Biomedical subjects

D H Paterson

Publications and source records attributed to D H Paterson.

At least 73 records · Page 4Linked to original sources

PubMed1993

Anthropometric and computed tomographic assessment of the thigh in young and old men.

Anthropometric (AP) and computed tomographic (CT) methods of determining limb and muscle-plus-bone cross-sectional area (CSA) and volume (Vol) were compared in 13 young (M = 24.5 yrs) and 11 old (M = 71.0 yrs) men. CSA of total thigh, muscle-plus-bone, quadriceps, and hamstring muscle compartments and muscle were measured from CT scans. Corresponding muscle Vol were estimated from anthropometric equations. Prediction equations for CT measures were developed from AP measures using multiple linear regression. AP and CT techniques produced different values for thigh component CSA and Vol, especially in the old men. AP overestimated muscle-plus-bone CSA and Vol (4-6%) and underestimated skin and subcutaneous tissue CSA and Vol (17-33%). Prediction equations for quadriceps CSA and Vol (R2 = 80-96%) were more accurate than equations for hamstrings (R2 = 42-65%). Specific thigh muscle CSA and Vol can be predicted from AP measures (SEE 5-15%). These findings may have clinical significance when normalizing strength per unit of muscle size.

Adult↗

PubMed1993

Evaluation of the VMM turbine for spirometry in the applied physiology laboratory.

The volume measurement module turbine (VMM) was evaluated in 51 subjects for spirometry in applied physiology against the Stead-Wells spirometer (SW) and Wright peak flow meter (WM). The volume and flow ranges (VMM) were, FEV1 1.32 to 3.94 L (mean 2.62, confidence interval [CI] 2.46 to 2.78); forced vital capacity (FVC) 1.97 to 5.06 L (mean 3.50, CI 3.29 to 3.71); and peak expiratory flow rate (PEFR) 290 to 624 L.min-1 (mean 434, CI 407 to 461). The mean difference for FEV1 was 0.09 L (CI 0.05 to 0.14), FVC 0.04 L (CI -0.02 to 0.10), and PEFR 18.0 L min-1 (CI 8.7 to 27.3) less than SW or WM. Bias with FEV1 and FVC was not significant, though PEFR demonstrated a significant proportional error. The repeatability coefficients for FEV1 and FVC were 0.18 and 0.20, comparable to the SW; but for PEFR they were greater, 58.4 versus 33.8 L.min-1 by WM. The VMM turbine is accurate and reliable for the measurement of FEV1 and FVC over the ranges studied; however, care should be taken when interpreting PEFR.

Adult↗

PubMed1993

Metabolic adaptations to endurance training in older individuals.

The purpose of this study was to describe the effects of moderate intensity exercise training on the muscle energy utilization, blood flow, and exercise performance of four sedentary older individuals (58 +/- 4 yrs). Subjects trained the dominant forearm each day for 12 weeks. The nondominant arm was not trained and served as a within-subject control. 31P nuclear magnetic resonance spectroscopy (31P NMRS) was used to identify the power output in watts (W) at the onset, or threshold, of intracellular acidosis (IT) in the exercising muscle during progressive exercise tests to fatigue. After 6 weeks of training, power output at the IT increased by 14% (p < 0.05) in the dominant arm; however, an additional 6 weeks of the same exercise program failed to produce a further increase in IT power. IT power of the nondominant forearm was not changed. In the dominant forearm, endurance time for a submaximal wrist flexion test was increased 34% and 58% at 6 and 12 weeks, respectively. Maximal voluntary strength was not affected by training, nor was resting or exercising blood flow. The training program delayed the onset of intracellular acidosis during progressive exercise and increased the capacity for submaximal work. These effects did not appear to depend on an increase in muscle blood flow.

Acidosis↗

PubMed1993

Cardiac output and left ventricular function in response to exercise in older men.

Studies of the cardiovascular response to exercise in older subjects have presented conflicting data regarding left ventricular function, the cardiac output-oxygen consumption (Q-VO2) relationship, and the pattern of change in Q, stroke volume (SV), and arteriovenous O2 difference. We have examined the cardiovascular response to submaximal and strenuous exercise in 96 men of mean age 63 years during an incremental treadmill test with Q determined by CO2 rebreathing, and in 12 subjects studied during incremental supine exercise with left ventricular volumes evaluated by radionuclide angiocardiography. During treadmill exercise the Q was approximately 10% lower than reported for younger samples, with a lower intercept of the Q-VO2 relationship. During near-maximal exercise Q was approximately 15 L.min-1, with SV of 95 mL plateauing or showing a small decline in heavy work. Peak arteriovenous O2 difference (150 + mL.L-1) approached values of the young. During the supine exercise SV increased from rest to exercise, with a consistent increase in ejection fraction (rest, 66%, to peak exercise, 76%). In contrast to a prior report, the end-diastolic volume was constant, with the increase of SV attributable to a reduced end-systolic volume. Also, in contrast to a number of reports in older subjects, our findings show only small losses in cardiovascular response, and in left ventricular performance during light through strenuous exercise.

Aged↗

PubMed1993

Transient changes in muscle high-energy phosphates during moderate exercise.

The purpose of this study was to use 31P-nuclear magnetic resonance spectroscopy to examine changes in wrist flexor muscle metabolism during the transitions from rest to steady-state exercise (on-transient) and back to rest (off-transient). Five healthy young males (mean age 25 +/- 2 yr) performed a series of square-wave exercise tests, each consisting of 5 min of moderate-intensity work followed by a 5-min recovery period. The subjects repeated this protocol six times, and each individual's results were pooled before analysis. ATP and intracellular pH did not change significantly during exercise or recovery. Phosphocreatine (PCr) declined progressively at the onset of exercise, reaching a plateau after approximately 2 min. A reciprocal increase in Pi occurred during the onset of exercise. During the recovery period PCr was resynthesized, whereas Pi returned to resting levels. The data were plotted as a function of time and fit with both first- and second-order exponential growth or decay models; however, the second-order model did not significantly improve the fit of the data. Time constants for the first-order model of the on- and off-transient responses for both PCr and Pi were approximately 30 s. These values are nearly identical to the time constants for oxygen consumption during submaximal exercise that have been reported previously by several authors. The results of this study show that the metabolism of muscle PCr during steady-state exercise and recovery can be accurately described by a monoexponential model and, further, suggest that a first-order proportionality exists between metabolic substrate utilization and oxygen consumption.

Adenosine Triphosphate↗

PubMed1993

Ventilatory sensitivity to CO2 in hyperoxia and hypoxia in older aged humans.

Findings from studies of the effects of aging on the human respiratory controller are equivocal. This study assessed the ventilatory response to CO2 in hyperoxia and hypoxia in groups of younger (YS) and older (OS) humans. Two protocols were used. In the first, end-tidal PCO2 (PETCO2) was clamped at 1-2 Torr above rest (eucapnia), and, in the second, PETCO2 was clamped at 7-8 torr above resting PETCO2 (moderate hypercapnia). End-tidal PO2 was clamped at 100 Torr throughout except for two 2-min periods at 500 and 50 Torr. The ventilatory responses for each subject at each PO2 were fitted to the linear equation, VE = S(PETCO2 - B), where VE is minute ventilation, S is the response curve slope, and B is the response curve threshold. In eucapnia, there were no differences in hypoxic and hyperoxic VE between YS and OS. In hypercapnia, hypoxic VE was 24% lower in OS [39.93 +/- 2.71 (SE) l/min] than in YS (52.16 +/- 3.17 l/min). In hypoxia, S was significantly lower in OS (3.25 +/- 0.38 l.min-1.Torr-1) than in YS (4.76 +/- 0.37 l.min-1.Torr-1). We conclude that, in older humans, VE is lower in hypoxia during moderate hypercapnia, resulting mainly from a decreased peripheral chemoreflex CO2 sensitivity.

Adult↗

PubMed1992

Influence of ageing on aerobic parameters determined from a ramp test.

The purpose of this study was to examine the four parameters of aerobic function, the maximum oxygen uptake (VO2max), ventilation threshold (ThVE), efficiency, and the effective time constant for oxygen consumption (tau'VO2), across age. In particular, the study was designed to observe whether there may be accelerated declines in aerobic function beyond 60 years of age. Seventy-nine sedentary men aged 30-84 years were studied. Each subject performed two maximal cycle ramp function tests, and data were collected on a breath-by-breath basis. The VO2max, from a plateau in VO2, was achieved in 87% of the subjects using the ramp test. The VO2max showed a significant decrease with increasing age (from linear regression, r = -0.81) at a rate averaging 0.037 l.min-1.year-1. The ThVE also declined with increasing age, but at a slower rate (0.013 l.min-1.year-1). The tau'VO2 was significantly increased across the age groups from 69 s for those aged 30-40 years to 98 s for those aged 60 years or more. There was no evidence of accelerated decline in these aerobic parameters beyond age 60 years, and there were no differences in efficiency (27.5-29.9%) across age. Although other forcing functions should be used to confirm this characterization of the oxygen kinetics, this slowed response with age would result in greater oxygen deficit and possibly earlier fatigue in response to even light exercise in older individuals.

Adult↗

PubMed1992

Cardiorespiratory adaptation with short term training in older men.

The purpose of this study was to assess the rate of training-induced cardiorespiratory adaptations in older men [mean (SD), 66.5 (1.2) years]. The eight subjects trained an average of 4.3 (0.3) times each week. The walk/jog training was in two phases with 4 weeks (phase 1) at a speed to elicit 70% of pre-training maximal oxygen consumption (VO2max), and 5 weeks (phase 2) at 80%. Maximal exercise treadmill tests and a standardized submaximal protocol were performed prior to training, at weekly intervals during the training programme, and after training. VO2max (ml.kg-1.min-1) increased significantly over both phases: 6.6% after the first 4 weeks, and an additional 5.2% after the final 5 weeks. The weekly changes in VO2max over phase 1 were well fitted by an exponential association curve (r = 0.75). The half-time for the rate of adaptation was 13.8 days, or 8.3 training sessions. Over phase 2, the change in VO2max did not plateau and a time course could not be determined. Submaximal exercise heart rate (fc) was reduced a significant 10 beats.min-1 after the first 4 weeks, and further 6 beats.min-1 over the final 5 weeks. The fc reductions showed half-times of 9.1 days (phase 1) and 9.8 days (phase 2) (or 5-6 training sessions). The anaerobic ventilation threshold was increased 13.9% over the 9 weeks of training and the respiratory exchange ratio during constant load heavy exercise was significantly reduced; however, these changes could not be described by an exponential time course. Thus, short-term exercise training of older men resulted in significant and rapid cardiorespiratory improvements.

Adaptation, Physiological↗

PubMed1992

Physiological responses of young and elderly men to prolonged exercise at critical power.

The critical power (CP) of a muscle group or individual may represent the highest rate of work which can be performed for an extended period. We investigated this concept in young (n = 13, 24.5 years) and elderly (n = 12, 70.7 years) active men by first determining CP and then comparing responses elicited by 24 min of cycle exercise at power outputs (omega) corresponding to CP. Values from the final 2 min of the 24-min ride were expressed relative to maximal values established in a ramp test. CP for the elderly was only 65% that for the young, but on a relative basis, it was significantly higher both in terms of omega (67 vs 62% of omega max) and oxygen consumption (VO2) (91.5 vs 85.2% of maximum oxygen consumption). There were no group differences in relative values for ventilation (VE), heart rate or respiratory exchange ratio (R). During the 24-min ride, VO2 and R achieved a plateau in both groups, while VE, blood lactate and arterial PCO2 continued to change in the young. It was concluded that CP can be determined in active elderly men, but that CP may not represent a true non-fatiguing work rate in either young or elderly men.

Adult↗

PubMed1992

Age and sex effects on mobility of the human ankle.

We investigated whether values for passive resistive torque, dorsiflexion strength, and active mobility of the ankle joint varied with age in a randomly selected sample of middle-aged and elderly males and females. The main effects of sex and age group were significant, without an interaction effect, on values for passive resistive torque and voluntary strength. The trends indicated that females had lower values for both variables and that passive torque increased and strength decreased with respect to age. Dorsiflexion range of motion also showed a highly significant trend to decrease across age groups, and more so for females than males. Mean values for middle-aged men vs old men went from 20.0 to 13.5 degrees, while corresponding values for women decreased from 20.7 degrees of dorsiflexion to 10.1. Functional ankle movement thus becomes limited with age, but could be improved by strengthening weak dorsiflexor muscles.

Aged↗

PubMed1992

Response rates in a survey of physical capacity among older persons.

A representative sample of 420 subjects aged 55 to 84 was sought for participation in a study of the relationship between physical activity and health. A stratified random sample with 35 subjects in each of 12 age-gender categories was designed, using lists generated consecutively until the target number for each category was reached. Although the protocol required walking and treadmill tests, 60.3 percent of those eligible participated, a figure comparable to that of NHANES II and superior to that of the Canada Fitness Survey. Participants were younger, more likely to be male, less likely to be currently married, and more likely to have had a white-collar job and some postsecondary education than were nonparticipants. Difficulties of obtaining subjects and methods for avoiding these difficulties include offering many opportunities to attend and determining accurately the reason for nonparticipation.

Age Factors↗

PubMed1992

Knee extensor and knee flexor strength: cross-sectional area ratios in young and elderly men.

The relationships between isometric and isokinetic-concentric knee extensor and knee flexor strength, and quadriceps and hamstring cross-sectional area (CSA) were determined in young (n = 13, M = 24.5y) and elderly (n = 12, M = 70.7y) men. Quadriceps and hamstring CSA was determined by computed tomography. Knee extensor and flexor strength at 0 degree/s and 120 degree/s was determined on a Kin-Com isokinetic dynamometer. Compared to the young men, elderly men had significantly smaller quadriceps muscles and were weaker (22-32%) in knee flexion and knee extension at both angular velocities. Strength:CSA ratios were similar at 0 degree/s, but elderly men had decreased ratios for both extensors and flexors at 120 degree/s. Correlations of knee extensor and flexor strength with muscle CSA were significant at both velocities in elderly men, but not at either velocity for the knee flexors in young men. The decrease in isometric strength in elderly men can be accounted for by their decrease in muscle CSA, but their decrease in isokinetic-concentric strength was greater than their loss of CSA. Further study is required to determine the reason for this nonproportional loss of isokinetic-concentric strength.

Adult↗

PubMed1992

Thigh composition in young and elderly men determined by computed tomography.

Computed tomography (CT) was used to quantify components of the thigh in young (n = 13) and elderly (n = 11) men. Cross-sectional areas (CSA) of the total limb, total muscle plus bone, quadriceps compartment, hamstring compartment and bone were measured at each of five scan sites along the length of the thigh. Non-muscle tissue (NMT) areas within the muscle compartments were measured using changes in density based on Hounsfield units. Skin plus subcutaneous fat areas and quadriceps and hamstring lean muscle areas were calculated by subtraction. Geometric formulae were used to calculate related volumes for each thigh component. Volumes were also predicted from regression equations employing thigh length and component CSA from single mid-limb CT scans. The results showed that while total thigh CSA was not different in elderly men, they had significantly smaller total muscle plus bone (13.0%), and quadriceps (26.4%), and hamstring (17.9%) muscle areas. The elderly men also had significantly greater CSA for skin plus subcutaneous fat (37.6%), and for NMT in the quadriceps (59.4%) and hamstring (127.3%) muscle compartments. These results suggest that comparisons of relative leg muscle strength between young and elderly men may be misleading due to the decrease in actual muscle tissue associated with ageing. Appropriate quantification of muscle size and CSA must be carried out before such comparisons can be meaningful.

Aging↗

PubMed1992

Endurance training of older men: responses to submaximal exercise.

The purpose of this study was to quantify the exercise response of older subjects on a time-to-fatigue (TTF) submaximal performance test before and after a training program. Eight older men (67.4 +/- 4.8 yr) performed two maximal treadmill tests to determine maximum oxygen uptake (VO2max) and ventilation threshold (TVE) and a constant-load submaximal exercise treadmill test that required an oxygen uptake (VO2) between TVE and VO2max. The submaximal test, performed at the same absolute work rate before and after the training program, was performed to volitional fatigue to measure endurance time. The men trained under supervision at an individualized pace representing approximately 70% of VO2max (80% maximum heart rate) for 1 h, four times per week for 9 wk. Significant increases were demonstrated for VO2max (ml.kg-1.min-1; 10.6%); maximal ventilation (VE, l/min; 11.6%), and TVE (l/min; 9.8%). Weight decreased 2.1%. Performance time on the TTF test increased by 180% (7.3 +/- 3.0 to 20.4 +/- 13.5 min). The similar end points for VO2, VE, and heart rate during the TTF and maximal treadmill tests established that the TTF test was stopped because of physiological limitations. The increase in performance time among the subjects was significantly correlated with improvements in VO2max and TVE, with the submaximal work rate representing a VO2 above TVE by 88% of the difference between TVE and VO2max pretraining and 73% of this difference on posttraining values.

Aged↗

PubMed1992

Eccentric and concentric torques of knee and elbow extension in young and older men.

The purpose of this study was to compare the strength of knee extensors and elbow extensors in young and older men under conditions of eccentric loading and concentric contractions. Twelve men ages 23 to 32 years and 12 ages 60 to 75 years were tested at two angular velocities of movement, 90 and 180 degrees.s-1, on a KinCom isokinetic dynamometer. Compared to young men, older men had lower concentric peak torque values for elbow (31%) and knee (32%) extensors (p less than 0.05). The older group showed lower eccentric peak torques on all elbow comparisons (21% lower), and for knee extension at the slower velocity (20%). At the faster velocity, knee extension eccentric peak torque did not differ from that of younger men. Differences between the age groups were significantly less for the eccentric muscle action than for the concentric one. The observation of maintained eccentric strength in older men, particularly at fast velocity, warrants research in defining the mechanism.

Adult↗

PubMed1992

The effect of interval and continuous training on the aerobic parameters.

The purpose of this study was to investigate changes in the parameters of aerobic function resulting from continuous training (CT) and interval training of both low power (LPO-IT) and high power output (HPO-IT). Untrained males (n = 17, 25.1 yrs) trained 10 weeks on cycle ergometers (four 40-min sessions a week) at 80% VO2max. Cycle ramp function tests at 0 and 10 weeks were used to determine the four aerobic parameters:VO2max, ventilation threshold (VeT), effective time constant for O2 uptake kinetics (MRT), and work efficiency (eta): VO2max increased significantly (3.30 to 3.66 l.min-1). Absolute VeT increased significantly (2.17 to 2.45 l.min-1) but there was no change in the relative threshold (VeT/VO2max). MRT decreased significantly from 38.8 to 33.1 seconds and there was no change in eta. There were no between-group differences; thus neither low power output nor high power output interval training offers an advantage over continuous training of the same average power output in altering the aerobic parameters.

Adult↗

PubMed1992

Effects of ageing on the cardiorespiratory system.

Ageing is characterized by a loss of functional capacity. A linear loss from age 30 to 65 years has been described for various measures. After age 65 years, evidence also suggests an accelerated decline in some measures, particularly those of muscle size and function. Nevertheless, up to 85 years, the rate of decline of VO2max across ages appears to remain rather constant. As well, the central cardiovascular capacity, despite some suggested age effects, would appear to be adequate to support the smaller muscle mass. Thus, despite the losses in absolute exercise capacity with age, the ability to sustain a relatively high intensity of aerobic exercise appears preserved. It has also been shown that cardiorespiratory training of older men and women is effective in increasing VO2max and results in the usual changes during submaximal exercise. These benefits of cardiorespiratory training are substantial in that the increases observed compensate for the losses with ageing described over the period of a decade or more.

Adaptation, Physiological↗

PubMed1991

Asymmetries of oxygen uptake transients at the on- and offset of heavy exercise in humans.

1. At work rates which do not result in a sustained increase in blood lactate ([L-]), oxygen uptake (VO2) approaches the steady state with first-order kinetics. However, when [L-] is increased, at least two kinetic components are required to characterize the VO2 response dynamics. The purpose of the present investigation was to determine whether these more-complex kinetics are best represented as: (a) two components which operate throughout the exercise or (b) a delayed slow component which is consequent to the lactic acidaemia and which does not influence the early development of the O2 deficit. 2. Six healthy subjects underwent an incremental ramp test on a cycle ergometer, to the limit of tolerance, for determination of the maximum VO2 (micro VO2) and and estimation [symbol: see text] of the threshold for lactic acidaemia (theta L) non-invasively. Subjects then performed, on different days, two to four repetitions of square-wave exercise from a baseline of unloaded pedalling ('O' Watts (W)) to work rates (WR) less than theta L (90% theta L) and greater than theta L (half-way between theta L and micro VO2). Ventilatory and pulmonary gas exchange variables were determined breath-by-breath. For each subject, the VO2 transitions were averaged prior to fitting a least-squares algorithm to the on- and off-transient responses. 3. The less than theta L test resulted in a mono-exponential VO2 response, with a time constant of 31.3 and 31.5 s for the on- and off-transients, respectively. 4. The VO2 responses to the greater than theta L test were fitted to three competing models: (a) a single exponential for the entire period; (b) a double exponential for the entire period; and (c) an initial single exponential with a subsequent phase of delayed onset. Model (c) yielded a significantly lower residual mean-squares error than methods (a) and (b), with a time constant for the initial component of 40.2 s for the on-transient and 32.9 s for the off-transient and a subsequent phase of VO2 increase for the on-transient which averaged 230 ml min-1. The delta VO2/delta WR for the early kinetics of the greater than theta L test were not different from the less than theta L test (9.6 and 9.5 ml min-1 W-1, respectively). 5. These data suggest that the slow phase of the greater than theta L VO2 kinetics is a delayed-onset process. This being the case, the O2 deficit during heavy exercise, as conventionally estimated, would be overestimated.

Exercise↗