How much muscle strength do you lose per year after the age of fifty?

Muscle mass shrinks from middle age onwards by roughly 1% per year. At first glance that sounds modest, but when you add it up over decades, someone in their eighties may have lost up to half of their original muscle mass.

Muscle strength, however, declines far more steeply than muscle mass alone. A large study of nearly 1,900 older adults found annual losses in leg strength of between 2.6% and 4.1%, depending on sex and background. Men lost strength almost twice as fast as women. That is three to four times faster than the loss of muscle tissue itself. The reason: not only does the amount of muscle decrease, its quality declines as well. Per kilogram, the muscle produces less force than it used to.

That loss of quality is no minor detail. The same study showed that people who maintained or even increased their muscle mass were still unable to stop their loss of strength. In other words, keeping up mass is not enough; the muscle itself functions differently as you age. This phenomenon is called anabolic resistance: your muscles respond less strongly to exercise and protein than they once did.

When this process has advanced far enough, it is called sarcopenia. That raises the risk of falls, fractures, reduced mobility and premature death. An estimated 5 to 10% of the population has this condition in a severe form.

Strength training is the only approach proven in humans to counter age-related muscle loss and strength loss. Nutrition also plays a role: at least 1.0 to 1.2 grams of protein per kilogram of body weight per day is the recommended minimum for healthy older adults. But diet alone is not enough; the combination with regular strength training yields the best results.