If you’re like most Americans, you know what it’s like to get fired up about an exercise routine, go hard for three weeks and then fizzle out. Statistics show, for example, that by February, about a third of Americans have abandoned their New Year’s resolutions, most of which involve eating better and exercising more.

If that describes you, new research published in Frontiers in Physiology gives you good reason to jump back in the game: It may be easier to get back in shape than it was to get in shape to begin with.

The research is complicated, but the gist it this: It suggests that changes in muscles cells once thought to dissipate when you stopped exercising actually stick around. The researchers examined muscles that had experienced hypertrophy (growth) and then atrophied down to their original size. They discovered that new muscle cell nuclei that had developed remained, even after muscle volume had shrunk. Then, three months later, researchers stimulated the muscles again and found they rapidly grew 36 percent in volume, compared with 6 percent for a control group.

The takeaway is this: Even if you dropped off your workout for a month or two, get back on it today. You may still be able to capitalize on gains you made back then—and make fitness down-payments for later.