"Exercise can reverse damage to sedentary aging hearts and help prevent risk of future heart failure  if its enough exercise and if its begun in time according to a new study by cardiologists at UT Southwestern and Texas Health Resources.    To reap the most benefit the exercise regimen should begin by late middle age before age  when the heart apparently retains some plasticity and ability to remodel itself according to the findings by researchers at the Institute for Exercise and Environmental Medicine IEEM which is a collaboration between UT Southwestern Medical Center and Texas Health Presbyterian Hospital Dallas.    And the exercise needs to be performed four to five times a week. Two to three times a week was not enough the researchers found in an earlier study.    Based on a series of studies performed by our team over the past  years this dose of exercise has become my prescription for life said senior author Dr. Benjamin Levine Director of the Institute and Professor of Internal Medicine at UT Southwestern. I think people should be able to do this as part of their personal hygiene  just like brushing your teeth and taking a shower.    The regimen included exercising four to five times a week generally in minute sessions plus warmup and cooldown    One of the weekly sessions included a highintensity minute workout such as aerobic interval sessions in which heart rate tops  percent of peak rate for  minutes with  minutes of recovery repeated four times a socalled  x .    Each interval session was followed by a recovery session performed at relatively low intensity.    One days session lasted an hour and was of moderate intensity. As a prescription for life Levine said this longer session could be a fun activity such as tennis aerobic dancing walking or biking.    One or two other sessions were performed each week at a moderate intensity meaning the participant would break a sweat be a little short of breath but still be able to carry on a conversation  the talk test. In the study exercise sessions were individually prescribed based on exercise tests and heart rate monitoring.    One or two weekly strength training sessions using weights or exercise machines were included on a separate day or after an endurance session.    Study participants built up to those levels beginning with three minute moderate exercise sessions for the first  months and peaked at  months when two highintensity aerobic intervals were added.    The more than  participants in the study were divided into two groups one of which received two years of supervised exercise training and the other group a control group which participated in yoga and balance training.    At the end of the twoyear study those who had exercised showed an  percent improvement in their maximum oxygen intake during exercise and a more than  percent improvement in compliance or elasticity of the left ventricular muscle of the heart Dr. Levine noted. He compared the change in the heart to a stretchy new rubber band versus one that has gotten stiff sitting in a drawer.    Sedentary aging can lead to a stiffening of the muscle in the hearts left ventricle the chamber that pumps oxygenrich blood back out to the body he explained.    When the muscle stiffens you get high pressure and the heart chamber doesnt fill as well with blood. In its most severe form blood can back up into the lungs. Thats when heart failure develops said Dr. Levine who holds the S. Finley Ewing Chair for Wellness at Texas Health Dallas and the Harry S. Moss Heart Chair for Cardiovascular Research. He also holds the Distinguished Professorship in Exercise Sciences at UT Southwestern which is celebrating its th anniversary this year.    Earlier research by UT Southwestern cardiologists showed that left ventricular stiffening often shows up in middle age in people who dont exercise and arent fit leaving them with small stiff chambers that cant pump blood as well.    However the researchers also found that the heart chamber in competitive masterslevel athletes remains large and elastic and that even four to five days of committed exercise over decades is enough for noncompetitive athletes to reap most of this benefit.    In the current study researchers wanted to know if exercise can restore the hearts elasticity in previously sedentary individuals  especially if begun in late middle age. Previous studies from Dr. Levines research program have shown substantial improvements in cardiac compliance in young individuals after a year of training but surprisingly little change if the training was started after age .    To start the study researchers recruited  participants ages  to . Many came from the Dallas Heart Study which includes  Dallas residents and is the only singlecenter heart study of its size and multiethnic composition. The Dallas Heart Study is designed to improve the diagnosis prevention and treatment of heart disease.        The new study appears in Circulation a journal of the American Heart Association. Collaborators on the study included first author Dr. Erin Howden Research Fellow with UT Southwesterns Graduate School of Biomedical Sciences and the IEEM and now a faculty member at the Baker Heart and Diabetes Institute in Melbourne Australia. Funding came from the National Institutes of Health and the American Heart Association.    About UT Southwestern Medical Center    UT Southwestern one of the premier academic medical centers in the nation integrates pioneering biomedical research with exceptional clinical care and education. The institutions faculty has received six Nobel Prizes and includes  members of the National Academy of Sciences  members of the National Academy of Medicine and  Howard Hughes Medical Institute Investigators. The faculty of more than  is responsible for groundbreaking medical advances and is committed to translating sciencedriven research quickly to new clinical treatments. UT Southwestern physicians provide care in about  specialties to more than  hospitalized patients  emergency room cases and oversee approximately . million outpatient visits a year."