It is important for elderly people to maintain or improve muscle strength and for clinicians to know the factors that affect muscle strength. Therefore, the purpose of this study was to compare the effects of fat mass (FM) and skeletal muscle mass (SMM) on muscle strength. The participants included 192 community-dwelling elderly women. The SMM and FM, grip strength, and knee extension strength were measured. Data were evaluated using stepwise multiple linear regression analysis, which was performed with grip or knee extension strength as a dependent variable and the SMM and FM of the upper and lower limbs as the independent variables. The SMM and FM of the upper limbs were associated with grip strength, whereas the SMM but not the FM of the lower limbs was associated with knee extension strength. These findings suggest that there may be thresholds for the SMM/FM ratio to affect muscle strength.

Skeletal muscle mass and muscle strength are positively correlated, but the relationship between grip strength and global muscle strength is controversial. This study aimed to clarify the changes in site-specific skeletal muscle mass by age group and determine the relationship between site-specific, age-related changes in skeletal muscle mass and physical function in community-dwelling elderly people in Japan. The participants were divided into age groups of five-year intervals (65-69 years, 70-74 years, 75-79 years, and ≥80 years) and were also categorized by sex. The skeletal muscle mass of the upper limbs, lower limbs, and trunk was measured using multifrequency bioelectrical impedance analyzers (InBody 430 (Biospace Co., Ltd., Seoul, Korea) and InBody 470 (InBody Japan Inc., Tokyo, Japan)). For physical function assessment, we measured grip strength, quadriceps strength, sit-up count, sit-and-reach distance, and standing time on one leg with eyes open and performed the timed up and go (TUG) test. The results showed that skeletal muscle mass decreased with age regardless of sex at all measured sites. Furthermore, a partial correlation analysis adjusted for age, physical constitution, and the presence/absence of exercise habits revealed that the highest correlation was between skeletal muscle mass in all sites and grip strength. Thus, monitoring grip strength may be used as a representative of systemic skeletal mass even in Japanese people.

Walking motor imagery ability is thought to be associated with a fear of falling; however, no studies have compared fall risk and motor imagery ability. This study aimed to ascertain the time difference between imagined and physical walking in older adults at low and high risks of falling. Motor imagery ability was assessed using mental chronometry, which measures the imagined time required for movement. Participants included 31 older adults classified as having a high (n = 15) or low (n = 16) risk of falling based on single leg stance time. The time required for imagined and physical walking was measured using 5 m long walkways with three different widths (15, 25, and 50 cm), and the temporal errors (absolute and constant error) were compared. Physical walking time was significantly longer in the high-risk group than in the low-risk group for the 15 and 25 cm wide walkways. The absolute error between the imagined and physical walking times was significantly larger in the high-risk group than in the low-risk group for the 15 and 25 cm wide walkways. There was also a significant difference in the constant error between the high- and low-risk groups between the imagined and physical walking times for all three walkways. Older adults who may be at a higher risk of falling showed longer walking times during action execution but overestimated their performance (i.e., they believe they would be faster) during motor imagery. Therefore, the time difference between imagined and physical walking could, in part, be useful as a tool for assessing fall risk based on motor imagery.

Studies involving the 30 s chair-stand test (CS-30) have shown that subjects’ movements can vary during the test, and that these variations may follow several patterns. The present study aimed to define these different patterns and their respective incidences among a population of community-dwelling older adults in Japan. We also investigated, among the patterns identified, potential associations with physical and mental characteristics. The study population comprised 202 community-dwelling older adults. Subjects were classified into four groups based on how their CS-30 performance (defined through sit–stand–sit cycle count) changed over three successive 10 s segments: “steady-goers,” “fluctuators,” “decelerators,” and “accelerators.” Several other measures were also evaluated, including sit-up count, knee-extension strength, toe-grip strength, and Mini-Mental State Examination score. We found that steady-goers and decelerators comprised 70% of the sample. Fluctuators and steady-goers showed comparable physical function. Decelerators exhibited significant correlations between CS-30 score (total cycles) and tasks involving persistence and repetitive actions (p < 0.05). In addition, accelerators showed significantly stronger knee extension than steady-goers (p < 0.01). Differences in temporal patterns of CS-30 performance corresponded to differences in certain dimensions of physical and mental function. Our findings may be useful for planning and evaluating intervention programs aimed at long-term-care prevention among community-dwelling older adults.

Background: Body mass index (BMI) is related to health in the elderly. The purpose of this study was to investigate the physical characteristics in underweight, overweight, and obese Japanese community-dwelling elderly women compared to normal-weight elderly women. Methods: The study participants included 212 community-dwelling elderly women. They were categorized as underweight (BMI < 18.5), normal weight (18.5 ≤ BMI ≤ 22.9), overweight (23 ≤ BMI ≤ 24.9), and obese (BMI ≥ 25). Data on skeletal muscle mass index (SMI), number of trunk curl-ups performed within 30 seconds, knee extension strength, one-leg standing time, and walking speed were recorded. Results: In the underweight group, the number of trunk curl-ups was significantly lower than that of the normal-weight group (p = 0.011) and the correlation between knee extension strength and walking speed was relatively higher than in the normal-weight group (r = 0.612 vs. r = 0.471). In the overweight group, the SMI was significantly increased (p < 0.001), but knee extension strength was not increased (p = 0.235) compared to that of the normal-weight group. In the obese group, one-leg standing time was significantly shorter than in the normal-weight group (p = 0.016). Conclusions: Physical characteristics vary according to BMI and these findings are useful in assessing and planning interventional programs to improve and maintain physical function in elderly women.