Exercise Inflammation and Cardiovascular Health
The effect of exercise on levels of atherosclerotic inflammatory markers – Iain Mactier
Atherosclerotic inflammatory markers are used as indicators of cardiovascular health, they act as indicators to show the amount of inflammation in the arteries and vascular system. Chronic low grade inflammation is involved in all stages of the pathogenesis of atherosclerosis (Markovitch et al 2008, Plaisance et al 2007). Circulating markers of inflammation, such as C-reactive protein (CRP) and interleukin-6 (IL-6) have been identified as having independent roles in this development (Olson et al 2007). As a result, elevated levels of inflammatory markers may serve as potential indicators of the risk of cardiovascular disease (Hammett et al 2006, Plaisance et al 2007). There is an inverse association between levels of physical activity and inflammatory markers (Hammett et al 2006, Kohut et al 2006, Markovitch et al 2008, Plaisance et al 2007) although the mechanisms through which exercise may cause a decrease in these markers is unclear (Kohut et al 2006).
After a single bout of high-intensity, long duration exercise, inflammatory markers have been shown to be elevated (Markovitch et al 2008, Olson et al 2007, Plaisance et al 2007) although this is likely to represent acute tissue damage (Plaisance et al 2007). It has been theorised that this transient increase in inflammatory markers may lead to subsequent up-regulation of anti-inflammatory pathways, such as interleukin-10 (IL-10) (Markovitch et al 2008). Plaisance et al (2007) studied the effect of a single exercise session on 21 men ascertained to be either moderately or highly fit through VO2max testing. Subjects were required to run at an intensity of 70% VO2 max to elicit an energy expenditure of 500kcal. No significant change in the levels any serum inflammatory markers was detected. There is the potential that a less fit population may experience greater tissue damage and thus express higher concentrations of inflammatory markers immediately after exercise (Plaisance et al 2007). Markovitch et al (2008) studied this by investigating the effect of one sole exercise trial upon 12 sedentary men. Subjects walked on a treadmill, set at 3% incline, at an intensity of 50% VO2 max for 30 minutes. Following this exercise trial, there was no detectable change in the concentration of serum IL-6, IL-10, or CRP.
The mechanisms through which exercise may lower inflammatory markers could be due to changes that accumulate over weeks and months (Markovitch et al 2008). Kohut et al (2006) evaluated 87 older adults who were assigned to either a CARDIO or FLEX group for 10 months. The cardiovascular exercise (CARDIO) group had reduced serum IL-6, IL-8, and CRP levels post intervention (p=0.02). The flexibility and resistance exercises (FLEX) did not have any effect on inflammatory markers. Adipose tissue is thought to be one source of circulating IL-6 and IL-8 (Kohut et al 2006, Olson et al 2007). The lower levels of inflammatory markers in the CARDIO group may be due to the greater effect of aerobic exercise in reducing levels of body fat (Hammett et al 2006). Statistical analysis revealed a trend towards lower BMI in the CARDIO group post-intervention though this was deemed not significant (p=0.1). Individuals who are obese often demonstrate elevated levels of inflammatory markers (Olson et al 2007). This is supported by fact that waist circumference has been shown to be positively associated with baseline levels of CRP (p<0.05) (Plaisance et al 2007). Olson al (2007) studied 32 overweight women for 12 months, assigning one half to a resistance training program and the other to a control group. Those in the exercise group had to complete at least two training sessions per week for the duration of the study. A significant improvement of 5.2% in post intervention lean body mass was observed in the exercise group (p=0.05). Levels of CRP in this group were significantly reduced (p=<0.01). Even relatively small changes in body composition may be enough to decrease inflammatory markers (Olson et al 2007). Hammett et al (2006) sought to isolate the effects of long term, regular exercise by adjusting their results for BMI. In this study, 152 females were assigned to either 12 weeks of exercise training or health education as a control. Fitness and circulating inflammatory levels were measured at baseline, 6 and 12 weeks. Subjects participated in three 45 minute exercise sessions, keeping their heart rate at 60-70% their maximum heart rate. Despite a significant improvement in fitness in the intervention group (p=<0.001), exercise training did not produce a decrease in inflammatory marker levels once results were adjusted for BMI through multivariate analysis.
To elicit a change in inflammatory marker levels through a single bout of exercise, it seems an intensity or duration threshold must be achieved. The longer term effect of exercise on markers of inflammation may be due to the anti-inflammatory changes induced by the last bout of activity but it seems more plausible that long term, regular exercise, may lower inflammatory markers through its effect on body and visceral fat.
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- Kohut ML. McCann DA. Russell DW. Konopka DN. Cunnick JE. Franke WD. Castillo MC. Reighard AE. Vanderah E. (2006) Aerobic exercise, but not flexibility/resistance exercise, reduces serum IL-18, CRP, and IL-6 independent of beta-blockers, BMI, and psychosocial factors in older adults. Brain, Behavior, & Immunity. 20(3):201-209
- Markovitch D. Tyrrell RM. Thompson D. (2008) Acute moderate-intensity exercise in middle-aged men has neither an anti- nor proinflammatory effect. Journal of Applied Physiology. 105\(1):260-5
- Olson TP. Dengel DR. Leon AS. Schmitz KH. (2007) Changes in inflammatory biomarkers following one-year of moderate resistance training in overweight women. International Journal of Obesity. 31(6):996-1003
- Plaisance EP. Taylor JK. Alhassan S. Abebe A. Mestek ML. Grandjean PW. (2007) Cardiovascular fitness and vascular inflammatory markers after acute aerobic exercise. International Journal of Sport Nutrition & Exercise Metabolism. 17(2):152-162