Posture

Most posture problems aren't one weak muscle — they're a pattern. The body adapts to whatever position it holds most often, and repeated thousands of times a day for years, that position reshapes which muscles get short and strong-in-that-shortened-range (tight) and which get long and switched off (weak). Stretching the tight side on its own rarely sticks, because the tightness is usually protecting a joint the weak side isn't controlling — the fix is retraining the whole movement pattern, not just the sore spot.