Isometric knee extension test: A practical, repeatable, and suitable tool for lower-limb screening among institutionalized older adults.

Abstract

We aimed to analyze the isometric knee extension test (IKE) test in terms of i) intra- and inter-session repeatability, and ii) relationship with functional and body composition factors of sarcopenia among institutionalized older adults. Thirteen institutionalized older adults (age=87±10years, body mass [BM]=73.1±10.9kg, body mass index [BMI]=28.5±3.8kg·m2) were recruited from a nursing home. Variability of maximal isometric force registered in three IKE trials performed on the same day was used to examine intra-session repeatability, whereas inter-session repeatability was analyzed by comparing maximal isometric force from two different days. Furthermore, functional (Handgrip, 6-m Gait Speed, Time Up and Go [TUG], and Sit-to-stand tests) and body composition (appendicular lean mass adjusted by BMI, ALM/BMI) evaluations were conducted. Statistics included the intraclass correlation coefficient (ICC) and the standard error of measurement (SEM), expressed in both absolute (N·kg-1) and relative terms (coefficient of variation, CV=100×SEM/mean). High to very high intra-session repeatability was found for both the dominant and non-dominant legs (CV≤6.0%, ICC≥0.989). Similarly, both legs showed high inter-session repeatability (SEM≤0.26N·kg-1, ICC≥0.959). On the other hand, significant relationships were found between Dominant and Non-dominant IKE tests and 6-m Gait Speed (r=0.77; r=0.58), ALM/BMI (r=0.62; r=0.58), and Non-dominant Handgrip/BM (r=0.60; r=0.68). In addition, a significant association was found between Dominant IKE/BM and TUG (r=-0.74), as well as between Non-dominant IKE/BM and Dominant Handgrip/BM (r=0.67). These findings suggest that the IKE test is a repeatable and suitable strategy for lower-limb screening in institutionalized older adults.