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Biomedical subjects

G M Andrew

Publications and source records attributed to G M Andrew.

At least 19 recordsLinked to original sources
PubMed1994

Development of physical fitness standards for Canadian Armed Forces older personnel.

The purpose of the study was to develop a minimum physical fitness standard for Canadian Forces personnel, 35 years and older, based on common criteria for physically demanding tasks. A random sample of 100 men and 76 women performed the Exercise Prescription (EXPRES) test and five physically demanding tasks that simulate common military tasks, while restricted, for safety reasons, to 90% maximal predicted heart rate. Results indicated poor predictive power, as variances ranged from 5 to 55% between EXPRES fitness scores and task performance. With approval from an expert panel, the 75th percentile score for each task was selected as the cutting criterion. The passing-group data were converted to Z-scores in order to determine the 5th percentile from each EXPRES item: these scores became the EXPRES fitness standard. The minimum fitness standard had a greater impact on women than on men but was representative of the passing groups for both sexes.

Adult↗
PubMed1993

Blood flow elevation increases VO2 maximum during repetitive tetanic contractions of dog muscle in situ.

Blood flow through the gastrocnemius-plantaris muscle of the dog in situ was increased by a pump in the arterial supply during a 30-min period of 1/s isotonic tetanic contractions. Compared with a control series of experiments with normoxemia and spontaneous flow, the pump increased flow 84%, from 1.51 +/- 0.08 to 2.78 +/- 0.15 ml.g-1.min-1. The perfusion pressure was increased from 125 to 196 mmHg. The pump hyperemia increased maximal O2 uptake (VO2) at 5 min of contractions by 31%, from 8.97 +/- 0.44 to 12.89 +/- 0.30 mumol.g-1.min-1. The extraction was decreased, and venous PO2 (PVO2) was increased. Fatigue, measured as a drop in power production from the highest level at 10 s to 30 min, was 49% during pump hyperemia and 54% in the control conditions. VO2 decreased 30% from the 5-min value to the 30-min value with pump hyperemia and 28% over the same time in the control conditions. At maximal VO2, the ratio VO2/PVO2 was increased by pump hyperemia compared with control conditions, suggesting an increased O2 diffusing conductance of the muscles. We conclude that the elevated perfusion pressure of pump hyperemia increased flow to raise maximal VO2 mainly in areas of the muscle that had restricted flow under control conditions.

Animals↗
PubMed1992

Force-velocity shifts with repetitive isometric and isotonic contractions of canine gastrocnemius in situ.

The force-velocity (F-V) relationships of canine gastrocnemius-plantaris muscles at optimal muscle length in situ were studied before and after 10 min of repetitive isometric or isotonic tetanic contractions induced by electrical stimulation of the sciatic nerve (200-ms trains, 50 impulses/s, 1 contraction/s). F-V relationships and maximal velocity of shortening (Vmax) were determined by curve fitting with the Hill equation. Mean Vmax before fatigue was 3.8 +/- 0.2 (SE) average fiber lengths/s; mean maximal isometric tension (Po) was 508 +/- 15 g/g. With a significant decrease of force development during isometric contractions (-27 +/- 4%, P < 0.01, n = 5), Vmax was unchanged. However, with repetitive isotonic contractions at a low load (P/Po = 0.25, n = 5), a significant decrease in Vmax was observed (-21 +/- 2%, P < 0.01), whereas Po was unchanged. Isotonic contractions at an intermediate load (P/Po = 0.5, n = 4) resulted in significant decreases in both Vmax (-26 +/- 6%, P < 0.05) and Po (-12 +/- 2%, P < 0.01). These results show that repeated contractions of canine skeletal muscle produce specific changes in the F-V relationship that are dependent on the type of contractions being performed and indicate that decreases in other contractile properties, such as velocity development and shortening, can occur independently of changes in isometric tension.

Animals↗
PubMed1992

Development of physical fitness standards for Canadian Armed Forces younger personnel.

The purpose of this study was to develop minimum physical fitness standards based on common task criteria for personnel younger than 35 years of age in the Canadian Armed Forces. A random sample of 66 men and 144 women performed the Exercise Prescription (EXPRES) test and five physically demanding tasks that simulated common military tasks. Common cutting scores were selected as the point at which 75% of the total weighted sample passed each task. Since there were significant differences between the sexes in task performance and technique execution, the groups were analyzed separately. Results indicated a range in variance of 14 to 48% between military task performance and physical fitness test score, thus suggesting that fitness measures are a poor predictor of task performance. Because of the low variance observed the passing group of each task was treated as a representative sample of subjects whose fitness profiles were indicative of those able to meet task criteria. The 5th percentile fitness scores of the passing group were proposed as the minimum fitness standard. These conditions resulted in fitness standards that were physically more demanding for women than for men.

Adult↗
PubMed1989

Isoinertial tests to predict lifting performance.

Previous research has found isoinertial strength testing to be superior to isometric and isokinetic strength testing for prediction of task performance. The purpose of this study was to investigate tests on an isoinertial lifting machine (ILM) and their ability to predict performance on actual lifting tasks. Sixteen male subjects performed two lifting tasks: maximum box lift to truck-bed height of 1.35 m; and 'speed lifts' of 60 concrete blocks (each 22.7 kg) to the same height. These performance tests were compared to three ILM tests: a maximal lift to 1.83 m, a second maximal lift to 1.52 m, and an endurance test that entailed 60 timed ILM lifts of 22.7 kg to 1.83 m. Pearson product-moment correlations between ILM tests and performance tasks varied from r = 0.55 to 0.71. Therefore, the isoinertial test protocols employed in this study were able to account for only 30% to 50% of the variance in the performance of maximal lifting and endurance tasks. In was concluded that prediction of maximal lifting ability or endurance ability using an ILM might be enhanced by closer approximation of specific task variables, or by inclusion of dynamic parameters to measure technique.

Adult↗
PubMed1988

Maximal blood flow and power output of dog muscle in situ.

The two goals of this study were: 1) to establish a stimulation pattern which would drive the gastrocnemius-plantaris muscle of the dog, in situ, to maximal work rate, W, and 2) to determine whether the surgical isolation of the circulation of this muscle, necessary to measure the muscle flow, Q, reduced the muscle's performance. The first goal was achieved in a preparation with minimal surgery, MS, to isolate the nerve and the tendon. The nerve was cut and connected to a stimulator, and the tendon was cut and connected to a pneumatic lever system. Wmax during 1.s-1 contractions occurred with a load of 270 g.g-1 and 200-ms trains of impulses at a frequency of 60.s-1. At 50 imp.s-1, the accepted maximal frequency which would occur in vivo, the Wmax which was maintained for 4 min was 19 mW.g-1. The second goal was met in a second series of experiments in which the venous circulation was isolated, FS. During a 20-min series of 30-s work periods with 2 min rest each, maximal W was 11.9 mW.g-1 at 50 imp.s-1. Following a 10-min additional rest, the muscle was stimulated for 10 min. The W, Q, and VO2 at 2-4 min were 10.0 mW.g-1, 1.73 ml.g-1.min-1 and 194 microliters.g-1.min-1, respectively. Q and VO2 were linearly related to W. Assuming a linear extrapolation, the FS early maximum in the brief tests as W = 11.9 mW.g-1, Q would be 2.06 ml.g-1.min-1 and VO2 would be 231 microliters.g-1.min-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Plasma beta-endorphin immunoreactivity during graded cycle ergometry.

The present study was undertaken to define the response of plasma beta-endorphin immunoreactivity (ir-BE) to exercise of increasing intensity. Nineteen healthy males performed continuous exercise for 32 min on a cycle ergometer, comprised of 8-min bouts at %VO2max approximating 25, 50, and 75% of maximal exercise. Venous blood samples were collected before exercise (T = -20 and 0 min), during exercise (T = 8, 16, 24, and 32 min), and in recovery (T = +15, +30 min). Ir-BE in plasma was measured by radioimmunoassay using Immuno Nuclear assay kits. Plasma ir-BE level (pg X ml-1) was not altered from pre-exercise (18.3 +/- 1.3) after 8 min of exercise at 25 and 50% VO2max intensity; however, ir-BE rose significantly after 8 min of 75% VO2max work intensity (27.1 +/- 2.4) and was further elevated at maximal exercise (74.1 +/- 8.6). Ir-BE level remained elevated 15 min (60.9 +/- 8.1) and 30 min (35.2 +/- 5.2) post-exercise. The response pattern was further characterized by a significant (P less than 0.05) inter-individual variation, both at rest and during exercise; also, regression analysis indicated the ir-Be levels attained at maximal exercise were inversely related to the relative VO2max (ml X kg-1 X min-1) of the subject (predicted ir-BE = 248.2 - 3.39 VO2max; r = -0.397, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Plasma catecholamines and their effect on blood lactate and muscle lactate output.

This study was designed to test the hypothesis that epinephrine (E) and norepinephrine (NE) increase net muscle lactate output (L) of in situ gastrocnemius-plantaris muscle group during contractions. Plasma [E] and [NE] were measured before and after the surgical isolation of the muscle and at 10-min intervals during the 60-min experiments. Plasma [E] and [NE] were increased threefold by intravenous infusions of E (n = 3) or NE (n = 3) at a rate of 1.5 micrograms X kg body wt-1 X min-1. Arterial and muscle venous blood samples for O2 and lactate concentrations were also obtained. The infusions began at min 11 and repetitive isometric contractions (4 tw/s) began at min 31. The presurgery plasma [E] and [NE] averaged 0.34 and 0.52 ng/ml, respectively, and rose to 1.12 and 1.19 ng/ml 10 min after surgery. Arterial and venous lactate concentrations (CaL and CvL) increased continuously during E infusion but remained constant during NE infusion. Maximal L during the first 10 min of contractions was significantly increased compared with an identical earlier study without infusions. O2 uptake was not changed by the infusions. It is concluded that E causes CaL to rise and that both E and NE increase maximal net lactate output during contractions.

Animals↗
PubMed1984

Effects of naloxone on exercise performance.

This study was designed to investigate the effects of naloxone on athletic performance in humans. Two groups of elite middle-distance runners performed a maximal or a submaximal exercise protocol following the double-blind intravenous injection of either naloxone (0.15 mg X kg body wt-1) or saline. The maximal test (group M) was comprised of a short-duration treadmill run to maximal intensity; the submaximal test (group S), a prolonged submaximal treadmill run to exhaustion. O2 uptake, heart rate, ventilation, and perceived exertion were determined during each test. Perception of pain was assessed after exercise by use of a modified McGill pain questionnaire. No significant differences between placebo and naloxone treatments were found in any of the measured variables at the usually accepted 5% (P = 0.05) confidence level; however, evidence suggesting differences (i.e., P = 0.1 to 0.05) in these important respects was observed. In group M, maximal exercise performance measured by maximal O2 consumption was not different between placebo and naloxone; results suggest that VE was increased (P = 0.08) following naloxone, but only at the final work stage. In group S, exercise performance time was reduced following naloxone (P = 0.09), whereas the affective component of pain was increased (P = 0.06); no differences in the measured physiological variables were observed. These results suggest the following: 1) the opiate receptor-endorphin system may alter the perception of pain associated with prolonged high-intensity submaximal exercise with a resultant significant effect on performance; and 2) it may play a role in the control of ventilation during maximal exercise.

Adolescent↗
PubMed1983

Characteristics that predicted recurrence of infarction within 3 years in the Ontario Exercise-Heart Collaborative Study.

Data on 13 baseline characteristics of 618 patients who had previously had a myocardial infarction and who had entered the Ontario Exercise-Heart Collaborative Study were analysed for their ability to predict recurrence of infarction within 3 years. These characteristics were age, serum levels of cholesterol and triglycerides, systolic and diastolic blood pressure, number of hours of competitive sports per week, number of hours of jogging per week, angina, type of occupation, smoking, cough and phlegm production, personality type and the number of previous infarctions. The characteristics showing independent statistical significance (p less than 0.05) were smoking and blue-collar occupation, with estimated adjusted relative odds of 2.3 and 2.1 respectively.

Adult↗
PubMed1983

Predictors of dropout from cardiac exercise rehabilitation. Ontario Exercise-Heart Collaborative Study.

The Ontario Exercise-Heart Collaborative Study was a multicenter randomized clinical trial of high intensity exercise for the prevention of recurrent myocardial infarction in 733 men. Of the 678 subjects who could have participated for at least 3 years, 315 (46.5%) dropped out. Stepwise multiple linear logistic regression analysis was carried out to examine the relation between subject characteristics and the probability of dropping out during the study. Analysis was performed on the entry group as a whole by considering those subjects who had reinfarction while complying with the program and also by excluding all subjects with reinfarctions. The consistent and statistically significant predictors of dropout in both analyses were smoking and a blue collar occupation. Angina was significantly associated with dropout only when reinfarctions were excluded. It may be important to consider these factors when investigating the potential for compliance-improving strategies in reducing dropout from exercise rehabilitation programs.

Adult↗
PubMed1981

Reasons for dropout from exercise programs in post-coronary patients.

The dropout rate in the 7-yr Ontario Exercise Heart Collaborative Study of post-coronary men engaged in exercise programs was examined in order to determine possible contributing factors. A questionnaire pertaining to psychosocial and program-related variables was distributed to 728 subjects who were previously assigned randomly on the basis of four prognostic risk factors (occupation, personality, hypertension, and angina) into exercise groups: low intensity exercise (LIE), and high intensity exercise (HIE). Comparisons of answers by the 639 respondents (266 dropouts; 373 compliers) were made initially by chi-square analysis to determine significant categories of questions and, subsequently, by a logistic transform to determine the specific questions which related significantly to the dropout rate. It was found that three main categories were associated with a high dropout rate: convenience aspects of the exercise center, perceptions of the exercise program, and family/lifestyle factors. These three main categories should be carefully considered when designing and implementing potential compliance-improving strategies for secondary prevention exercise programs entailing long-term adherence.

Angina Pectoris↗
PubMed1978

Hypoxia, smoking history, and exercise.

Six nonsmokers and six cigarette smokers, 22-34 years old, performed bicycle work (53% sea level VO2 max) for 30 min in an altitude chamber under four conditions: SL, simulated sea level (PIO2 = 159 torr, PB = 523 torr) with 0.5% HbCO; SLCO, simulated sea level with 4.2% HbCO; and ACO, altitude with 4.2% HbCO. During work at altitude, heart rate (HR), minute ventilation and tidal volume increased and diastolic blood pressures decreased relative to SL. Cardiac output (Qc), stroke volume (SV), and arterial-mixed venous oxygen difference (a--vO2) were similar in smokers and nonsmokers at SL, SLCO, and A. At ACO, nonsmokers increased Qc and SV and decreased a--vO2, but these were not influenced in the smokers. Smokers showed a graded increase in HR when exposed to work in SLCO, A, and ACO. Their lower finger temperatures during A and ACO suggested vasoconstriction in the extremities. Cigarette smokers may be partially adapted to hypoxia.

Adult↗
PubMed1976

Influence of growth and athletic training on heart and lung functions.

Studies were performed at rest and during exercise of varied intensity on 52 boys of pre- and post-pubescent age. Each age group consisted of boys who were engaged in a strenuous prolonged hockey training program; this group was compared with a matched control group who did not participate in a regular training program. Any differences observed in the measured lung functions could be explained on the basis of physical size. Relationship of pulmonary capillary blood flow (Qc) and pulmonary diffusing capacity (DLco) to oxygen consumption were similar to those reported for adults and no difference between the trained and control groups was found in either the pre- or post-pubertal aged boys. Similarily, the trained pre-pubertal boys did not differ significantly from their matched control group in respect to the relationships of heart rate (HR) and stroke volume (SV) for any level of oxygen consumption. In contrast, the post-pubertal trained boys had significantly lower HR and higher SV (P less than 0.01) at each level of work than the control group. These differences between the trained and control post-pubertal boys are consistent with training effects observed in adults. The lack of differences between the trained and control pre-pubertal groups was surprising. Whether the differences in the post-pubertal groups due to a detraining effect in the post-pubertal control boys (as compared to the pre-pubertal control group) or to a continued high level of physical activity during and after the on-set of puberty in trained boys cannot be answered by this study. The findings suggest the importance of high intensity exercise programs during the growth period of adolescence if the efficiency of the oxygen delivery system, and possibly its ultimate dimensions, are to be enhanced.

Adolescent↗