Popeye has been bulking up with spinach for nearly 100 years, and researchers just recently discovered what the sailor man knew all along: Eating leafy green vegetables every day can improve your muscle function.

How well your muscles move and work — your muscle function — is a basic marker of your overall health and directly tied to your bone strength as you age. Muscle function slowly starts to decline after the age of 45. As you get older, frailty and poor muscle function put you at an increased risk for falls and fractures.

Just one cup of leafy green vegetables every day improved muscle function.

A quarter of Americans over the age of 65 fall each year leading to broken bones, head injuries or a fear of falling that can prevent them from going on with their daily activities. So it is important to find ways to prevent falls and the often-serious consequences of them.

The strength of muscle function in the legs appears closely tied to nitrates, a substance found primarily in vegetables, an Australian study has found. Edith Cowan University (ECU) researchers analyzed information on over 3,700 people who were part of the Baker Heart and Diabetes Institute AusDiab study in Melbourne.

People who ate the most nitrate-containing foods had 11 percent greater strength in their legs compared to those who ate the lowest amount, and their walking speeds were up to four percent faster. Just one cup of leafy green vegetables every day improved muscle function.

The study's findings underscore the important link between what you eat and your overall health. Diet is only one part of the equation for building muscle strength, however, researcher, Marc Sim, of ECU's Institute for Nutrition Research, explained. Regular exercise combined with weight training and a balanced diet that includes plenty of green, leafy vegetables is the best way to keep leg and other muscles strong.

Fewer than 10 percent of Americans eat the recommended amount of vegetables — for older Americans, that's about 2½ to 3½ cups a day. Because greens are light and fluffy, a serving of leafy greens is bigger than say, a serving of carrots or peas. Two cups of raw leafy vegetables are considered one serving, as in a salad. And since raw greens shrink when they are cooked, it takes two cups to equal a one-cup serving, or one cup to equal a ½ cup serving. Everyone should aim for at least one serving of a leafy green vegetables — the darker the better — each day.

Spinach may still not be among the most popular vegetables, but it along with leafy greens like kale, romaine lettuce, arugula, beetroot, collard and mustard greens are probably the most important. Not only do they benefit your bones and muscles, they provide cardiovascular and cancer prevention benefits, too.

The study is published in the Journal of Nutrition.