Exercise, particularly resistance training (lifting barbells, pressing weights with our legs, using elastic bands), is a potent countermeasure against this muscle loss at any age; in fact, there are no other established treatments. While a training program that continues indefinitely is ideal, most people will not continue consistently for prolonged periods. Sustainability remains a challenge (the same is true of dieting and pill-taking, of course). What then is the minimum exercise dose you have to maintain to prevent the reversal of gains after you’ve stopped training?  

 

First, a few basics. When muscles stretch during exercise, they produce a chemical known as mechano growth factor (MGF) that activates stem cells already present in the muscle. These immature cells begin to divide, creating additional muscle fibers and increasing the size and strength of the muscle. In addition to exercise, muscles need to be stimulated by growth hormone (GH) in order to release MGF. The natural decrease in the levels of growth hormone as we age, combined with the lack of intensive physical activity, causes muscle wasting (when MGF and GH are used by athletes it’s called doping).

 

Resistance training increases strength and mobility (higher muscle mass to body size also improves insulin sensitivity and glucose metabolism). When we train (3 times per week is recommended for muscle growth, and greater intensity of training—more weight, longer sessions—yields greater effects than moderate or low intensity), muscle cells enlarge and trigger more rapidly, no matter what our age. While younger people who start lifting can grow muscles faster, within four months of regular training, a 65-year-old can develop the muscle fiber size of a 40-year-old who is not in training. Even though individual muscle cells enlarge modestly (2-10%), middle-aged and older adults in training demonstrate large increases in strength (35-65%) within 16 weeks.

 

At any age, the positive effects on muscle size and function are reversed when training completely ceases. Declines in strength associated with de-training occur more slowly than the gains made, but the older we are, the faster we experience such declines. 

Intriguingly, maintenance of strength during detraining is, for the most part, not dependent on maintenance of muscle mass. Both the young and old retain substantial improvements in specific strength despite de-training. Non-muscle mass adaptations (e.g., improved muscle firing, better fiber coordination) that affect strength performance persist much longer than the transient muscle size increase. Even eight months after a four-month program of regular heavy resistance training has ended, older adults remain 25% stronger than they were at baseline. So for those who can manage a substantial training period, there are positive implications for walking, climbing stairs, balance, and reducing the risk of falls, for a long time after the effort.

 

Here’s more good news: ongoing once-per-week resistance training (one third the dose of the original, intensive regimen) is generally sufficient to maintain the original neuromuscular improvements. Training twice a month keeps us stronger than before we started our 4 months of intensive training. In other words, you can stop or take a break once you’ve done the hard work, but if you’re elderly and do not keep up at least some level of training, the functional gains will eventually deteriorate.

 

As we age, the most important factor in day-to-day functioning—getting out of a chair, walking—is our muscle strength. The natural deterioration in strength can be slowed by training. If you are not ready for pumping iron, training can begin with exercises you can do using your own body weight including squats, standing up out of a chair, modified push-ups, as well as non-traditional exercises that progress through a full range of motion, such as Thai Chi or Yoga. After that, you can move on to more advanced weight training. For most people into their 80s, muscle function can be restored, or at least improved. Few elderly persons currently practice strength (resistance) training, but to preserve independence into retirement, intermittent binges of intensive training with regular but less frequent maintenance will be critical.

MD Stein

 

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