Enhanced echo intensity (EI) on an ultrasound image of skeletal muscle indicates changes in muscle quality, including increases in intramuscular fibrous and adipose tissues. However, it is not known whether muscle quality assessed from the EI of computer-aided gray-scale analysis of an ultrasound image is associated with the muscle strength or body composition of a subject. The objectives of this study were to investigate whether muscle quality assessed from EI measured using gray-scale analysis is associated with muscle strength independently of age or muscle thickness (MT), and to examine the relationship between muscle EI and body composition. Ninety-two healthy women with a mean age of 70.4 ± 5.5 years (range, 51-87 years) dwelling in Kyoto, Japan, participated in the study. The MT, subcutaneous fat thickness (FT), and EI of the quadriceps femoris on the right extremity were assessed from transverse ultrasound images. Knee extensor isometric strength was used as a measure of the quadriceps femoris muscle strength. EI was significantly correlated with quadriceps strength independently of age or MT, and stepwise regression analysis revealed that MT and EI were independently associated with quadriceps strength. Importantly, EI showed no significant correlations with FT, percentage of body fat (%BF), or body mass index (BMI), while FT, BMI, and %BF did not significantly influence muscle strength. These data suggest that muscle quantity (i.e., MT) and muscle quality assessed from EI measured using computer-aided gray-scale analysis independently contribute to muscle strength in middle-aged and elderly persons.

BackgroundIt is well known that loss of muscle mass (quantitative change) is a major change that occurs with aging. Qualitative changes in skeletal muscle, such as increased intramuscular fat, also occur as one ages. Enhanced echo intensity (EI) on ultrasonography images of skeletal muscle is believed to reflect muscle quality. Recent studies evaluating the quality of skeletal muscle using computer-aided gray scale analysis showed that EI is associated with muscle strength independently of age or muscle size in middle-aged and elderly women. The aim of the present study was to investigate whether muscle quality based on EI is associated with muscle strength independently of muscle size for elderly men.MethodsA total of 184 elderly men (65–91 years) living independently in Kyoto, Japan, participated in this study. The EI, muscle thickness (MT), and subcutaneous fat thickness (FT) of the anterior compartment of the right thigh were determined by assessing ultrasonography images. The maximum isometric torque of knee extension at a knee angle of 90° was measured.ResultsThe EI showed a significant negative correlation with muscle strength (r = −0.333, P < 0.001). Multivariate regression analysis revealed that the MT and EI of the knee extensor muscle were independently associated with maximum isometric knee extension strength. Even when partial correlation analysis was performed with age, height, weight, and FT as control variables, EI was still significantly correlated with muscle strength.ConclusionThe results of this study indicate that aging-related changes in muscle quality contribute to diminishing muscle strength. Ultrasonography is a low-cost, easily accessible, and safe method suitable for the assessment of EI as an index of muscle quality.

Total daily energy expenditure (“total expenditure”) reflects daily energy needs and is a critical variable in human health and physiology, but its trajectory over the life course is poorly studied. We analyzed a large, diverse database of total expenditure measured by the doubly labeled water method for males and females aged 8 days to 95 years. Total expenditure increased with fat-free mass in a power-law manner, with four distinct life stages. Fat-free mass–adjusted expenditure accelerates rapidly in neonates to ~50% above adult values at ~1 year; declines slowly to adult levels by ~20 years; remains stable in adulthood (20 to 60 years), even during pregnancy; then declines in older adults. These changes shed light on human development and aging and should help shape nutrition and health strategies across the life span.

The ECW/TW ratio increases in the lower leg with age. The results suggest that the expansion of ECW relative to ICW and the LV masked actual muscle cell atrophy with aging.

This study was performed to ascertain the relationships between oral motor functions, such as those of the tongue and lips, and age in the community-dwelling elderly, as well as to investigate the effects of these factors on masticatory performance. The subjects were 268 healthy elderly Japanese living in Kyoto. They were divided into four age groups and further classified into the following two groups by the presence or absence of posterior occlusal support: Eichner A or B1-B3 (group A), and Eichner B4 or C (group B). They were wearing removable or fixed dentures if they had missing teeth. Oral function evaluation items included (1) masticatory performance and (2) oral motor skills. Significant differences were noted among the age groups in tongue pressure within group A (P < 0.01) and group B (P < 0.05), and in the number of repetitions of the syllables /ta/ and /ka/ in group B (/ta/: P < 0.05, /ka/; P < 0.01). The number of natural teeth (beta = 0.463, P < 0.001) in group A and tongue pressure (beta = 0.436, P < 0.001) in group B were the only predictors of masticatory performance when the data were analyzed by multiple regression analysis. The tongue may compensate for the missing teeth in masticatory performance of those elderly who have lost their natural teeth. The results of this study highlight the importance of tongue function in masticatory performance.