Scaling of adult human bone and skeletal muscle mass to height in the US population

Abstract

Objectives: The scaling of structural components to body size is well studied in mammals, although comparable human observations in a large and diverse sample are lacking. The current study aimed to fill this gap by examining the scaling relationships between total body (TB) and regional bone and skeletal muscle (SM) mass with body size, as defined by stature, in a nationally representative sample of the US population. Methods: Subjects were 17,126 non-Hispanic (NH) white, NH black, and Mexican American men and women, aged ≥18 years, evaluated in the National Health and Nutrition Examination Survey who had TB and regional bone mineral (BMin) and lean soft tissue (LST) mass measured by dual-energy X-ray absorptiometry. BMin and appendicular LST served as surrogate bone and SM mass measures, respectively. The allometric model, BMin or LST = α(height) β , in a logarithmic form was used to generate scaling exponents. Results: The findings were similar across all gender and race groups: body mass scaled to height with powers of~2.0 (mean β ± SE, 1.94 ± 0.08-2.29 ± 0.09) while TB and appendicular BMin and appendicular LST scaled to height with consistently larger powers than those for body mass (eg, all P < .05 in NH white men and women); the largest BMin and LST scaling powers to height were observed in the lower extremities. Conclusions: Bone and SM mass, notably those of the lower extremities, increase as proportions of body mass with greater adult height. Metabolic and biomechanical implications emerge from these observations, the first of their kind in a representative adult US population sample.

Allometric models of adult regional body lengths and circumferences to height: Insights from a three‐dimensional body image scanner

“…The geometric models of the head, limbs and trunk were consistent with the results found in Heymsfield et al () and Schuna Jr. et al (). Arms and trunk mass held scaling exponents smaller than leg mass.…”

“…This means that taller individuals increase leg mass at disproportionally higher rates than shorter individuals and taller individuals increase head mass at disproportionally lower rates than shorter individuals. In Heymsfield et al () and Schuna Jr. et al () it was found that arm mass scaled to powers slightly lower than 2.0 and leg mass scaled to powers slightly larger than what we found in this study. We attribute our overestimation to the unrefined simple geometrical models that rely on cylinders for limbs.…”

“…While Quetelet's observation that body mass scales to height squared has been repeatedly validated (Heo, Kabat, Gallagher, Heymsfield, & Rohan, ; Heymsfield et al, ; Hood et al, ), the whole‐body mass scaling masks regional measurement scalings (Heymsfield et al, ; Schuna Jr. et al, ). Recent reports have extended these analyses to regional mass and skeletal muscle mass scalings (Heymsfield et al, ; Schuna Jr. et al, ). Here we advance and confirm these analyses by leveraging regional length and circumference data automatically captured in US military basic training recruits by a 3D body‐imaging scanner.…”

“…Body mass increases across adults as height squared , according to Quetelet's rule, after controlling for age and adiposity (Heymsfield, Gallagher, Mayer, Beetsch, & Pietrobelli, ; Schuna Jr. et al, ). Many other anatomic and metabolic processes are linked with stature scaling relations (Heymsfield et al, ). The most well known of these is Kleiber's law for mammals which states that metabolic rates scale to body mass to the ¾ power (Kleiber, ).…”

“…Schuna Jr. et al reported that the height power of 2 observed in adult body mass scaling studies reflects a much lower height power for head mass (<∼0.8‐1), intermediate powers for arm and trunk mass (∼1.8‐2.3), and higher powers (>2.3‐2.6) for lower extremity mass (Schuna Jr. et al, ). Follow‐up studies associated these “macro” observations with height‐scaling patterns for brain (Heymsfield et al, ), visceral organs (Heymsfield, Gallagher, et al, ), skeletal muscle (Heymsfield et al, ), and bone mass (Heymsfield et al, ). These collective scaling patterns describe how body shape and composition vary across people differing in body size as defined by stature.…”