You’re more likely to fall and seriously injure yourself, Dr. Lyon points out, which “causes survivability to plummet.” Being less able to care for and nourish yourself also increases your chance of illness, just as being more sedentary lowers mental activity and lessens circulation, which can put you on a path to cognitive decline, Deborah M. Kado, MD, a board-certified internist and geriatrician, and codirector of the Stanford Longevity Center, tells SELF. Meanwhile, the movement necessary to build muscle both shunts blood to your brain and exercises its coordination abilities, Dr. Kado says, helping safeguard cognition.
Perhaps less evident, if just as important, are the many functions of muscle beyond keeping you upright and agile. For one, it’s a critical factor in metabolic health, serving as the biggest storage location in the body for glucose, Dr. LaBrasseur says. The more muscle you have, the better you can clear sugar from your blood—and the lower your odds of developing type 2 diabetes. At the same time, active muscle breaks down triglycerides (a type of cholesterol) for fuel, Dr. Lyon says, reducing the level in your blood. Taken together, these shifts power up your metabolism, in turn lowering your risk for heart disease.
Muscle is also “an endocrine organ,” Dr. Lyon says: When you contract it, it oozes proteins called myokines, which act like hormones, trickling throughout the body and signaling a variety of beneficial effects. Doctors suspect these agents, like brain-derived neurotrophic factor (which supports memory and learning) and interleukin-6 (which lessens inflammation), could explain how muscle-building seems to lend a hand to far-off organs.
And finally, robust skeletal muscle seems to function like body armor, Dr. Lyon says, making you more resilient in the face of intense physical stressors. For example, those with ample muscle seem to fare better during chemo and recover more easily from critical illness, Dr. LeBrasseur points out. By contrast, frailty—or a weak state of low muscle mass and limited mobility—can make you more vulnerable to negative health outcomes, like longer hospital stays, poor tolerance for medical interventions, and yep, premature death.
How to measure your personal musclespan
You can get a sense of your musclespan by assessing your strength. To gauge your lower extremity strength, Dr. LeBrasseur recommends a basic chair stand test: See how quickly you can stand and sit back down in a chair five times in a row—if you’re under age 40, you should be able to finish in fewer than 10 seconds (add a second for ages 40 to 70 and for each decade after that). And to assess your upper body strength, see how long you can dangle from a pull-up bar in a dead hang; 10 seconds is great for a beginner, and longer is better.