A member of Thames Rowing Club, Arthur Long appeared in two Henley finals in 1922. He was in the coxless fours that won the Wyfold Challenge Cup, and also a member of the eights beaten in the final of the Grand Challenge Cup by Leander. The following year, however, he was on the winning crew that beat Pembroke College, Cambridge, to win the Grand. In 1924 he was also in the Thames eight that represented Great Britain at the Paris Olympics and, despite setting an Olympic best time in their first round heat, they missed out on a medal after finishing fourth, just half-a-length behind bronze medallists Italy. Long appeared in his third Grand final at Henley in 1925, when Thames were again beaten by Leander.