Arm and leg composition determined by computed tomography in young and elderly men

Abstract

Five computed tomography (CT) scans were taken at measured intervals of the legs and arms of young (n = 7) and elderly (n = 13) men. Cross-sectional areas (CSA) of the total limb, muscle plus bone and bone were measured in each scan, and skin plus subcutaneous tissue areas were calculated by subtraction. In addition, in the arm scans the CSA of the extensor and flexor compartments were measured, and in the leg the CSA of the plantar flexor compartment. A value for lean muscle within these compartments was calculated by excluding non-muscle tissue using density measurements based on Hounsfield units. Related volumes for the various components were also calculated using geometric formulae. The results showed that elderly limbs were of a similar overall size as the young, but elderly muscles were smaller (28-36%) with greater amounts of non-muscle tissue located within a muscle, particularly in the plantar flexors (81% more than in the young). Elderly arms had a greater amount of skin plus subcutaneous tissue than the young, but there was no difference in the legs. Muscle volumes were similar to in vitro results reported from cadaver studies and can be predicted from single mid-limb CT scans using regression equations. These results illustrate that, due to the substantially reduced amount of 'pure' muscle tissue in the elderly, comparisons of relative strength with other populations may be misleading unless appropriate measurements of muscle size are considered. Methods to estimate in vivo physiological CSA, which is considered the best means of normalizing strength, have been demonstrated in this study.

Plantaris muscle weakness in old mice: relative contributions of changes in specific force, muscle mass, myofiber cross-sectional area, and number

“…In the human m. vastus lateralis, this amounted to approximately 30 % between 40 and 80 years (Janssen et al 2000;Klitgaard et al 1990;Maden-Wilkinson et al 2014;Overend et al 1992; Rice et al 1989;Young et al 1984;Young et al 1985). In rodents, at ages representative of these ages in humans, a similar age-related reduction in muscle mass is observed (Ballak et al 2014).…”

Hormone Replacement Therapy, Insulin Sensitivity, and Abdominal Obesity in Postmenopausal Women

“…Mid-thigh low-density lean tissue, a marker of fat content within and around the muscles (22), increases with age and inactivity and is associated with body fat and insulin resistance (22,25,48,49). Therefore, intramuscular fat could differ between postmenopausal women on and not on HRT and could contribute to variations in insulin resistance.…”

The influence on sarcopenia of muscle quality and quantity derived from magnetic resonance imaging and neuromuscular properties

“…Many studies have attempted to improve basic CSA measurements by eliminating apparent noncontractile tissue (Kent-Braun et al 2000;Klein et al 2001;Rice et al 1989). Muscle CSA or volume allows for the calculation of normalized (specific) strength (i.e., force or torque per amount of tissue), but it cannot assess intrinsic MQ.…”