Biomedical subjects

D H Paterson

Publications and source records attributed to D H Paterson.

97 records · Page 6Linked to original sources

PubMed1979

Effects of physical training on cardiovascular function following myocardial infarction.

Three to twelve (7.1 +/- 3.2) months after myocardial infarction, subjects under 54 (45.0 +/- 4.7) yr were assigned randomly to high-intensity (HIE, n = 37) or low-intensity (LIE, n = 42) exercise programs. Cardiac outputs (Q) during graded bicycle ergometer exercise were measured by a CO2-rebreathing method on entry and after 6 and 12 mo of training. The initial exercise Q was low in relation to work load, due to a low stroke volume (SV). Over the year of training, the predicted maximal O2 intake of the HIE group increased significantly (from 26.0 to 30.3 ml.kg-1.min-1), while that of the LIE group showed no significant alteration. During the first 6 mo, the heart rate of the HIE group was significantly reduced at each work level. There was an associated widening of arteriovenous oxygen difference, but SV was unchanged. These findings were attributed to extracardiac factors, including a redistribution of blood flow, biochemical changes in the trained muscle, and a secondary reduction of sympathetic drive. Over the second 6 mo, the SV of the HIE group increased 10%; this may reflect an increase of intrinsic myocardial contractility that develops if high-intensity training is sustained. The LIE group showed no major changes of cardiovascular function over the year of observation.

Adult↗

PubMed1979

Respiratory and cardiovascular aspects of intermittent exercise with regard to ice hockey.

The purpose of this review paper was to analyze the cardiorespiratory demands involved in playing ice hockey. Heart rate (HR) monitoring, by radiotelemetry during actual game performance, has indicated near-maximal cardiorespiratory efforts for the 2 1/2 to 3 minute on-ice shifts. Analyses of the temporal characteristics of the game, and thus the intermittent exercise (IE) schedules involved were also utilized to elucidate the cardiorespiratory demands of the sport. Compared to continuous exercise, at the same average power output, IE performance represents greater demand on both the central circulation and oxidative metabolism in the muscle cell. In IE, of time and intensity components typical of those found in ice hockey, laboratory data, compared to continuous exercise, showed a higher cardiac output, yet widened arterio-venous oxygen difference in the active muscles compensating for a lower muscle blood flow. Further, the literature suggested a reduced efficiency of the thermoregulatory system in IE, placing added demand on the cardiorespiratory system. The analysis suggests that training programs to increase aerobic power would be beneficial for ice hockey players.

Adult↗

PubMed1977

Reliability and reproducibility of maximal oxygen uptake measurement in children.

Maximal aerobic capacity of 66 ten year old ice hockey players was measured on a treadmill twice over a 4 to 5 month period. This time approximated mid (T1) to post (T2) competitive season. The results of these VO2 max tests were grouped according to the presence or absence of a plateau in the oxygen uptake (less than 2.1 ml/kg-min) during the last work loads before fatigue. The mean values for T1 and T2 were not significantly different for any of the measurements made; the reproducibility was considered to be high. The reliability of the measures varied with the presence or absence of a plateau at maximum, for example; VO2 max, plateau r = 0.74, no plateau r = 0.27; heart rate, plateau r = 0.92, no plateau r = 0.40. The differences between the mean values for the "double plateau" group when compared to the "no plateau" group were not significant for VO2 max, HR or VE. The differences were significant for the post-exercise blood lactate and respiratory exchange values at T2 only; the "double plateau" group reached higher values in each case (R = 1.00 vs 0.92; blood lactate 6.5 vs 5.4 mM/1).

Child↗

PubMed1976

Comparison of methods to calculate cardiac output using the CO2 rebreathing method.

A comparison was made of methods used to calculate cardiac output by the indirect (CO2) Fick procedure (equilibrium method). Alternative methods for calculation of arterial PCO2, mixed venous PCO2, and conversion of gas tension to content were tested. Cardiac output values determined with a "corrected" equilibrium PCO2, to approximate mixed venous PCO2, were observed to be closest to cardiac output values determined on similar populations by the dye dilution method. Arterial PCO2 was best estimated from the Bohr equation using a dead space in exercise from prediction equations in the literature applicable to the populations under study. CO2 dissociation curves used to derive the veno-arterial CO2 content difference, were shown to differ considerably. For the present, the curve by McHardy [25], as modified by Jones (personal communication), and similar to the standard Comroe curve [5], was chosen.

Adolescent↗

PubMedDate not supplied

Lung function in older humans: the contribution of body composition, physical activity and smoking.

An allometric model was used to determine the important factors related to the decline in forced expiratory volume (FEV1.0) across ages 55-86 years in independently living men and women. Measurements were available from a randomized sample of 181 men and 203 women residing in London, Ontario, Canada. The effects of height, age, sex, adiposity, fat free mass (FFM), grip strength and physical activity (PA) on FEV1.0 were assessed using an allometric model to test the hypothesis that sex differences in lung function would be due in part to sex-related differences in the aforementioned variables and would therefore be eliminated by our analysis. The following model was linearized and parameters were identified using standard multiple regression: FEV1.0 = height(beta1) x FFM(beta2) x grip strength(beta3) x PA(beta4) x exp(beta0 + beta5age + beta6sex + beta7smoking + beta8%body fat) x epsilon. Results indicate that the amount of FFM and heavy intensity physical activity participated in by the elderly may be more important in influencing forced expiratory function than previously recognized. In addition, results from this study have confirmed the importance of age and height in the prediction of FEV1.0 and demonstrated a negative effect of smoking on lung function. Individuals with a greater FFM and physical activity level tended to be associated with an above average lung function performance. The cross-sectional rate of decline in FEV1.0 determined from our model was approximately 12% per decade.

Aged↗

PubMedDate not supplied

Body mass indices and skeletal size in 394 Canadians aged 55-86 years.

Demispan (finger web to midline) is the preferred index of stature in the study of the elderly where height is unreliable because of age-related loss or distortion. As a consequence, two alternative mass indices, Demiquet (male mass. demispan-2) and Mindex (female mass. demispan-1), have been proposed for use in the elderly, in place of body mass index calculated from height, which might be suspect. These gender-specific indices reflect the squared and linear relationship of height to mass in men and women respectively. To assess the independence of Demiquet and Mindex from stature and the reliability of demispan, height, demispan (second fingerweb to midline), and mass were recorded in a random sample of independent Canadian men (182) and women (212) aged 55-86 years. Both Demiquet and Mindex were highly correlated with mass, r = 0.81 (p = 0.001) and r = 0.96 (p = 0.001), respectively. In both gender groups these mass indices were independent of height and demispan. The demispan within- and between-observer errors were small -0.04(-0.16 to 0.08)cm and -0.09(-0.22 to 0.03) cm and the between-observer intraclass correlation estimate of reliability was 0.96 (lower-bound one-sided 95% CI 0.90). Demispan is a reliable and reproducible measure of stature in the elderly. Demiquet and Mindex are useful mass indices, independent of stature and suitable for use in the study of the elderly where the use of mass indices based on height may be questionable.

Aged↗

PubMedDate not supplied

An outcome measure to quantify passive stiffness of the ankle.

The primary aim of this research project was to develop a method to quantify a specific variable of neuromuscular function, passive stiffness of the ankle. It was then used to determine if values for the outcome measure varied with age and sex in a sample of elderly men and women between 55 and 85 years old. Subjects were screened for medical conditions contraindicative to testing, e.g. severe arthritis, other history of bone or muscle disorders, ankle fracture, neural disorder causing spasticity or contracture. A rotatable footplate which recorded position and resistive torque with a potentiometer and strain gauge, respectively, was linked to an electric, computer-controlled torque motor. Passive elastic stiffness, defined as the slope of the passive resistance curve at 10 degrees dorsiflexion (in N.m/degree), was greater in males, (p < .001), and increased with age (p = .002). There was a significant effect of age group on passive range of motion (ROM) values for ankle dorsiflexion (p < .001), but also a significant sex by age interaction (p = .001). Females showed a large drop from a mean of 19.3 degrees +/- 3.2 in the youngest group (55-60 yr) to 12.1 degrees +/- 5.5 in the 81 to 85 yr olds. Corresponding mean values for the middle-aged males were 15.4 degrees +/- 4.3 versus 13.1 degrees +/- 3.5 of dorsiflexion in the group of 81 to 85 yr old men. It was concluded that passive ROM of the ankle into dorsiflexion showed decreases in the elderly, which seemed to reflect less complaint tissue structures.

Aged↗