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Biomedical subjects

R J Shephard

Publications and source records attributed to R J Shephard.

At least 127 records · Page 7Linked to original sources
PubMed1994

Effects of 12 weeks of aerobic exercise plus dietary restriction on body composition, resting energy expenditure and aerobic fitness in mildly obese middle-aged women.

This study investigated the effects of 12 weeks of aerobic exercise plus voluntary food restriction on the body composition, resting metabolic rate (RMR) and aerobic fitness of mildly obese middle-aged women. The subjects were randomly assigned to exercise/diet (n = 17) or control (n = 15) groups. The exercise/diet group participated in an aerobic training programme, 45-60 min.day-1 at 50%-60% of maximal oxygen uptake (VO2max), 3-4 days.week-1, and also adopted a self-regulated energy deficit relative to predicted energy requirements (-1.05 MJ.day-1 to -1.14 MJ.day-1). After the regimen had been followed for 12 weeks, the body mass of the subjects had decreased by an average of 4.5 kg, due mainly to fat loss, with little change of fat free mass (mff). The absolute RMR did not change, but the experimental group showed significant increases in the RMR per unit of body mass (10%) and the RMR per unit of mff (4%). The increase in RMR/mff was not correlated with any increase in VO2max/mff. The resting heat production per unit of essential body mass increased by an average of 21%, but the resting heat production rate per unit of fat tissue mass remained unchanged. We concluded that aerobic exercise enhances the effect of moderate dietary restriction by augmenting the metabolic activity of lean tissue.

Body Composition↗
PubMed1994

Differential expression of interleukin-2 receptor alpha and beta chains in relation to natural killer cell subsets and aerobic fitness.

Immunophenotyping by dual parameter flow cytometry was used to compare the expression of interleukin-2 receptor alpha and beta chains on lymphocyte subsets in the peripheral blood of 7 trained and 6 untrained volunteers (respective VO2max 57.0 +/- 6.1 and 39.0 +/- 4.5 ml.kg-1.min-1). Venous blood samples were collected at least 36 h after the most recent exercise session. The trained subjects had higher circulating counts (10(9).l-1) of total leukocytes (5.80 +/- 0.83 vs. 4.63 +/- 0.21, p < 0.05), granulocytes (3.14 +/- 0.72 vs. 1.90 +/- 0.30, p < 0.05), and NK cells (CD16+, 0.32 +/- 0.14 vs. 0.16 +/- 0.05, p < 0.05; CD56+, 0.41 +/- 0.14 vs. 0.21 +/- 0.03, p < 0.01), but lower lymphocyte counts than their sedentary peers (1.90 +/- 0.22 vs. 2.26 +/- 0.25, p < 0.05). Counts for T cells (CD3+) and B cells (CD19+), and the CD4+/CD8+ ratio did not differ between the two subject groups. The p55-IL-2 receptor alpha expression (CD25+: 0.63 +/- 0.11 vs. 0.69 +/- 0.17) was unrelated to training, but the p70-75-IL-2 receptor beta expression was higher in the active group (p70/Mik-beta 1+: 0.42 +/- 0.09 vs. 0.20 +/- 0.06, p < 0.001; p75/TU27+: 0.36 +/- 0.08 vs. 0.17 +/- 0.07, p < 0.005). Beta chain co-expression was also higher on NK cell subsets (p < 0.001) in trained than in sedentary subjects. Aerobic power was strongly correlated with IL-2R beta expression (r = 0.914, p < 0.001 for Mik-beta 1; r = 0.884, p < 0.005 for TU27).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Exercise and training: influences on cytotoxicity, interleukin-1, interleukin-2 and receptor structures.

Exercise responses are discussed with particular reference to the functional system involving interleukin-1, interleukin 2 and cytotoxicity. Prolonged endurance exercise causes an increase in plasma levels of interleukin-1, possibly as a response to muscle injuries, but plasma interleukin-2 levels generally fall. The latter change probably reflects stronger binding, consequent upon increased expression of p70-75 receptors for IL-2, and changes in the distribution or activity of target cells; IL-1 secretion may enhance the responsiveness of peripheral blood mononuclear cells, but prostaglandin secretion decreases their IL-2 production. Moderate exercise increases the cytolytic action of NK cells, but there is a prolonged fall of cytolytic activity after exhausting or psychologically stressful exercise; again these responses probably reflect altered IL-2 levels or receptor expression. Appropriately graded training reduces the adverse immune reactions associated with challenging exercise. Cross-sectional comparison and training experiments both show an increased expression of p70-75 IL-2 receptors on the NK cells of active individuals. Moreover, moderate training reduces the exercise-induced suppression of IL-2 production. However, training that is pursued to the level of staleness, nutrient deficiency or muscle damage has a negative impact upon both the production of interleukins and the leukocyte response. Coaches must thus gauge training programs to optimize not only physiological function but also immune responses.

Cytotoxicity, Immunologic↗
PubMed1994

A simple formula for the estimation of maximal oxygen intake during cycle ergometry.

Exercise prescription has traditionally been based on the heart rate/work rate relationship. Many post-myocardial (MI) patients are now taking medications such as beta-blockers that alter this relationship, necessitating an alternative method for exercise prescription. The directly measured maximal oxygen intake (VO2max) is not substantially affected by such medications, but direct determinations of VO2max are time consuming, costly, and vulnerable to both local muscle weakness and poor motivation. We have therefore re-examined the relationship between work rate and maximal oxygen intake in order to derive a simple formula which will give an indirect estimate of the latter. Our results, obtained on 28 patients receiving beta-blockers, 13 receiving calcium channel blockers, 10 receiving combined therapy, and 49 who received neither treatment, indicate that the peak oxygen intake can be estimated accurately, using the expression VO2max.ml.min-1 = 2W, where W is the peak power output, measured in kp.m.min-1, or 12.3 W, where W is the peak power output in Watts.

Exercise Test↗
PubMed1994

Potential impact of physical activity and sport on the immune system--a brief review.

Description is given of methods that can evaluate the main functional elements of the immune system. Acute responses to exercise depend on the intensity and duration of the required activity relative to the individual's fitness level. Moderate endurance exercise causes either no change or an enhancement of such indices as total leucocyte count, granulocyte, monocyte, lymphocyte and natural killer cell count, total T cell count, helper:suppressor cell ratio, cell proliferation in response to mitogens, serum immunoglobulin levels, and in vitro immunoglobulin production. However, exhausting exercise tends to produce adverse changes in these same indices, particularly if the physical activity is accompanied by environmental or competitive stress. Moderate, appropriately graded training reduces reactions to any given absolute intensity of exercise. When pursuing a more demanding training regimen, it is important that the exerciser optimize immune responses. If athletic preparation is pursued to the level of staleness and/or muscle damage, it can have substantial negative implications for many aspects of immune function, including resistance to acute infections, HIV infections, ageing, cancer and other conditions influenced by the immune system.

Antibody Formation↗
PubMed1994

Population evaluations of health related fitness from perceptions of physical activity and fitness.

The possibility of predicting health related fitness using questions on occupational and leisure activity was explored in 172 men and 178 women. ANOVA and multiple regression equations related questionnaire responses to objective fitness measures including body mass index, circumferences, skinfolds, body fat, blood glucose, uric acid, total cholesterol, HDL-cholesterol and triglycerides, PWC150, blood pressures, and resting heart rate. Reported occupational activities bore little relationship to health related fitness. Self-perceptions of moderately frequent and moderately intense leisure activity, plus at least average perceived fitness relative to age-matched peers, were associated with a favorable body fat content and lipid profile, whereas indicators of cardiovascular health (a low resting heart rate and a high PWC150) were linked with perceptions of frequent and intense activity, plus a perceived fitness level higher than that of a peer reference group. Based on these findings, a simple scoring of reported activity for use in fitness counseling is suggested.

Adult↗
PubMed1994

Principal components of fitness: relationship to physical activity and lifestyle.

Interrelationships between metabolic and cardiorespiratory health were examined in 350 healthy adults. Four principal components accounted for 66.7% of the variance in 172 males (M) and for 62.4% in 178 females (F). Factor 1, "obesity," related to body mass index, abdominal circumference, total skinfold thickness, and (M only) abdominal/hip circumference ratio. Factor 2, "cardiovascular fitness," had loadings from resting heart rate and PWC150/kg. Factors 3 and 4 were related to total cholesterol and HDL-cholesterol, respectively (plus blood pressures, particularly in F). Factor 1 was linked to caffeine consumption and to exercise frequency (F) or perceived intensity (M). Factor 2 was linked to perceptions of activity relative to others (M and F) and to the intensity of activity (M only). Factors 3 and 4 were associated with perceived fitness and physical activity relative to others. Because perceptions of physical activity and fitness lack consistency, it is suggested that health be judged more directly from simple measures of health related fitness that require little subject cooperation.

Adult↗
PubMed1994

Acculturation and the growth of lung function: three cross-sectional surveys of an Inuit community.

The influence of acculturation to a sedentary lifestyle upon the growth and development of lung volumes has been studied in Inuit children aged 9-19 years. Surveys were conducted in the circumpolar community of Igloolik (69 degrees 40'N, 81 degrees W) in 1969/70, 1979/80 and 1989/90. Over this period, the children showed little change of height or body mass at any given age, but a progressive loss of what initially had been a high level of health-related fitness. The sample for each survey comprised about 70% of children in the chosen age range: in the most recent study 87 males and 65 females. Respiratory data included forced vital capacity, one-second forced expiratory volume, maximal mid-expiratory flow rate (second and third surveys only), smoking habits and respiratory health. In each of the 3 surveys, many of the older children in the community were regular smokers. The average cigarette consumption currently rises progressively to 13 +/- 8 cigarettes/day in 87% of males and 11 +/- 7 cigarettes/day in 95% of females over 17 years of age. Nevertheless, lung volumes show the anticipated increase as a logarithmic function of stature. Furthermore, statistically fitted curves show only minor inter-survey differences in volumes for a given standing height. We thus conclude that the deterioration in other aspects of health-related fitness has not yet influenced the growth and development of respiratory function within this Inuit population.

Acculturation↗
PubMed1994

The ageing of lung function: cross-sectional and longitudinal studies of an Inuit community.

Three surveys (1969/1970, 1979/1980 and 1989/1990) have examined the impact of acculturation to a sedentary lifestyle on the pulmonary function of a circumpolar native Inuit community. The sample comprised more than 50% of those aged 20-60 yrs, most recently 119 males and 92 females. Forced vital capacity (FVC), forced expiratory volume in one second (FEV1) and maximal mid-expiratory flow (MMEF) were measured by standard spirometric techniques, and information was obtained on smoking habits and health. Multiple regression equations showed that lung function was affected by height and age, but usually not by age squared. Cross-sectional age coefficients for FVC and FEV1 increased over the period 1969/1970 to 1989/1990. Parallel longitudinal trends were seen in FEV1 (males only). Multiple analysis of variance (MANOVA) showed age-decade*cohort effects for FVC and FEV1 (males but not females). Almost all of the population now smoke (mean +/- SD males 13 +/- 8 cigarettes.day-1; females 11 +/- 7 cigarettes.day-1). However, smoking bears little relationship to lung function perhaps due to limited variance in consumption. About a third of the community have physician-diagnosed and/or radiographically visible chest disease, but with little effect upon pulmonary function. We conclude that an apparent secular trend to a faster ageing of lung function in men is not explained by disease or domestic air pollution. Possible factors include increased lung volumes in young adults, greater pack-years of cigarette exposure, nonspecific respiratory disease, increased inspiration of cold air or altered chest mechanics due to operation of high-speed snowmobiles, and loss of physical fitness.

Acculturation↗
PubMed1994

Infection in athletes.

Coaches and athletic team physicians have provided anecdotal information and case studies to support their beliefs that athletes may be unusually prone to illness during strenuous training or competition. Many athletes, in contrast, believe that physical activity improves their resistance to infectious disease. However, it is generally agreed that the stress of competition may make athletes temporarily more susceptible to infectious illness. A review of the literature shows that upper respiratory tract infections and skin infections are more prevalent in top level athletes than in the general population, particularly during periods of intensive training. Exercise induced changes occur in both the innate and adaptive components of the immune system; however, the relative importance of each component is unknown. Strenuous exertion and contact sports may compromise host defence both by reducing physical protection and by impairing immunosurveillance. Skin lacerations, vigorous sweating and maceration of the dermis impair the defence normally provided by the skin surface. In addition, adverse changes in soluble and cellular components of the immune system can increase susceptibility to infection. Persistence with strenuous training during an infectious illness can have deleterious effects; not only is athletic performance impaired, but the severity of the disease process can be augmented.

Exercise↗
PubMed1994

Exercise and the immune system. Natural killer cells, interleukins and related responses.

The main methods for the evaluation of natural killer (NK, CD16+ CD56+) cells, interleukins and related subsets of lymphocytes are briefly described. Moderate endurance exercise causes either no change or an increase in lymphocyte and NK cell counts, total T cell (CD3+) count, the ratio of T helper (CD3+ CD4+) to T suppressor (CD3+ CD8+) cells, mitogen-induced lymphocyte proliferation, serum immunoglobulin levels and in vitro immunoglobulin production. Plasma levels of interleukin-1 increase but interleukin-2 (IL-2) levels generally fall. Decreases in plasma IL-2 levels reflect increased expression of beta (CD122) receptors for IL-2, and thus increased binding of IL-2, changes in cell distribution or a lesser production of IL-2 by peripheral blood mononuclear cells. Exercise to exhaustion induces adverse changes in many of these indices of immune function, particularly if the physical activity is accompanied by psychological or environmental stress. Moderate, appropriately graded training reduces the adverse reactions initially associated with a given bout of exhausting exercise, and cross-sectional comparisons show an increased expression of beta IL-2 receptors on the peripheral blood mononuclear cells of trained individuals. However, excessive training, nutrient deficiency and/or muscle damage has adverse consequences for both the production of interleukins and the response of the immune system to these cytokines.

Exercise↗
PubMed1994

Changes of physical performance as indicators of the response to enhanced physical education.

The value of field performance tests in the assessment of a programme of enhanced physical education has been examined in a 3-factor study of students over all 6 primary school grades. The enhanced programme under review offered a one hour of required physical education daily from age 7 to 12 years, taught by a specialist physical educator. Control students from immediately preceding and succeeding classes continued with the standard programme, a standard single period of physical education per week taught by a nonspecialist. Subjects were classed by gender, environment (urban vs rural school) and the experimental intervention to allow analysis by MANOVA. Students in the experimental programme showed small but statistically significant gains in laboratory measures of aerobic power and muscle strength relative to controls. In general, these responses were mirrored by gains in scores on the Canadian Association for Health Physical Education and Recreation (CAHPER) field performance test battery. The latter tests also suggested gains of anaerobic power, coordination and muscular endurance. It is concluded that an enhanced programme of physical education can enhance function in primary school students, but the size of gains is not a strong argument for such programmes. Further, gains in performance test scores indicate the direction, but not necessarily the magnitude of programme responses.

Anaerobic Threshold↗
PubMed1994

Testing for inter-group contamination in a controlled longitudinal study of added physical education.

OBJECTIVE: This case report examines whether there was any cross-contamination between students enrolled in classes that received additional physical education, and their siblings who were enrolled in preceding and succeeding class-cohorts. EXPERIMENTAL DESIGN: A controlled longitudinal study extending over 6 years of primary school. SETTING: An urban and a rural primary school in Québec. PARTICIPANTS: 546 primary students, comprising approximately equal numbers of boys and girls from the urban and the rural school. INTERVENTION: Entire class-cohorts were given and hour of additional physical education ach day throughout their primary schooling, with immediately preceding and succeeding class-cohorts serving as controls. MEASURES: The measured data included standing height, body mass, maximal oxygen intake (direct treadmill test) and PWC170. RESULTS: We found no evidence of cross-contamination between siblings in experimental and control class-cohorts. CONCLUSION: Although a theoretical possibility, cross-contamination between students in preceding and succeeding class-cohorts does not seem an important source of error in primary school students, presumably because such children prefer to play with friends from their immediate age cohort.

Bias↗
PubMed1994

Infectious diseases in athletes: new interest for an old problem.

Interest in infectious disease among athletes has been greatly stimulated over the past decade by the development of modern automated systems that can enumerate specific elements of the immune system. Research has confirmed earlier clinical and animal studies in showing that either a single bout of exhausting exercise or persistent over-training can increase susceptibility to upper respiratory and other viral infections, although resistance to bacterial infections is apparently unaltered. Such findings do not seem a non-specific response to cooling and drying of the tracheal mucosa. Rather, heavy exercise has a depressant effect upon the T cell/interleukin/NK cell system which may persist for a week or more. In contrast, moderate training enhances immune defences. Given the negative impact of acute viral infections upon both competitive performance and morale, plus the occasional incident of sudden death associated with viral myocarditis, it is important that sports physicians minimize the incidence of viral infections in the athletes for whom they are responsible. Potential tactics include maintenance of immunization schedules, minimizing of exposure to infection, avoidance of over-training, maintenance of an adequate diet, and reduction of psychological and environmental stress. In top athletes, the regular monitoring of immune status may also be warranted, with the possible administration of immunoglobulins and prostaglandin inhibitors as required.

Communicable Diseases↗
PubMed1994

Physical activity and reduction of health risks: how far are the benefits independent of fat loss?

This paper considers how far the postulated health benefits of exercise are attributable to a decrease of body fat. Some of the well-accepted gains such as a reduction in the risk of ischemic heart disease are seen even when the data are controlled for body mass. However, other responses such as a reduced incidence of some types of cancer and a decrease of waking blood pressure are closely linked to body fat content and associated metabolic disturbances. The medium-term weight loss is relatively similar for an exercise programme and a dietary regimen, but exercise tends to conserve lean tissue. Exercise also has unique beneficial effects upon musculo-skeletal disorders and mood state. Perhaps most importantly, it improves the quality of life, helping to maintain physical abilities and thus independence into extreme old age. Nevertheless, the optimum recommendation for the moderately obese patient is usually to combine a progressive exercise regiment with a moderate restriction of food intake.

Adipose Tissue↗
PubMed1994

Guarding against pitfalls in multivariate analysis. An illustration from fitness testing of the spinally-injured.

Potential pitfalls in the multivariate analysis of data, and methods of overcoming such problems, are illustrated by reference to recent research that has examined relationships between fitness variables and overall productivity in a population of young male paraplegics. Particular attention is directed to the need for residual analysis, tests of multiple collinearity, and a cautious approach to interpreting the theoretical meaning of individual coefficients in multiple regression equations.

Humans↗
PubMed1994

Secular and age trends in the height of adults among a Canadian Inuit community.

The height of adults living in the Inuit settlement of Igloolik (69 degrees 40'N, 81 degrees W) had been determined in three surveys, conducted in the winters of 1969/70, 1979/80 and 1989/90. The Inuit are shorter than the general Canadian population, as surveyed in 1981, the discrepancy amounting to about 11 cm for males, and 9-10 cm for females. The decrease in height over the course of adult life, as seen in cross-sectional data, occurs at approximately the same speed in Igloolik as in Southern Canada. However, the causes of this trend seem to be different. Until the seventh decade of life, the decrease observed in southern Canada is due to a substantial secular trend to an increase of stature. In contrast, the Inuit living in Igloolik have become about 2 cm shorter at any given age over the past 2 decades. The trend to loss of stature is strongest in continuing hunters. In the men, the trauma associated with the operation of high-speed snowmobiles over rough terrain may be an important factor. The women do not drive snowmobiles to any great extent; however, they now carry small children on their back less frequently than in previous decades because of a smaller average family size and the adoption of store-purchased clothing which lacks the traditional amauti. In consequence, they may now be less well protected against a low calcium and vitamin D intake. We conclude that because of this secular trend, cross-sectional surveys currently under-estimate the decrease in height that the Inuit will sustain over the adult lifespan.

Adult↗