Have you ever taken months off training – maybe due to an injury, a new baby or crushing work deadlines – and come back convinced you were starting from zero?

Research from our team has some good news: At the cellular level, you probably weren’t.

We found that muscle and liver cells store memories from every training session in ways that may help improve endurance, control blood sugar levels and even slow weight regain after inactivity.

Use it or lose it? Maybe not

For most of the past century, long before fad diets and fancy workout trends took off, exercise was considered one of the most effective lifestyle changes to lower the risk of heart disease, Type 2 diabetes, several cancers and early death for people of all ages. But people typically understood exercise as something whose beneficial effects fade away over time: You use it or lose it.

When you stop training, your maximum oxygen uptake, muscle gains and insulin sensitivity drift back to where they started, often within weeks. Physical activity guidelines are built on this fact, which is why they emphasize consistency above all else.

Consistency, however, is a luxury that roughly 3 in 4 American adults aren’t able to enjoy. People can experience injuries, illness, pregnancy or jobs that limit their time for or ability to exercise. If adaptation really resets, every time you step into the gym would be as if you’ve never been there before. But that scenario doesn’t match what coaches and returning athletes typically describe: In practice, people who have trained before can get fit again faster........

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