ABSTRACT
OBJECTIVE: We aimed to examine whether lower-limb muscle quantity and quality assessed by bioelectrical impedance analysis (BIA) were associated with knee extension strength and if the association differed with knee osteoarthritis (OA) severity. METHODS: We included 1,525 participants (63.6% women; mean age, 68.0±5.3 years) from the Nagahama Prospective Cohort. Knee extension strength was measured during maximum voluntary isometric contraction. Lower limb muscle mass and extracellular-to-intracellular water (ECW/ICW) ratio were used as indicators of muscle quantity and quality, respectively, and assessed via a BIA device. We executed multiple linear regression analyses to investigate the association of muscle quantity and quality with knee extension strength. Additionally, participants were classified into three groups with respect to OA severity and symptoms: control, early, and advanced OA groups; subgroup analyses were also executed. RESULTS: The muscle mass (p<0.001) and ECW/ICW ratio (p=0.009) were significantly associated with knee extension strength. In the subgroup analysis, the muscle mass was significantly associated with knee extension strength (p<0.001), but there was no association between ECW/ICW ratio and knee extension strength (p=0.731) in the control group. In the early and advanced OA groups, the muscle mass (both p<0.001) and ECW/ICW ratio (early OA: p=0.034, advanced OA: p=0.015) were significantly associated with knee extension strength. CONCLUSIONS: Lower limb muscle quality was associated with knee extension strength, and the association was stronger in patients with knee OA. These findings suggest that both muscle quantity as well as quality should be assessed to better understand muscle function in patients with knee OA.
ABSTRACT
BACKGROUND: Overall spinal curvature is evaluated by calculating the difference between the angles of lumbar lordosis (LL) and thoracic kyphosis (TK) and is expressed as LL minus TK (LL-TK). It is unclear whether LL-TK is associated with physical function in community-dwelling older adults and whether it is more relevant than TK or LL alone. OBJECTIVE: This study aimed to identify whether LL-TK is associated with physical function in community-dwelling older adults, and whether it is strongly associated than TK or LL alone. METHODS: The participants comprised 1,674 community-dwelling older adults who underwent physical assessments (women, n = 1,099; mean age, 67.4 ± 5.3 years). As spinal alignment indices, TK and LL were measured using skin surface methods, and LL-TK was calculated as the difference between them. Decreased LL-TK indicated increased overall spinal curvature. Physical function was determined by measuring single-leg standing, five-times chair-stand, and usual gait speed. Stepwise multiple regression analyses were performed with each physical function as the dependent variable and spinal alignment indices as the independent variables, with adjustments. RESULTS: Multiple regression analyses showed that single-leg standing (ß = 0.092, 95% confidence interval [CI] = 0.071 to 0.214, p < .001) and five-times chair-stand (ß=-0.142, 95% CI = -0.037 to -0.019, p < .001) were significantly associated with LL-TK, but not LL. Both LL-TK (ß = 0.121, 95% CI = 0.001 to 0.004, p < .001) and LL (ß = 0.087, 95% CI = 0.001 to 0.003, p = .003) were significant determinants of usual gait speed. CONCLUSIONS: This study showed that decreased LL-TK may be associated with poor physical function. This association may be stronger than that observed for TK or LL alone.