Exercise and the lymphatic system: implications for breast-cancer survivors.

This article summarises the current research on the lymphatic system related to exercise and critically evaluates the implications for exercise performance by breast-cancer survivors. The primary role of the lymphatic system during exercise is to assist in the regulation of tissue volume and pressure by carrying fluid and plasma proteins that have leaked into the interstitial space from tissues back to the cardiovascular system. During steady-state exercise in humans, lymph flow has been shown to increase to levels approximately 2- to 3-fold higher than at rest. Although the lymphatic system does not typically limit exercise performance in the normal population, the function of this system can be impaired in 27-49% of women who have survived breast cancer. Breast cancer-related lymphoedema (BCRL) is a chronic swelling that can occur in the ipsilateral hand or arm of women treated for breast cancer and results in a number of physical and psychological sequelae. Exercise was once believed to be a factor in the development of BCRL as it was thought that the damage to the axillary lymphatics from breast-cancer treatment resulted in a primary obstruction to lymph flow. However, the exact aetiology and pathophysiology of BCRL appears to be multi-factorial and not as simple as a 'stop-cock' effect. Furthermore, recent studies have shown that participating in vigorous, upper-body exercise is not related to an increase in arm volume, which would indicate the development of BCRL. It is still not known, though, how long-term exercise affects lymphatic system function in breast-cancer survivors with and without BCRL.