The following is an English translation of my old note made almost 30 years ago of an article in Zhongguo Qingnian Bao (China Youth Newspaper), March 22, 1981, issue#3689. The article is titled "Which sports have the highest exercise values?". It has no information on what methods they used to create this table and what medical science research was behind the numbers. But for what it's worth, it looks interesting, and seems to be consistent with our common sense.
The word "gymnastics" is actually "柔软体操" in Chinese, or "flexibility gymnastics" literally, and "walking" is "散步" or "slow walking", not vigorous walking as in modern day health advice. Needless to say, the sports in the table are to be treated as sports, not leisurely activities. For instance, swimming does not mean you immerse your body in the pool for a whole afternoon and swing your arms once every few minutes, and biking is not slowly cycling around a beautiful lake in a family outing. Have you heard of people say they gained weight by "swimming"? Now you know why.