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Biomedical subjects

D A Cunningham

Publications and source records attributed to D A Cunningham.

At least 127 records · Page 7Linked to original sources
PubMed1988

Age-related changes in speed of walking.

Self-paced walking was used as a measure of the neuromuscular slowing observed with aging. The effects of age on the choice of speed of walking, stride length, and step frequency were described for 289 males and 149 females aged 19 to 102 yr. These subjects were asked to walk at three self-selected paces (slow, normal, and fast) over an 80-m indoor course. Sixty-two years coincided with an accelerated decline in speed of walking. Before 62 yr, there was a 1 to 2% per decade decline in normal walking speed. After 63 yr, females showed a 12.4% per decade decrease and males showed a 16.1% per decade decrease. The eldest group (63 yr and older) had a significantly slower speed of walking and smaller step length than the younger groups (19 to 39 and 40 to 62 yr) for all paces. Heart rate at the three paces was not changed across age. In a multiple regression analysis, the only significant independent variable for walking speed at all three paces was (age), which accounted for 19 to 38% of the variance. When the population was divided into two age ranges (19 to 62 and 63 to 102 yr), walking speed was associated with height before 62 yr and with height and age after 62 yr.

Adult↗
PubMed1987

Uptake of 99mTc-DTPA by a renal oncocytoma.

In a patient with a large vascular renal mass, a preoperative DTPA scan showed retention of the activity within the tumour. On histology, the tumour proved to be an oncocytoma.

Adenoma↗
PubMed1987

Ageing and isokinetic plantar flexion.

Isokinetic torques (Cybex II) of the plantar flexors in 25 healthy men were compared at 5 angular velocities (30, 60, 90, 120 and 180 degrees X s-1). The purposes were to compare plantar flexion torques in young and old subjects, and to determine whether the expected decrease was significantly associated with age, physical activity, or aerobic fitness. Four groups were studied: young (21.7 +/- 2.0 years) and older (63.3 +/- 2.8 years), active and sedentary. Measurements of height, weight, % body fat, VO2max, and daily leisure energy expenditure (questionnaire) were determined for each subject. Statistical measures of analysis of variance were used to determine significant differences among groups; product moment correlation and stepwise regression analysis were used to describe the degree of association between the dependent variable of plantar flexion torque and the independent variables at each velocity. A decline in torque was observed as the isokinetic velocity of angular motion increased. Age alone was a significant determinant of plantar flexion torque, whereas at the slowest speed, when VO2max was used as an explanatory variable, age was not a significant determinant of torque. At 30 degrees X s-1 47% of the variance in torque was explained by VO2max while at 180 degrees X s-1 49% of the variance was explained by age.

Adult↗
PubMed1987

Exercise training of men at retirement: a clinical trial.

The effects of one year of exercise training on cardiorespiratory fitness, levels of daily leisure activity, and blood lipids (cholesterol and high density lipoproteins) were studied in a prospective, randomized clinical trial. Two hundred and twenty-four men aged 55 to 65 years volunteered for the study and were randomly allocated to a control (n = 111) or an activity (n = 113) group with stratification on blue or white collar job classification. After the attrition due to loss to follow-up, 100 men remained in each of the control and activity groups. The exercising men met an average of 2.5 times per week over the year and their VO2 max or peak VO2 (ml X kg-1 X min-1) increased significantly (p = .001, 11%) compared with controls. There were no significant changes in maximal heart rate (155 bpm) and respiratory exchange ratio (1.1), although ventilation (80 to 90 l X min-1) increased significantly in the trained group. In addition, the VO2 at a heart rate of 125 bpm increased significantly (p less than .001) in the trained group (14.7%) over that observed in the control (1.9%). There were no significant differences between the groups with respect to the remaining end-points.

Blood Pressure↗
PubMed1987

Longitudinal study of ventilation threshold and maximal O2 uptake in athletic boys.

Ventilation threshold (VET) and peak O2 uptake (VO2max) were determined annually from ages 11 to 15 yr in 18 athletic boys. The treadmill protocol consisted of a constant-run speed with grade increments every second minute. Ventilation, VO2, and CO2 production were measured using online open-circuit spirometry. Coefficients of variation for determination of VO2max and VET were 3.4 and 5.6%, respectively. VO2max increased across age 11-15 yr, from 60.8 to 68.0 ml X kg-1 X min-1. VET at 11 yr was 34.4 and at 15 yr 41.9 ml X kg-1 X min-1, thus increasing from 56 to 62% of VO2max. Previous studies of children have shown a decline of VET relative to VO2max across age; however, in the present study the increase may have been due to the training of the boys in competitive athletics. However, the trained youth did not achieve the high relative threshold of trained adults. Across age, both VO2max and VET scaled to weight to the power 1 (in a log-log transformation). The increase in VO2max (l/min) showed greatest increments corresponding to gains in size (a growth curve), whereas increases of VET were consistent year to year. Thus VET was altered independently of VO2max. Factors other than size (and presumably muscle mass) such as the maturation of an enzymatic profile of fast glycolytic fibers might have an important influence on the threshold during youth.

Adolescent↗
PubMed1987

Oxygen uptake kinetics and lactate concentration during exercise in humans.

For constant-load exercise of moderate intensity, oxygen uptake (VO2) increases monoexponentially, reaching a constant value within 3 min, i.e., steady state. However, at work rates associated with increased blood lactate, i.e., above the lactate threshold (LT), VO2 continues to increase slowly beyond 3 min; this delays or precludes steady state. We therefore correlated the characteristics of this slow phase of the VO2 kinetics with the increase in blood lactate during 6 randomized, constant-load cycle exercise tests in 6 normal men. One test was below and the others were at various levels above our gas exchange estimate of LT. The slow kinetic phase of VO2, characterized as the increase between the third and the sixth minute of exercise [delta VO2 (6-3)] or the third minute and termination of exercise [delta VO2 (term-3)], was linearly correlated with the blood lactate increase. The VO2 at termination of a given work rate above LT was greater than predicted from the sub-LT VO2 versus work-rate relationship. Work rates less than approximately 50% of the difference between VO2max and LT resulted in lactate and VO2 curves that reached recognizable asymptotes. At the higher work rates, both the lactate and VO2 curves continued to rise to the point of fatigue. We conclude that positive values for delta VO2 (6-3) and delta VO2(term-3) during constant-load exercise only occur at work rates above the LT, and the magnitudes of which are highly correlated with the increase in blood lactate.

Adult↗
PubMed1986

Recovery O2 and blood lactic acid: longitudinal analysis in boys aged 11 to 15 years.

Nineteen boys were tested annually from age 11 to 15 years. Recovery O2 (or O2 debt in l and ml X kg-1) and blood lactate ([La], mmol X l-1) were measured following supramaximal treadmill tests (20% grade) designed to stress the anaerobic energy systems maximally. The purpose was to describe the rate of development of anaerobic capacity (AnC) from pre-puberty to adolescence. AnC improved from age 11 to 15 years, as indicated by a tripling of recovery O2 (l), 80% increase in recovery O2 per kg and 45% in [La]. Changes were similar from year to year with average yearly increments in recovery O2 of 0.8 l or 9 ml X kg-1 and in [La] of 0.9 mmol X l-1. Individual data also were plotted in relation to age of peak height velocity (PHV, 12.9 +/- 1.2 years). Changes in the measures of AnC were not significantly different when related to biological rather than chronological age. Development of AnC did not show a growth function curve and was not closely correlated with size, nor was the development of AnC enhanced immediately following maturation. Thus, in this longitudinal study, recovery O2 and [La] as measures of AnC showed large increases from age 11 to 15 years, but the gains were similar year to year rather than related to size growth, per se, or hormonal influences at maturation postulated to induce qualitative changes in glycolytic potential of muscle.

Adolescent↗
PubMed1986

Personality (hardiness) as a moderator of job stress and coronary risk in type A individuals: a longitudinal study.

This research study uses longitudinal data to determine if Type A individuals, initially classified as "hardy," show differential cardiovascular and biochemical responses in the encounter with a common job stressor. Role ambiguity was utilized as a job stressor and "hardiness" was defined using the second-order factor dependence/independence from the 16-personality factor (16PF) questionnaire. The results indicated that those individuals classified as Type A1 showed blood pressure and triglyceride elevations with increased ambiguity and that dependence/independence (hardiness) moderated this effect. When all Type A's (A1 + A2) were included in the analysis similar results were found only on systolic blood pressure. The results appear consistent with earlier findings concerning the cardiovascular reactivity of Type A's. In addition, it is suggested that dependence/independence is either a major component of the concept of "hardiness" or may be a dimension of personality which distinguishes two classes of Type A behavior. It is suggested that these results may raise the interesting possibility of providing a means of identifying greater or lesser susceptibility to the coronary effects of Type A behavior.

Adult↗
PubMed1986

The effects of personal interaction on triglyceride and uric acid levels, and coronary risk in a managerial population: a longitudinal study.

This two year longitudinal study of managers investigated whether the level of interaction with other individuals was a job stressor that influences coronary risk factors. The results presented here show that increased levels of interaction were associated with increased serum triglyceride and increased serum uric acid levels. It is suggested that past research positing stress effects from responsibility for people may be due to interaction levels rather than responsibility per se. It was also found that Type A behavior and physical activity levels moderated these effects. While it is difficult to say that personal interaction, as a job stressor, contributes very significantly to either coronary risk factors or coronary heart disease the evidence supports the hypothesis that the amount of interaction has some specific stress effects.

Administrative Personnel↗
PubMed1986

Physical conditioning effects on cardiac dimensions: a review of echocardiographic studies.

Echocardiographic studies related to chronic exercise effects on cardiac dimensions were reviewed. Sources of error in M-mode echocardiography include its resolving power, changes in transmission velocity in a nonhomogeneous medium, subjective analysis of records, and assumptions to predict ventricular volume and mass from one-dimensional data. Existing studies document larger values for left ventricular internal diastolic dimension (LVIDd) in endurance athletes, and for septal and posterior wall thicknesses (ST, PWT) in endurance, strength-type and anaerobic-type athletes compared to nonathletes. Values for the athletes were lower than in cardiac disease states. Short-term conditioning studies generally reported unimpressive changes in ventricular dimensions. Existing literature also does not clearly support a relationship between training intensity and the degree of cardiac enlargement, or changes in the heart's trainability with age. Hereditary and/or familial factors appear to influence heart size to some degree and a correlation with anthropometric variables may exist. Further study concerning hereditary and long-term conditioning effects is recommended.

Adolescent↗
PubMed1985

Personality as a moderator of the effects of cigarette smoking on coronary risk.

This study pursues an earlier investigation by G. D. Friedman et al. [Prev. Med. 12, 533-540 (1983)] which reported that a group of psychological questions moderated the effects of cigarette smoking on myocardial infarction. In a group of 65 smokers drawn from a study of 278 middle-aged men it is shown that, among smokers, the personality dimension entitled dependence/independence appears to have a significant moderating effect on the relationship between the amount smoked and the elevations of diastolic blood pressure, cholesterol, triglycerides, and uric acid. It is suggested that the moderating effects of this personality dimension, which is sometimes called "Promethean Will," and which appears similar to the concept of hardiness introduced by S. C. Kobasa [J. Pers. Soc. Psychol. 37, 1-11 (1979)] may be attributable to either the differential effect of coincident dietary behavior or variation in sympathetic response. It is noted that this type of investigation may provide greater insight into how cigarette smoking affects coronary risk, and it is suggested that a potentially interesting future investigation would examine whether, among smokers, such personality dimensions have associated dietary effects or might moderate the relationship between the amount smoked and catecholamine response.

Adult↗
PubMed1985

Ventilation threshold and aging.

The ventilation threshold (VeT) in 60 healthy men ages 22 to 65 years was determined on a maximal treadmill test. The VeT was identified as the highest VO2 before the ventilatory equivalent for oxygen began to increase without a corresponding increase in the ventilatory equivalent for carbon dioxide. The VO2 max was significantly lower in the 60 compared with the 20-year-old group (with age, r = -.81). The VeT was significantly lower in the oldest compared with the youngest group (with age, r = -.69); however, the VeT as a percentage of VO2 max was significantly greater in the oldest group, (with age, r = .37). The reserve capacity (VO2 max minus VeT) was significantly lower in the older men (with age, r = -.75) and was due to a greater reduction in VO2 max than in VeT. With multiple regression analysis, the variability in VeT was determined primarily by VO2 max (65.8%) and not age. Decrease in strenuous activity with age may account for the large reduction in VO2 max, whereas maintained submaximal activity may attenuate the reduction in VO2 at the ventilation threshold, thus resulting in a large loss in functional reserve above the level of the VeT.

Adult↗
PubMed1985

Exercise training and "ventilation threshold" in elderly.

Dynamic exercise training of the elderly increases maximal O2 uptake (VO2max); however, the effects of training on the ventilation threshold (VET) have not been studied. VET was identified as the final point before the ventilatory equivalent for O2 (VE/VO2) increased, without an increase in the ventilatory equivalent for CO2 (VE/VCO2). Inactive elderly males (mean age, 62 yr) were randomly assigned to a control (C, n = 44) or activity (A, n = 45) group. VO2max and VET were determined from an incremental treadmill test. Initial VO2max was not different between the C (2.34 +/- 0.42 l X min-1) and A (2.28 +/- 0.44 l X min-1) groups, nor was there a significant difference in the VO2 at the VET (C = 1.39 +/- 0.26 l X min-1; A = 1.31 +/- 0.23 l X min-1). The activity group trained for 30 min/day, 3 days/wk at an intensity of approximately 65-80% of VO2max. After 1 yr of training the activity group exhibited an 18% increase in VO2max (A = 2.70 +/- 0.54 l X min-1), but the change in VET was not significant (A = 1.39 +/- 0.28 l X min-1). There was no significant change in VO2max (C = 2.45 +/- 0.68 l X min-1) or VET (C = 1.38 +/- 0.31 l X min-1) in the control group. VET/VO2max declined significantly in the activity group (from 58 to 52% of VO2max). Change in VET/VO2max with training was not correlated with the initial VO2max value. We conclude that increases in aerobic capacity are more readily effected than alterations of the VET in elderly subjects.

Humans↗
PubMed1985

Abnormal ventilation scans in middle-aged smokers. Comparison with tests of overall lung function.

We have assessed the uniformity of regional ventilation during tidal breathing using continuous inhalation of krypton-81m in 43 male, lifelong nonsmokers and 46 male, current cigarette smokers (mean daily consumption 24.1 cigarettes/day) between 44 and 61 yr of age and with mild or no respiratory symptoms. All subjects had normal chest radiographs. The results of the ventilation scans were compared with tests of overall lung function (spirometry, maximal expiratory flow-volume curves, and single-breath N2 test). Diffuse abnormalities of the ventilation scan were found in 19 (41%) of the 46 smokers but in none of the nonsmokers. Focal abnormalities were found in 7 smokers and 3 nonsmokers. Smokers showed the expected abnormalities in overall lung function (reduced FEV1 and VC, increased single-breath N2 slope, and closing volume), but in individual smokers there was only a weak relation between the severity of abnormality of overall lung function and an abnormal ventilation scan. Abnormal scans could be found when overall lung function was normal and were not invariably found when significant abnormalities in FEV1/VC or N2 slope were present. There was no relation between the presence of chronic expectoration and an abnormal scan. The prognostic significance of an abnormal ventilation scan in such smokers remains to be established.

Adult↗
PubMed1985

Determinants of the training response in elderly men.

As part of a prospective randomized trial of the effect of regular exercise in older men, factors determining the magnitude of VO2max increase observed with endurance training were examined in 88 elderly [age 62.9 +/- 3.0 (SD) yr] males. VO2max before and after training was recorded as the highest VO2 observed during two incremental treadmill tests. One year of thrice weekly training sessions increased VO2max (12%, P less than 0.05) in the training group relative to baseline and to a control group (n = 100). The association between the post-training VO2max (VO2max, T2) and the following explanatory variables was assessed using multiple regression analysis: the initial VO2max (VO2max, T1); the reason for stopping the initial treadmill test: leisure time activity during the year previous to the study: the training intensity (speed of walking or running, pulse rate during training, and percentage of heart rate reserve); pulmonary function (forced expiratory volume in 1 s); adiposity (skinfold thickness at 8 sites) and frequency of training. VO2max T1, speed of walking or running during training, reason for stopping the treadmill test, and skinfold thickness were significantly related to post-training VO2max. The intensity and frequency of the training stimulus explained over 10% of the variance in the training effect. Subjects whose test was halted because of fatigue increased VO2max more than those whose test was discontinued for medical or other reasons, even when speed of running was held constant. Previous activity had only a weak effect on training response. The total variance explained by these independent variables was 62%.

Aged↗
PubMed1985

Age specific prediction of maximal oxygen uptake in boys.

Maximal oxygen uptake was determined in 62 boys each year from age 11 to 15 years. Multiple regression analyses were used to predict treadmill VO2 max at yearly age intervals from size measures and submaximal cycle heart rates. Derived equations were validated in an independent sample of 98 boys of the same age range. In boys aged 12 to 15 years approximately 80% or more of the variance in VO2 max was accounted for by age specific equations employing mass, height and skinfolds as explanatory variables. Prediction of VO2max was not as strong for 10 and 11 year olds, with less than 70% of the variance explained. Measures of VO2 or work rate and heart rate were not useful in predicting VO2max either by themselves or in conjunction with the size measures. The findings clearly demonstrated that submaximal exercise testing to predict VO2max, or cardiorespiratory fitness, in boys was of questionable value. The prediction of VO2max in boys aged 12 to 15 by in the independent sample was shown to have a mean absolute error of 6 to 8% while the value for age 11 y was 10%. The error is similar in magnitude to that of predicting VO2max with an exercise test in adults. The present age specific equations resulted in smaller errors of estimation than found in previous studies of VO2max estimation in children.

Adolescent↗