By Dr. Gabe Mirkin, MD Muscles are made up of thousands of muscle fibers just as a rope is made up of many strands. Each muscle fiber has a nerve that innervates it. With aging you can lose nerve fibers that, in turn, cause you to lose the corresponding muscle fibers, but exercising against resistance will make the remaining muscle fibers larger so they can generate more force.
A recent experiment measured the force that a rat’s muscle fiber generates when it is electrically stimulated at the nerve or at the muscle. Electrically stimulating the muscle directly showed that the muscles of young rats generated 40 percent more force than those of old rats. On the other hand, when the nerve endings were stimulated electrically for five minutes, the muscles of the old and young rats generated the same amount of force. The authors suggest that loss of strength with aging is primarily due to loss of nerve function rather than just muscle function (Experimental Gerontology, March 2018). The repetition of a regular and consistent training program teaches your brain how to contract your muscles more efficiently.
Researchers at the University of Guelph have another explanation why people, even those who exercise regularly, lose muscle size and strength as they age. They showed that aging causes loss of mitochondria, the tiny furnaces in cells that turn food into energy (Cell Reports, March 13, 2018). This causes the accumulation of breakdown products called Reactive Oxygen Species (ROS) that delay healing and weaken muscles (Cell Metabolism, March 2017;25(3):581–592).
More New Studies on Muscle Growth for Older People
• Osteoporosis: Lifting weights helps to strengthen bones of postmenopausal women who suffered from osteoporosis (J of Bone and Min Research, February 2018;33(2):211-220).
• Protein Intake: Several studies show that older people do not gain any additional muscle size or strength from increasing their intake of protein above the current RDA (recommended dietary allowance) of 0.8 gm/kg of body weight/day. Even older men who are taking extra testosterone do not gain any extra strength or muscle growth from increasing their intake of protein to 1.3 g/kg/day (JAMA Internal Medicine, April 2018).
• High-Plant Diet after Menopause: Older women who follow a Mediterranean-type diet (based on plants, with fish but restricting red meat and added sugars) have larger muscles and bones after the menopause than women who eat the typical Western diet (ENDO 2018, the Endocrine Society annual meeting in Chicago, March 19, 2018).
• Recovery Time: Older people who do strength training need to realize that their muscles will not heal as fast from workouts as muscles of younger people because aging causes their mitochondria to become smaller in number and size (Cell Metabolism, March 2017;25(3):581–592).
Starting a Resistance Program
The most effective way to slow down the loss of muscle strength with aging is to start a resistance exercise program that includes using strength training machines or lifting weights. A review of 25 well-designed and performed scientific studies shows that resistance training can grow larger and stronger muscles in older men and women (Sports Med, Dec 2015;45(12):1693-720). Older people who use strength training machines two or three times a week can make themselves stronger to decrease their risk for falling, breaking bones, and suffering osteoporosis, arthritis, heart attacks, diabetes, and premature death (Am J Prev Med, Oct 2003;25(3 Suppl 2):141-9). See Slowing Loss of Bone and Muscle Strength with Aging
Preventing Muscle Loss
Before you start a new weight training program, check with your doctor and get expert advice from a trainer so you can learn proper lifting techniques for the equipment you will be using. Most beginners will be far more successful on weight lifting machines, rather than using free weights. The machines are safer because they can guide the way you move the weights with the specific muscles for each machine.
How to Make Muscles Stronger
Just exercising does not make a muscle stronger. The stimulus to make a muscle larger and stronger is to exercise that muscle against resistance to the point where you feel a burning in that muscle. However, if you continue to exercise after you start to feel that burn, you run the risk of injuring the muscle, so most older people can prevent injuries by stopping each set of lifting as soon they feel a burn in their muscles. You can exercise to the burn by using heavy weights with few repetitions or by using lighter weights with more repetitions. Older people gain the most strength by doing more sets of lower repetitions per set than using fewer sets with higher numbers of repetitions per set (Experimental Gerontology, March 29, 2018;108:18-27). The lighter the weight you use, the more repetitions you have to do to feel the burn. For example, several sets of three repetitions each is safer than performing fewer sets of the same weight with sets of 10 repetitions. For more detailed suggestions see Strength Training Guidelines from Dr. Richard Winnett of Virginia Tech.
Aging can take away much of your quality of life unless you keep your muscles strong enough to perform all of your daily activities. A regular strength training program will help you to move faster, walk with more security, be less likely to fall and hurt yourself, and have more confidence in every movement of your body.
CAUTION:People with blocked arteries leading to their hearts can suffer heart attacks with exercise. Check with your doctor before starting a new exercise program or increasing the intensity of your current program.
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. His website is http://drmirkin.com/. Click to read Gabe's full bio.