The authors report the case of an unfit patient who, following intensive and prolonged physical exercise involving the abdominal muscles, presented a massive and diffuse subcutaneous edema (abdomen, scrotum, chest and face) together with abdominal and thoracic pain which increased in response to finger pressure. In addition, this was accompanied by a marked increase in CK, CK-MB and LDH, and TGO and TGP. Chest or heart pathologies were excluded by monitoring ECG and other clinical parameters, like heart rate and blood pressure, and by performing a chest X-ray. Muscular ultrasonography confirmed the massive subcutaneous edema and abdominal MR showed a slight edema in the suprasacral region, as well as confirming the subcutaneous edema. Hematological data gradually reduced and returned to normal after a week. Edema and pain also regressed gradually: the former finally disappeared after one week and the latter after five days. The authors conclude that clinical and laboratory findings were particularly severe because the subject was unfit and subcutaneous edema was larger than the free liquid in the abdominal cavity because the latter was absorbed by the peritoneum which acted as a dialysing membrane.