RBR Newsletter

Preventing Loss of Muscle with Aging

By Gabe Mirkin, MD

If you don’t exercise vigorously, expect to lose muscle size and strength as you age.

Between 40 and 50 years of age, you lose about 8 percent of your muscle size. This loss increases to 15 percent per decade after age 75. The people who lose the most muscle usually are the least active, exercise the least and are the ones who die earliest.

Older people who lose muscles are four times more likely to be disabled, have difficulty walking and need walkers or other mechanical devices to help them walk (Am J Epidemiol, 1998; 147(8):755–763). The authors say “Exercise decreases body fat and obesity, increases muscle strength, improves balance, gait, and mobility, decreases likelihood of falling, improves psychological health, reduces arthritis pain, and heart attacks, osteoporosis, cancer, and diabetes.”

How Aging Causes Loss of Muscle

Muscles are made up of thousands of individual muscle fibers. Each muscle fiber is innervated by a single nerve. With aging, humans lose the nerves that innervate muscle fibers, and with each nerve loss, they lose the associated muscle fiber. For example, the vastus medialis muscle in the front of your thigh contains 800,000 muscle fibers when you are 20. At age 60, it will have only 250,000 fibers.

Exercise Reduces Loss of Muscle

Inactivity causes tremendous loss of muscle size and strength. If you inactivate a leg by putting it in a cast, you lose a large amount of muscle size in just four days. However, if you make the inactivated leg muscles contract by stimulating them with an electric current, some of the loss of muscle size is prevented (Nutrition, Acta Physiol (Oxf). March 2014; 210(3):628-41).

You can enlarge muscles by exercising against resistance as you age (The Journals of Gerontology, August, 2012), but not by eating more protein (Clin Interv Aging, July, 2012 ;7:225 – 234). Resistance exercise increases muscle size and strength in older people (Med. Sci. Sports Exerc, 2011; 43 (2): 249–58); however, with aging you need to work much harder to gain the amount of strength that a younger person would get with the same program (Med. Sci. Sports Exerc, 2011; 43 (2): 249–58).

Prolonged periods of stopping exercising due to bed rest, injured nerves, casting or even decreasing the force of gravity cause loss of muscle tissue, which causes insulin resistance, higher blood sugar levels, and a tendency toward becoming diabetic (Med Hypotheses, 2007;69(2):310-21). Gaining fat decreases your ability to respond to insulin and shortens your life.

Exercising as You Age Keeps More Fast-Twitch Fibers

Muscles are made up primarily of two types of fibers: fast-twitch fibers that govern strength and speed, and slow-twitch fibers that govern endurance. Inactivity causes a far greater loss of the fast-twitch muscle fibers that govern strength and speed (J Cell Mol Med, 2009 Sep;13(9B):3032-50), so exercise makes you stronger by causing your muscles to retain more fast-twitch fibers.

Benefits of Life-long Exercise

Life-long competitive athletes over 50 who train four to five times per week do not lose as many of the nerves that innervate muscles, and therefore retain more muscle size and strength with aging (The Physician and Sportsmedicine, October, 2011;39(3):172-8).

Other studies show that life-long competitive runners over 60 had almost the same number of muscle fibers as 25-year-olds. If you are not a life-long exerciser, there is still plenty of benefit from exercise; studies in animals show that elderly rats that had been sedentary throughout their adult lives formed new muscle fibers 13 weeks after they were put on an aggressive running program.

How to Grow Larger Muscles

The stimulus to enlarge a muscle is to exercise against resistance vigorously enough to damage your muscles. Muscles grow when they heal from injury. You can tell that you are causing muscle damage because of the burning you will feel in muscles when you are exercising and the delayed onset muscle soreness (DOMS) that you feel 8 to 24 hours after you finish exercising.

Then you take easier workouts until the soreness goes away, usually in 24 to 48 hours. If you take hard workouts when muscles are sore, you are likely to tear them and not be able to exercise again until your muscles heal.

Older People Should Lift Lighter Weights with More Repetitions

Older men gained more muscle strength by spending more time lifting weights, whereas younger men gained more muscle strength by lifting heavier weights. In younger men, doubling exercise volume by spending more time lifting weights produced limited added muscle enlargement. In older men, it resulted in much larger muscles and far more strength (The Journals of Gerontology, August 2012).

Join a Gym

First check with your doctor to make sure you do not have a condition that will be harmed by vigorous exercise. Then join a gym and ask for instructions on how to use the weight-training machines. As a general rule, on each machine, you will try to lift a weight 10 times in a row, rest a minute, and then do two more sets of 10. In the beginning, you should lift very light weights and go home without sore muscles. After a few weeks of lifting weights three times a week, not on consecutive days, you can gradually try to add more weight on your machines.

[Another excellent resource for cyclists is Coach Harvey Newton’s Strength Training for Cyclists System, which consists of a 132-page electronic Strength Training for Cyclists Manual, plus the 42-minute DVD Training Program and 28-page hard copy Quick Start Guide.]

Reprinted with permission from Dr. Gabe Mirkin’s Fitness and Health e-Zine. Gabe Mirkin, M.D., is a sports medicine doctor and fitness guru. A practicing physician for more than 50 years and a radio talk show host for 25 years, Dr. Mirkin has run more than 40 marathons and is now a serious tandem bike rider with his wife, Diana, often doing 30-60 miles in an outing. His website is


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