During training, we cause stress and microscopic damage on a cellular level in our bodies, fatiguing us and actually decreasing our performance for a short period. This stress and damage acts as a catalyst for change, forcing us to adapt. As we recover, we improve, which means we’re able to perform at a higher level next time we work out.
That means gains are made during recovery, not training.
Every time you work out, you inflict microscopic damage on your muscles, which is then repaired naturally by your body with a tiny new layer of muscle tissue. As these layers are formed, you build visible muscle. You don’t need to have muscle soreness every time you work out in order to see progress. In fact, it’s not advisable to push yourself to the point where you’re sore after every workout. In general, if you’re sore for 2-4 days, you’re in the safe zone. If you’re experiencing DOMS for more than 4 days, you may have gone too hard.