Effects of Different Doses of Physical Activity on C-Reactive Protein among Women

Abstract

Elevated C-reactive protein (CRP) is associated with an increased risk of cardiovascular disease. Physical activity has been inversely associated with CRP. However, the clinical trials examining the effect of exercise training have produced conflicting results.Purpose-The purpose of this study was to examine the influence an exercise training program on CRP in postmenopausal women.Methods-Sedentary, overweight/obese, postmenopausal women with elevated systolic blood pressure (120.0 to 159.9 mm Hg) (N= 464) were randomized into 1 of 4 groups: a non-exercise control or 1 of 3 aerobic exercise groups; exercise energy expenditure of 4, 8, or 12 kcal/kg/week (KKW), for 6 months at a training intensity of 50% of peak VO 2 .Results-Complete data was available of 421 participants and mean baseline CRP was 5.7 (5.5) mg/L with no significant differences across groups. While VO 2 increased in a dose response manner, there were no significant changes in CRP in any of the exercise intervention groups compared to the control group. Change in fitness was not associated with change in CRP, whereas change in weight was significantly associated with change in CRP.Conclusion-Despite increasing fitness, six months of aerobic exercise training did not improve CRP. However, improvements in CRP were associated with reductions in weight.

Inflammatory Marker Changes in a Yearlong Randomized Exercise Intervention Trial among Postmenopausal Women

“…In the ALPHA Trial exercisers lost, on average, 2.3 kg of body weight and 2.4 kg and 2.0% of body fat (31). In the second RCT, a significant intervention effect on CRP levels was found only in the subgroup who lost more than 2.0% body fat (25), whereas in the DREW Trial, the mean change in CRP, adjusted for baseline CRP and intervention group, was significantly more in women who lost the most weight (>2.6 kg) during the trial than the other subgroups (27). In the fourth RCT of postmenopausal women, in which CRP decreased independently of weight loss (suggesting the involvement of a fatindependent mechanism), an average of only 1.3 kg of body fat was lost in the exercise group (26).…”

“…Two other RCTs in postmenopausal women (25,27) also revealed adiposity-related CRP changes, whereas another comparable RCT showed CRP decreases that were unrelated to weight loss (26). Conflicting reports may be due to the extent of fat loss in these trials.…”

“…Weaker evidence suggested that effects on IL-6 were stronger in women with higher baseline BMI and that TNF-a levels may also be moderated by baseline BMI. To our knowledge, 5 comparable RCTs have described the isolated effect of long-term exercise on circulating CRP, IL-6, or TNF-a levels exclusively in cancer-free postmenopausal women (22)(23)(24)(25)(26)(27). These 5 studies were 6 (22, 27) or 12 months (23)(24)(25)(26) in duration involving mainly aerobic exercise.…”

“…Our secondary analysis of exercise adherence similarly implied that higher exercise dose may be more effective for decreasing circulating CRP levels, with the greatest decreases occurring in women who exercised at least 150 minutes per week. A comparable RCT in postmenopausal women also showed a dose-response relation between exercise duration and CRP changes (25) but the Dose Response to Exercise in Women (DREW) Trial, which was an RCT designed specifically to test the effect of exercise dose on physiologic outcomes, did not show a doseresponse trend with CRP changes in 421 postmenopausal women (27). Women prescribed the highest level of exercise in the DREW Trial exercised, on average, 192 minutes (3.1 sessions) per week with an intensity goal of only 50% VO 2max .…”

“…In developing a disease prevention strategy, however, it is important to understand in whom exercise is most beneficial, at what dose, and the underlying biologic mechanisms involved. Very few randomized controlled trials (RCT) of exercise, independent of any dietary intervention, have studied these questions exclusively in postmenopausal women (22)(23)(24)(25)(26)(27), and findings were conflicting. Postmenopausal women represent a population subgroup that may respond differently to exercise given that female sex and older age have been associated with higher CRP levels (28) that may be partly related to a general increase in intraabdominal adiposity that occurs after menopause (29).…”