W. G. Squires

Benefits of aerobic exercise for the paraplegic: a brief review

The importance of exercise for the general population is emphasized widely; therefore, it must be even more important for paralegics who are already threatened with poor health due to the sedentary nature of their lifestyle. The effects of functional degeneration are vast and greatly reduce the overall health of paraplegics, particularly within the musculoskeletal and cardiovascular systems, thereby increasing their risk for cardiovascular disease. Recent investigations suggest that this process may be reversible through exercise training and that paraplegics respond to exercise training in essentially the same manner as the non-handicapped individual. In addition, exercise training has been reported to decrease the resorptive process of the skeleton by decreasing bone and collagen catabolism and possibly aiding in new bone formation. This review attempts to summarize the available literature on the effects of exercise on the paraplegic and will hopefully provide some direction not only for further research but also recommendations for practitioners working in the field.

Effect of exercise training on plasma high-density lipoprotein cholesterol in coronary disease patients.

The effects of chronic exercise training on plasma high-density lipoprotein cholesterol (HDL-C) were studied in 18 male coronary patients. Exercise consisted of aerobic activities utilizing approximately 70% of maximal oxygen uptake (VO2 max) for 20 to 40 minutes, three times weekly for 3 months. Significant increased in VO2 max, HDL-C, HDL-C/total cholesterol, and a decrease in percent body fat were documented after training. No significant changes were found in total cholesterol, triglyceride, body weight, or low-density lipoprotein cholesterol. Vigorous physical training can contribute to increased in HDL-C in patients with coronary disease without changes in total cholesterol or body weight.

Exercise and HDL Cholesterol in Middle-Aged Men

Raising high-density lipoprotein levels with exercise seems to protect against coronary heart disease. Dr. Hartung attempts to show how much exercise is necessary.

Aerobic fitness: I. Response of volume regulating hormones to head-down tilt

We investigated the relationship of aerobic fitness to the response of volume-regulating hormones to acute simulated microgravity. Six untrained (UT) and six endurance-trained (ET) healthy young males were studied in the head-down tilt (HDT) position of -6 degrees for 4 h. Peak oxygen uptake (VO2peak) and plasma volume (PV) were significantly greater in the ET (VO2peak = 61.7 +/- 1.6 ml.min-1.kg-1 and PV = 53.1 +/- 2.8 ml.kg-1) than in the UT (VO2peak = 38.4 +/- 1.7 ml.min-1.kg-1 and PV = 38.8 +/- 1.0 ml.kg-1). Plasma concentrations of atrial natriuretic peptide (ANP), arginine vasopressin (AVP), norepinephrine (NE), renin activity (PRA), and aldosterone (PA) were measured prior to HDT and at minutes 2, 5, 15, 30, 60, 120, 180, and 240 during HDT. PRA and PA significantly decreased during the time of HDT in both groups. The changes in ANP and NE concentrations were not significantly different between the groups nor across time. However, in the ET subjects, the changes in PRA and NE were significantly correlated with the changes in ANP (r = 0.49, P less than 0.01; and r = 0.86, P less than 0.001, respectively); in the UT subjects, the changes in AVP, PRA, and PA were significantly associated with changes in NE (r = 0.34, P less than 0.03; and r = 0.59; and r = 0.53, P less than 0.01, respectively). PV significantly decreased during HDT, and was primarily related to the decrease in PA in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Aerobic fitness. II: Orthostasis and VO2peak following head-down tilt

To determine whether endurance exercise trained (ET) subjects would experience greater reductions in peak oxygen delivery and orthostatic tolerance (OT) than untrained (UT) subjects, both peak oxygen uptake (VO2peak) during upright bicycle ergometry and tolerance time during 70 degrees head-up tilt (HUT) were compared within and between groups before and after 4 h of -6 degrees head-down tilt (HDT). Eight ET subjects with a mean VO2peak of 61.7 +/- 1.6 ml.kg-1.min-1 were matched for age, height, and weight with eight UT subjects (VO2peak = 38.4 +/- 1.7 ml.kg-1.min-1). Following HDT, decreases in plasma volume (PV) were larger for ET subjects (-3.7 +/- 0.5 ml.kg-1) than for UT subjects (-2.3 +/- 0.3 ml.kg-1), P less than 0.03. Reductions in VO2peak for ET subjects (-5.4 +/- 1.1 ml.kg-1.min-1) were also greater than for UT subjects (-2.4 +/- 0.8 ml.kg-1.min-1), P less than 0.05. The ET (N = 6) subjects also had a significant decrease in OT time (-13.0 +/- 4.2 min) during post-HDT HUT, which was not observed for the UT group (N = 6). A significant inverse correlation was found pre-HDT VO2peak and the change in OT time, r = -0.74, P less than 0.01. The decrease in OT was also significantly correlated to the PV decrease, r = 0.59, P less than 0.04. The UT subjects had significantly augmented pressor responses to HUT manifested by the increases in both HR and MAP following HDT.(ABSTRACT TRUNCATED AT 250 WORDS)

Astronaut adaptation to 1 G following long duration space flight

The paper reviews the results of studies of changes undergone by several physiological systems (including the cardiovascular system, the fluid and electrolyte characteristics, the red blood cells, the bone and the muscle tissues, and the exercise capacity) due to the exposures to microgravity and to the adaptation to 1 G after a long-duration space flight. Special attention is given to the effects of various training protocols and countermeasures used to attenuate the physiological problems encountered upon return from space.

Hemodynamic responses to 6 degree head-down rest in dogs: effect of aerobic conditioning.

The -6 degree head-down position is used in humans to produce fluid shifts that resemble those occurring in microgravity. Alternative animal models of microgravity may be helpful for extensive exploration of this unique condition. The dog may be a viable candidate. Sixteen dogs were assigned to one of three conditions: anesthetized open chest, anesthetized closed chest, and awake. Dogs in groups 1 (N = 6) and 2 (N = 6) were divided into an exercise or a sedentary treatment, and dogs in group 3 (N = 4) served as their own controls. Following instrumentation the dogs were put in the head-down position for 1 h. Measurements included right atrial pressure, heart rate, and mean arterial pressure for all groups, left ventricular pressure and LV dp/dt for group 1, and cardiac output and iliac flow for group 2. Right atrial pressure increased for all groups. Heart rate demonstrated non-significant changes over time or group. Significant differences were noted for mean arterial pressure, left ventricular pressure and LV dp/dt for exercise condition in response to HDR. It appears that -6 degrees of head-down rest produces similar cardiovascular responses in dogs as those observed in humans and that exercise has a minor effect on those responses.

Evaluation of the NASA/JSC blood pressure screening clinic.

This study evaluated the NASA/Johnson Space Centers blood pressure screening program, which was designed to identify the proportion of NASA employees who were hypertensive and to identify self-report variables related to elevated pressures. In 1978, a random sample of 3892 employees was selected from over 2,100 NASA employees. Twenty-eight percent were classified as hypertensive by the criterion of systolic pressure of 140 or above or diastolic pressure of 90 or greater. Approximately 16% of all employees had a history of hypertension; the remaining 12% of the identified hypertensives were unaware of their potential health problem. Multivariate analysis showed that elevated systolic pressures were more prevalent in the older, heavier employees. Of hypertensives under treatment, about 74% were under poor control as judged from blood pressures randomly taken at their place of employment. These results demonstrated the effectiveness of screening for unsuspecting hypertensives in industry.

Analysis of commercial samples of dimethyl sulfoxide

Refractive index measurements and spectral data (IR and NMR) were used to verify the purity claimed by commercial samples of dimethyl sulfoxide.