If You Were Fit Once, It Might Be Easier for You to Get Back in Shape

Remember back in high school—before you turned into an office schlub—when you could bench some ungodly amount of weight?

Yeah, your muscles remember your glory days too, even if sprints to the office vending machine are all you use them for these days. In fact, recent research shows strength training can grant long-term change to muscles, both by altering its DNA and by adaptations to the muscle cell’s nuclei. This means that those of us who were fit kids may have an advantage training for that midlife crisis CrossFit competition. Perhaps more importantly, though, the effects of steroids and other performance enhancing drugs may linger well after a suspension has been served.

Since the 1960s, scientists have had some clue that working out now could benefit you later, but they weren’t sure why, says Kristian Gundersen, a professor of physiology and cell biology at the University of Oslo. “What is new is that we discovered that nuclei are ‘never’ lost,” he adds. This discovery came in two studies, one done in 2010 and one done in 2013. “It was previously thought that nuclei were recruited during hypertrophy [or, in layman’s terms, getting swoll] and then lost if the muscle mass was lost [called atrophy]. We found that this is not the case, and this is the foundation for muscle memory.”

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In the 2013 study, which was published in the Journal of Physiology, Gundersen and other researchers shot steroids into mice and watched them get huge. Meanwhile, the placebo group trudged through workouts without the juice. The researchers then pulled the mice off drugs for three months, and the mice in both groups returned to their baseline muscle mass. Finally, the researchers subjected the mice to hard, muscle-building work again. Sure enough, the mice who had been on steroids before grew their muscle mass by 30 percent over six days—without any steroids. Meanwhile the control group saw no significant gains.

Gundersen’s research has focused on the formulation of new nuclei within the muscle cells. Contrary to what you learned in middle school biology class, muscle cells can have more than one nuclei. Strength training seems to be the catalyst by which they form these extra nuclei. And even after you stop working out, the nuclei stay there, although no one knows exactly for how long. In the 2013 study, the three-month period in between tests constituted 10 percent of the mouse’s average lifespan.

Adding additional weight to the argument that exercise has lifelong effects is a 2018 study published in Scientific Reports. This paper found that muscle growth could actually change our DNA. Researchers in this study looked at 850,000 spots on human DNA and found that specific genes were untagged during strength training. When “they are tagged less [or untagged] the genes are switched on,” explains Adam P. Sharples, the lead author on the study and a senior lecturer in cell and molecular muscle Physiology at Keele University in the UK. “Exercise-induced muscle growth actually untagged the DNA more, so that more genes could be switched on and help the muscle tissue grow.” Even after participants had stopped actively trying to grow their muscles, the changes to the DNA stuck around.

“Studies like this are hard to do in humans,” Sharples says, adding that the volunteers were complete weight lifting newbies who agreed to be put through seven weeks of really intense iron pumping. “They were very sore,” he says. Even worse, after they gained that muscle, they had to then lose it all, to make sure the markers didn’t go away as the muscles shrank to their original size. Finally, they had to repeat the muscle training to see if the DNA changes helped them gain guns faster than last time. Sure enough, they did.

It’s important to note that this study was not done with performance enhancing drugs, and so we don’t yet know whether muscle growth inspired by steroid use would alter our DNA. Also, the sample size was small, with just eight subjects. Finally, all of this research has looked at strength training. While there is some preliminary research on how endurance exercise may change DNA, at this point Gundersen says that there’s not much evidence that you can gain additional nuclei by running long.

Still, the idea that you can change your body forever—or at least for a good long while—through a few weeks of strength training is encouraging, even if those muscles aren’t doing all that much work this very moment.

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