Cut-off points of knee extension strength allometrically adjusted to identify sarcopenia risk in older adults: A cross-sectional study

Abstract

Purpose: Handgrip strength used to identify sarcopenia is not representative of overall strength, especially as greater muscle volume and consequent autonomy-mobility are concentrated in the lower limbs. While absolute strength or relative to body mass is used to define sarcopenia, this relationship is not always linear. The aim of this study was to establish allometrically adjusted cut-off points of lower limb (quadriceps) muscle strength to identify sarcopenia risk in older adults.

Methods: ninety-four physically independent individuals over the age of 60 were measured by DXA and sarcopenia was identified. The one-repetition maximum (1RM) test of knee extension strength was estimated using the extensor chair by the submaximal repetition protocol. The six-minute walk test performance was recorded. 1RM values were scaled by body mass (1RM/body mass) and allometrically adjusted (1RM/body mass^b). Cut-off points for sarcopenia from 1RM were defined with ROC curve and Youden index with functional limitation (walking distance<400 m). Analyzes considered sex (α = 5%).

Results: Sarcopenia was present in 10.6 % of participants. The exponents ^b obtained were 0.70 for women and 0.96 for men. Except for absolute 1RM in women, all areas under the curve were acceptable (>0.70). The cut-off points for women and men were respectively, 38.1 and 56.1 kg for 1RM, 0.53 and 0.85 for 1RM/body mass, 1.48 and 1.00 for 1RM/body mass^b.

Conclusions: 1RM of knee extension scaled by body mass or allometrically adjusted is an effective parameter to identify sarcopenia in older adults. The proposed cut-off points could be used to monitor sarcopenia risk in geriatrics.

Keywords: Anthropometry; Elderly; Frailty; Quadriceps muscle; Reference values; Sarcopenia.