This is not normal post-workout soreness. Dark, tea-coloured urine after a hard session is a hallmark sign of rhabdomyolysis, a condition where overworked muscle fibres break down and release toxic proteins into the bloodstream. A 2024 systematic review in Apunts Sports Medicine identified this across 63 cases linked to high-intensity training. Left untreated, it can cause kidney failure. Your Urine Has Turned Dark Brown