"We now have increasing evidence that weight training can favorably modify several risk factors for heart disease including lipids and cholesterol levels, blood pressure, body fat levels and glucose metabolism," says Barry Franklin, Ph.D., a co-author of the advisory, Resistance Exercise in Individuals With and Without Heart Disease: Benefits, Rationale, Safety and Prescription. The advisory appears in the Feb. 22 issue, but it is being released today.
Weight training improves cardiovascular function by decreasing an individual's blood pressure and heart rate when lifting or carrying objects, says Franklin, a physiologist and director of the cardiac rehabilitation program and exercise laboratories at William Beaumont Hospital, Royal Oak, Mich.
The progressive resistance exercise prescription outlined in the American Heart Association Science Advisory calls for a single set of 8-15 repetitions, using 8-10 different exercises, 2-3 times per week.
Although the American Heart Association supports weight training, it does not recommend isometric exercise for people with high blood pressure. Isometric exercise involves tensing one set of muscles, for a period of seconds, in opposition to another set of muscles or an immovable object.
A study in the February issue of Hypertension: Journal of the American Heart Association offers additional evidence in support of the American Heart Association Science Advisory. The study, published today, finds that weight training can help lower resting blood pressure.
"Even though these reductions in resting blood pressure are small, they still can decrease an individual's risk for heart disease and stroke," says lead author George A. Kelley, D.A., director of the meta-analytic research group, department of kinesiology and physical education at Northern Illinois University, DeKalb.
Kelley says, "Individuals who regularly did progressive resistance exercise experienced about a 2 percent reduction in their resting systolic blood pressure and a 4 percent reduction in their resting diastolic blood pressure." Systolic blood pressure is the pressure while the heart is beating and diastolic is the pressure while the heart is resting between beats. You don't have to pump iron like a super hero to reap the benefits, researchers say. The study participants, which included both men and women ages 18 and older, worked out anywhere from two to five times per week and exercised between 20 and 60 minutes per session.
Researchers analyzed 11 studies conducted over three decades between January 1966 and December 1998. Although the individual studies were small, in total they comprised 320 people – 182 who participated in weight training and 138 who didn't.
The decreases in resting blood pressure were similar whether the exercisers performed conventional weight training or circuit training. Conventional training generally consists of lifting heavier weights with longer rest periods between exercises, whereas circuit training involves lifting lighter weights and resting for shorter periods between exercises.
In addition to the decreases in resting blood pressure levels, Kelley says weight training also led to reductions in body fat and increases in lean muscle mass. Participants also increased their muscular strength from 15 percent to 62 percent.
"Not only can weight training help stave off osteoporosis and build muscle and reduce fat, now we know that it can help lower blood pressure. This is important because about 50 million Americans have high blood pressure and many of them don't even know it. Unfortunately, only about 16 percent of Americans between the ages of 18 and 64 say they participate in progressive resistance exercise," says Kelley.
"Future studies need to examine whether progressive resistance exercise could be used as a treatment for people with higher levels of blood pressure," Kelley says. "This study offers evidence of the importance of a well-rounded exercise regimen that includes both cardiovascular exercise for your heart and lungs as well as weight training."
In addition to its other benefits, Franklin says weight training is beneficial to people who are watching their waistline. "The more muscle you have, the higher your metabolic rate and the more calories you will burn each day," he says.
Franklin says studies have shown that weight training is safe in healthy adults and low-risk cardiac patients. However, the safety of weight training in moderate-to-high risk cardiac patients requires additional study.
He adds that certain individuals should not do traditional resistance exercise, such as patients with unstable angina, uncontrolled high blood pressure, uncontrolled arrhythmias (irregular heartbeat), severe valvular disease, or heart failure patients who have not been evaluated by a physician or effectively treated.
The co-authors of the Scientific Advisory are Michael L. Pollock, Ph.D. (deceased); Gary J. Balady, M.D.; Bernard L. Chaitman, M.D.; Jerome L. Fleg, M.D.; Barbara Fletcher, M.N., R.N.; Marian Limacher, M.D.; Ileana L. Pina, M.D.; Richard A. Stein, M.D., Mark Williams, Ph.D.; and Terry Bazzarre, Ph.D.
The co-author of the study was Kristi Sharpe Kelley, M.Ed.
Media Advisory: Dr. Franklin can be reached at (248) 258-3705. Dr. Kelley can be reached at (815) 753-1418. (Please do not publish numbers.)