Heavyweight Shannon Briggs is staying in the hospital because of an injury to his left biceps from his weekend loss to Vitali Klitschko.
Briggs lost the WBC title fight by unanimous decision but did not go down despite being pounded by his Ukrainian opponent Saturday.
In a statement by Briggs and distributed by the hospital, the U.S. fighter said he incurred ''no severe head injuries.'' Briggs said it was his decision to keep fighting although his corner wanted to stop the one-sided bout.
''Hopefully I showed you the heart of a lion and the perseverance of a champion,'' Briggs said.
Briggs, who also has asthma, said he injured his arm in the first round and came to the hospital ''strictly as a precautionary measure.''
Briggs' manager, Greg Cohen, told RTL, the broadcaster of the bout, the fighter would have surgery on his arm. Briggs did not mention that in his statement and the hospital declined to answer questions on his condition, citing privacy laws. RTL also said Briggs had broken bones around both eyes.
Briggs remained standing after the bout, answered questions on live television, talked with Klitschko and left the hall on his own. Bild newspaper said the 38-year-old fighter collapsed while trying to give a urine sample for the post-fight doping test.
RTL said Klitschko visited Briggs in the hospital on Sunday.
German media have criticized British referee Ian John-Lewis and Briggs' corner for not stopping the fight. Cohen said he would have thrown in the towel but Briggs insisted on fighting.
''Unfortunately, the injury kept me from fully executing my fight plan. Not to take anything away from a brilliant performance by Vitali Klitschko Saturday night, had I had not injured my arm early on, who knows how the fight would have concluded,'' Briggs said.
Referee John-Lewis had gone to Briggs' corner late in the bout but made no move to stop it. He said he thought Briggs had enough left to keep fighting.
German media said Briggs took 302 blows to the head and the body, with 171 of them counting as clean hits.
''Despite prior reports, throughout the contest my trainer, Herman Caicedo, wanted to stop the fight, but I made it cleat that stopping was not an option,'' Briggs said.
