How Muscles Change With Age

Most eighty-year-olds can’t out-lift a thirty-year-old in the gym or out-sprint them either. With age, you gradually lose muscle mass, and the loss is substantial in people who don’t challenge their muscles through resistance training. Fortunately, you don’t have to be relegated to lifting little pink weights at the gym as you age. Muscles have a remarkable ability to respond to strength training regardless of a person’s age. In fact, many health problems in the elderly could be avoided if more of them trained with weights.

At What Age is Muscle Strength at Its Peak?

Both men and women reach their peak of muscle strength between the ages of 20 and 40. After that point, they gradually lose muscle cross-sectional area and muscle fibers atrophy. This process begins slightly earlier in men than in women and continues throughout life. Lower body muscles decline in strength more quickly than those in the upper body, so arm strength is preserved longer than leg strength.

Fast-Twitch Fibers Are Affected More Than Slow-Twitch

You have two basic types of muscle fibers, fast-twitch, and slow-twitch. Fast-twitch muscle fibers contract with great force, but they also fatigue more quickly. They’re recruited during activities that require force and power such as sprinting, jumping or lifting a heavy weight. Slow-twitch fibers are designed for endurance activities such as long-distance running. They generate less force, but they’re also less resistant to fatigue.

With aging, you lose more fast-twitch fibers than you do slow-twitch ones. With the loss of fast-twitch muscle fibers, the ability to generate maximal muscle force decreases. Slow-twitch fibers are less affected by aging, so older people retain more of their ability to do activities that require endurance. It’s not unusual to see someone in their eighties running a marathon, but it’s less common to see an older person running a short race that requires speed and power.

It’s sobering that sedentary people lose as much as 50% of their muscle mass over time. This is one of the primary reasons that older people become frail and are more prone to falling.

The Good News

Resistance training can slow down age-related loss of muscle strength and mass. One study showed that men in their early seventies who started strength training at age 50 had the muscle strength and cross-sectional muscle area comparable to that of a 28-year old. Even elderly people in their nineties can build muscle strength through strength training.

Even though fast-twitch muscle fibers are lost with age along with smaller numbers of slow-twitch muscle fibers, resistance training increases the size of the fast-twitch fibers that are left, which increases strength and muscle mass.

The Bottom Line?

You lose muscle mass and strength starting around the age of 30, but your muscles still retain the ability to respond to strength training throughout life, and resistance training one of the best things you can do to ward off old-age frailty and sarcopenia, the loss of muscle mass with age. It’s never too late to start. Even people in their nineties can increase their strength through resistance training.

References:

Exercise Physiology: Energy, Nutrition, and Human Performance. Fifth edition. 2001.
Am. J. Sports Med. July 1998. Vol. 26. No. 4. 598-602.

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