All those hours you've spent in the gym aren't just good for your looks. The longer you spend getting stronger, the longer you might have to live.

New research from the University of Michigan found that your strength level might be a key factor in extending your lifespan. The researchers, led by Dr. Kate Duchowny, concluded that people with lower levels of muscle strength are 50 percent more likely to die earlier than individuals who are stronger than a baseline measurement of grip strength.

“Maintaining muscle strength throughout life — and especially in later life — is extremely important for longevity and aging independently,” Duchowny told Michigan News.

Grip strength is specifically important because it can be used as a predictor of overall health and longevity, and might even be more effective for the task than other commonly-used measurements like muscle mass, according to Duchowny.

The stat is relatively easy to gauge, requiring a simple test in which patients squeeze a tool called a dynamometer to measure strength in kilograms. Other groups of researchers have also found that grip strength could be a strong indicator of overall health in people of all ages.

The UM team analyzed data collected as part of the university's Health and Retirement Study, which tapped into a nationally representative sample of 8,326 men and women aged 65 and older. Levels of strength were determined by tiered thresholds or "cut-points," with "muscle weakness" being classified as a hand grip strength of less than 39 kg for men and 22 kg for women.

The researchers found that 46 percent of the people in the data group were classified as "weak" under that criteria — a massive break from the other research from less representative population samples, which have concluded that only 10 to 13 percent of people could be considered weak and therefore, at risk of dying earlier.

That finding led to Duchowny and the team to emphasize just how important measuring grip strength should be for doctors in patients, even before they begin to show other indicators of aging-related health problems.

“Having hand grip strength be an integral part of routine care would allow for earlier interventions, which could lead to increased longevity and independence for individuals,” Duchowny said. “We believe our cut-points more accurately reflect the changing population trends of older Americans and that muscle weakness is a serious public health concern."

You should stay healthy at any age by keeping up an active strength training regimen, but if you're specifically concerned about your grip, check out our go-to exercises to help hone your forearms. You can also pick up tools to specifically build up your strength, like the Ergo Strength System above. Just keep moving and stay strong — it could help you live a better, longer life.