Key to strong heart could be strong legs — here’s why

PRAGUE, Czech Republic — Need some motivation not to skip leg day? Look no further. Researchers working with the European Society of Cardiology report that patients with especially strong legs are less likely to develop heart failure following a heart attack.

Myocardial infarction (a heart attack) is actually the most common cause of heart failure, with roughly six to nine percent of heart attack patients going on to develop a form of heart failure. Prior studies, meanwhile, reveal that having strong quadriceps has an association with a lower risk of death among patients with coronary artery disease.

For this latest project, study authors tested their hypothesis that leg strength does indeed have a link to a lower risk of heart failure post-acute myocardial infarction. This study encompassed 932 patients hospitalized between 2007 and 2020 with acute myocardial infarction. All of the patients did not have heart failure before entering the hospital, and did not develop heart failure complications during their hospital stay. The average age of these patients was 66 and 81 percent of the participants were men.

The team used maximal quadriceps strength as their indicator of leg strength. Patients sat on a chair and contracted their quadriceps muscles as hard as they could for five seconds, all while a handheld dynamometer attached to the ankle recorded the maximum value in kilograms.

The study performed this measurement on each leg, with researchers using the average of both values. Strength was expressed relative to body weight, which means that quadriceps strength (in kilograms) was divided by body weight (in kilograms) and multiplied by 100 for a percentage body weight value. The team then classified each patient as having either “high” or “low” strength depending on whether their value was above or below the average for their sex.

Woman Using a Leg Press Machine
Photo by RDNE Stock project from Pexels

The average value for women was 33 percent body weight and the median value for men was 52 percent body weight. In all, 451 patients had low quadriceps strength while another 481 had high strength. Next, over the course of an average follow-up period of four-and-a-half years, 67 patients (7.2%) went on to develop heart failure. Heart failure incidence was 10.2 per 1,000 person-years in patients with high quadriceps strength and 22.9 per 1,000 person-years among patients with low strength.

The research team specifically analyzed the association between quadriceps strength (low vs. high) and heart failure risk. The analysis, of course, was also adjusted for a variety of factors known to have a connection to the development of heart failure after myocardial infarction including age, sex, body mass index, prior myocardial infarction or angina pectoris, diabetes, atrial fibrillation, chronic obstructive pulmonary disease, peripheral arterial disease, and kidney function.

In comparison to low quadriceps strength, a high strength level displayed a connection to a 41-percent lower risk of heart failure. Study authors also analyzed the association between quadriceps strength as a continuous variable and the risk of heart failure. They found that each five percent body weight increment in quadriceps strength was associated with an 11-percent lower chance of heart failure.

“Quadriceps strength is easy and simple to measure accurately in clinical practice. Our study indicates that quadriceps strength could help to identify patients at a higher risk of developing heart failure after myocardial infarction who could then receive more intense surveillance. The findings need to be replicated in other studies, but they do suggest that strength training involving the quadriceps muscles should be recommended for patients who have experienced a heart attack to prevent heart failure,” says study author Kensuke Ueno, a physical therapist at the Kitasato University Graduate School of Medical Sciences, in a media release.

This research was presented at Heart Failure 2023, a scientific congress of the European Society of Cardiology (ESC).

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