Researchers reporting in the March issue of Cell Metabolism have found that when healthy but inactive men and women exercise for a matter of minutes, it produces a rather immediate change to their DNA. Perhaps even more tantalizing, the study suggests that the caffeine in your morning coffee might also influence muscle in essentially the same way. The underlying genetic code in human muscle isn't changed with exercise, but the DNA molecules within those muscles are chemically and structurally altered in very important ways. Those modifications to the DNA at precise locations appear to be early events in the genetic reprogramming of muscle for strength and, ultimately, in the structural and metabolic benefits of exercise. The DNA changes in question are known as epigenetic modifications and involve the gain or loss of chemical marks on DNA over and above the familiar sequence of As, Gs, Ts, and Cs.