Standing just over 1.5 metres (5 feet) tall, Miyake was introduced to weightlifting while attending Hosei University, where Japanese weightlifters trained outdoors with little coaching or modern equipment. It was there that they perfected the distinctively Japanese “frog-leg” style (heels together, knees far apart) for the start of Olympic lifts. Miyake eventually became a lieutenant in Japan's National Self-Defense Force.

As a bantamweight (weight limit 56 kg 【123 pounds】), Miyake shot into fame when he executed a world-record snatch of 107.5 kg (237 pounds) at the 1958 Asian Games in Tokyo. Then at the 1960 Olympics in Rome he became the first Japanese weightlifter to win an Olympic medal, placing second to American Charles Vinci (Vinci, Charles T.). Moving up to featherweight (weight limit 60 kg 【132 pounds】) for the 1964 Olympics in Tokyo, Miyake earned his first gold medal, setting a world record in front of a home crowd. His three-lift (snatch, clean and jerk, and clean and press) total of 397.5 kg (876 pounds) was 15 kg (33 pounds) better than that of silver medalist Isaac Berger of the United States. Miyake defended his featherweight title in the 1968 Olympics in Mexico City, lifting a total of 392.5 kg (865 pounds). Among those he defeated was Miyake Yoshiyuki, his younger brother, who earned the bronze medal.

Miyake won six world titles (1962–63, 1965–66, 1969, and 1971) and set 25 world records. He retired in 1972 after finishing in fourth place in the Olympics in Munich, West Germany. He later coached Japan's national weightlifting team.