Their main questions were: Which of these metrics deteriorates faster and at what rate? Those answers will help medical professionals create more targeted treatments to slow these declines.

Clinicians chose these tests because balance, muscle strength, and an efficient gait—your walking pattern—contribute to quality of life as you age, and are especially important for older adults to maintain independence.

Of the tests, the study concluded that the single-leg balance is the best indicator of healthy aging. It was the one exercise that showed the steepest decline with age.

Balance is vital for healthy aging

“Balance is important because it reflects how well the body systems are working together,” says Kenton Kaufman, lead author of the study, director of the Motion Analysis Laboratory, and orthopedist at Mayo Clinic.

Around age 50 is when balance starts to decline, Kaufman says. That can put you at risk for falling, which is the leading cause of injury for adults over age 65, according to the CDC. 

“If you can’t stand on a single leg for 5 seconds, then [you] might be at risk for falling,” Kaufman tells Fortune.

Kaufman says good single-leg balance shows that the neurological, vision, and vestibular (your inner ear, which helps you maintain balance and spatial orientation) systems are well-coordinated. 

“A good test of [balance] is putting your trousers on in the morning,” Kaufman says.

How to improve your single-leg balance

Practice standing on one leg, but don’t be discouraged if you can’t stay balanced for a full 30 seconds, Kaufman says. It’s just a goal to shoot for.

There are numerous at-home exercises to help improve single-leg balance. Here are a few to try from the Mayo Clinic.

• Weight shifts: Stand with your feet hip-width apart. Shift your weight from one leg to the other. Lift your opposite foot off the ground for as long as you can hold it. Then shift to the other leg. Repeat.
• Tandem walking: Place one foot directly in front of the other while walking. Think of the “sobriety test” that police officers use.
• Tai chi: Look for group classes at local fitness centers or senior centers, where you can practice this slow, balance-focused movement.
• Hip strength: Kaufman recommends strengthening your hip abductors, with exercises like clamshells with a resistance band or single leg raises while lying on your side.

For more on healthy aging:

• Will you have a stroke? These 17 factors can be predictors, say new prevention guidelines
• Poor sleep is tied to faster brain aging, new study says. Here’s how it impacts people as young as 40
• Middle-aged women can thrive in the second half of their lives—if they pay attention to these 3 things