The young Nabokov was an amateur gymnast and athlete. At age 27 he waded into a distressing OJ-type situation of the time:

… a scandal had broken in Berlin around a Rumanian violinist named Kosta Spiresco, whose wife was found hanged, covered with the marks of a severe beating. Though Spiresco’s regular assaults were the cause of her suicide, he escaped punishment. German newspapers commented that no decent restaurant would hire him after this, but a Russian restaurant defied the prediction and a number of blowsy women began to buzz around the restaurant’s new violinist in perverted admiration. … Nabokov, an individualist in his notion of justice as in everything else, would always dismiss the concept of collective guilt but insist fiercely on collective accountability … he and his friend Mikhail Kaminka visited the restaurant with their wives, and drew straws to be first to hit the “hirsute, ape-like” Spiresco (Nabokov’s description). Nabokov won, slapped him on the cheek, and then, according to the newspaper report, “graphically demonstrated upon him the techniques of English boxing.” Kaminka pitched in against the rest of the orchestra, who took Spiresco’s side. At the police station where the three principals were taken, Spiresco refused to take charges, hinting instead that he would call them out to a duel. He declined however to take the addresses they proffered, and Nabokov and Kaminka waited at home in vain the next two or three days for Spiresco’s promised seconds.

The sources are the contemporary Russian emigre paper Rul’ and notes given by Nabokov to Andrew Field in 1973.

From Brian Boyd’s Vladimir Nabokov: The Russian Years