Training creates the signal; recovery — sleep, food and rest — is when muscles, tendons and the heart adapt.
Practical
Adequate sleep, enough total energy and protein, and gradual increases in training load are the best-supported recovery basics.
Myth check
Muscle soreness isn't a reliable measure of a good workout.
Evidence & sources
Adults should sleep 7 or more hours per night on a regular basis to promote optimal health. Evidence: strong. Known: Consensus statement based on systematic review. Unknown: Individual needs vary. Source: American Academy of Sleep Medicine & Sleep Research Society, Recommended Amount of Sleep for a Healthy Adult (2015).