Strength Training: Why you need to lift weights

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(First of three articles on strength training)

Q. Why is strength training so important for older people?

Starting in their late 30s or early 40s, most people lose about a quarter of a pound of muscle every year. By the time they?re 80, they?ve typically lost about a third of their muscle mass. The loss of muscle as we grow older is called sarcopenia. We don?t know how much is hardwired to the aging process and how much is caused by poor nutrition and physical inactivity.

Q. Why does muscle matter?

Muscle is the absolute centerpiece of staying healthy, vital and independent as we grow older. It keeps us strong and mobile. It tugs on bone to help bone stay strong. And it burns more calories than fat burns. Muscle and lean body mass are the metabolic engines of your body. So more muscle means your metabolic rate goes up, which makes it easier to stay trim. Muscle is also where most of our blood sugar, or glucose, goes. When you eat, glucose goes into the bloodstream and most of it gets deposited in the muscle as stored glycogen.

Q. So building more muscle means lower blood sugar?

Yes. We?re seeing an epidemic of Type 2 diabetes not only because people are not eating well, but also because they?re not activating their muscles. When muscles aren?t used, their cells become resistant to the insulin that the pancreas secretes. If your muscle cells are resistant to insulin, you have a higher risk of heart disease. And if resistance leads to more glucose going around in the bloodstream, that can cause diabetes.

Q. What if you already have diabetes?

In a study by one of my Tufts colleagues on 62 older men and women with the disease, those who had 16 weeks of strength training became stronger, gained muscle, lost body fat, improved their blood sugar control and lowered their blood pressure. Even one bout of strength-building exercise will stimulate the muscles to be less resistant to insulin.

Q. Does strength training lower the risk of osteoporosis?

Yes. Each year after menopause, a woman typically loses 1 percent of her bone mass?even more during the first five years after menopause. Over time, the bone loss can lead to osteoporosis, when bones are so porous that they can easily break. Our study followed 40 healthy, sedentary postmenopausal women for a year. Half maintained their usual lifestyle. The others came to our laboratories twice a week and lifted weights. The women who didn?t exercise lost about 2 percent to 3 percent of their bone density by the end of the year. But the women who strength trained gained 1 percent. The strength-trained group also improved their balance by 14 percent, while balance fell 9 percent in the women who didn?t exercise.

Q. Can you prevent fractures?

Preliminary evidence suggests that you can. More than 10 years ago, scientists at the Mayo Clinic randomly assigned a group of 50 women ages 58 to 75 to do strengthening exercises of the back muscles for two years or to serve as controls. Eight years later, the researchers brought the women back into the lab. Those who had originally been strength training not only had stronger back muscles and better bone density, they also had less than half as many spinal fractures as the control group. That?s dramatic.

Q. Muscle loss leads to frailty?

And then to dependence. The typical woman who lives into her late 80s, as many women now do, will need about five to 10 years of assistance because she?s so frail. The same is true for men who live into their 90s.

Q. So falls often send people to nursing homes?

It?s one of the leading causes. The odds are 30 percent that a 70-year-old woman will break her hip if she lives to 90. And, depending on the age of the person, 50 percent to 60 percent of people who break a hip will need care, and 20 percent to 50 percent will die within a year. If a 65-year-old falls and has a fracture, it can be devastating, but not as devastating as if it?s an 85-year-old.

Q. Does the fear of falling make some people inactive?

Yes. It?s usually because they?ve had a fall or a friend has had a fall and they see what happens. There?s a good reason why they?re afraid, but then they become less active and don?t go out as much and they get less fit, so they start spiraling downward. We?ve done some home-based strength training and balance training. People love the balance training because their improved balance and coordination make them less afraid of falling.

Q. Can that confidence help fight depression?

Yes. Many people don?t realize that depression disproportionately affects older people and disproportionately affects older women. My colleague Maria Fiatarone did a study on 32 older individuals who were moderately depressed. After 10 weeks, those who were assigned to a supervised strength-training program three times a week had quite a remarkable reduction in depression and improvements in sleep and self-confidence. Since then, we?ve seen the same reductions in depression in our study of people with arthritis. Other studies have found reductions in depression with aerobic exercise, but Maria?s was the first to see it with strength training.

Q. Are sleep problems also common in older people?

Yes. Sometimes their internal clock is so out of whack that they?re up from three to six in the morning and then they?re wiped out, so they sleep from four to seven in the afternoon. Everything is off-kilter. But with strength training, they sleep deeper, they sleep longer and they have fewer awakenings.

Q. How does muscle strength reduce arthritis pain?

We don?t know the mechanism, but we?ve found that it works with both rheumatoid arthritis and osteoarthritis, which is the leading cause of disability in older adults. Many people with moderate to severe arthritis have weak muscles. For example, with a knee joint, the hamstrings, the muscle in the back of the leg, is much weaker than the quadriceps, the muscle in front. So the muscles are out of balance. If you strengthen the hamstrings, the knee works better. Also, when you walk, there is a jarring on the knee joint with each step you take. That?s what causes a lot of the pain. When the muscles are stronger and in balance, they absorb more of that shock. They?re like the shock absorbers in your car. We?ve also seen signs that cartilage degradation goes down and cartilage formation goes up with strength training, but that was just a preliminary study.

Q. Do people improve quickly?

They do. I?ve been here for 21 years, and I think the most rewarding work has been with people who have arthritis. You see them walk better and with less pain. In our study of 38 people with arthritis of the knee, we saw about a 45 percent reduction in pain. A lot of other stuff that we measure, like bone density or glucose metabolism, you can?t feel. It?s amazing to actually see people feel better.

Q: Does strength training reduce the risk of heart disease?

A recent report from the Physicians Health Study showed that men who lifted weights for at least 30 minutes a week had a reduced risk of heart disease. We don?t have enough women doing strength training to see if it also protects them.
Q: Does strength training curb back pain?
Yes. Many people who sit at a desk all day, like I do, have weak abdominal and lower-back muscles, which is a risk factor for lower-back pain. Strengthening those muscles can reduce the pain.

Q: Do people who do strength training look better?

Yes. It?s wonderful when I hear that a woman all of a sudden starts wearing sleeveless shirts because she?s so proud of the way her arms look. Some women start wearing shorts again because their legs have firmed up. Others find that weight control has become easier because their metabolism is a little better. With any exercise program, many women drop a couple of dress sizes, but with aerobics, you don?t get any stronger muscles.

Q: What about men and middle-aged or younger women?

Strength training is important for everyone, except maybe 20-year-old guys. They have so much anabolic hormones floating around, they?re going to be strong no matter what. But that?s not true for women in their 20s. It?s the last time in their lives where they?re still gaining bone. If a woman can step up her peak bone mass then, she can lower her risk of osteoporosis after menopause. By their 40s, as women are approaching menopause, they start to lose some bone and muscle. Men start to lose, too. So that?s also a good time for them to start. Having said that, we?ve started people strength training at 93 and they gained tremendous benefit. ???

Miriam Nelson is director of the John Hancock Center for Physical Activity and Nutrition at Tufts University?s Friedman School of Nutrition Policy and Science in Boston. This article was reprinted with permission from Nutrition Action Healthletter.