Researchers followed 2,560 men from eastern Finland with no history of cancer and asked them how often they exercised.
The men, aged between 42 and 61, filled in questionnaires and undertook physical tests to measure the intensity of their exercise.
They were followed for an average of almost 17 years and were aged 53 on average at the start of the follow-up.
The intensity of exercise was measured in metabolic units (MET or metabolic equivalents of oxygen consumption).
Walking was measured as having an average intensity of 4.2 MET, jogging 10.1 MET, swimming 5.4 MET, gardening 4.3 MET and cycling to work 5.1 MET.
Skiing was 9.6 MET, rowing 5.4 MET, ball games 6.7 MET and gymnastics, dancing or weight-lifting 5 MET.
The study, published in the British Journal of Sports Medicine, found that men who did an average of 5.2 MET activity for at least 30 minutes a day had around half the risk of cancer death of those who exercised less.
This was also true after adjusting for factors likely to influence the results, including age, smoking, body mass index and calorie intake.
The average duration of physical activity was 462 minutes per week, or almost eight hours. However, the study found people must exercise for at least 30 minutes a day.
The authors, from Kuopio and Oulu universities in Finland, said high intensity exercise was best for lowering the risk of getting cancer and dying from it, particularly lung and gastrointestinal cancers.
The study said: "The intensity of leisure time physical activity had a strong and independent association with cancer mortality.
"Men with a mean (average) intensity of leisure time physical activity of over 5.2 MET had a greatly reduced risk of cancer death." It added: "The intensity of physical activity should be at least moderate so that beneficial effect of physical activity for reducing overall cancer mortality can be achieved."
Research paper details:
Laukkanen JA, Rauramaa R, Makikallio TH, et al. Intensity of leisure-time physical activity and cancer mortality in men. Br J Sports Med. Published Online First: 28 July 2009.