A dynamometer is used to measure grip strength. It's an easy, noninvasive… (Keith Brofsky / Getty Images )
Getting a good grip on your health may mean … getting a good grip. The force you can muster when squeezing an object or a weight doesn't only reveal how strong your hand and arm are. It can be a measure of overall muscle function and — according to one recent study — even portend how long you're likely to live.
That's not as nutty as it seems, says Richard Bohannon, a professor of physical therapy at the University of Connecticut. "Grip strength reflects your overall muscle status and a general sense of how much muscle mass you have" he says. "If you have more muscle in your upper body, you probably have more in your lower body as well." And if your muscles are wasting, you're further down the road to frailty.
The readings naturally change with time: A woman age 30 to 34 has an average grip strength of 70 pounds, Bohannon says, whereas an 80- to 84-year-old woman has an average grip strength of 37.6 pounds. That's because after middle age, muscle mass starts declining at the rate of approximately 1% per year, in a process called sarcopenia. But sarcopenia can be warded off. And readings that are abnormally poor for one's age can be a good wake-up call that something is amiss and that maybe it's time to take charge and build up your strength.
Scientists, physical therapists and physicians often assess grip strength because it's an easy, noninvasive test that measures overall muscle power fairly accurately. Patients, or study subjects, simply grip a hand-held dynamometer with a spring or hydraulic mechanism that registers pounds of compression. Sometimes the dominant hand is measured, sometimes the nondominant, and sometimes both.
Not everyone is tested for hand-grip strength routinely. A college soccer player with an ACL tear probably won't undergo a grip test, because he or she has ample muscle stores. But a frail elderly person might, or someone who has lost muscle mass through illness or medical treatments such as chemotherapy.
The test has its limitations, says Duane Knudson, chairman of the Department of Health and Human Performance at Texas State University in San Marcos. "If you're trying to make sure an older person has enough strength to do the activities of daily living, it's very valuable," he says. "If you're trying to make a more global prediction of how healthy they'll be, it's not as good. It depends on what the purpose is."
Weak grip strength has been associated with higher mortality rates, however. For example, a 2010 study in the Canadian Medical Assn. Journal found that among 555 85-year-olds, those who lost the most hand grip strength over a period of four years died in greater numbers over a 9.5-year period. And in a 2006 study, scientists found a correlation between better hand-grip strength and higher cognitive function and hemoglobin levels among 3,522 people age 71 to 93.
Grip strength "does reflect vitality," Bohannon says.
Other interesting grip-strength correlations have emerged in studies. One has to do with diet. A 2008 report in the Journal of the American Geriatrics Society showed a correlation between eating more fatty fish — a rich source of omega-3 fatty acids — and better grip strength among 2,983 men and women age 59 to 73. Other studies have shown that omega-3 fatty acids may promote muscle protein metabolism.
And it looks as though early events may influence the grip strength — and presumably overall muscle strength — you get. A 2007 study found that women in their 20s and 30s with higher birth weights had greater grip strength than those with lower birth weights — implying that fetal development could influence muscle strength later in life.
A weak grip may not always need shoring up, Bohannon says. Not being able to get out of a chair or walk without falling has more serious consequences than, say, not being able to open a jar. But if it interferes with daily functions, then strengthening exercises may be in order — though that doesn't mean grabbing one of those hand grippers or a palm-size ball and squeezing away.
"Exercise physiologists and sports medicine specialists want you to use large muscle groups that burn calories and train the heart and vascular systems," Bohannon says. "In the weight room, you'll constantly be using those gripping muscles," as well as other muscle groups.
The larger take-home message from all of this is less about grip strength per se and more about the importance of staying generally fit and strong throughout life.
"A strength program is important, no doubt about it," Bohannon says. "Even if your grip strength is normal, you still want some reserves."