Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA.
Center on Aging and Health, Johns Hopkins University, Baltimore, Maryland, USA.
J Gerontol A Biol Sci Med Sci. 2021 Sep 13;76(10):e281-e289. doi: 10.1093/gerona/glab127.
Physical activity becomes increasingly fragmented with age, which may be an early marker of functional decline. Energetic cost of walking and energy capacity are also linked with functional decline, but their associations with activity fragmentation, and the potential modifying roles of total daily physical activity and age, remains unclear.
A total of 493 participants (50-93 years) from the Baltimore Longitudinal Study of Aging underwent measures of energetic cost of usual-paced overground walking (mL/kg/m), energy demand during slow walking (mL/kg/min) on a treadmill (0.67 m/s, 0% grade), and average peak walking energy expenditure (mL/kg/min) during a fast-paced 400-m walk. A ratio of slow walking to peak walking energy expenditure ("cost-to-capacity ratio") was calculated. Activity fragmentation was quantified as an active-to-sedentary transition probability (ASTP) using Actiheart accelerometer data. Linear regression models with ASTP as the dependent variable were used to test whether poorer energy cost and capacity were associated with higher ASTP and whether the associations differed by daily physical activity or age.
After adjusting for demographics, body composition, comorbidities, and daily physical activity, every 10% higher cost-to-capacity ratio was associated with 0.4% greater ASTP (p = .005). This association was primarily driven by the least active participants (pinteraction = .023). Peak walking energy expenditure was only associated with ASTP among participants aged ≥70 years.
Higher cost-to-capacity ratio and lower energy capacity may manifest as more fragmented physical activity, especially among those less active or aged ≥70 years. Future studies should examine whether an increasing cost-to-capacity ratio or declining energy capacity predicts subsequent activity fragmentation.
随着年龄的增长，身体活动会变得越来越分散，这可能是功能下降的早期标志。步行的能量消耗和能量能力也与功能下降有关，但它们与活动碎片化的关联，以及总日常体力活动和年龄的潜在调节作用仍不清楚。
巴尔的摩纵向衰老研究中的 493 名参与者（50-93 岁）接受了常规地面行走能量消耗（mL/kg/m）、在跑步机上慢走时的能量需求（mL/kg/min，0.67 m/s，0%坡度）以及快速行走 400 米时的平均峰值行走能量消耗（mL/kg/min）的测量。计算了慢走与峰值行走能量消耗的比值（“成本-能力比”）。使用 Actiheart 加速度计数据，将活动碎片化量化为主动到静止的过渡概率（ASTP）。使用 ASTP 作为因变量的线性回归模型，用于检验较差的能量消耗和能力是否与较高的 ASTP 相关，以及这些关联是否因日常体力活动或年龄而异。
在校正了人口统计学、身体成分、合并症和日常体力活动后，成本-能力比每增加 10%，ASTP 增加 0.4%（p =.005）。这种关联主要是由最不活跃的参与者驱动的（p 交互 =.023）。在≥70 岁的参与者中，峰值行走能量消耗仅与 ASTP 相关。
较高的成本-能力比和较低的能量能力可能表现为更碎片化的身体活动，尤其是在那些不活跃或年龄≥70 岁的参与者中。未来的研究应检验成本-能力比的增加或能量能力的下降是否预示着随后的活动碎片化。
