Paraspinal muscle aging differs in Bolivian foragers and US adults
In a study of 741 adults, the age-related difference in extensor density was 41% smaller in Tsimane men than in Framingham Heart Study men.
bioRxiv
In a study of human aging, researchers analyzed computed tomography scans from 330 Bolivian Tsimane forager-horticulturalists and 411 participants from the US Framingham Heart Study, aged 50 to 90 years. They measured the cross-sectional area and density of trunk extensors and the psoas major muscle at the L3 vertebra, adjusting for height and weight.
Tsimane women showed 11% to 14% larger and denser trunk extensors, but 17% to 26% smaller and less-dense psoas major muscles than Framingham women. Tsimane men had 8% to 21% smaller and less-dense psoas major muscles compared to Framingham men. Additionally, the age-related difference in trunk extensor density was 41% smaller in Tsimane men than in Framingham men. Other age-related differences between cohorts were not statistically significant.
Why it matters
Reduced paraspinal muscle size and density are associated with vertebral fractures and back pain. Comparing subsistence and post-industrial populations offers insight into how lifestyle and physical activity patterns may alter musculoskeletal aging.
Caveats
The study is a preprint and has not yet undergone peer review. Its cross-sectional design prevents causal conclusions, and the specific lifestyle or environmental drivers of these muscle differences remain to be determined.
The paper
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Fjóla Jóhannesdóttir, Shreyas Durga, Daniel K. Cummings, Michael Gurven, Hillard S Kaplan, Benjamin C. Trumble, Jonathan Stieglitz,Massachusetts General Hospital · Beth Israel Deaconess Medical Center
bioRxiv · 1 Oct 2026 · CC BY-NC-ND · Preprint, not peer-reviewed