M.R. Orenstein and C.M. Friedenreich
To review systematically all publications of the effects of exercise on endogenous insulin-like growth factor (IGF) to clarify the nature of this association.
We reviewed 115 research studies in humans by subgroup of population (age; sex; athletic training status), physical activity exposure (resistance vs. aerobic activity; duration of activity) and study design.
Fifty percent of studies reviewed found no difference in total circulating IGF-1 as a result of exercise; 37% showed an increase, and 13% observed decreases in IGF-1 levels with exercise. Age influenced the effects of exercise on IGF levels. Exercise appeared to decrease IGF-1 levels in children, but to increase levels in young adults. Similar results were found for IGFBP-3.
It is not yet possible to determine if exercise affects IGF levels. Important methodologic differences among studies, as well as concerns about study quality, limit the ability to draw firm conclusions.
Fabiola E. Aparicio-Ting, Christine M. Friedenreich, Karen A. Kopciuk, Ronald C. Plotnikoff and Heather E. Bryant
Little is known about the intrapersonal and social factors associated with sufficient physical activity (PA) for cancer prevention, which is greater than for cardiovascular health.
1087 and 1684 randomly selected men and women, age 35–64, completed self-administered questionnaires on PA behavior and psycho-social characteristics. Using gender-stratified logistic regression, we investigated correlates of compliance with Canadian Society for Exercise Physiology PA guidelines for general health (150 min/wk), and the American Cancer Society (ACS; 225 min/wk) and World Cancer Research Fund/American Institute for Cancer Research (WCRF/AIRC; 420 min/wk) guidelines for cancer prevention.
Only 39% and 19% of men and women met ACS and WCRF/AICR guidelines, respectively. Self-efficacy, scheduling PA and friend social support were positively correlated with recommended PA for cancer prevention. In men, poor self-rated health and perceived negative outcomes were negatively correlated and hypertension was positively correlated with meeting cancer prevention guidelines. For women, not being married and having a companion for PA were positively correlated with meeting cancer prevention guidelines.
Few adults participate in sufficient PA for cancer risk reduction. Multidimensional public health strategies that incorporate intrapersonal and social factors and are tailored for each gender are needed to promote PA for cancer prevention.