As people age without regular exercise, the heart's left ventricle gradually stiffens, impairing its ability to fill with blood — a condition called diastolic dysfunction that can progress to heart failure. This completed clinical trial enrolled 61 sedentary middle-aged men and women (ages 45–64) and randomized them to either vigorous aerobic and strength training four to five days per week, or a control program of balance and flexibility work, for two full years. The central question was whether this exercise dose could restore cardiac and vascular compliance to levels comparable to lifelong exercisers and sedentary young adults. Researchers at UT Southwestern hypothesized that middle age may represent a critical window of cardiovascular plasticity — the last practical opportunity to reverse structural changes before they become permanent.
