When young adults get back into training, certain genes in their muscles 'remember' past fitness thanks to chemical tags on DNA—these genes stay more active and less methylated, like a fitness memo...

After doing intense workout intervals, your muscles keep some chemical changes for at least three months—even if you stop exercising—suggesting your body might be 'remembering' the training at a genetic level.

When people do long-term workouts like running or lifting weights, their muscle cells show tiny changes in a biological tagging system called DNA methylation—mostly fewer tags in areas that control metabolism and muscle function.

Doing intense interval workouts for 8 weeks can change how your genes are switched on or off in your muscles — and this study says it affects over 14,000 spots in your DNA.

Even if your muscles don't get stronger or fitter after working out again, your body might still remember the old workout at a molecular level—like a biological bookmark keeping track of past exercise.