Middelkamp was the first Dutchman to win a stage in the Tour de France. When he came to the Tour, he had never even seen mountains, coming from the very flat parts of the Netherlands. However, in his first Tour, on July 14, 1936, he won the difficult mountain stage from Aix-les-Bains to Grenoble, which went over the Col du Galibier. That year, he finished 23rd overall. In 1937 he had to quit the Tour because of a fall, in which he broke a finger.