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Biomedical subjects

D H Paterson

Publications and source records attributed to D H Paterson.

At least 55 records · Page 3Linked to original sources
PubMed1996

Kinetics of pulmonary oxygen uptake and muscle phosphates during moderate-intensity calf exercise.

The purpose of this study is to directly compare the dynamic responses of phosphocreatine (PCr) and P(i) to those oxygen uptake (VO2) measured at the lung during transitions to and from moderate-intensity exercise. Changes in PCr and P(i) were measured by 31P-nuclear magnetic resonance spectroscopy, and changes in VO2 were measured breath by breath by mass spectroscopy during transitions to and from moderate-intensity square-wave ankle plantar flexion exercise in 11 subjects (7 men and 4 women; mean age 27 yr). Three repeated transitions were averaged for improvement in signal-to-noise ratio of phosphate data, and 12 transitions were averaged for VO2 measurements. Averaged transitions were fit with a monoexponential curve for determination of the time constant (tau) of the responses. Mean tau values for on transients of PCr, P(i), and phrase 2 VO2 were 47.0, 57.7, and 44.5 s, respectively, whereas means tau values for off transients were 44.8, 42.1, and 33.4 s, respectively. There were no significant differences between tau values for phosphate- and VO2-measured transients or on and off transients. The similarity of on and off kinetics supports linear first-order respiratory control models. Measurement of phase 2 pulmonary VO2 kinetics to and from moderate-intensity small-muscle-mass exercise reflect muscle phosphate kinetics (and muscle oxygen consumption).

Adult↗
PubMed1996

Cardiorespiratory kinetics during exercise of different muscle groups and mass in old and young.

The purpose was to compare cardiorespiratory kinetics during exercise of different muscle groups (double-leg cycling vs treadmill walking and single-leg ankle plantar flexion) in old and young subjects. Oxygen uptake (VO2) during exercise transitions was measured breath by breath, and the phase 2 portion of the response was fit by a monoexponential for determination of the time constant (tau) of VO2. Two separate studies were performed: in study 1, 12 old (age 66.7 yr) and 16 young (aged 26.3 yr) subjects were compared during cycling and ankle plantar flexion exercise, and in the study 2, five old (aged 69.6 yr) and five young (24.4 yr) subjects were compared during cycling and treadmill walking. VO2 transients during square-wave cycling exercise were significantly slower in the old compared with the young groups. In contrast, VO2 kinetics did not differ between old and young groups during plantar flexion exercise. Heart rate (HR) kinetics followed the same pattern, with tau HR being significantly slower in the old vs young groups during transitions to cycling but not to plantar flexion. In study 2 tau VO2 and tau HR during on-transients to treadmill square-wave exercise were significantly slower in the old group compared with the young group, but tau VO2 was significantly faster during treadmill exercise than during cycling in the old group. The differences with aging between the modes of exercise may be related to the muscle mass involved and the circulatory demands. On the other hand, slowed VO2 kinetics with age appear to occur in a mode (cycling) in which the muscles are not accustomed to the activity, whereas in a mode of normal activity (walking) and with the muscle groups (plantar flexors) accustomed to the activity, VO2 kinetics are not slowed to the same degree with age.

Adult↗
PubMed1995

Sleep deprivation: effects on work capacity, self-paced walking, contractile properties and perceived exertion.

The primary purpose of this study was to examine the effect of a 48-hour period of sleep deprivation on the performance of selected physical work tasks [30-45% of maximum oxygen consumption (VO2max)]. In addition, this study assessed the effect of continual performance of physical work during sleep deprivation on standardized physiological and psychological test scores. Nineteen male subjects performed six different physical tasks, designed to involve all major muscle groups, during a 48-hour period of sleep deprivation. Fourteen subjects served as sleep-deprivation controls. Performance on all physical work tasks decreased significantly. Neither sleep deprivation (SD) or sleep deprivation in conjunction with continuous physical work (SDW) had any effect on muscle contractile properties, anaerobic power measures or resting blood glucose and lactate concentrations. Only SD subjects demonstrated a decline in cardiorespiratory function. Self-selected walking pace decreased and perceived exertion increased significantly in the SDW group. Positive and negative mood scores were adversely affected in both groups, the total change being greatest in SD subjects. The results indicate that performance of physical work tasks requiring 30-45% VO2max declines significantly over a 48-hour period of sleep deprivation. However, maximal physiological function is not unduly compromised by either the work tasks in conjunction with sleep deprivation or by sleep deprivation alone.

Adult↗
PubMed1995

Estimation of arterial PCO2 in the elderly.

Arterial PCO2 (PaCO2), determined directly in the radial artery, was compared with indirect estimates of PCO2 in six elderly men (mean age 73.8 yr). Estimates of PaCO2 included arterialized venous PCO2 (PavCO2); end-tidal PCO2; mean alveolar PCO2, calculated by using a reconstruction of the alveolar oscillation in PCO2 and accounting for the presence of dead space (time-weighted mean for PCO2 throughout the respiratory cycle); and values calculated by using the empirical formula developed by Jones et al. (N. L. Jones, D. G. Robertson, and J. W. Kane. J. Appl. Physiol. 47: 954-960, 1979), which incorporates end-tidal PCO2 and tidal volume (PaCO2 derived from end-tidal PCO2 and VT). Measurements were made at rest and during cycle ergometry at 25 and 50 W while the subjects breathed various gas mixtures (euoxic-eucapnic, hypoxic-eucapnic, hyperoxic-eucapnic, and hyperoxic-hypercapnic). The mean differences between the estimates and the actual PaCO2 at rest and in 25- and 50-W exercise were as follows: PavCO2, 0.3 +/- 0.7 (SD), -0.1 +/- 0.7, and 1.8 +/- 1.2 Torr; end-tidal PCO2, 2.9 +/- 1.7, 4.0 +/- 3.1, and 3.7 +/- 3.2 Torr; time-weighted mean of alveolar PCO2, 2.6 +/- 1.9, 3.3 +/- 3.1, and 3.6 +/- 3.8 Torr; and PaCO2 derived from end-tidal PCO2 and VT, 2.4 +/- 1.3, 1.3 +/- 3.0, and 0.6 +/- 2.9 Torr. It is concluded that mean PavCO2 agreed most closely with mean PaCO2 both at rest and in exercise. All methods of deriving PaCO2 using measurements from the respired gases overestimated arterial values at rest. Of the noninvasive techniques, mean estimates calculated using the regression equation developed by Jones et al. corresponded most closely with PaCO2 in exercise.

Adult↗
PubMed1994

Rowing performance and selected descriptive, field, and laboratory variables.

The purpose of this study was to determine the relationships among measures of rowing performance and selected descriptive, field, and laboratory variables. Rowing performance of 20 intercollegiate oarswomen was assessed using a 2,500-m time test on a Concept II rowing ergometer, the rower's competitive experience, and the coach's ranking of the rowers. The oarswomen also underwent standardized descriptive tests including anthropometric measurements, field tests including 90-s rowing ergometer distance and weight lifting tests, and laboratory tests including VO2max and isokinetic knee extensor strength tests. Rowing ergometer times were highly related to competitive experience (rho = -0.86; p < 0.01) and coach's ranking (rho = 0.87; p < 0.01). VO2max was the only other variable to produce correlations greater than 0.71 with rowing performance. Although most of the correlations observed in the present study were poor to modestly high, they do document and quantify relationships, and suggest that training and testing techniques should be modified to be more rowing specific and that their usefulness with respect to positive transfer and prediction should be examined.

Adult↗
PubMed1994

Oxygen uptake kinetics in cardiac transplant recipients.

Our purpose was to examine the gas exchange response to exercise in heart transplant (HT) patients and to characterize the O2 uptake kinetics (tau VO2) during successive square-wave on-transients from loadless cycling to moderate exercise. We hypothesized that with a slow heart rate response (and O2 transport limitation) O2 kinetics would be slowed but that with a repeated exercise initiated while the heart rate remained elevated the tau VO2 would be faster. Six male HT patients performed two ramp-function tests to determine peak O2 uptake (1.32 +/- 0.23 l/min) and ventilation threshold (1.02 +/- 0.16 l/min). Patients subsequently completed two repeats of a square-wave forcing function and repeated this on 2 days. Alveolar gas exchange was measured breath by breath. A monoexponential fit of signal-averaged data of the first exercise on-transient (between days) yielded a significantly slower tau VO2 in HT subjects than in healthy men (mean age 47 yr; n = 8) (77 +/- 26 vs. 45 +/- 4 s). With successive exercise (2nd transition) initiated while HR remained elevated the tau VO2 of HT patients was 46 +/- 17 s. The faster O2 kinetics of the second transition suggests that O2 delivery was enhanced and therefore that the tau VO2 may reflect bioenergetic processes controlling the rate of oxidative metabolism.

Blood Gas Analysis↗
PubMed1994

Ventilatory response to exercise in men and women 55 to 86 years of age.

This study examines the relationship between minute ventilation (VE) and carbon dioxide production (VCO2) during exercise in men (n = 128) and women (n = 96), 55 to 86 yr of age. The means for the slopes of VE-VCO2 (delta VE/delta VCO2), examined for graded exercise below the ventilation threshold (TVE), increased significantly for men (p < 0.0001), from 25.0 +/- 0.7 (SEM) at mean age 58 (55 to 59) yr to 32.2 +/- 1.8 at mean age 83 (80 to 86) yr, but did not change for women (p = 0.0812), from 22.3 +/- 0.9 at mean age 58 (56-59) yr to 24.2 +/- 2.4 at mean age 79 (75 to 85) yr. A correlation that was significantly greater than zero was found between delta VE/delta VCO2 and age. The increase in delta VE/delta VCO2 was 0.29/yr for men (r = 0.47, p < 0.001) and 0.20/yr for women (r = 0.28, p = 0.0051). In both cases, the explained variance was small (men = 22%; women = 8%). VE, tidal volume (VT), and breathing frequency (fb) were examined at VCO2 = 1.0 L/min, the highest intensity that most older men and women could exercise without exceeding TVE. VE was significantly higher by 14% in men 80 to 86 yr of age (38.2 +/- 1.4 L/min) compared with men 55 to 59 yr of age (33.5 +/- 0.8), whereas there were no differences in VE for the women.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

Verapamil improves left ventricular filling and exercise performance in hypertensive and normotensive elderly individuals.

OBJECTIVE: To study the effect of verapamil slow release (SR) upon left ventricular diastolic function and exercise capacity in newly diagnosed older hypertensive subjects compared with normotensive elderly and young controls. DESIGN: Cross-sectional prospective trial. INTERVENTIONS: Doppler echocardiography at rest and graded maximal exercise testing (with breath-by-breath gas analysis) before and 4 h after administration of oral verapamil SR 240 mg, and before and after 12 weeks of daily medication. MAIN RESULTS: Verapamil administration normalized resting blood pressure in the older hypertensive group, but did not alter blood pressure in older normotensive or young groups. Resting heart rate was not altered in any of the groups. Both the older hypertensive and normotensive groups showed improvement in measures of diastolic filling after verapamil ingestion. Specifically, the older hypertensive group showed significantly faster isovolumic relaxation time (IVRT). In the older normotensive group IVRT was not changed, but the E:A ratio (the ratio of early to late peak transmitral flow velocity) was increased after verapamil. No differences were observed between the effects of verapamil after acute ingestion (4 h) or with chronic use (12 weeks) in any of the variables measured. In the younger group diastolic filling was not altered after verapamil ingestion. In both the elderly normotensive and hypertensive groups maximum oxygen consumption was significantly improved following verapamil ingestion. Again, no differences were observed between 4 h and 12 weeks. In the younger subjects exercise performance was not changed after verapamil ingestion. CONCLUSIONS: Verapamil SR improved left ventricular diastolic function and exercise performance in hypertensive and normotensive elderly individuals. Verapamil normalized blood pressure in the hypertensive subjects, but did not alter blood pressure in the normotensive elderly or younger subjects.

Adult↗
PubMed1994

Exercise on-transient gas exchange kinetics are slowed as a function of age.

The purpose was to characterize gas exchange kinetics following the on-transient of exercise in men aged 30-80 yr. Forty-six men completed square wave exercise tests from loadless cycling to subventilatory threshold (V(E)T) work rates with gas exchange measured breath-by-breath. Signal averaged data were fit with a monoexponential equation to derive time constants (tau) for gas exchange and ventilation (tau VO2, tau VCO2, tau VE) and heart rate (tau HR). There was a significant slowing of ventilation and gas exchange kinetics across age with linear regression yielding an increase of 0.67 s.yr-1 for tau VO2 (39 s in young to 61 s in old), 0.57 s.yr-1 for tau VCO2, and 0.65 s.yr-1 for tau VE, whereas tau HR (44 to 41 s) was not changed significantly. The slowed VO2 kinetics with age may reflect limitations in muscle blood flow or in control of the rate of oxidative metabolism. The less marked slowing of tau VCO2 compared with tau VO2 across age may reflect reduced CO2 storage capacity with loss of muscle tissue. The tau VE change across age was similar to that for tau VCO2 (tau VE/tau VCO2 unchanged). The present study demonstrated marked age-related slowing of gas exchange dynamics at exercise onset.

Adult↗
PubMed1994

Effects of aerobic endurance training on gas exchange kinetics of older men.

The kinetics of gas exchange at the on-transient of exercise are appreciably slowed in older individuals. Eight older men (72 yr) completed 6 months of aerobic cycle training. Ventilation and gas exchange kinetics were determined at the onset of a below threshold (ventilatory threshold, V(E)T) square wave exercise function and compared with control values (N = 4, age 70 yr). Gas exchange data were measured breath-by-breath and signal averaged data were fit with a monoexponential function to determine the time constants (tau). The training group showed significant increases in VO2max (20%) and VO2 at V(E)T (21%). The tau for oxygen uptake kinetics decreased significantly (62.2 +/- 15.5 to 31.9 +/- 7.0 s). The tau VCO2 (70.9 +/- 10.9 to 43.8 +/- 11.4 s) and tau VE (89.2 +/- 18.0 to 50.4 +/- 11.3) also were significantly faster posttraining; however, tau HR (38.1 +/- 20.5 to 28.6 +/- 7.2) was not significantly altered. Thus, with a vigorous training program, the kinetics of gas exchange of older individuals were faster, and approached values reported in fit young subjects.

Aged↗
PubMed1993

Strength training alters contractile properties of the triceps brachii in men aged 65-78 years.

Voluntary and electrically evoked contractile properties were studied in the triceps brachii following a 24-week dynamic strength training program in ten men aged 65-78 years. Eight men of a similar age were control subjects. A resistance overload program was undertaken three times per week with subjects performing four sets of six to eight repetitions at 80% of their one repetition on maximum (1RM). Maximum voluntary contraction (MVC) and contractile properties were measured at 0, 12, and 24 weeks in the exercise group and at 0 and 24 weeks in the controls. The 1RM was used to assess dynamic strength at 0 and 24 weeks in the exercise group. Contractile measures consisted of supramaximal isometric twitch and post-activation twitch parameters. Muscle size was estimated from anthropometric measurements. Compared with the control group, the exercise group MVC increased by about 20% and time to peak tension was slowed by about 11%. Also in the exercise group the peak rate of torque development of the potentiated twitch was reduced by about 10%. Twitch potentiation was substantial in both groups (about 140%) and unaffected by training. The 1 RM increased by about 30%, and there was a non-significant positive change of 8.6% in the muscle plus bone cross-sectional area in the exercise group. The results show that the force generating capacity of the triceps brachii in these men can be significantly improved for up to 24 weeks using concentric overload training. Furthermore, the finding of slowed twitch properties and no change in peak twitch amplitude substantiate and extend the limited data currently available on intrinsic contractile changes in the elderly.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

The human ventilatory response to step changes in end-tidal PO2 of differing amplitude.

This study assessed whether the form of the peripheral chemoreflex response to hypoxia depends on the magnitude of the stimulus. Two amplitudes of square-wave hypoxic stimulation were employed: small amplitude (SO) PETO2 from 63.2 to 54.9 Torr, and large amplitude (LO) PETO2 from 73.0 to 48.0 Torr. Each was studied at two levels of PETCO2: 2 Torr above resting PETCO2 (EC), and 7 Torr above resting PETCO2 (HC). Each protocol was repeated 6 times on 5 subjects. To assess the form of the response, a simple first-order model was fitted to the data which incorporated a pure delay (Td) and time constant (tau). Average parameter values (sec) were: ECSO tau = 4.07, Td = 6.69; ECLO tau = 8.82, Td = 4.91; HCSO tau = 5.22, Td = 7.08; HCLO tau = 9.96, Td = 4.39. ANOVA demonstrated modest but significant differences for loge(tau) (P < 0.01) and Td (P < 0.02) between the two hypoxic step magnitudes, with tau longer and Td shorter for the larger step size, but no differences were found between the parameter values for the two CO2 levels. We conclude that the form of the response of the peripheral chemoreflex to hypoxia depends upon the magnitude of the stimulus.

Adolescent↗
PubMed1993

Gas exchange dynamics with sinusoidal work in young and elderly women.

The objective of this study was to model the dynamics of, and interrelationships among, gas exchange, ventilation, and heart rate responses to sinusoidal forcing in young and elderly women. Nineteen females, 22-28 years (n = 10) and 62-73 years (n = 9) volunteered for the study. All experiments were conducted at work rates below the ventilatory threshold (TVE). A sine wave test consisted of 4 min of cycling (60 rpm) at a work rate equal to the mean of the limits of sinusoid (60% TVE) followed by 16-20 min of a sinusoidally varying work rate (30-90% of TVE) and ending with 4 min of cycling at 60% TVE. The periods were 0.75, 1.0, 1.5, 3.0, 6.0, 10.0 min, assigned randomly. The averaged data were used to determine amplitude and phase lag of the sinusoidal response of VO2, VCO2, VE, fH, PETCO2, and PETO2. Bode plots demonstrated that the dynamics of the cardiorespiratory responses were all well-described by a first-order exponential equation with a delay for both young and elderly subjects. The time constants were much longer in the elderly. Nevertheless, there appeared to be a strong link between the relative slowing of the four components of the gas transport system (VO2, VCO2, VE, and fH). This may suggest one single factor is reflected in the slowing of all components in older subjects.

Adult↗
PubMed1993

Determinants of independence in the elderly.

The purpose of this study was to compare strength, flexibility, and cardiorespiratory fitness of the elderly living independently (n = 64) with those in rest or nursing homes (n = 61), and to identify those variables most strongly associated with an independent lifestyle. Quantitative levels of independence (Incapacity Index) and of activity were determined by questionnaires. Flexibility was measured using the Leighton Flexometer. Strength was measured using a modified sphygmomanometer. Cardiorespiratory fitness was measured using a self-paced walking test. Body size factors were also determined. Independent and dependent subjects were significantly different in age, which imposed a limitation on interpretation of these data. However, this factor was accounted for statistically in the analyses. Independent individuals compared to dependent ones showed significantly greater flexibility, activity levels, and choice of walking speed. Through multiple regression analysis, it was found that 40% of the variance in Incapacity Index was associated with participation in outdoor activities, greater shoulder flexibility, and a faster normal walking speed (> 1.0 m.s-1).

Activities of Daily Living↗