Abstract：
Using a novel approach, this exploratory study investigated whether the physical activity (PA) paradox extends to cardiovascular load and musculoskeletal pain. At baseline, 1-2 days of 24 h heart rate was assessed in 72 workers from construction and healthcare. Workers then reported pain intensity in 9 body regions (scale 0-3) every 6 months for two years. The 2 year average of musculoskeletal pain (sum of 9 pain scores; scale 0-27) was regressed on time spent during work and leisure above three thresholds of percentage heart rate reserve (%HRR), i.e., ≥20 %HRR, ≥30 %HRR, and ≥40 %HRR, using a novel ilr structure in compositional data analysis. Analyses were stratified for several important variables. Workers spending more time in physical activity at work had higher pain, while workers with more time in physical activity during leisure had less pain (i.e., the PA paradox), but none of the associations were statistically significant. Higher aerobic capacity and lower body mass index lowered the pain score among those with higher physical activity at work. This exploratory study suggests that the PA paradox may apply to musculoskeletal pain and future studies with larger sample sizes and additional exposure analyses are needed to explain why this occurs.
摘要：
使用一种新颖的方法，这项探索性研究调查了体力活动(PA)悖论是否延伸到心血管负荷和肌肉骨骼疼痛.在基线,在来自建筑和医疗保健的72名工人中评估了1-2天的24小时心率。然后，工作人员在两年内每6个月报告9个身体区域的疼痛强度（0-3级）。肌肉骨骼疼痛的2年平均值（9个疼痛评分的总和；量表0-27）在工作和休闲期间花费的时间超过心率储备百分比（％HRR）的三个阈值，即，≥20%HRR,≥30%HRR,且HRR≥40%，在成分数据分析中使用新的ILR结构。对几个重要变量进行了分层分析。在工作中花费更多时间进行体育锻炼的工人疼痛更高，而休闲期间体力活动时间较多的工人疼痛较少(即，PA悖论)，但这些关联均无统计学意义.较高的有氧能力和较低的体重指数降低了工作中体力活动较高的人的疼痛评分。这项探索性研究表明，PA悖论可能适用于肌肉骨骼疼痛，未来的研究需要更大的样本量和额外的暴露分析来解释为什么会发生这种情况。
