How long does it take for muscles to recover after one year of not training?

Generally speaking, after a year without training, muscle can be restored within two months. The detailed explanation is as follows:

After stopping exercise for a period of time, muscles can relatively quickly recover when resuming moderate physical training. This is due to the muscle's inherent "muscle memory" effect and adaptability. The muscle memory effect refers to the ability of muscles to more rapidly recall and adapt to previous exercise patterns and intensities when training resumes. This occurs because ceasing exercise does not mean muscles have completely lost their strength or adaptive capacity; instead, they retain certain neural structures and cell nuclei, which help restore strength and size more quickly once training restarts. Additionally, muscle adaptability enables it to respond faster to stimuli during resumed training. Through various physiological responses—such as protein synthesis, neural adaptation, and improved blood supply—muscles enhance their responsiveness to stimulation. These adaptive processes can occur in a relatively short time, thereby promoting rapid muscle recovery and growth. Therefore, even after a year of inactivity, muscle mass and strength may largely be regained within two months of retraining.

If you plan to resume exercising, it is recommended to gradually increase training intensity and frequency, while ensuring proper nutritional intake, to support effective muscle recovery and adaptation.