Muscle Memories

Let me tell you about one of the dumbest workouts I've ever seen.

No, it wasn't somebody doing sprints in Shape Ups. Last week I saw an oldish man in my building's workout room, wearing khakis and a plaid button-down (always a red flag). When I arrived, he was doing bicep curls with 3-pound weights, one in each hand. Aw, I thought, he has to use really light weights because he's older. And he's counting out loud because he can't remember how many reps he's done! (It was 20.)

Then he put down the 3-pound weights and picked up the 5-pounders, and did the same 20 bicep curls. Then the 8-pounders: 20 bicep curls. Sure enough, standing in front of my elliptical machine, he worked his way down the entire rack of free weights. Then he moved to the heavier weights on the other wall. "Unh...one! Unh...two!" He grunted through sets of 20 bicep curls on increasingly giant dumbbells. Then suddenly he was holding a stretchy rubber cord with handles. He stepped on the cord with his right foot and stood with one end in each hand. Don't do it, I thought. He did a bicep curl. "One!" Twenty curls later, he switched feet.

The moral of this story--besides that I now know exactly how many pieces of equipment in our workout room can be used for a bicep curl--is that some workouts are obviously counterintuitive. Why waste your time on 3- and 5-pound weights when you can lift 25-pounders? (And how big do your biceps need to be if they're the only part of your body you're working out?) If you've ever exercised, you can feel that your body gets stronger only as you challenge it.

Muscle cells don't look quite like those textbook fried-egg cells, with a nice round yolk in the middle and a bunch of goo outside. Instead, they're very long fibers that can have many nuclei. When you exercise, your stressed-out muscle fibers absorb some of the little helper cells that live around them. Then the extra nuclei (it seems) help your muscle fibers grow thicker.

In a new study, Norwegian scientists made mice exercise a certain muscle for three weeks, and observed the extra nuclei--54% more than the mice started with--being added to the muscle fibers. After the nuclei started to increase, the muscle fibers increased in thickness.

The scientists worked another group of mice for two weeks and then severed the nerves connected to the muscle, forcing it to atrophy. They found that even though the muscle fibers shrank dramatically, the number of nuclei stayed essentially the same over the following two weeks. Even three months later, there were still extra nuclei in the muscle fibers.

This might be the reason, they say, why it's easier to gain muscle where you've had muscle before. Even if you haven't exercised in a long time, you're not starting from scratch because you might still have extra nuclei in your muscle fibers. The authors point out that three months is a pretty long time for a mouse, which only lives a couple of years. So who knows how long the effect might last in humans?

Athletes who are known to have used steroids in the past are still allowed to compete--but what if it turns out that steroids give muscles a boost that lasts for many years? Even if previously bulked-up steroid users seem to have returned to normal, what if their muscles retain extra strength or efficiency? "The benefits of using steroids might be permanent," the authors say. Should everyone who's ever used steroids be banned for life?

The authors also suggest that by "filling up" muscles with nuclei earlier in life, people could prevent some of the weakness that comes with old age. Once people are older, it's much harder for them to build muscle mass--no matter how many bicep curls they do.