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Biomedical subjects

R J Shephard

Publications and source records attributed to R J Shephard.

At least 361 records · Page 20Linked to original sources

Some factors affecting accuracy of Canadian Home Fitness Test scores.

Factors affecting the accuracy of Canadian Home Fitness Test scores have been evaluated in male and female office workers. At a first attempt, the typical subject underestimates his 10 sec post-exercise pulse count by 1 beat, with a superimposed probable error of 2 beats. However, the modest experience of pulse counting gained in an employee fitness programme corrects the systematic error, while the probable random error is reduced to approximately 8 beats/min. Taking account also of variations in the fficiency of stepping, the probable error of an Astrand prediction of V O2(max) is approximately 10.3%. Comparison with directly measured values in a subsample of 22 men shows an actual random discrepancy of 9.5%, plus a systematic error of approximately 19% due to an increase of heart rate with anticipation of the maximum test. The Jetté prediction formula has a random discrepancy of approximately 8%, plus a systematic error of approximately 10.6%. Assuming the latter can be corrected by evaluation of a larger population, the fitness scores should give most people an indication of both their initial fitness and responses to a training regimen.

Adult↗

Influence of running pace upon performance: effects upon oxygen intake, blood lactate, and rating of perceived exertion.

Three different techniques of middle distance running (fast/slow, slow/fast, and steady pace) have been compared in terms of oxygen intake, blood lactate and ratings of perceived exertion (RPE). The subjects (10 middle distance and long distance male runners) carried out the three patterns of running on the laboratory threadmill according to a randomly ordered sequence, on each occasion covering 1400 m in 4 min. The fast/slow protocol resulted in a rapid and sustained on-transient of oxygen intake, less lactate accumulation, and a lower rating of perceived exertion during the final 2 min of th4 min run. Physiological data thus support coaching impressions of the superiority of the fast/slow protocol.

Adult↗

Cigarette smoking and reactions to air pollutants.

There are many mechanisms whereby recent exposure to cigarette smoke augments the toxicity of common air contaminants: the total pollutant burden is increased, there is cumulative irritation of the airways, pollutants are deposited selectively in the airways, ventilatory patterns are altered, mucus production is increased, ciliary function is depressed, mucosal characteristics are altered, macrophage activity is depressed and specific allergic reactions may occur. In the longer term adverse changes of form and function may develop in the lining of the airways.

Aerosols↗

Training and oxygen conductance in the elderly. I. The respiratory system.

Static lung volumes, closing volumes and pulmonary diffusing capacity have been measured in a group of 19 subjects (9 M, 10 F) 60 - 76 years old, all volunteers for an exercise training program (nominal 4 hours per week for 11 weeks). Initial static lung volumes were larger than in some previous series, perhaps because our sample was health-conscious and mainly nonsmokers. Training produced no significant changes in any of the pulmonary variables tested, despite a 10% increase of maximum oxygen intake seen in those members of the group who progressed to intensive training (heart rate 145 - 155/min). This reflects the fact that oxygen transport depends more on blood transport than on the respiratory system.

Age Factors↗

Training and oxygen conductance in the elderly. II. The cardiovascular system.

CO2 rebreathing measurements of cardiac output have been made in 8 men and 7 women aged 60--76 years, before and immediately after participation in an 11-week endurance training programme. Initial values showed a lower heart rate than in younger subjects at a given percentage of maximum oxygen intake. Stroke volume decreased slightly over the range of 40--80% of maximum oxygen intake. Relative to younger subjects, metabolic needs were thus met to a larger extent by a widening of arterio-venous oxygen difference and redistribution of blood flow. Over the period of observation, training induced a decrease in heart rate and cardiac output at a given sub-maximum work load, with no change in stroke volume or arterio-venous oxygen difference.

Age Factors↗

Effects of cigarette smoking on intraocular pressure and vision.

In a survey of 426 patients of Toronto ophthalmologists the correlations of reported smoking habits with (1) intraocular pressure and (2) visual acuity were examined. Average tonometer readings were closely similar in smokers, ex-smokers, and non-smokers, and multiple regression analysis showed similar age coefficients for the 3 categories. However, in women (but not in men) there was also a significant coefficient related to total cigarette exposure (puff-pack-years). It is suggested that this was due to recent smoking rather than a permanent effect on tonometer pressures, pointing the need to standardise this aspect of ocular pressure measurements. Visual acuity showed similar age coefficients in smokers, ex-smokers, and non-smokers, with no independent effect of exposure to cigarette smoke.

Adult↗

Exercise prescription--North American experience.

The principles of exercise prescription are reviewed with respect to North American experience. The required regimen must be safe, therapeutically effective, and ensure a high rate of compliance. Precautions to increase the safety of exercise are discussed. Cardiac emergencies are sufficiently rare events (less than 1 in 200,000 hours even in post-coronary classes) that the need for immediate medical supervision of a well-designed programme can be questioned. The prime determinant of the response to training is the intensity of effort relative to the individual's initial fitness. Post-coronary patients often have a great potential for training due to their previous inactivity, but this will not be realised if the prescribed exercise is of insufficient intensity. Exercise programmes are plagued by a high 'drop-out' rate; 50% of normal middle-aged volunteers are lost in 6 months, and even with post-coronary programmes losses can be 60--70% over 4 years. Simple suggestions are made for improving compliance with the required exercise prescription.

Adult↗

Carbon monoxide, nicotine and the 'safer' cigarette.

15 healthy adults (5 women, 10 men) have been exposed to each of four experimental conditions: rebreathing of air or carbon monoxide, and the smoking of two low-nicotine (0.3 mg) or medium-nicotine (1.2 mg) cigarettes. The dose of carbon monoxide selected (80 ml) had no effect on resting heart rate or electrocardiogram, nor did it modify the exercise heart rate, ventilation, oxygen consumption or electrocardiogram. Both types of cigarette produced variable changes in the blood carboxyhaemoglobin level, increments being greatest in heavy smokers, and least in former smokers, pipe and cigar smokers, Gains of carboxyhaemoglobin were less with low-nicotine than with medium-nicotine cigarettes. Both types of cigarette produced some increase of resting heart rate, but the smoking of two cigarettes was insufficient to modify the exercise heart rate, ventilation, or oxygen consumption. The electrocardiogram also showed no signs of ischaemia during either rest or effort. It is suggested that, for the light and moderate smoke, the 'safest' cigarette may be one with a low tar and a very low nicotine yield. On the present data, this would also induce only small increments of blood carboxyhaemoglobin levels.

Adult↗

Personality and sexual behavior of the adolescent smoker.

The adolescent smoker (aged 14 to 17 years) shows little difference from the non-smoker in terms of scores on the Cattell 16 personality factor inventory. In particular, there is no evidence of tension, extroversion, or reversal of sexually-biased personality characteristics. The sexual promiscuity of the adolescent smoker is probably related more to liberal attitudes and a propensity for risk-taking behavior than to uncertainty regarding sexuality. In this age group the decision to start smoking regularly may depend more on the influence of parents and friends than on an inherent personality structure.

Adolescent↗

The effect of cigarette smoke on the human tear film.

We used a corneal microscope to measure the break up time of the tear film (BUT) in 14 young volunteers; four were men and all were non-smokers. Values under controlled conditions and after ten minutes of exposure to filtered air or to cigarette smoke in a room of 14.6 m3 were determined. Exposure to cigarette smoke was associated with a substantial (35--40%) and statistically significant (P less than 0.001) reduction of BUT. This may reflect an alteration in the relative proportions of the three constituents of the tear film. The chemical responsible, and the way in which it increases the flow of watery constituents and suppresses mucus and lipid secretion demand further research.

Adult↗

Performance and efficiency of intercollegiate cross-country skiers.

Ten male intercollegiate cross-country skiers were studied to identify factors influencing competitive performance and to estimate the efficiency of energy expenditure in skiing. The variables examined were maximum oxygen intake, as determined by both uphill treadmill running and by maximal level skiing, physical characteristics, strength and experience in cross-country skiing and racing. Multiple regression analysis showed that racing experience, cardiorespiratory fitness, and body fat percentage were significant factors in racing success. The net mechanical efficiency at this level of competition was estimated at 21.3%.

Adolescent↗