Invited Commentary

Excerpt

In this study, the authors selected a subset of individuals from the Finnish twin cohort and described a fascinating, innovative approach to investigating muscle morphology and its relationship to several factors. The use of axial (transverse) view lumbar magnetic resonance images (MRIs) provided a high-resolution, in vivo representation of lumbar muscle cross-sectional area (CSA). The authors report that genetic and environmental factors had a much stronger association with lumbar muscle CSA than factors related to physical activity did.

These findings are quite thought-provoking, although there are some limitations with this descriptive design. Classifying twins as “discordant” is a challenging task involving multiple variables. In this study, the classification appears to be based on the judgment of the examiners rather than the use of specific numeric cutoff points. As the authors point out, twins often choose similar lifestyles.…