Exercise and inflammatory markers in older adults

Introduction

Cholesterol screenings alone do not identify half of the individuals who go onto have myocardial infarctions (Rifai and Ridker 2001) corroborating the idea that models incorporating markers of inflammation, beyond the lipid profile, are better predictors of atherogenic events. The aging process has been associated with a rise in inflammatory activity (Pedersen et al. 2003), and some (Wannamethee et al. 2002) have suggested that physical activity is beneficial in atherosclerotic disease, at least in part, by reducing the inflammatory level.
The purpose of the present study was to investigate the effects of regular aerobic and strength-based physical activity programs on hs-CRP serum levels, upper and lower body strength, aerobic resistance, BMI, body weight and waist circumference of an elderly population. A follow-up period was also included in the study to assess the detraining effects.

Methods
Forty-five women and men (aged >64 years), with ambulatory capacity, volunteered for the study. Those that had undergone major surgery in the preceding 6 months were excluded from the study. We also excluded participants with hs-CRP values higher than 15 mg/L. Participants were randomly assigned to a control group (C, N = 13), to a strength-based training group (ST, N = 14), and to an aerobic-based training group (AT, N = 18). Body weight, waist circumference, BMI, and functional fitness were taken. Blood samples were collected in the morning, after 12 h fasting. Determination of CRP concentration was done by immunoturbidimetry, using a high-sensitivity CRP kit with a range of 0–10 mg/L and with a sensitivity of 0.12 mg/L (high-sensitivity CRP kit, Randox Laboratories Ltd, UK). ANOVA for repeated measures was performed. F and P values from the Pillai test were calculated for within participant’s comparisons. LSD tests were used for multiple comparisons. Statistical significance was set at P < 0.05.

Results
At the 32-weeks evaluation the AT group experienced a significant reduction of 51% on the hs-CRP, and the ST group a 39% reduction, although not statistically significant, when comparing to the baseline, while the C group only experienced a 13% reduction over the same period. Comparing the 16-weeks evaluation with the baseline, a decrease of 10% was observed in the AT group, 11% in the ST group and 2% in the C group. BMI did not change during the study in exercising groups, while body mass and waist circumference only decreased in AT group at 32-weeks. Lower and upper-body strength and aerobic endurance improved after the 16-weeks training period in both exercising groups. After the off training period (32-weeks), these participants still showed a tendency to retain some functional fitness gains, when compared to the baseline evaluation.

Discussion
The key findings are that both exercising programs promoted a chronic reduction of the hs-CRP concentration in older adults, more pronounced in the aerobic-based training than in the strength-based training program. The results seem to suggest that although some of the mechanisms underlying the changes in hs-CRP maybe dependent of adiposity changes, they are not the only ones at work here, physical fitness being an important arm of this equation. Although we did not find an association between hs-CRP concentration and the physical fitness parameters studied, the replacement of muscle mass with adipose tissue with age is probably one of the factors responsible for the increased production of TNF-α seen in chronic low-grade inflammation (Coppack 2001).
In summary, these results support a chronic training induced reduction on hs-CRP concentrations in older adults when both adiposity loss and strength gains are present. The key factors, more important than weight reduction, would be the increase in muscular mass, a reduction in body fat, and a reduction in chronic systemic inflammation.

References
Rifai N, Ridker PM (2001). Clin Chem 47:403-411.
Pedersen BK et al. (2003) J Muscle Res Cell Motil 24(2-3):113-9.
Wannamethee SG et al. (2002). Circulation 105:1785-1790.
Coppack SW (2001). Proc Nutr Soc. 60(3):349-56.