Lower Limb Entheseal Variation in Modern Athletes and an Early Medieval Population: Implications for Activity Reconstruction.

OBJECTIVES: Entheses are commonly used to infer past activity patterns, yet their interpretation is limited by the combined effects of mechanical loading and intrinsic biological factors. This study addresses this issue by integrating an Early Medieval population from Pohansko (Czechia; 9th-10th centuries CE) with a Spanish modern professional athlete reference sample characterised by well-defined activity regimes. MATERIALS AND METHODS: Lower limb entheseal areas of the gluteus medius, gluteus maximus, vasti, gastrocnemius, and soleus muscles were quantified in the archaeological individuals and in Modern Athletes (sprinters, endurance runners, climbers) using 3D modeling and the VERA protocol. Non-adjusted and size-adjusted data were analysed using univariate and multivariate approaches. RESULTS: Modern Athletes exhibit significantly larger entheseal areas than Pohansko individuals for all muscles except the soleus, supporting the relationship between cumulative mechanical loading and entheseal development. Multivariate analyses differentiate both samples and distinguish locomotor strategies among athletes, with the soleus enthesis contributing most strongly to functional variation. Sexual dimorphism is consistent and male-biased in athletes but variable and enthesis-specific in the Pohansko sample. DISCUSSION: Our results highlight the potential and limitations of entheseal areas for reconstructing behavioral and functional variation in past populations. In Modern Athletes, only the soleus enthesis distinguished climbers from runners, regardless of sex, but not sprinters from endurance runners. In Pohansko, it displayed marked female-male differences, consistent with a sex-based division of labour. These findings suggest that lower limb entheses differ in their sensitivity to mechanical loading, with the soleus primarily reflecting locomotor loading rather than sex differences.