HEALTHY LIFE AND EXERCISE

The Aging Population. According to the American College of Sports Medicine, by the year 2030, the number of individuals in the United States 65 years and over will reach 70 million, and people 85 years and older will be the fastest growing segment of the population. Some of you may already be there, while others may be approaching. But whatever your age, exercise can help. Below is a description of what happens to our bodies as we age and how exercise can make all the difference.

What happens to muscles as we age? Muscle mass decreases as we age. Beginning in the fourth decade of life, adults lose 3%-5% of muscle mass per decade, and the decline increases to 1%-2% per year after age 50. Muscle keeps us strong, it burns calories and helps us maintain our weight, and it contributes to balance and bone strength. Without it, we can lose our independence and our mobility.

Is it ever too late to build muscle? The good news is that muscle mass can increase at any age in response to exercise. In an important study of weight lifting and older adults conducted with 100 male and female residents of a nursing home in Boston (age range: 72 to 98 years of age; average age 87), subjects lifted weights with their legs three times a week for 10 weeks. At the end of the study, there was an increase in thigh mass of 2.7%, walking speed increased 12%, and leg strength increased a whopping 113%! In a similar study of adults 65-79 years old, subjects who lifted weights three times a week for three months increased their walking endurance by 38% (from 25 minutes to 34 minutes) without appreciable increases in mass. Ida Weiss, a 91-year-old participant in the Boston study, had the following to say after the study, "It's very beneficial for me. Things that I couldn't do when I came here, I can do now. I didn't think that I was going to live anymore, but I feel different now." Can I get stronger without building big muscles? Importantly, strength isn't just a function of mass. It's also a function of something called "neurological patterning." In layman's terms, patterning is when the brain sends electrical signals via the nervous system to muscles to make them contract.

For example, when you think about walking down the street, bending over to pick something up, or any other movement for that matter, the brain first processes the thought and figures out what muscles are needed to make the move and then sends the signal over the nerves to the particular muscles that are necessary for the movement. The muscles move (and so do you) once the signal reaches them. (See "How muscles work" for more detail.) The good news here is that muscle patterning improves within days of starting a weight-lifting program, even without any increase in muscle mass. This explains the 113% increase in strength experienced by the residents of the nursing home in Boston I just mentioned. In a different study that specifically investigated this phenomenon, 67- to 81-year-old men lifted weights for six weeks while hooked up to electrodes that measure nerve and muscle patterning (an electromyogram machine). The results showed that the men experienced a 25% increase in the patterning of the muscle along with a 35% increase in strength, all without significant increases in size. What happens to endurance as we age? Endurance decreases as we age. In one study of more than 3,000 70-79-year-old men and women, researchers investigated the relationship between the speed at which these subjects walked ¼ of a mile and their risk of premature mortality, cardiovascular disease, and mobility limitation.

The results showed that those with the slowest walk times (>6 minutes) had a higher risk of death, cardiovascular disease, and mobility limitation than those who walked the distance in less than four and a half minutes. In fact, every additional minute of walking time was associated with higher and higher degrees of risk; approximately 13% of the participants could not even complete the distance due to fatigue or symptoms (breathlessness, cramping, etc.). There's good news when it comes to fitness, walking endurance, and health. In a classic study of walking and mortality in 700 men enrolled in the Honolulu Heart Program, the mortality rate among the men who walked less than one mile per day was nearly twice that among those who walked more than two miles per day (studies of women show equally potent results). In another equally impressive study, data collected on more than 41,000 men and women from 1990 to 2001 were analyzed to find the relationship between walking and mortality. It was reported that men and women who walked 30 minutes or more per day during the study period had fewer deaths than those who walked less than 30 minutes. Interestingly, even men and women who smoked or were overweight were protected from early death if they walked more than 30 minutes per day.