Abstract
This study aimed i) to compare relative sit-to-stand power (STSrel) values yielded by the different equations reported in the literature; ii) to examine the associations between STSrel, derived from the equations, and age, sex, frailty and habitual gait speed (HGS); and iii) to compare the ability of the different STSrel equations to detect frailty and low HGS in older adults. 1568 participants (>65years) were included. STSrel was calculated according to four validated equations. Frailty was assessed using the Frailty Trait Scale and HGS as the time to complete 3m. ANOVA tests, regression analyses and receiver operator characteristic curves were used. There were significant differences among the STSrel values yielded by all the equations, which were higher in men compared to women and negatively associated with age (r=-0.21 to -0.37). STSrel was positively and negative associated to HGS and frailty, respectively, in both men (r=0.29 to 0.36 and r=-0.18 to -0.45) and women (r=0.23 to 0.45 and r=-0.09 to -0.57) regardless of the equation used. Area under the curve values varied between 0.68 and 0.80 for Alcazar's, 0.67-0.80 for Ruiz-Cárdenas's, 0.51-0.65 for Smith's, and 0.68-0.80 for Takai's equations. Low STSrel indicated an increased probability of having both low HGS and frailty (OR [95%CI]=1.6 to 4.5 [1.21 to 5.79]) for all equations with the exception of Smith's equations for frailty in women. All the equations presented adequate criterion validity, however, the Alcazar's equation showed the highest level of clinical relevance according to its ability to identify older people with frailty and low HGS.
Highlights
Aging is associated with a reduction in the functional reserve of the neuromuscular system, resulting in impaired mechanical muscle per formance that translates into a reduced functional capacity to perform activities of daily living (ADL) (Aagaard et al, 2010)
STS performance has been used as an assessment of strength and power, some researchers argue that it should not be considered a measure of older adults' muscle strength or power, but a measure of physical per formance (Lindemann et al, 2007)
All the equations showed higher relative STS power values in men compared to women, which were significantly and negatively associated with age
Summary
Aging is associated with a reduction in the functional reserve of the neuromuscular system, resulting in impaired mechanical muscle per formance that translates into a reduced functional capacity to perform activities of daily living (ADL) (Aagaard et al, 2010). Several investigations have used sit-to-stand (STS) performance as an indirect measure of muscle strength or power in older adults (Jones et al, 1999; Hardy et al, 2010). In this sense, poorer STS performance was associated with falls (Buatois et al, 2008), disability (Makizako et al, 2017) and mortality (Cooper et al, 2010). STS performance has been used as an assessment of strength and power, some researchers argue that it should not be considered a measure of older adults' muscle strength or power, but a measure of physical per formance (similar to other functional measures such as gait speed or stair climbing performance) (Lindemann et al, 2007)
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