Can dual energy X-ray absorptiometry provide a valid assessment of changes in thigh muscle mass with strength training in older adults?

Abstract

Objective: To determine how dual-energy X-ray absorptiometry (DXA) compares to computed tomography (CT) for measuring changes in total thigh skeletal muscle (SM) mass with strength training (ST) in older adults. Subjects: Fifty previously sedentary, relatively healthy older men (n ¼ 23, 60 (s.d. ¼ 7.5) years) and women (n ¼ 27, 60 (s.d. ¼ 9.3) years). Results: Results indicate that there was a significant increase in thigh SM mass with ST measured by both CT (3.970.4%) and DXA (2.970.6%) methods (both Po0.001), and there was not a significant difference in percent change between the two methods, although there was a substantial absolute difference (B2 kg) at baseline between the two methods. Although BlandAltman plots indicate overall agreement between the percent thigh SM mass changes of DXA vs CT methods, the 3.4% error associated with DXA was greater than the thigh SM mass change from DXA. However, the CT measured change in thigh SM mass was greater than its error (0.6%). Conclusions: DXA overestimates baseline and after ST thigh SM mass, and may not be able to detect small changes in thigh SM mass with ST due to its higher error. Although DXA has certain advantages that warrant is used in epidemiologic and intervention studies, improvements to DXA are needed for the accurate assessment of small changes in thigh SM mass.

Accelerated atrophy of lower leg and foot muscles—a follow-up study of long-term diabetic polyneuropathy using magnetic resonance imaging (MRI)

“…This is in contrast to the study by Park et al, who observed a small but significant difference in intrinsic muscle strength in a large group of older type 2 diabetic patients using dual-energy x-ray absorptiometry (DEXA) to evaluate muscle mass [40]. Overestimation of muscle mass by DEXA could account for the lower muscle quality observed [41], as could increased fat infiltration of the muscle, which is found more frequently in type 2 diabetic patients [42]. Analysis of magnetic resonance images allows exclusion of fat and fibrous tissue within muscle compartments.…”

Chronic disuse and skeletal muscle structure in older adults: sex-specific differences and relationships to contractile function

“…1A), as might be expected with long-standing muscle disuse. As an aside, discordant findings between DEXA and CT imaging may relate to limitations of DEXA to discriminate these differences in older adults (15,39). Whole muscle CSA deficits (Ϫ19%) were paralleled by reductions in fiber CSA, which were evident in the three most prevalent fiber types examined (I, IIA, and IIAX).…”

“…However, measurements at the whole muscle level may not adequately reflect adaptations in muscle size and structure at the cellular, subcellular, and molecular levels (15,25,39). Because skeletal muscle size and structure at these more basic anatomic levels are well-known regulators of function, characterization of muscle morphology with aging and disease at the cellular and subcellular levels may provide greater insight into functional phenotypes than assessments at the whole tissue level.…”

Regulation of Increased Blood Flow (Hyperemia) to Muscles During Exercise: A Hierarchy of Competing Physiological Needs

“…This hypoxemia is due to the complex interactions between the very high cardiac outputs detailed above, flow limitation at very high minute ventilations, ventilation perfusion matching, pulmonary diffusing capacity, and physiological shunts through the lung. The predominant mechanism or mechanisms accounting for this desaturation is a matter of ongoing debate in the pulmonary and exercise physiology communities (3,118,122,198,219,233,353,366,367). It is also important for the nonexpert to recognize that in male endurance elite athletes, minute ventilations in excess of 150 l/min are frequently seen (8,493).…”