The effects of exercise training on the pharmacokinetics of digoxin.

BACKGROUND: Studies have shown that digoxin binds to the working muscles during an acute bout of exercise, with a concomitant decrease in serum digoxin concentration. This study investigated the effects of 16 weeks of endurance exercise training on the pharmacokinetics of digoxin in old and young adults. METHODS: Twelve subjects, aged 68.5 +/- 4.5 years, and six subjects, aged 30.3 +/- 3.8 years, completed the study. All subjects were healthy, sedentary, and taking no cardiovascular medications. After initial testing and maximum oxygen consumption (VO2max) measurements, subjects were hospitalized for 28 hours for renal function testing and digoxin clearance studies and then randomly assigned to an exercise (EG) or control (CG) group. The EG completed 16 weeks (three 1-hour bouts/week) of aerobic training at 75% to 85% of maximum capacity. The CG did not exercise. All tests were repeated at the end of the 16-week study period. RESULTS: In the older EG subjects, VO2max increased by 3.4 ml/kg/min, or approximately 16% (P = 0.0002). VO2max increased in the younger EG subjects by 1.1 ml/kg/min, but the increase was not significant (P > 0.05). There were no significant changes in body composition, renal function, or time of onset, peak concentration, or elimination phase half-life of digoxin in either the old or young exercise or control groups (P > 0.05 for all variables). CONCLUSION: Although 16 weeks of endurance exercise training improves cardiorespiratory fitness, the pharmacokinetics of digoxin are neither improved nor adversely affected in healthy old and young adults.

Exercise training reduces myocardial lipid peroxidation following short-term ischemia-reperfusion.

PURPOSE: The purpose of these experiments was to test the hypothesis that endurance exercise training will reduce myocardial lipid peroxidation following short-term ischemia and reperfusion (I-R). METHODS: Female Sprague-Dawley rats (4 months old) were randomly assigned to either a sedentary control group (N = 13) or to an exercise training group (N = 13). The exercise trained animals ran 4 d.wk-1 (90 min.d-1) at approximately 75% V02max. Following a 10-wk training program, animals were anesthetized, mechanically ventilated, and the chest was opened by thoracotomy. Coronary occlusion was achieved by a ligature around the left coronary artery; occlusion was maintained for 5 min followed by a 10-min period of reperfusion. RESULTS: Although training did not alter (P > 0.05) myocardial activities of antioxidant enzymes (superoxide dismutase and glutathione peroxidase), training was associated with significant increase (P > 0.05) in heat shock protein (HSP72) in the left ventricle. Compared with controls, trained animals exhibited significantly lower levels (P < 0.05) of myocardial lipid peroxidation following I-R. CONCLUSION: These data support the hypothesis that exercise training provides protection against myocardial lipid peroxidation induced by short-term I-R in vivo.

The effects of endurance exercise training on ambulatory blood pressure in normotensive older adults.

This study investigated the effects of 16-weeks of endurance exercise training (EET) on ambulatory blood pressure in older adults. Twenty-one men and women, 68.5 +/- 4.7 (mean +/- SD) years of age were randomly assigned to an exercise group (EG, n = 11) or to a control group (CG, n = 10). Subjects were normotensive (mean resting BP 132.0 +/- 8.6/80.1 +/- 6.6 mm Hg), free from overt cardiovascular or renal diseases, and were taking no vasoactive or diuretic medications. Maximal oxygen uptake (VO2max), body composition, resting BP, and 24-hr ambulatory systolic (ASBP) and diastolic (ADBP) blood pressures were measured in all subjects before and after the study period. The EG completed 16 weeks (3, 1-hour bouts/wk) of EET, progressing in intensity from 50% to 85% of maximal workload. The CG did not exercise. In the EG, although body composition and resting BP did not change (p > 0.05), VO2max increased by 14% (p = 0.001), mean 24-hr ASBP decreased 7.9 mm Hg (p = 0.0001), and mean 24-hr ADBP decreased 3.6 mm Hg (p = 0.002). In the CG, there were no significant changes in these variables (p > 0.05). These data suggest that EET can improve both aerobic fitness and "real-life" blood pressures in healthy older adults and may help inhibit increases in blood pressure associated with normal aging.