Is There an A for Effort with Exercise?

Exercise intensity matters for heart attack risk

(RxWiki News) In order to reap the health benefits associated with exercise, you may need to change the intensity of your workouts.

A recent study found that low intensity exercise was associated with a reduced risk of acute myocardial infarction (heart attack) in people 65 and older. But for younger people, exercise had to be at least moderately intense to lower the risk for heart attack.

"Speak to your doctor about age-appropriate physical activity."

This study was led by Roberto Elosua, MD, PhD, at the Institut Hospital del Mar d’Investigacions Mèdiques in Barcelona, Spain. The research team examined the relationship between leisure time physical activity (both amount and intensity) and having a heart attack, and whether this relationship changed based on age.

The study sample included 1,339 heart attack patients from four Spanish hospitals between the ages of 25 and 74, and 1,339 individuals who had not had heart attacks and who were the same sex, close in age to and from the same area as the heart attack patients.

These participants reported the amount and intensity of their physical activity using the Minnesota Leisure-Time Physical Activity Questionnaire. Total energy expenditure (calories burned) during physical activity was then determined based on their responses.

The researchers split physical activity into three categories: light intensity (less than 4 METs), moderate intensity (4-5.9 METs) and high intensity (6 or more METs).

MET (metabolic equivalent) is the ratio of calories that the body burns during an activity to calories that the body burns at rest. A 4-MET activity burns four times the amount of calories than what the body burns while at rest.

Participants were separated into two age groups: 25 to 64 years and 65 to 74 years. The researchers took into account smoking status and history of diabetes, hypertension or dyslipidemia (abnormal level of cholesterol or fat) when analyzing their findings.

The researchers found that people who got around 1,500 MET-min/week had the lowest chance of having a heart attack. They noted that most of the population could achieve this level of physical activity by walking at 3 miles per hour for at least 140 minutes per week, which would reduce the risk of having a heart attack by 40 to 60 percent.

For individuals 65 and older, the researchers found that physical activity of light intensity was associated with a reduced chance of having a heart attack. Interestingly, the researchers found that when the physical activity intensity was higher, this association lost significance.

For younger individuals, physical activity of at least moderate intensity was required to lower the risk of having a heart attack.

Sarah Samaan, MD, FACC, a board certified cardiologist at Legacy Heart Center in Plano, Texas, told dailyRx News, "This study highlights the importance of regular exercise in heart attack prevention."

"There is a misperception that high intensity exercise is required in order to achieve any benefit. The idea of working out in the gym or going to an aerobics class can be intimidating to someone who is new to exercise, but this study should help to reassure seniors that even a regular, light-intensity walking program can pay big health dividends," said Dr. Samaan, who was not involved in this study.

"For middle aged and younger adults, however, more intensive exercise is needed to help keep our risk of heart disease and stroke low. Although it's never too late to start exercising, the sooner it becomes part of our daily life, the healthier we can be and the better we'll feel," Dr. Samaan said.

This study is currently in press and will be published in an upcoming issue of Preventive Medicine.

The authors did not report any conflicts of interest.

Review Date: 
August 15, 2013