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Exercise Controls Gene Expression

The activity level of skeletal muscle modulates a range of genes that produce dramatic molecular changes—and keep us healthy

P. Darrell Neufer, Frank Booth

Consider what likely would happen in the game show Jeopardy if the category what tissues do were to roll up on the game board. The $200 answer: "It moves the body." The contestant delivers the question—"What is Muscle?"—earns her money, and the game quickly moves on. This scenario typifies how muscle is generally viewed—as a simple part of the human anatomy that locomotes us.

Perhaps late-night television would allow a more sophisticated treatment of muscle's function. Suppose David Letterman were to ask people on the street "What is skeletal muscle?" Some of the answers might be: "What I see at the meat counter"; "what I feel the day after those rare occasions that I exercise"; and "what I saw on TV during the Olympics."

Figure 1. Skeletal muscle...Click to Enlarge Image

All these responses in fact vastly underplay the role of muscle, even the subcategory of skeletal muscle, in our bodies. In the following paragraphs, we hope to present a more sophisticated view of the function of skeletal muscle from a genetic and molecular standpoint, and in particular to emphasize the role of skeletal muscle in human health and well-being. Let's start by recognizing that skeletal muscle is the largest single tissue type in the human body: We have more than 640 muscles, accounting for between 30 and 40 percent of total body weight. Skeletal muscle also uses as much as 25 percent of the energy consumed by the body at rest.

Furthermore, although today we consider Olympic athletes to be extraordinarily fit, most of our ancestors from tens of thousands of years ago had bodies and muscles that were almost as fit. Many of the metabolic characteristics of modern humans evolved to support high levels of work efficiency and physical activity, a fact that undoubtedly contributes to the health problems facing sedentary 21st-century societies. Our underuse of skeletal muscle may play an underrecognized role in the rise of chronic diseases as a cause of modern mortality. Given these few simple facts, it is clear that the importance of skeletal muscle to humans extends well beyond athletics.

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