Vallecillo-Bustos Anabelle, Compton Abby T, Swafford Sydney H, Renna Megan E, Thorsen Tanner, Stavres Jon, Graybeal Austin J
School of Kinesiology and Nutrition, University of Southern Mississippi, Hattiesburg, MS, USA.
School of Psychology, University of Southern Mississippi, Hattiesburg, MS, USA.
J Electr Bioimpedance. 2024 Aug 5;15(1):89-98. doi: 10.2478/joeb-2024-0010. eCollection 2024 Jan.
Advances in wearable technologies now allow modern smartwatches to collect body composition estimates through bioelectrical impedance techniques embedded within their design. However, this technique is susceptible to increased measurement error when postural changes alter body fluid distribution. The purpose of this study was to evaluate the effects of postural orientation on body composition and total body water (TBW) estimates produced by smartwatch bioelectrical impedance analysis (SWBIA) and determine its agreement with criterion measures. For this cross-sectional evaluation, 117 (age: 21.4±3.0 y; BMI: 25.3±5.7 kg/m) participants (F:69, M:48) completed SWBIA measurements while in the seated, standing, and supine positions, then underwent criterion dual-energy X-ray absorptiometry (DXA) and bioelectrical impedance spectroscopy (BIS) assessments. In the combined sample and females, body fat percent, fat mass, and fat-free mass using SWBIA were significantly different between the supine and standing positions (all p<0.001), though group level agreement with DXA was similar across positions. Supine SWBIA TBW estimates were significantly different between seated and standing estimates (all p≤0.026), but further analyses revealed that this was driven by the supine and seated differences observed in females (p=0.003). SWBIA TBW demonstrated similar group and individual level agreement with BIS across body positions with slight improvements observed during seated and supine assessments for females and males, respectively. SWBIA may demonstrate slight intra- and inter-device differences in body composition and TBW when measured across postural orientations, though further evaluations in external/clinical samples are necessary. While sex/position-specific guidelines may improve precision, these findings highlight the importance of standardized body positioning when using SWBIA.
可穿戴技术的进步使得现代智能手表能够通过其设计中嵌入的生物电阻抗技术来收集身体成分估计值。然而，当姿势变化改变体液分布时，这种技术容易出现测量误差增加的情况。本研究的目的是评估姿势取向对智能手表生物电阻抗分析（SWBIA）产生的身体成分和总体水（TBW）估计值的影响，并确定其与标准测量方法的一致性。在这项横断面评估中，117名参与者（年龄：21.4±3.0岁；体重指数：25.3±5.7kg/m²）（女性69名，男性48名）在坐姿、站姿和仰卧位时完成了SWBIA测量，然后接受了标准双能X线吸收法（DXA）和生物电阻抗光谱法（BIS）评估。在合并样本和女性中，使用SWBIA测量的体脂百分比、脂肪量和去脂体重在仰卧位和站立位之间存在显著差异（所有p<0.001），尽管各姿势下与DXA的组水平一致性相似。仰卧位SWBIA的TBW估计值在坐姿和站姿估计值之间存在显著差异（所有p≤0.026），但进一步分析表明，这是由女性中观察到的仰卧位和坐姿差异所驱动的（p=0.003）。SWBIA的TBW在不同身体姿势下与BIS在组水平和个体水平上表现出相似的一致性，分别在女性和男性的坐姿和仰卧位评估中观察到略有改善。当在不同姿势取向进行测量时，SWBIA在身体成分和TBW方面可能会表现出轻微的设备内和设备间差异，不过在外部/临床样本中进行进一步评估是必要的。虽然特定性别/姿势的指南可能会提高精度，但这些发现凸显了使用SWBIA时标准化身体姿势的重要性。
