Biomedical subjects

A A Hartzell

Publications and source records attributed to A A Hartzell.

4 recordsLinked to original sources

PubMed1989

Alterations in plasma lipids consequent to endurance training and beta-blockade.

Alterations in plasma lipids consequent to endurance training and beta-blockade. Med. Sci. Sports Exerc., Vol. 21, No. 3, pp. 288-292, 1989. The chronic use of beta adrenergic blockers (BAB) has been associated with reductions in HDL-cholesterol (HDL-C) and increases in triglycerides (TG). This study evaluated the impact of concurrent endurance exercise training and chronic medication with BAB on plasma lipid and lipoprotein profiles in healthy young adult males. Changes in plasma lipids and lipoproteins were investigated while exercise training under the influence of one of two nonselective BAB [sotalol (320 mg.d-1) and propranolol (160 mg.d-1)], one beta 1 selective BAB [atenolol (100 mg.d-1)], or a placebo control. Total cholesterol (TC), HDL-C, LDL-cholesterol (LDL-C), TG, and the ratios of TC/HDL and LDL/HDL were determined before and after endurance training programs of either 14 (N = 27, sotalol) or 15 (N = 47, propranolol/atenolol) wk duration. The subjects exhibited increases in maximal oxygen uptake of 12-20%. Despite increased endurance capacity, the subjects in both BAB and placebo control groups failed to demonstrate the expected increase in HDL-C and decrease in TG. In fact, HDL-C was significantly decreased post-training in the propranolol group. The placebo groups did decrease TC, LDL-C and the TC/HDL and LDL/HDL ratios, improving their CHD risk profile. Similar changes were not observed in the groups on BAB. Thus, with respect to the present population, BAB does appear to interfere with the usual training-induced improvements in the lipid profile. Endurance training may, however, reduce the deterioration in the lipid profile known to occur with BAB.

Adrenergic beta-Antagonists↗

PubMed1985

Acute response to submaximal and maximal exercise consequent to beta-adrenergic blockade: implications for the prescription of exercise.

Forty-seven healthy male subjects, 17 to 34 years old, completed a test to exhaustion on a motor-driven treadmill to determine their maximal oxygen uptake. A second test was administered 2 days later during which the subject walked for 20 to 25 minutes at a steady-state level representing 60% of the maximal oxygen uptake as determined in the first test. The grade was then increased every 2 minutes until the subject reached the state of exhaustion. After the second test, the subjects were randomly assigned, in a double-blind manner, to either placebo, propranolol (160 mg/day), or atenolol (100 mg/day) treatment for 7 days. Exactly 1 week from the time of the second test, and 3 hours after the last medication, the subjects completed the final exercise test using the same treadmill protocol administered in the second test. Heart rate and systolic blood pressure at rest and during submaximal steady-state exercise were significantly reduced by both drugs, whereas diastolic pressure was unaffected. During submaximal steady-state exercise, cardiac output was reduced in both the placebo and atenolol groups, stroke volume was increased in both atenolol and propranolol groups, oxygen uptake was reduced in the atenolol group, pulmonary ventilation was reduced in both propranolol and atenolol groups, and the respiratory exchange ratio remained unchanged. With maximal exercise, treadmill time was significantly reduced with propranolol, pulmonary ventilation and heart rate were reduced significantly with both drugs, but maximal oxygen uptake remained unchanged. Thus, beta blockade does not appear to limit ability to exercise. However, there appears to be a significant advantage to using a cardioselective rather than a nonselective beta-blocking agent.

Adolescent↗

PubMed1985

Cardiorespiratory alterations consequent to endurance exercise training during chronic beta-adrenergic blockade with atenolol and propranolol.

A study was undertaken to determine if normal healthy subjects can increase their endurance capacity consequent to endurance training during chronic beta-adrenergic blockade. Forty-seven subjects, 17 to 34 years of age, were randomly assigned to 1 of 3 treatments (placebo, propranolol, 160 mg/day, and atenolol, 100 mg/day) and then completed a 15-week aerobic exercise training program. All groups reduced their submaximal steady-state heart rates consequent to training; submaximal oxygen uptake was slightly reduced; submaximal stroke volume was increased only in the placebo and atenolol groups; submaximal cardiac output was generally lower; and arterial-mixed venous oxygen difference was increased after training in all 3 groups, suggesting decreased muscle blood flow and increased oxidative capacity. Maximal oxygen uptake and maximal treadmill time were increased in all 3 groups after training. However, while still on medication the atenolol group had significantly greater increases in maximal oxygen uptake and maximal treadmill time compared with the propranolol group. Because most patients will remain on medication, these results suggest a distinct advantage for cardioselective blocking agents. It is concluded that beta-adrenergic blockade does not reduce the ability of normal healthy subjects to gain the benefits associated with cardiorespiratory endurance training.

Adolescent↗

PubMed1985

Effects of cardioselective and nonselective beta-adrenergic blockade on the performance of highly trained runners.

Twenty-five highly trained runners with a maximal oxygen uptake (VO2 max) of 64.7 +/- 4.3 ml . kg-1. min-1 were administered clinically equivalent doses of a nonselective (propranolol) and a cardioselective (atenolol) beta-blocking agent as well as a placebo. The subjects performed a horizontal treadmill test on the eighth day and a 10-km track race on the tenth day of each treatment. Beta blockade decreased submaximal heart rate and propranolol caused the largest decrease. Beta blockade caused a decrease in maximal heart rate, VO2 max, maximal ventilation, maximal respiratory exchange ratio and treadmill time. Propranolol caused a greater decrease than atenolol in each of these values. The 10-km race times were significantly slower during beta blockade, and propranolol race times were significantly slower than atenolol race times. It is concluded that the performance of highly trained distance runners is significantly altered by beta-adrenergic blockade and that nonselective agents reduce performance to a greater extent than cardioselective agents.

Adult↗