Biomedical subjects

D H Paterson

Publications and source records attributed to D H Paterson.

At least 91 records · Page 5Linked to original sources

PubMed1991

Coincident thresholds in intracellular phosphorylation potential and pH during progressive exercise.

Dynamic changes in intracellular phosphocreatine (PCr), inorganic phosphate (Pi), and pH in human forearm muscle were studied from rest through heavy exercise by means of a ramp exercise protocol and 31P nuclear magnetic resonance spectroscopy. Eighteen healthy volunteers performed an isotonic wrist flexion exercise of repeated contractions at a frequency of 0.5 Hz. Work rate was increased continuously (ramped) at approximately 0.13 W each minute from 0.34 to 1.5 W or until fatigue. Pi/PCr was used as an estimate of the cellular phosphorylation potential of the muscle. Exercise caused a progressive increase in Pi/PCr with an initial slow and later fast component. The transition between these components was distinct and corresponded to the onset of pH decline in all subjects. These changes in Pi/PCr and pH were best fit (P less than 0.05) by a piecewise linear regression model with a break point or threshold. Repeated ramp testing of six subjects showed that the threshold was reproducible (r = 0.98). The results of this study demonstrate the existence of an intracellular metabolic threshold and suggest that indirect threshold measures (lactate and ventilatory thresholds) may reflect events at the cellular level.

Adult↗

PubMed1990

A comparison of anthropometry with computed tomography in limbs of young and aged men.

Arm and leg composition determined by anthropometry (AP, girths, and skinfolds) were compared with computed tomography (CT) in 7 young (mean age 31.4y) and 13 old (74.8y) males. Five transverse CT scans, girths, and skinfold measurements were made. In each CT image, total cross-sectional area (CSA), bone CSA, muscle compartment CSA, and "pure" muscle CSA within the compartment were measured. Corresponding volumes were also calculated. Total limb and muscle plus bone CSA and volumes were estimated from AP measures. The two methods were compared, and multiple regression analyses were used to predict component CSA and volumes from AP measures. In both groups, AP component measures in the leg provided more accurate values than in the arm. Skin plus subcutaneous tissue in the old was not well estimated by AP. The greater preponderance of nonmuscle tissue in the muscle compartments of the old, as determined from CT images, was not related to any AP estimates. Prediction equations for various component areas and volumes were derived. Some equations derived for the young could not be obtained for the old due to the reduced ability of AP to accurately assess limb composition of aged men.

Adult↗

PubMed1989

Comparison of twitch potentiation in the gastrocnemius of young and elderly men.

The capacity for twitch potentiation in the gastrocnemius muscle was determined following maximal voluntary contractions (MVC) in 11 elderly (means +/- SD; 66.9 +/- 5.3 years) and 12 young (25.7 +/- 3.8 years) men. Potentiation was observed by applying selective stimulation to the muscle belly, 2 s after a 5 s MVC. With this procedure, both groups showed significant (P less than 0.05) increases in twitch tension in the gastrocnemius (ratios of potentiated twitch to baseline were means = 1.68 +/- 0.40 for young vs means = 1.40 +/- 0.20 for the elderly, P less than 0.001). Time to peak tension of the twitch decreased from means = 101.5 +/- 17.9 ms to means = 88.0 +/- 15.8 ms in the young men following potentiation; the respective values for the older men were 136.7 +/- 17.9 ms and 133.1 +/- 28.6 ms. These changes resulted in a greater rate of tension development in the potentiated state. The elderly gastrocnemius thus showed qualitatively similar changes in the isometric twitch following potentiation, but reduced and prolonged responses in comparison to young adults. Slowed muscle contraction and reduced capacity for potentiation may be physiological correlates of the reported morphological changes in aged skeletal muscle.

Adult↗

PubMed1989

Arm and leg composition determined by computed tomography in young and elderly men.

Five computed tomography (CT) scans were taken at measured intervals of the legs and arms of young (n = 7) and elderly (n = 13) men. Cross-sectional areas (CSA) of the total limb, muscle plus bone and bone were measured in each scan, and skin plus subcutaneous tissue areas were calculated by subtraction. In addition, in the arm scans the CSA of the extensor and flexor compartments were measured, and in the leg the CSA of the plantar flexor compartment. A value for lean muscle within these compartments was calculated by excluding non-muscle tissue using density measurements based on Hounsfield units. Related volumes for the various components were also calculated using geometric formulae. The results showed that elderly limbs were of a similar overall size as the young, but elderly muscles were smaller (28-36%) with greater amounts of non-muscle tissue located within a muscle, particularly in the plantar flexors (81% more than in the young). Elderly arms had a greater amount of skin plus subcutaneous tissue than the young, but there was no difference in the legs. Muscle volumes were similar to in vitro results reported from cadaver studies and can be predicted from single mid-limb CT scans using regression equations. These results illustrate that, due to the substantially reduced amount of 'pure' muscle tissue in the elderly, comparisons of relative strength with other populations may be misleading unless appropriate measurements of muscle size are considered. Methods to estimate in vivo physiological CSA, which is considered the best means of normalizing strength, have been demonstrated in this study.

Adult↗

PubMed1989

Strength in an elderly population.

Strengths of several upper- and lower-limb muscle groups were measured in an elderly population by using a simple, adaptable dynamometer. The bladder of a sphygmomanometer was modified by folding and surrounding it in a sewn cloth bag. It was then attached to a board for improved stability during the tests. Thirty-seven men and 81 women aged 62 to 102 years were tested. Four muscle groups were statistically determined to best represent strength-two for upper limb and two for lower limb. These strength measures were correlated with anthropometric indices, and a step-wise multiple regression was used to determine the degree of association between the variables. Men were significantly stronger than women in absolute strength, but were not different when strength was expressed relative to body weight. Within each sex, however, age was the most important variable related to loss of strength; body weight was secondary or not significant. These results suggest that age is the most important factor for relating differences in strength in an older elderly population (those aged 75 to 90 or more years). This factor must be accounted for just as body weight or cross-sectional muscle area often are, when comparing strengths in a younger population.

Aged↗

PubMed1988

Comparison of the histochemical and contractile properties of human triceps surae.

Contractile and histochemical properties of the triceps surae were compared in 16 males and 4 females aged 20 to 49 years. Surface electrical stimulation was used to determine twitch, tetanic and fatigue parameters. From these tests, twitch tension (Pt), time to peak tension (TPT), half relaxation time (1/2 RT), tetanic tensions at 10, 20 and 50 Hz and an index of fatigue (FI) were calculated. A maximal voluntary contraction (MVC) was also performed. Muscle samples from the belly of the lateral gastrocnemius were obtained using the needle biopsy technique. The samples were treated histochemically for myosin ATPase and NADH-tetrazolium reductase in order to classify the fibres as either Type I, slow twitch (ST) or Type II, fast twitch (FT) and to determine fibre areas. Correlations were performed between the grouped male and female contractile and histochemical variables. The results demonstrated significant positive relationships demonstrated significant positive relationships between percentage of ST fibres (%ST) and TPT (r = 0.49), and %ST and the ratio of tetanic forces at 10 Hz to 50 Hz (Po10/Po50) (r = 0.55). No significant relationships were obtained for Pt, 1/2 RT, MVC or FI with any histochemical parameter. The results suggest that fibre type distribution determined using myosin ATPase is related to electrically stimulated isometric contractile speeds and not to voluntary force generation (MVC) or electrically induced fatigue.

Adult↗

PubMed1988

Fatigue and recovery contractile properties of young and elderly men.

The 24 h recovery pattern of contractile properties of the triceps surae muscle, following a period of muscle fatigue, was compared in physically active young (25 years, n = 10) and elderly (66 years, n = 7) men. The fatigue test protocol consisted of 10 min of intermittent submaximal 20 Hz tetani. The maximal twitch (Pt) and tetanic force at 3 frequencies (10, 20 and 50 Hz) were determined at baseline and at 15 min, 1, 4 and 24 h after fatiguing the muscle. Maximal voluntary contraction (MVC) and vertical jump (MVJ) were also assessed. The loss of force during the fatigue test was not significantly different between the young (18 +/- 13%) and elderly (22 +/- 15%). Both groups showed similar and significant reductions of Pt (15%), tetanic force (10 to 35%) and rate of force development (dp/dt) (20%) 15 min and 1 h into recovery. The loss of force was greater at the lower stimulation frequencies of 10 and 20 Hz. Time-to-peak tension was unchanged from baseline during recovery in either group. The average rate of relaxation of twitch force (-dPt/dt) was decreased (p less than 0.05) and half-relaxation time significantly increased at 15 min and 1 h in the elderly but not the young. The findings indicate that after fatiguing contractions, elderly muscle demonstrates a slower return to resting levels of the rate and time course of twitch relaxation compared to the young.

Adult↗

PubMed1988

Comparison of cardiovascular response to passive tilt in young and elderly men.

To test the hypothesis that altered hemodynamic responses to postural changes are associated with aging, cardiovascular responses to head-up tilt (HUT) and head-down tilt (HDT) were examined in 12 healthy young (average age, 24.6 +/- 1.7 years) and 12 healthy elderly (average age, 68.6 +/- 2.2 years) men. Subjects were passively tilted from supine to 30 degrees, 60 degrees, and 90 degrees HUT and HDT. Responses to these perturbations were determined 5 min after tilting with measures of heart rate (HR), blood pressure (SBP, DBP), and echocardiographically determined left ventricular diameter in systole and diastole (LVIDs, LVIDd). In HUT there were no significant age effects. In both young and elderly, SBP decreased significantly (p less than 0.05), and DBP and HR increased significantly. Ejection fraction (EF), mean arterial blood pressure (MABP), and rate-pressure product (RPP) were unchanged in both groups. In HDT, the hemodynamic responses of the young and elderly were in opposite directions and significant age effects were found for SBP, DBP, HR, LVIDs, EF, MABP, and RPP. In HDT, the young appear to increase cardiac output primarily due to an increase in EF and end-diastolic volume (LVIDd), while HR is unchanged and SBP is decreased. MABP is unchanged, suggesting a small decrease in total peripheral resistance. The elderly may increase cardiac output slightly, owing to an increase in LVIDd with no change in EF, and a large increase in HR. Afterload increased markedly, therefore attenuating any increase in cardiac output.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

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

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↗

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↗

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

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↗

PubMed1984

Development of cardiorespiratory function in circumpubertal boys: a longitudinal study.

To investigate cardiorespiratory function during circumpubertal growth, 62 boys (aged 9-10 yr) were studied annually for 6 yr. Measurements of O2 uptake (VO2), cardiac output, and arteriovenous O2 difference were made during a submaximal bicycle test. Values were interpolated to a heart rate of 155 beats X min-1 (VO2 at a heart rate of 155) for comparisons across ages 10.8-14.8 yr. To account for growth differences among the boys, data were also aligned at yearly intervals relative to their individual age of peak height velocity (PHV; maturative age). The group was further divided into early, mid, and late maturers based on their year of PHV. VO2 and stroke volume (SV) of late maturers were larger at each maturative age. SV mirrored the increase in VO2 at all stages of development except during the period of most rapid growth. Arteriovenous O2 difference showed an increase in the year of peak growth with little change during any of the other maturative age intervals. Multiple regression analysis indicated that VO2 was determined primarily by the size of SV throughout this age range.

Child↗

PubMed1983

Relationship of selected variables to performance in women's basketball.

Twenty women were measured on physiological, anthropometric, motor fitness and skill related variables in order to provide a current profile of elite female basketball players. Performance of each subject was evaluated firstly to determine the relationship between performance and selected variables and secondly to determine which variables best discriminated between the top and lower ranked performers. The profile of the elite female player had changed considerably subsequent to rule changes. The better basketball players exhibited a superior aerobic power and anaerobic capacity, were more accurate shooters and possessed less body fat. The factors which best discriminated between high and low performers were accuracy shooting, percent fat and VO2max. These variables could be used in a test battery to assist in the selection and development of potential basketball players.

Adipose Tissue↗

PubMed1982

The consistency of cardiac output measurement (CO2 rebreathe) in children during exercise.

Exercise cardiac output (Q) was determined using the CO2 rebreathing equilibrium method. Five repeat tests in 12 boys and two tests over a 4 month interval in 47 boys were performed. Regression equations to predict Q from VO2 were in close agreement with dye dilution studies in boys (Eriksson and Koch 1973). Group mean data were reproducible from trial to trial. The day-to-day variability of Q, with a coefficient of variation of 7-8%, was found to be higher than when the CO2 method has been applied in adults. This greater variability was related, in part, to a larger biological variation in children as depicted in such relatively simple measures as submaximal exercise heart rate. The larger variability was also related to inaccuracies in the methods of PaCO2 estimation in children. Estimation from end-tidal CO2 concentrations requires further research to establish a correction for the alveolar-arterial gradient during exercise in children. Estimation of the child's dead space in exercise, with subsequent derivation of PaCO2 from the Bohr equation, also could be improved. Nevertheless, Q estimates in children exercising above VO2 1.01 X min-1 showed a day-to-day and long term stability acceptable for use in research and clinical studies.

Adolescent↗

PubMed1981

The effect of different treadmill speeds on the variability of VO2 max in children.

Eight boys aged 10-12 years performed three tests on each of three treadmill protocols. Each test was a continuous, progressively graded performance to exhaustion, but protocols differed in speed--(walk: 90 m . min-1, jog: 110 m . min-1, run: 130 m . min-1). The walk protocol was found inappropriate for VO2 max determination in children. Compared to the faster speeds, the walk test elicited a lower VO2 at exhaustion, and had lower reliability (0.56) and a high coefficient of variation (8%). For the Vo2 at exhaustion on the jog and run protocols the coefficient of variation was 3-5% and the reliability coefficient averaged 0.90, comparable to values seen for repeated trials in adults. The usually accepted VO2 max criterion of a plateau of VO2 with increasing work levels was inappropriate for use with children. Attempts to derive plateau criteria suitable for use with children proved unsuccessful. Plateau criteria may be difficult to achieve with children in light of their apparently weaker glycolytic energy capacity. Nevertheless, the highest VO2 measured at jog or run speeds has a consistency similar to that found for Vo2 max measurement in adults.

Child↗

PubMed1981

Daily energy expenditure of young boys as related to maximal aerobic power.

Daily energy expenditure, and participation in regular physical activity over one year, were determined in 28 boys (age 12.3 years) by (1) heart rate (fh) recorded on an oxford Medilog tape recorder and used to approximate energy expenditure using individual fh-VO2 relationships established from a standard step test; total daily average energy expenditure, time spent, and energy expended in activity above a defined threshold, training fh = (.6 (fh max - fh rest) + fh rest) and, (2) a questionnaire designed to determine involvement in regular physical activities over the preceeding year. Maximal oxygen uptake (2.47 +/- 0.36 l-min-1) was measured on a treadmill test. A step-wise multiple regression analysis was used to describe the association between maximal aerobic power and the measures of body size (wt. - 43.8 kg, ht. - 152.2 cm), fatness (sum of skinfolds -67.4 mm), daily energy expenditure (11.66 MJ), and participation in regular physical activity. Body mass and fatness made the only significant contributions to the variance (R2 = 0.77). The relationship was VO2 (l.min-1) = 0.47 (body mass- kg) -0.04 (sum of 6 skinfolds) + 0.71. Measures of daily energy expenditure, the time the heart rate was above a training threshold, and the number of regular physical activities, added little to the measured variance (R2 = 0.78) above that accounted for by body mass amd fatness.

Adolescent↗