Comparison of lumbar paraspinal muscle size and density between members of the US Framingham Heart Study and Tsimane forager-horticulturalists of Bolivia

A study from the Framingham Heart Study and Tsimane forager-horticulturalists in Bolivia found differences in paraspinal muscle size and density between the two groups. Paraspinal muscles support and move the spine, and reduced size and density can lead to increased risk of vertebral fracture and back pain.

The researchers compared cross-sectional area (CSA) and density of trunk extensors and psoas major at L3 in 411 Framingham Heart Study members and 330 Tsimane individuals, ranging from 50 to 90 years old. The study used computed tomography scans to measure muscle size and density.

After accounting for height, weight, and other factors, Tsimane women had 11-14% larger and denser extensors, while also having 17-26% smaller and less-dense psoas major compared to FHS women. Among men, Tsimane had 8-21% smaller and less-dense psoas major, but no significant differences in extensor size and density.

Interestingly, Tsimane men exhibited a 41% smaller age-related decrease in psoas major density compared to FHS men. The study observed a distinct difference in the balance between trunk extensor and psoas major size and density between the two groups.

The researchers suggest that this difference may be due to variations in physical activity patterns between subsistence-oriented forager-horticulturalists (Tsimane) and more sedentary post-industrialized individuals (Framingham Heart Study members). Further research is needed to determine the exact impact of lifestyle and environmental factors on paraspinal muscle size and density.