Markers of chronic inflammation with short-term changes in physical activity.

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-α 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-α 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.

Confusion and conflict in assessing the physical activity status of middle-aged men.

BACKGROUND: Physical activity (including exercise) is prescribed for health and there are various recommendations that can be used to gauge physical activity status. The objective of the current study was to determine whether twelve commonly-used physical activity recommendations similarly classified middle-aged men as sufficiently active for general health. METHODS AND FINDINGS: We examined the commonality in the classification of physical activity status between twelve variations of physical activity recommendations for general health in ninety men aged 45-64 years. Physical activity was assessed using synchronised accelerometry and heart rate. Using different guidelines but the same raw data, the proportion of men defined as active ranged from to 11% to 98% for individual recommendations (median 73%, IQR 30% to 87%). There was very poor absolute agreement between the recommendations, with an intraclass correlation coefficient (A,1) of 0.24 (95% CI, 0.15 to 0.34). Only 8% of men met all 12 recommendations and would therefore be unanimously classified as active and only one man failed to meet every recommendation and would therefore be unanimously classified as not sufficiently active. The wide variability in physical activity classification was explained by ostensibly subtle differences between the 12 recommendations for thresholds related to activity volume (time or energy), distribution (e.g., number of days of the week), moderate intensity cut-point (e.g., 3 vs. 4 metabolic equivalents or METs), and duration (including bout length). CONCLUSIONS: Physical activity status varies enormously depending on the physical activity recommendation that is applied and even ostensibly small differences have a major impact. Approximately nine out of every ten men in the present study could be variably described as either active or not sufficiently active. Either the effective dose or prescription that underlies each physical activity recommendation is different or each recommendation is seeking the same prescriptive outcome but with variable success.