Sore feet: 1 Mark
Hot water bath: 2 Marks
Lactic acid is a normal byproduct during anaerobic respiration in muscles, but it can irritate muscles and cause discomfort and soreness. Adding warm water increases the blood circulation around the sore area. As a result oxygen supply to the muscle cells also increases. The increase in the supply of oxygen results in the complete breakdown lactic acid into carbon dioxide and water. 
Skin appears red after a hot water bath. The reason as we know is that, warm water increases the blood circulation in that particular area.