מתוך medicontext.co.il
WESTPORT, CT (Reuters Health) – Even substantial decreases in cardiovascular fitness resulting from decades of inactivity can be substantially reversed with modest endurance training, according to two reports, by the same research team, in Circulation: Journal of the American Heart Association for September 18.
The findings are based on a study of five men who participated in the Dallas Bed Rest and Training Study. In 1966, when the men were 20 years of age, their cardiovascular fitness was evaluated at baseline and after 20 days of bed rest.
"Twenty days of bed rest really compromised their cardiovascular fitness in most hemodynamic measures," lead investigator Dr. Darren K. McGuire, from the University of Texas Southwestern Medical Center at Dallas, told Reuters Health.
When the men were in their early 50s, Dr. McGuire and colleagues reevaluated their cardiac fitness. Only one of them had engaged in regular physical activity.
"The most interesting finding is that using the baseline data from the 1966 study, 30 years of aging appear to be not as bad on cardiovascular fitness as 20 days of bed rest was when the subjects were 20 years old," Dr. McGuire said.
Over 30 years the average body weight of the men increased by 25% and the percent of body fat doubled. Average maximal oxygen uptake decreased (11%), as did maximal heart rate (6%), and maximal stroke volume increased (16%) with no difference in cardiac output, the researchers found. In addition, maximal AV oxygen difference decreased by 15%.
In the second part of the study the men underwent a 6-month endurance training program consisting of walking, cycling or jogging.
"The encouraging finding is that these men, after a relatively modest 6-month endurance training program, were able to get back to an aerobic power level consistent with their 20-year-old baseline," Dr. McGuire said. "So we were able to reverse a substantial portion of that aerobic power that had been lost over the years."
When the men were 20 years old their response to exercise training was both central and peripheral adaptation, Dr, McGuire noted. Cardiac function, the ability to maximize cardiac output with training, and the body's ability to take up and use oxygen improved, he explained.
"We found that when these subjects were 50 years old almost the entire decrease in cardiovascular fitness occurred as a result of a loss of the ability to take up and use oxygen," Dr. McGuire said. The gain that the men achieved was all peripheral adaptation. The reasons for this change in cardiovascular response to exercise with age are unknown, he said.
But one thing is clearer, Dr. McGuire stressed. "It appears that it is never too late to start exercising."
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