The guy had relatively high but round calves from the start, having 16-17 inch calves at age 17 is by no means weak. Ali had similiar calf shape, not very thick but have roundness and depth. Some people have good shape and size with relatively short muscle bellies, Albert Beckles for biceps, Boyer Coe has good triceps but lacking one topic head relatively. So Arnold had a unique potential in his calves.