At the 1960 Olympics he swam the fastest leg in the 4×200 m relay, yet hist team lost to the United State. Yamanaka studied in college at the University of Southern California, where he broke the 200 m world record three times within two months in 1961. He set two more records over 200 m earlier in 1958-1959, but unfortunately for him this distance was not an Olympic event in those years.
Yamanaka also set a world record over 400 m in 1959 and three world records in the 4×200 m relay in 1959 and 1963.
Yamanaka graduated from Waseda University and later headed the Itoman Swimming School in Osaka. In 1983 he was inducted into the International Swimming Hall of Fame.
In 1995, he unsuccessfully ran for the House of Councillors. Yamanaka"s coach used pebbles to communicate with him during the training sessions – whenever Yamanaka would relax the coach would throw a pebble in his back.
After the training Yamanaka had to collect the pebbles from the pool bottom.