Exercise and Inflammation
Over the last two decades the role of inflammation in the progression toward disease has emerged as a primary focus of researchers and clinicians alike. While all body tissues seem to be at risk for the effects of inflammation, heart disease has been the primary focus of investigation. Today, inflammatory markers are routinely used as indicators of cardiovascular health. They act as indicators to show the amount of inflammation in the arteries and vascular system and are emerging as the best and most reliable test not only for determining whether or not a patient has suffered a cardiovascular episode such as heart attack or stroke, but also as an indicator of the level of health (or disease) in patients who have not yet suffered such an event. Chronic low grade inflammation is involved in all stages of the pathogenesis of atherosclerosis.(1) Circulating markers of inflammation, such as C-reactive protein (CRP), interleukin-6 (IL-6), and interleukin-8 (IL-8) have been identified as having independent roles in this development.(2) As a result, elevated levels of inflammatory markers may serve as potential indicators of the risk of cardiovascular disease.(3) Studies have also shown that there is an inverse association between levels of physical activity and inflammatory markers(4). However, not all forms of exercise exert this anti-inflammatory effect. In a landmark study, subjects were separated into two groups: one which underwent daily cardiovascular exercise (CE), and one group which underwent flexibility and strength training exercise. At the end of ten months the CE group had reduced serum IL-6, IL-8, and CRP levels, while the flexibility and strength training group did not show any any change in inflammatory markers.(5)
How CE acts to lower inflammation is not yet completely understood. The release of inflammation suppressing hormones and/or the suppression of pro-inflammatory hormones may be part of the story. But one mechanism by which CE exerts this effect seems clear: CE causes a reduction in adipose tissue. As discussed in Part I of this series, abdominal fat (adipose tissue) releases various pro-inflammatory substances, including IL-6 and IL-8.(6) In the above mentioned study, the CE group showed a reduction in adipose after 10 months, whereas the group performing flexibility and strength training did not.