In previously sedentary healthy middle-aged adults, two years of exercise training improved maximal oxygen uptake and decreased cardiac stiffness, found a University of Texas study.
“Based on a series of studies performed by our team over the past five years‚ this "dose" of exercise has become my prescription for life‚” said Benjamin Levine‚ director of the Institute for Exercise and Environmental Medicine at the University of Texas. “People should be able to do this as part of their personal hygiene – just like brushing your teeth and taking a shower.”
The report says the regimen involves exercising four to five times a week‚ generally in 30-minute sessions‚ plus time to warm up and cool down:
– One of the weekly sessions included a high-intensity 30-minute workout‚ such as aerobic interval sessions in which heart rate tops 95% of peak rate for four minutes‚ with three minutes of recovery‚ repeated four times (a so-called “4×4”).
– Each interval session was followed by a recovery session performed at relatively low intensity.
– One day's session lasted an hour and was of moderate intensity. Levine said it could be tennis‚ aerobic dancing‚ walking or cycling.
– 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.
– One or two weekly strength training sessions using weights or exercise machines were included on a separate day‚ or after an endurance session.
The report says study participants built up to those levels‚ beginning with three‚ 30-minute‚ moderate exercise sessions for the first three months and peaking at 10 months when two high-intensity aerobic intervals were added.
The 50-plus participants in the study‚ aged between 45 and 64‚ were divided into two groups. One received two years of supervised exercise training and the other participated in yoga and balance training.
At the end of the two-year study‚ those who had exercised showed an 18% improvement in their maximum oxygen intake during exercise and a more than 25% improvement in elasticity of the left ventricular muscle of the heart. Levine compared the change in the heart to a stretchy‚ new rubber band versus one that has become stiff while sitting in a drawer.
Sedentary ageing can lead to a stiffening of the muscle in the left ventricle‚ the chamber that pumps oxygen-rich blood back out to the body‚ he explained. “When the muscle stiffens‚ you get high pressure and the heart chamber doesn’t fill as well with blood. In its most severe form‚ blood can back up into the lungs. That’s when heart failure develops‚” Levine is quoted in the report as saying.
Abstract
Background: Poor fitness in middle age is a risk factor for heart failure, particularly heart failure with a preserved ejection fraction. The development of heart failure with a preserved ejection fraction is likely mediated through increased left ventricular (LV) stiffness, a consequence of sedentary aging. In a prospective, parallel group, randomized controlled trial, we examined the effect of 2 years of supervised high-intensity exercise training on LV stiffness.
Methods: Sixty-one (48% male) healthy, sedentary, middle-aged participants (53±5 years) were randomly assigned to either 2 years of exercise training (n=34) or attention control (control; n=27). Right heart catheterization and 3-dimensional echocardiography were performed with preload manipulations to define LV end-diastolic pressure-volume relationships and Frank-Starling curves. LV stiffness was calculated by curve fit of the diastolic pressure-volume curve. Maximal oxygen uptake (Vo2max) was measured to quantify changes in fitness.
Results: Fifty-three participants completed the study. Adherence to prescribed exercise sessions was 88±11%. Vo2max increased by 18% (exercise training: pre 29.0±4.8 to post 34.4±6.4; control: pre 29.5±5.3 to post 28.7±5.4, group×time P<0.001) and LV stiffness was reduced (right/downward shift in the end-diastolic pressure-volume relationships; preexercise training stiffness constant 0.072±0.037 to postexercise training 0.051±0.0268, P=0.0018), whereas there was no change in controls (group×time P<0.001; pre stiffness constant 0.0635±0.026 to post 0.062±0.031, P=0.83). Exercise increased LV end-diastolic volume (group×time P<0.001), whereas pulmonary capillary wedge pressure was unchanged, providing greater stroke volume for any given filling pressure (loading×group×time P=0.007).
Conclusions: In previously sedentary healthy middle-aged adults, 2 years of exercise training improved maximal oxygen uptake and decreased cardiac stiffness. Regular exercise training may provide protection against the future risk of heart failure with a preserved ejection fraction by preventing the increase in cardiac stiffness attributable to sedentary aging.
Authors
Erin J Howden, Satyam Sarma, Justin S Lawley, Mildred Opondo, William Cornwell, Douglas Stoller, Marcus A Urey, Beverley Adams-Huet, Benjamin D Levine
[link url="https://www.timeslive.co.za/news/sci-tech/2018-01-08-doctors-write-exercise-prescription-to-repair-a-damaged-heart/"]The Times report[/link]
[link url="http://circ.ahajournals.org/content/early/2018/01/03/CIRCULATIONAHA.117.030617"]Circulation abstract[/link]