Relationship between sonographic index of muscle quality and quadriceps muscle strength in nursing-home residents – a proof-of-concept study

Abstract

Background: Age-related neurological and muscular changes lead to low strength and function in older people. The proportional contribution of these changes to strength decline alters with increasing age. However, it is not clear how the muscle changes in older people which have excessive loss of strength due to multimorbidity and inactivity. Unlike community-living older adults, intramuscular alterations are rarely evaluated in nursing-home residents despite their potential importance for specific sarcopenia assessment and guiding interventions to improve strength. Objectives: To explore potential relationships between muscle strength, muscle quantity, contractile quality and physical activity in older nursing-home residents. Design: A cross-sectional proof-of-concept study. Setting: A nursing-home in Switzerland. Participants: 24 nursing-home residents, median age (range) 86.5 (68-103) years. Measurements: Sonographic measures of muscle thickness and echotexture were used as surrogate measures of muscle quantity and contractile quality of the quadriceps muscle. The relationship between sonographic measures and isometric strength of the knee extensors, gait speed and physical activity was evaluated using Pearson’s and Spearman’s correlation coefficients. A subgroup analysis of low (n=12) and normal (n=12) physical activity, based on energy expenditure cut off values of 383 kcal/week for men and 270 for women, was also undertaken. Results: In nursing home residents with normal physical activity, muscle quality positively correlated with knee extensor strength (r=0.727, p=.007) and gait speed (r=0.588, p=.044) while muscle thickness was not (p=0.966 and p=.564 respectively). There was no correlation among variables for n=24 or the subgroup with low physical activity. Conclusions: The results provide proof of concept that poor muscle quality is associated with low strength in older nursing-home residents that are physically active. Ultrasound derived muscle quality assessment has potential to detect activity-related muscle differences in old age, associated with sarcopenia, and may be more appropriate than muscle thickness measures.