For Your Other 600 Muscles

By Howard Schneider
Tuesday, June 12, 2007

The People Who Know What's Good For Us have made life progressively difficult, moving from general recommendations such as "maintain ideal weight" to detailed orders for 60 to 90 minutes of exercise every day.

You can now add weightlifting to the creeping set of obligations. It's not explicit in the government's overall guidelines, but the more detailed suggestions from agencies such as the Centers for Disease Control and Prevention recommend a couple of rounds of resistance training each week. (And, yes, Vicky, that includes you cardio junkies out there because aaaallllll thaaaaatttt time on the treadmill won't guarantee that you can sit up straight when 27 becomes 77.)

This won't make a lot of us happy. The basic exercise recommendations are pretty easy to cope with: Take a walk. Ride a bike. Lather, rinse, repeat.

Weightlifting, on the other hand, conjures the threat of being stuck next to some grunting mesomorph who will one day be governor. The chance of injury is greater. The advice gets confusing and may include a lecture about how, if you don't disrupt the Z lines between your sarcomeres, it's a waste of time.

It's manageable, however, if you understand some basics. The reason there is so much varying advice -- over what exercises to do, how frequently and how intensely -- is that this is an enterprise that should be tailored to your goals and your body. Cardio focuses on training just one muscle, the heart. There are more than 600 others that need attention.

Here are a few underlying principles:

Age is not a barrier. The capacity to build muscle remains as we grow older. It may slow, as our diet and neurology change. And a natural atrophy kicks in at early middle age. But you can still get stronger.

"When you start training, muscle comes back," regardless of age, said Gary Reinl, a consultant with Nautilus who developed a compact set of six exercises used to help people retain the ability to perform such basic tasks as walking and sitting erect, which becomes particularly useful as we age and after happy hour.

Don't mistake cardio by another name. Our nature makes it easy to store fat (future fuel for a crisis, right?), but you have to persuade your body to invest the energy to add and sustain more muscle.

This is not easy. Muscle fibers are long strands of protein supported by multiple nuclei. There is a store of extra nuclei, called satellite cells, sort of hanging out, waiting for the right message. That message, said J.P. Hyatt, an assistant professor in the Department of Human Science at Georgetown University, comes in the form of damage. When the structure of the muscle is torn and disrupted through exercise, satellite cells move into the fiber and support the accumulation of more protein.

More protein, more strength. But not just any amount of exertion works. The muscle needs to hit a point of momentary failure -- showing that what's there is inadequate -- to prompt your body to invest in that new infrastructure.

The muscle also has to fail in a certain way. You can flap your arms over and over and at some point not be able to do it anymore (try it at lunch!), but this will not trigger muscle growth. As Reinl notes, that's why marathon runners don't have tree-trunk legs.

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