PURPOSE: Regular exercise is inversely related to markers of chronic inflammation, but we do not know to what extent these changes are the product of recent exercise behavior. The aim of the present investigation was to examine the stability of markers of chronic inflammation in the face of short-term positive and negative changes in physical activity in middle-aged men. METHODS: Two studies were conducted using a randomized counterbalanced design. In the first study (Study 1), eight highly active men (age = 56 +/- 5 yr, body mass index (BMI) = 23.3 +/- 3.2 kg.m(-2), VO(2max) = 50.7 +/- 7.0 mL.kg(-1).min(-1)) undertook two trials; withdrawal of exercise for 1 wk versus control (normal exercise behavior). In the second study (Study 2), 10 sedentary men (age = 57 +/- 2 yr, BMI = 27.9 +/- 3.6 kg.m(-2), VO(2max) = 30.4 +/- 4.6 mL.kg(-1).min(-1)) undertook 30 min of daily walking at 60% VO(2max) for 1 wk versus control (normal sedentary behavior). RESULTS: The withdrawal of exercise for 1 wk in highly active men (Study 1) and the imposition of 1 wk of daily exercise in sedentary men (Study 2) did not elicit any substantial changes in the inflammatory proteins C-reactive protein (CRP), IL-6, and TNF-alpha and circulating leukocyte concentration. The differences in inflammatory proteins between active (Study 1) and sedentary (Study 2) men were marked; for example, baseline CRP was 0.85 +/- 0.79 and 3.02 +/- 2.30 mg.L(-1), respectively. CONCLUSIONS: The inflammatory markers CRP, IL-6, and TNF-alpha are stable and not affected by large short-term positive or negative alterations in exercise behavior. This stability strengthens the use of these markers in clinical and research settings because differences and changes are not simply the product of recent exercise behavior.
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