Background The usual accelerometry-based measures of physical activity (PA) are dependent on physical performance. We investigated the associations between PA relative to walking performance and the prevalence and incidence of early and advanced walking difficulties compared to generally used measures of PA. Methods Perceived walking difficulty was evaluated in 994 community-dwelling participants at baseline (age 75, 80, or 85 years) and 2 years later over 2 km (early difficulty) and 500 m (advanced difficulty). We used a thigh-mounted accelerometer to assess moderate-to-vigorous PA, daily mean acceleration, and relative PA as movement beyond the intensity of preferred walking speed in a 6-minute walking test (PArel). Self-reported PA was assessed using questionnaires. Results The prevalence and incidence were 36.2% and 18.9% for early and 22.4% and 14.9% for advanced walking difficulty, respectively. PArel was lower in participants with prevalent (mean 42 [SD 45] vs 69 [91] min/week, p < .001) but not incident early walking difficulty (53 [75] vs 72 [96] min/week, p = .15) compared to those without difficulty. The associations between absolute measures of PA and incident walking difficulty were attenuated when adjusted for preferred walking speed. Conclusions The variation in habitual PA may not explain the differences in the development of new walking difficulty. Differences in physical performance explain a meaningful part of the association of PA with incident walking difficulty. Scaling of accelerometry to preferred walking speed demonstrated independence on physical performance and warrants future study as a promising indicator of PA in observational studies among older adults.

中文翻译：

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作为老年人步行困难的预测指标的体育活动与首选步行速度相比：2 年随访

背景 通常基于加速度计的身体活动 (PA) 测量取决于身体表现。与常用的 PA 测量相比，我们调查了 PA 与步行性能之间的关联，以及早期和晚期行走困难的患病率和发生率。方法 在基线（年龄 75、80 或 85 岁）和 2 年后超过 2 公里（早期困难）和 500 米（高级困难）时，对 994 名社区居民参与者的感知步行困难进行了评估。在 6 分钟步行测试 (PArel) 中，我们使用安装在大腿上的加速度计来评估中度到剧烈的 PA、每日平均加速度和相对 PA，作为超过首选步行速度强度的运动。使用问卷评估自我报告的 PA。结果早期和22岁的患病率和发病率分别为36.2%和18.9%。高级步行困难分别为 4% 和 14.9%。PArel 在普遍存在的参与者中较低（平均 42 [SD 45] vs 69 [91] 分钟/周，p < .001）但未发生早期行走困难（53 [75] vs 72 [96] 分钟/周，p = .15) 与没有困难的人相比。当调整首选步行速度时，PA 的绝对测量值与事件步行困难之间的关联减弱。结论 习惯性 PA 的变化可能无法解释新的行走困难发展的差异。身体表现的差异解释了 PA 与意外行走困难的关联的一个有意义的部分。