Comment by lucideng

There seems to be some truth to 'walk it off'.

My theory is exercise, within certain limits of the injury, increases blood flow to the injury, allowing it to heal faster. If there is inflammation, that means restricted blood flow, so getting your heart to push more blood into those areas from physical activity makes sense to help recovery. No blood flow, no healing.

We can also only remove waste 3 ways. Urinating, defecating and sweating. Sweating is less 'efficient' from a waste removal perspective, but it does help regulate lactic acid and electrolytes. If you're riding the couch, you won't be activating this system. Increased blood flow from exercise throughout would also improve the other waste removal systems in your body, aiding recovery.