kg.h-1) were not accompanied by any statistically significant increase in sweat evaporation when wearing NBC protective clothing. Moreover, tolerance times were unchanged in either normal combat (116-120 min) or NBC protective clothing (47-52 min). We conclude that neither endurance training nor heat acclimation do much to improve exercise tolerance when wearing NBC protective clothing in hot environments, because any added sweat secretion decreases blood volume and increases discomfort without augmenting body cooling.

Acclimatization↗