Hard physical effort causes microscopic damage to muscle fibres. That is normal, and it is the trigger for adaptation. Over the following hours and days the body clears damaged material, repairs the fibres and builds them back slightly stronger than before.
Recovery happens in overlapping stages: a short inflammatory phase that cleans up the area, a repair phase in which specialised cells fuse with damaged fibres, and a remodelling phase in which new protein is laid down. Muscle soreness usually peaks between 24 and 72 hours after unfamiliar exercise.
The signals that direct repair
Repair is coordinated by chemical messengers released from the damaged tissue, nearby blood vessels and the immune system. Many of these messengers are peptides, meaning short chains of amino acids. They tell cells when to move into the area, when to grow new blood vessels and when to start building new tissue.
Tendons and ligaments follow the same sequence but more slowly. They have a much lower blood supply than muscle, so nutrients and repair signals reach them less easily.
Where amino acids come in
- They are the building material. Muscle protein is built from amino acids. Nine of them are essential, which means they have to come from food.
- They switch the process on. Certain amino acids, leucine in particular, act as a signal that tells muscle cells to begin building new protein.
- They form connective tissue. Collagen, the main protein in tendons and ligaments, is especially rich in glycine and proline.
- Timing and total both count. Active people generally need more protein than sedentary people, commonly cited at about 1.2 to 2.0 grams per kilogram of body weight per day, spread across meals.
What influences recovery day to day
- Sleep, which is when much of the body's repair activity takes place
- Enough total energy and protein
- Sensible training load with rest between hard sessions
- Hydration
- Age and training history
This article is for general educational purposes only and is not medical advice.
Frequently asked questions
What happens to muscle after exercise?
Fibres sustain microscopic damage, the body clears and repairs it, and new protein is added. Repeated over time, this is how muscle adapts.
Why do muscles feel sore a day or two later?
Delayed soreness reflects the inflammation and repair process after unfamiliar or intense effort. It normally peaks within 24 to 72 hours and then fades.
How do amino acids support recovery?
They are the raw material for new muscle and connective tissue, and some of them also act as signals that start the rebuilding process.
Why do tendons and ligaments take longer to recover than muscle?
They have a much poorer blood supply, so the delivery of nutrients and repair signals is slower.
How much does sleep matter?
A great deal. Much of the body's repair and rebuilding activity happens during deep sleep, so short or poor sleep slows recovery.
Is this medical advice?
No. This article is general educational information. Speak to a qualified healthcare professional about injuries or personal health decisions.