Soreness after swimming can be caused by muscle strain, lactic acid accumulation, cold and calcium deficiency. 1. Muscle strain: Soreness after swimming may be caused by insufficient preparatory activities before swimming and long swimming time, which may result in muscle strain and cause soreness. 2. Lactic acid accumulation: due to the usual exercise is not much, or a sudden large amount of swimming activities, resulting in muscle metabolism produced a large amount of lactic acid, metabolic products can not be completely discharged, lactic acid accumulation, body aches and pains, the symptoms can be reduced through rest. 3. Cold: when swimming after the sweat, wind and cold, can cause muscle spasms, soreness, keep warm after the symptoms can be reduced. 4:Calcium deficiency: When calcium deficiency occurs, it is easy to increase muscle excitability, muscle spasm, muscle pain, and some will have cramps. If the soreness after swimming is not alleviated after resting, you need to go to the hospital for examination to identify the specific causes for treatment.