WASHINGTON, Dec. 28 (Xinhua) -- U.S investigators have found that leisure-time physical activity was linked to a lower risk for seven cancers, with multiple cancer types having a "dose/response" relation.

The study published in this week's Journal of Clinical Oncology showed that certain amounts of activity (7.5 to 15 metabolic equivalent hours per week) was associated with a statistically significant lower risk of seven of the 15 cancer types, with the reduction increasing with more exercises.

A metabolic equivalent or MET is the ratio of the rate of energy expended during an activity to the rate of energy expended at rest. For example, if a person does a two MET activity for two hour, he or she has done four MET hour of physical activity.

Researchers from the U.S. National Cancer Institute, the American Cancer Society and Harvard University pooled data from nine prospective cohorts with self-reported leisure-time physical activity and follow-up for cancer incidence.

They found that physical activity was linked with a lower risk of colon cancer in men (8 percent for 7.5 MET hours/week; 14 percent for 15 MET hours/week), female breast cancer (6 percent-10 percent), endometrial cancer (10 percent-18 percent), kidney cancer (11 percent-17 percent), myeloma (14 percent-19 percent), liver cancer (18 percent-27 percent), and non-Hodgkin lymphoma (11 percent-18 percent in women).

The findings provided direct quantitative support for the levels of activity recommended for cancer prevention and actionable evidence for ongoing and future cancer prevention efforts, according to the researchers.