Association of strength, power, and function with muscle thickness, echo intensity, and lean tissue in older males

Dual-energy X-ray absorptiometry (DXA) appendicular lean tissue is used to screen older adults for sarcopenia. However, emerging data indicates that ageing-related muscle atrophy largely occurs within specific muscles, which may be masked using appendicular lean tissue. Comparisons between appendicular lean tissue and site-specific measures of muscle in relation to strength and physical function are needed to advance our understanding of these features in the context of poor muscle function in aged adults. Our primary objective was to compare correlations between lean tissue and site-specific muscle characteristics in relation to strength and physical function in older males. Older males (≥65 years) were evaluated for muscle strength, physical function (6-minute walk and 30-second sit-to-stand), and muscle size (appendicular and site-specific) and composition (echo intensity) using DXA and ultrasound. Of the 32 older males (75.4 ± 7.9 years), 12 had low appendicular lean tissue. All DXA and ultrasound muscle characteristics were associated (r = 0.39 to 0.83, p < 0.05) with torque or power producing capabilities. Except for the knee flexors, no differences in correlation coefficients were observed between muscle thickness or regional lean tissue in relation to muscle strength. Neither DXA nor ultrasound muscle characteristics were associated with physical function. In older males, ultrasound-based muscle thickness and DXA lean tissue provided similar associations with strength. Novelty: Lean tissue and muscle thickness provide similar associations with strength. Muscle thickness can distinguish low and normal appendicular lean tissue in older adults.

Length-dependent changes of lower limb muscle morphology in Chronic Inflammatory Demyelinating Polyneuropathy assessed with magnetic resonance imaging

The objective of the present study was to assess muscle quantity of the thigh and leg in patients with chronic inflammatory demyelinating polyneuropathy (CIDP) compared to age and sex matched controls in exploring length-dependent changes of innervated muscles. In five people with CIDP and seven controls, magnetic resonance imaging was used to assess muscle morphology of the four parts of the quadriceps and medial hamstring muscles. Findings were compared to the triceps surae from a subset of participants. The CIDP group had less contractile tissue in the quadriceps (11.5%, P<0.05), hamstrings (15.6%, P<0.05) and triceps surae (35.9%, P<0.05) compared to controls. Additionally, CIDP had less contractile tissue (18.7%) in the triceps surae compared to the hamstrings (P<0.05). Muscle quantity in the quadriceps and hamstrings in CIDP was less than controls, but differences were greater for the distal triceps surae. These findings support a length-dependent affect of CIDP on limb musculature composition.

Older males exhibit reduced anterior upper leg and anterior abdominal muscle thickness compared to younger males when matched for relative appendicular lean tissue

Background Ageing-related muscle atrophy does not occur uniformly across the body; rather, atrophy occurs to a greater extent in specific muscle groups compared to others. However, site-specific comparisons of muscle mass between older and younger adults typically do not account for relative muscle mass (i.e., matched for age- and sex-specific percentiles), which may confound site-specific differences. Furthermore, the uniformity of ageing-related differences in muscle composition (e.g., intramuscular adipose tissue) across the body are not well characterized. Purpose To examine site-specific muscle mass and composition differences between younger and older males matched for relative muscle mass. Methods Younger (18-44 years old, n = 19) and older (≥65 years old, n = 19) males were matched for relative appendicular lean tissue index (NHANES age- and sex-specific Z-scores) measured using dual-energy x-ray absorptiometry. Site-specific differences in skeletal muscle size (thickness) and composition (echo-intensity) were evaluated using ultrasound for 8 distinct landmarks across the body. Results Relative appendicular lean tissue mass was well matched between younger and older males (Z-score difference: -0.02, p = 0.927). Compared with younger males, older males had smaller muscle thickness for the anterior upper leg (difference: -1.08 cm, p < 0.001) and anterior abdomen (difference: -0.53 cm, p < 0.001). However, older adults displayed higher echo intensity across all muscles (p < 0.05), except for the posterior upper arm (p = 0.377), in comparison to the younger males. Conclusions When matched for relative appendicular lean tissue, muscle thickness differences between younger and older males are not-uniform across the body, whereas echo intensity was more uniformly higher in the older males.