Karl won in 1933 his first German championship with the aft of the Würzburg Rowing Club of 1875. A year later Rudolf Eckstein, Anton Rome, Martin Karl and Wilhelm Menne changed in the coxless four and victorious after winning the German Championship also at the European Championships in Lucerne. Missing in 1935 Charles Martin, for him sat Ernst Gaber from Mannheim RV in the same boat. 1936 returned to Karl Martin and Eckstein, Rome, Karl and Menne won at the Olympic Games in Berlin in 1936 before the British boat.
Martin Karl died in the Second World War on the Eastern Front as a lieutenant. He was leader of the Machine Gun Company of Infantry Regiment 42 of the 46th Infantry Division of the Wehrmacht.