This study aimed to examine the effect of age on the mechanical properties, muscle size, and muscle quality in the upper and lower limb and trunk muscles.
Methods
2We evaluated the shear modulus (G), muscle thickness (MT), and echo intensity (EI) of the upper and lower limb and trunk muscles of 83 healthy women (21-83-year-old). The G values of some limb muscles were measured in relaxed and stretched positions.
ResultsRegarding the effect of age on G at the distinct positions, the G of the upper limb muscles were not significantly correlated with age in the relaxed and stretched positions. In contrast, the G of the iliacus showed a significant negative correlation in both positions. Additionally, the G of the rectus femoris had a significant negative correlation only in the relaxed position.Regarding differences among body parts, the G of the lower limb and oblique abdominal muscles showed a significant negative correlation, but no correlation in the upper limb, rectus abdominis, and back muscles. Moreover, MT showed a significant negative correlation with age in the lower limb, abdominal, and erector spinae muscles, but no correlation was detected in the upper limb and lumbar multifidus muscles. EI had a significant positive correlation in all the muscles.
ConclusionThe effect of age on G depended on body parts, and the G of the lower limb and oblique abdominal muscles negatively associated with age. Additionally, G in the relaxed position may be more susceptible to aging than G in the stretched position.
Rotator cuff tear is a common shoulder injury that causes shoulder dysfunction and pain. Although surgical repair is the primary treatment for rotator cuff tear, it is well recognized that impaired force exertion of muscles connecting to the involved tendon and subsequent complemental change in the force exertion of synergist muscles persist even after repair. This study aimed to identify the compensation strategy of shoulder abductors by examining how synergist muscles respond to supraspinatus (SSP) muscle force deficit in patients with rotator cuff repair. Muscle shear modulus, an index of muscle force, was assessed for SSP, infraspinatus, upper trapezius, and middle deltoid muscles in repaired and contralateral control shoulders of 15 patients with unilateral tendon repair of the SSP muscle using ultrasound shear wave elastography while the patients passively or actively held their arm in shoulder abduction. In the repaired shoulder, the shear modulus of the SSP muscle declined, whereas that of other synergist muscles did not differ relative to that of the control. To find the association between the affected SSP and each of the synergist muscles, a regression analysis was used to assess the shear moduli at the population level. However, no association was observed between them. At the individual level, there was a tendency of variation among patients with regard to a specific muscle whose shear modulus complementarily increased. These results suggest that the compensation strategy for SSP muscle force deficit varies among individuals, being nonstereotypical in patients with rotator cuff injury.
Purpose The primary purpose of this study was to clarify the occurrence of sites of edematous changes using the measured circumferences of the thigh and lower leg via 3D body scanning. The secondary purpose was to determine the relationship between the volume changes using 3D body scanning and the resistance changes as indicator of extracellular water (ECW) via segmental-bioelectrical impedance spectroscopy (S-BIS).Methods Fifteen healthy women participated. Limb circumferences were measured using 3D body scanning at 10% intervals between 50 and 80% in the thigh circumference and between 0 and 80% in the lower-leg circumference. The resistance of the ECW component (RECW) and total body water (RTBW) was measured using S-BIS in the thigh and lower-leg segments. These measurements were conducted at baseline and 6-h post-observation. A paired t-test was conducted for the differences in these parameters, and the effect sizes were calculated using Cohen's d. Correlations between changes in segmental volume and RECW were analyzed.Results Measurement-site circumferences and segmental volume significantly increased in the lower leg at post-observation but not in the thigh. The effect size (ES) of circumference changes in the lower leg's central region was larger (ESs were 0.40-0.71 at 30-50%) than in other regions. A significant correlation was observed between changes in segmental volume and RECW of the lower leg (ρ = -0.79, p<0.001).
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