Generally it’s the time it takes for you to get back to physiological baseline. If you do a lot of activity, the amount of exertion can be measured in EPOC - h

Generally it’s the time it takes for you to get back to physiological baseline. If you do a lot of activity, the amount of exertion can be measured in EPOC - how much extra oxygen your body needs for the extra metabolism to support repair (this is when any gains happen, growth, endurance, efficiency). When that’s back to baseline your body has done repairing, you’ve “recovered”. If you aren’t recovered, your body still hasn’t repaired the damage you’ve done to it in the previous round, and you probably won’t be able to repeat the effort, whichever discipline. You’re digging yourself deeper in a hole. If you keep doing this, that’s overtraining, and you can get worse. If you never experienced this, congratulations, you were operating inside your body’s natural limits! You may have good genes, and having good sleep and nutrition is probably more important than supplements.