The 31 year-old, making the first defence of the belt he took from Daniel Geale, appeared to suffer an injury early in the fight and Sturm took full advantage to claim a fourth world championship.
Barker was put on the canvas twice before trainer Tony Sims halted the contest from the corner in just the second round, with the Londoner downhearted and distraught at losing the status that meant so much to him.
The defeat now puts serious doubt on whether the Matchroom-promoted boxer can come back from another injury setback and Barker may now have to think long and hard about whether the ailment could worsen if he carries on with his career.
For crowd-favourite Sturm, the triumph means yet another world title to add to his collection at 34, as the talented German moves his record to 39-3-2 with his second knockout win of the year.
On the undercard, Susi ‘Killer Queen’ Kentikian successfully defended her Women’s WBA flyweight title with a comprehensive points win against Simona Galassi over ten two minute rounds.
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