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Biomedical subjects

B A Stamford

Publications and source records attributed to B A Stamford.

At least 19 recordsLinked to original sources
PubMed1992

Potentiating effects of cigarette smoking and moderate exercise on the thermic effect of a meal.

The purposes of this study were: (i) to determine the relative thermic effects of smoking and exercise in fasted and postprandial states, and (ii) to determine whether there is a weight-controlling caloric advantage of moderate exercise in the postprandial state which might be used upon smoking cessation. The subjects were ten physically fit, young, male smokers. Twenty minutes of smoking (two cigarettes) while fasted resulted in a 6.0% (12.5 kcals/3h) increase in resting metabolic rate (RMR), and 20 minutes of walking (5.8 km/h) while fasted increased post-exercise RMR by 5.8% (11.7 kcals/3h). The thermic effect of a meal (TEM) (740 ml, 874 kcals) increased RMR 21.0% (42.3 kcals/3h), which was increased to 22.1% by smoking (45.0 kcals/3h). Exercise after a meal increased RMR 29.1% (58.1 kcals/3h). Post-prandial exercise potentiated the TEM, as the energy cost was 4.0 kcals/3h greater than the sum of the thermic effect of the meal plus the thermic effect of exercise in the fasted state. Postprandial exercise expended 112.2 kcals/20 min vs. 101.6 kcals/20 min for fasted exercise, a difference of 10.4%. The difference increased to 14.6% when the post-exercise thermic effect was included. It was concluded that the thermic effect of smoking and exercise were similar in the fasted state, but were substantially different postprandially. Moderate postprandial exercise appears to offer a substantial weight-controlling advantage when compared with fasted exercise.

Adult↗
PubMed1988

Exercise and the elderly.

Data from cross-sectional studies suggest that VO2max declines in adulthood at a rate of 0.40-0.45 ml.kg-1.min-1 per year in males and 0.30 ml.kg-1.min-1 per year in females. Longitudinal studies suggest that the loss is much greater for males, approximating 1.0 ml.kg-1.min-1 per year or more. The rate of loss may be greater in sedentary compared to active individuals. The decline in VO2max with age appears to be inevitable, and a major contributing factor may be the decline in maximal cardiac output. A reduced maximal heart rate is a consistent finding, and this may be due to decreased end-organ sensitivity to catecholamines. Maximal stroke volume may or may not decrease, and physical training status may be a determining factor. The most recent evidence suggests increased dependence upon the Frank-Starling mechanism, resulting in an increased stroke volume to offset the decline in maximal heart rate. Cardiac output is thought to be maintained in this manner. Use of this mechanism may depend upon the absence of underlying disease. Therefore, investigators who vigorously screen potential subjects for occult coronary disease may report findings different from those who do not. Maximal a-vO2 difference may or may not decline in the elderly. The research is divided, and there is support for both beliefs. Several factors typical of the elderly, including a decline in muscle mass, increased blood distribution to the skin during exercise, and a potentially lower capillary/fiber ratio, would contribute to a lower a-vO2 difference. On the other hand, in those subjects with reduced cardiac output, there may be greater dependence upon a-vO2 difference during maximal exercise. Pulmonary function does not appear to limit VO2max, although the elderly may be less efficient while breathing during exercise. However, the higher ventilation and higher ventilatory equivalent for oxygen observed during submaximal exercise could be due to higher relative stress in the elderly. Elderly males and females are capable of demonstrating a training effect in response to endurance training regardless of previous physical activity patterns and current training status. The degree of change with training, expressed in relative terms, appears to be comparable to that demonstrated by younger subjects. Physiological factors contributing to an increased VO2max as a result of training appear to be similar in elderly and younger subjects, with the possible exception of no change in maximal a-vO2 difference in the elderly. This point is somewhat controversial.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗
PubMed1987

Intensity and energy cost of weighted walking vs. running for men and women.

The energy cost and intensity of exercise performed at 0% grade were determined for walking at 2, 3, and 4 mph, running at 5, 6, and 7 mph, and walking at 2, 3, and 4 mph with ankle and/or hand weights. Subjects were young moderately trained males (4) and females (3). The energy cost per kilogram of body weight was similar between sexes, and data were combined for among-treatment comparisons. Intensity of effort and energy cost per minute and per mile were increased when weight was added during walking and were increased more with hand weights compared with ankle weights regardless of speed. The average increase in O2 uptake (ml X kg-1 X min-1 X 100 g-1 of added wt) was 0.8% for ankle, 1.3% for hand, and 0.9% for ankle and hand weights. Gross energy cost per mile during weighted walking (120-158 kcal/mile) was comparable to and in some cases exceeded that of running which was independent of speed (120-130 kcal/mile). During nonweighted walking, the energy cost (kcal/mile) was significantly greater at 4 mph compared with 2 and 3 mph which did not differ. The intensity of walking at 4 mph with ankle and hand weights was comparable to running at 5 mph.

Adult↗
PubMed1986

Effects of smoking cessation on weight gain, metabolic rate, caloric consumption, and blood lipids.

Thirteen sedentary adult females successfully quit smoking cigarettes for 48 days. Mean daily caloric consumption increased 227 kcal and mean weight gain was 2.2 kg. There were no measurable acute effects of smoke inhalation and no chronic net effects of smoking cessation on resting metabolic rate, as determined by oxygen consumption and respiratory exchange ratio. After 1 yr, subjects who continued to abstain gained an average of 8.2 kg. HDL-cholesterol increased 7 mg/dl in 48 days; however, this effect was lost in those who returned to smoking. Increased caloric consumption accounted for 69% of weight gained immediately following smoking cessation. Factors other than changes in caloric consumption and metabolic rate may be responsible for a significant proportion (31%) of the weight gained in individuals who quit smoking.

Adipose Tissue↗
PubMed1985

Gas exchange and lactate anaerobic thresholds: inter- and intraevaluator agreement.

Twenty-four coded graph sets of gas exchange variables and blood lactate concentration (LA) plotted against time at 15-s intervals were analyzed by nine evaluators who determined the gas exchange (ATGE) and LA (ATLA) anaerobic thresholds. In addition, ATGE and ATLA were determined by a linear regression computer program. Agreement between ATGE and ATLA was poor; the median intraclass correlation coefficient (ri) was 0.53. Among evaluators, ATLA agreement (median ri = 0.81) was better than ATGE agreement (median ri = 0.70). In general, the ability of any evaluator to choose similar values from duplicate plots for either ATGE (median ri = 0.97) or ATLA (median ri = 0.995) was good. There was better agreement between the mean ATLA of the evaluators and the computer ATLA (ComLA) (ri = 0.88) than between the mean ATGE of the evaluators and the computer ATGE (ComVE), (ri = 0.58). Agreement between ComVE and ComLA was poor (ri = 0.29). These results suggest that ATGE does not accurately predict ATLA and that different evaluators choose different thresholds from the same data. Further assessment of the validity and precision of ATGE based on breath-by-breath and minute-by-minute data is needed.

Adult↗
PubMed1984

Cigarette smoking, exercise and high density lipoprotein cholesterol.

Cigarette smoking is associated with depressed levels of HDL-C, whereas exercise is associated with elevated levels of HDL-C. The purpose was to determine effects of smoking and exercise on blood lipids and lipoproteins in middle-aged males. It was hypothesized that smoking may attenuate the effects of exercise to elevate HDL-C. A total of 269 males (70 smokers) met all criteria for inclusion in the study population. Age, height, weight, body fatness via hydrostatic weighing, daily caloric consumption and alcohol intake, and smoking habits and history were determined. Interviews concerning physical activity patterns were conducted and cardiovascular responses to treadmill exercise were determined. Subjects were grouped as sedentary (low activity), participants in vigorous recreational activities (moderate activity) and joggers/runners (high activity). Analysis of covariance with adjustments for factors which may affect blood lipids and lipoproteins was employed. Smokers demonstrated lower HDL-C and higher total cholesterol levels than nonsmokers. High activity subjects demonstrated significantly higher HDL-C levels than the low and moderate groups which did not differ. High activity smokers did not differ from low activity nonsmokers with respect to HDL-C. This supports the proposed hypothesis. Nonsmokers were higher in weight and body fatness than smokers even though smokers consumed 288 more calories per day on the average. This suggests that smoking may account for a significant number of calories through altered metabolism or some other means.

Adult↗
PubMed1984

Cigarette smoking, physical activity, and alcohol consumption: relationship to blood lipids and lipoproteins in premenopausal females.

A total of 164 premenopausal female subjects were randomly selected for evaluation from a much larger pool of volunteers. The relationships between blood lipid and lipoprotein levels as dependent variables and cigarette smoking, physical activity, and alcohol consumption were determined from partial regression coefficients. A lower HDL-C level (10.1 mg/dL) was seen in smokers v nonsmokers. For each ounce of alcohol consumed, HDL-C level was higher by 2.8 mg/dL, and greater physical activity was associated with a higher HDL-C level of 8.6 mg/dL. An analysis of covariance with covariance adjustments for age and body fat revealed that smokers who regularly exercise or consume alcohol had significantly lower HDL-C levels than nonsmokers with similar habits. Subjects who both exercise and consume alcohol demonstrated higher HDL-C levels than those who indulge in one or the other separately. Results suggest that cigarette smoking may attenuate the effects of chronic exercise or alcohol consumption, or of both, to raise HDL-C levels. Also, chronic exercise and alcohol consumption may exert an additive effect, raising HDL-C level.

Adult↗
PubMed1979

Recovery from maximal effort exercise: lactate disappearance and subsequent performance.

The effects of differing recovery patterns following maximal exercise on blood lactate disappearance and subsequent performance were examined. Nine subjects completed four randomly assigned experimental sessions. Each session consisted of a 5-min maximal effort performance test conducted on a Monark bicycle ergometer (T1) followed by 20 min of recovery and a second 5-min maximal effort performance test (T2). Blood lactate levels were measured during min 5, 10, 15, and 20 of recovery. Recovery patterns consisted of passive recovery (PR), active recovery below anaerobic threshold (AR less than AT), active recovery above anaerobic threshold (AR greater than AT), and active recovery above anaerobic threshold while breathing 100% oxygen (AR greater than AT + O2). Blood lactate levels prior to T2 were significantly different across treatments (P less than 0.05). Comparison among treatments and between T1 and T2 revealed no significant differences in work output. It was concluded that while lactate disappearance following severe exercise can be affected by varying the recovery pattern, elevated levels of blood lactate exert no demonstrable effect on maximal effort performance of 5-min duration.

Adult↗
PubMed1978

Effects of severe prior exercise on assessment of maximal oxygen uptake.

Five moderately fit males (50.8 ml.kg-1.min-1) performed 14 continuous type VO2 max tests on a motor-driven treadmill. Randomly assigned experimental sessions, consisting of three tests each and separated by 10 (tests 1, 2, 3), 20 (tests 4, 5, 6), 30 (tests 7, 8, 9), or 40 (tests 10, 11, 12) min, were conducted at a consistent hour for each subject every 4th day. Two separately performed tests were also included in the random assignment with the test eliciting the highest VO2 max value designated as the standard reference (SR). VO2 max values for tests 1 through 12 were not significantly different from the SR in spite of elevated pretest blood lactate concentrations ranging from 5 mM to 16 mM. Performance time was reduced for all tests other than tests 1, 4, 7, and 10, reaching the level of statistical significance (P less than 0.05) in tests 2, 3, 5, 6, and 9. It was concluded that valid and reliable assessment of VO2 max is possible even though testing is initiated with subjects in varying stages of exhaustion.

Adult↗
PubMed1978

Effects of pedalling rate changes on maximal oxygen uptake and perceived effort during bicycle ergometer work.

The present investigation determined the efficacy of progressively increased pedalling rate (P) or resistance (R) during assessment of maximal oxygen uptake (VO2max) on the bicycle ergometer. Twenty male and nine female university students performed randomly assigned discontinuous P and R maximal stress tests. Male subjects immedicately repeated each test within the same experimental session. Regardless of test protocol, VO2max was quite similar. Magnitude estimates of perceived effort were significantly lower for male subjects during P testing (P less than .05) and 80% of male subjects preferred P testing. Conversely, magnitude estimates were significantly lower for female subjects for R testing (P LESS THAN .05). P testing could be reliably repeated within the same experimental session whereas with R testing VO2max was significantly reduced (P LESS THAN .05). It was concluded that progressively increased pedalling rate offers a physiologically acceptable means to VO2max assessment on the bicycle ergometer for males and females. In addition, progressively increased pedalling rate offers a perceptually preferable means to VO2max assessment for males but not for females.

Adolescent↗
PubMed1978

Status of police officers with regard to selected cardio-respiratory and body compositional fitness variables.

Physical performance and body composition characteristics of members (n = 75) and recruits (n = 61) of the Louisville Police Department (total n = 136) were assessed. Members were randomly selected males and ranged in age from 20 to 55 years and were ranked from the newest inductee through and including the Chief of Police. Members between the ages of 20 and 29 years assigned to active duty possessed average cardio-respiratory fitness (Vo2max). With age, cardio-respiratory fitness decreased and body weight and body fatness progressively increased. Male and female recruits entering basic training also demonstrated average cardio-respiratory fitness. Significant (P less than .05) increases for males and females in Vo2max and decreases in body fatness (males) were found following 4 months of physically rigorous recruit training. Fifteen of the male recruits who completed training were retested following 1 year of active duty. During active duty, physical activity involvement was limited to job requirements with no additional physical training imposed. Cardio-respiratory fitness and body fatness reverted to pre-training levels. It was concluded that the physical demands associated with police work are too low to permit maintenance of physical fitness.

Adult↗