CHAPTER 102 • CANCER AND THE ATHLETE 601evidence suggests higher intensities confer a
greater level of protection (Friedenreich and
Orenstein, 2002).- Many risk factors are similar for both breast and
endometrial cancer. Decreased risk of endometrial
cancer most likely stems from the same estrogen
decreasing effects of exercise on estrogen. - Prostate cancer
- The evidence for an association between physical
activity and prostate cancer is less convincing than
for breast and colon cancer and is classified as prob-
able. Fifteen or 30 studies have found a reduction in
physically active men regarding prostate cancer. It
may be that activity done at an early age may be
more protective than exercise later in life, but most
studies have been performed on older men
(Friedenreich and Orenstein, 2002).
•Lower levels of free testosterone occur with exer-
cise-induced increases in sex-hormone binding
globulin. - One way physical activity may prevent cancer is
through weight control. There are several biological
mechanisms associated with excess weight, particu-
larly abdominal adiposity that could contribute to
cancer. Reduced weight and increased physical activ-
ity are associated, but each appears to confer an inde-
pendent benefit in cancer reduction (Friedenreich and
Orenstein, 2002). - Moderate to vigorous activity should be performed
at least 45 min most days of the week to achieve
maximum preventive effect for colon and breast
cancer. According to the American College of
Surgeons (ACS) guidelines, moderate activities are
defined as a brisk walk. Vigorous activities are
those that use larger muscle groups, cause sweat-
ing, and increase pulse and respirations (Byers
et al, 2002).
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