AI-rewritten: This is a summary of an article from The Conversation, rewritten by AI (Qwen, running locally) to make it easier to read. The facts come from the original article – read it for the full story.

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Research indicates that muscle and liver cells store memories of past workouts, meaning fitness gains may persist even after a break from exercise. For decades, the "use it or lose it" rule suggested that benefits like improved oxygen uptake and insulin sensitivity fade within weeks of stopping training. However, scientists have found that retrained individuals often get fit faster than those who never trained before, suggesting their cells retain a record of previous sessions.

In studies using mice, researchers observed that skeletal muscle memory accelerates growth during retraining. Retrained muscles grew larger fibers and better matched energy production to demand without needing further exercise. This benefit persisted even when the animals ate a high-fat diet. Additionally, liver cells also store exercise memory by releasing higher levels of specific enzymes called carboxylesterases. These enzymes help deliver fat to muscle more efficiently for burning during growth.

These cellular records may even extend beyond an individual’s lifetime. Studies on mice showed that endurance exercise in parents protected their offspring from poor blood sugar levels and excess weight gain for a year after birth. While scientists are still exploring exactly how prenatal exercise influences children, this suggests lifestyle habits could provide fitness advantages across generations. Previously thought to be memoryless, many cell types now appear capable of retaining records of inflammation, obesity, and exercise.