Haemodynamic adaptation at rest and during exercise to long-term antihypertensive treatment with combination of beta-receptor blocking and vasodilator agent.
(9/4418)
Systemic and pulmonary haemodynamics were studied at rest in the supine and upright position, and during exercise in the sitting position at 75 and 150 Watt, in 13 hypertensive men aged 50-8 +/- 8-7 years before and after 13 months treatment with oral oxprenolol (120 to 160 mg t.i.d.) supplemented by oral hydrallazine (50 to 75 mg t.i.d.) during the last 6 months. Pressures were recorded by means of catheters inserted percutaneously into the pulmonary and brachial artery; cardiac output was determined according to Fick. Treatment resulted in a significant reduction of systemic systolic, diastolic, and mean pressures at rest in the supine position and during exercise, and of systolic pressures in the upright posture. Pulmonary systolic and mean pressures increased slightly at rest in the supine position and during exercise, and no changes occurred at rest in the upright position. The left ventricular filling pressure was unchanged at rest both in the supine and upright position; it increased slightly during exercise. The haemodynamic changes by which systemic pressure was reduced were those typical of beta-adrenergic blockade: reduction of cardiac output resulting from a decrease of both heart rate and stroke volume, while the total systemic vascular resistance was unchanged at rest in the supine position but increased in the upright posture and during exercise. The A-V O2 difference increased remarkably. This long-term observation again suggests that the acute haemodynamic effects of an antihypertensive regimen can be modified during long-term application. It did not give evidence of a readjustment of the vascular resistance occurring, at least not in the upright position and during exercise, as has been suggested for long-term beta-adrenergic blockade. (+info)
Heart rate--left ventricular ejection time relations. Variations during postural change and cardiovascular challenges.
(10/4418)
Regression equations for heart rate (HR)--ejection time (LVET) relations provide the appropriate factors for predicting or correcting left ventricular ejection time at any HR. We investigated HR-LVET regressions under different conditions common to both physiological and clinical studies of LVET which had been selected because of predictably different physiological responses. Ten normal subjects were studied during both supine and sitting rest and during isometric handgrip (IHG) in both supine and sitting postures and 10 during head-up tilt. Unexpectedly, as compared with pre-exercise rest on a bicycle ergometer, the slope for the resting state on a chair was slightly flatter, and LVET values were uniformly higher throughout the range of HRs measured. Differences among HR-LVET slopes and intercepts appeared to reflect the established behaviour of stroke volume and ejection rate under the conditions studied. Differences observed among intercepts, especially in supine vs. upright postures, are substantial and require that the appropriate intercept be applied in predicting LVET at a given HR. differences among slopes, while not statistically significant, may, under practical conditions, lead to unacceptable error if the appropriate slope factor is not used in correcting LVET for HR. (+info)
Effect of prolonged exercise of serum testosterone levels in adult men.
(11/4418)
The purpose of the study was to: 1) identify the differences in serum testosterone levels among four groups of adult men differentiated on the basis of physical fitness and age, and 2) determine the effect of a four-month physical fitness programme consisting of running, calisthenics and recreational activities on the serum testosterone levels of the four groups. The groups were designated: high-fit, young aged about 32 (n = 7); high-fit, old aged about 52 (n = 7); low-fit, young (n = 7), and low-fit, old (n = 7). The subjects were selected and grouped according to physical fitness scores obtained using the regression equation of Ismail et al. Serum testosterone was determined by a radioimmunoassay method. The pre-test ANOVA revealed that the high-fit groups had a significantly (p less than .01) higher testosterone level (754.29 ng/100 ml) than the low-fit groups (548.07 ng/100 ml) and the high-fit, young group (925.01 ng/100 ml) was significantly (p less than .01) higher than the other three groups. Post-test values were adjusted using pre-test testosterone values as covariates. No significant differences among the groups were found indicating that the serum testosterone levels were the same regardless of different ages and fitness levels. The findings were discussed in light of physiological, biochemical and psychological factors. (+info)
Sudden deaths among Finnish conscripts.
(12/4418)
The epidemiology of sudden deaths was studied among conscripts in Finland in 1948-72 (660 000 man-years) and among Finnish men aged 15-24 years in 1969-70 (900 000 man-years). The incidence of sudden deaths among the conscripts was 6-8/100 000 man-years. The onset of acute symptoms occurred during strenuous exercise in a third of the conscripts but in only a few of the other young men. Cardiovascular diseases caused two-thirds of the deaths in both groups. Sudden death tended to be more common among conscripts than among other young men during the corresponding period, but overall non-violent deaths were less common among conscripts than among other young men. On the basis of health records an attempt was made to separate the sudden deaths among conscripts from those among the controls by multiple discriminant analysis. For all practical purposes, however, the separation power proved poor. (+info)
The sources of external work in level walking and running.
(13/4418)
The work done at each step during level walking and running to lift the centre of mass of the body, Wv, and to increase its forward speed, Wf, and the total mechanical energy involved (potential + kinetic) Wext, have been measured at various 'constant' speeds (2-32 km/hr) with the technique described by Cavagna (1975). 2. At intermediate speeds of walking (about 4 km/hr) Wv = Wf and Wext/km is at a minimum, as is the energy cost. At lower speeds Wv greater than Wf whereas at higher speeds Wf greather than Wv: in both cases Wext/km increases. 3. The recovery of mechanical energy, through the pendular motion characteristic of walking, was measured as (/Wv/ + /Wf/ - Wext)/(/Wv/ + /Wf/): it attains a maximum (about 65%) at intermediate speeds. 4. A simple model, assuming that in walking the body rotates as an inverted pendulum over the foot in contact with the ground, fits the experimental data better at intermediate speeds but is no longer tenable above 7 km/hr. 5. In running the recovery defined above is minimal (0-4% independent of speed), i.e. Wext congruent to /Wv/ + /Wf/: potential and kinetic energy of the body do not interchange but are simultaneously taken up and released by the muscles with a rate increasing markedly with the speed (from about 1 to 4 h.p.). 6. Wext increases linearly with the running speed Vf from a positive y intercept owing to the fact that Wv is practically constant independent of Vf. On the contrary, Wf = aVf2/(1 + bVf), where b is the ratio between the time spent in the air and the forward distance covered while on the ground during each step. (+info)
Exercise-induced bronchocontriction, skin sensitivity, and serum IgE in children with eczema.
(14/4418)
Forty-two children with eczema were studied for exercise-induced asthma (EIA), skin sensitivity to prick testing, blood eosinophil count, and immunoglobulins. 29 had a fall in peak expiratory flow rate after exercise greater than 20% and of these, 23 had symptoms of wheezing. 13 of the eczematous children showed a fall of less than 20%. The children with EIA showed greater cutaneous sensitivity (p less than 0.001) and a higher total serum IgE (p less than 0.025). 3 of the group with a fall of less than 20% had allergic rhinitis with skin sensitivity to grass pollen. The remaining 10 had no clinical evidence of allergic disease, other than eczema and skin sensitivity, and total IgE fell within the normal range. It is suggested that in a proportion of chilren with eczema there is little evidence of reaginic allergy. (+info)
Is long-term maintenance of health-related physical activity possible? An analysis of concepts and evidence.
(15/4418)
The phenomenon of maintenance of health-related physical activity is explored through an analysis of the underlying concepts and of the existing empirical evidence. The following targets were used for the analysis: (1) the concept of health-related physical activity, (2) the concept of maintenance, (3) common manifestations of maintenance in everyday living, (4) the promotional and behavioral characteristics of health-related physical activity, (5) the known determinants of free-living physical activity, and (6) intervention trials on physical activity in free-living groups. The analyses revealed the inherent resistance to adoption and maintenance of physical activity, particularly that of high-intensity and program-centered activities, the persistence, however, of many simple everyday routines and habits, the multiple determinants discovered for free-living physical activity and a few empirical demonstrations of the successful promotion of the maintenance of physical activity over a year or two. The promotion of the maintenance of health-related physical activity seems thus a distinct possibility provided that (1) the promotional situation is analyzed thoroughly, (2) the activity is chosen carefully with an emphasis on moderation in intensity and integration into the participant's life-style, (3) multiple promotional contacts are used, and (4) support from the participant's social and physical environment is provided. There is a need for more research on the maintenance of health-related physical activity using the stages of change models, behavior modification principles, self-control concepts, the concept of intrinsic motivation and the Relapse model. The method of analysis used here could apply to other health-related behaviors as well. (+info)
Interaction of factors determining oxygen uptake at the onset of exercise.
(16/4418)
Considerable debate surrounds the issue of whether the rate of adaptation of skeletal muscle O2 consumption (QO2) at the onset of exercise is limited by 1) the inertia of intrinsic cellular metabolic signals and enzyme activation or 2) the availability of O2 to the mitochondria, as determined by an extrinsic inertia of convective and diffusive O2 transport mechanisms. This review critically examines evidence for both hypotheses and clarifies important limitations in the experimental and theoretical approaches to this issue. A review of biochemical evidence suggests that a given respiratory rate is a function of the net drive of phosphorylation potential and redox potential and cellular mitochondrial PO2 (PmitoO2). Changes in both phosphorylation and redox potential are determined by intrinsic metabolic inertia. PmitoO2 is determined by the extrinsic inertia of both convective and diffusive O2 transport mechanisms during the adaptation to exercise and the rate of mitochondrial O2 utilization. In a number of exercise conditions, PmitoO2 appears to be within a range capable of modulating muscle metabolism. Within this context, adjustments in the phosphate energy state of the cell would serve as a cytosolic "transducer," linking ATP consumption with mitochondrial ATP production and, therefore, O2 consumption. The availability of reducing equivalents and O2 would modulate the rate of adaptation of QO2. (+info)