Tibial vascular grooves: ambulatory physical activity and overall muscle activation

The vascular grooves on the lateral surface of the tibial diaphysis have been suggested as a qualitative indicator of mobility and physical activity. We study here the association between these grooves and an external index of cross-sectional circularity of the tibia, a biomechanical variable related to mobility. Three Iberian skeletal samples were selected for study, representing the Chalcolithic, Early Modern and Contemporary periods, a time span where a significant decrease in ambulatory activity has been documented in European samples. For each tibia, the circularity index and the presence of vascular grooves were recorded. The Chalcolithic sample presented a higher circularity index compared with the other two samples, indicating higher levels of ambulatory physical activity. It also presented a higher frequency of vascular grooves. The association between the circularity index and the presence of vascular grooves was significant, but considerable overlapping in the index was observed between tibiae with few and several grooves. These grooves are associated to the tibialis anterior muscle, which is activated during the gait cycle but also in what has been called “active rest” postures, and possibly in other nonambulatory activities involving foot hyperdorsiflexion. The age- and sex-related changes in the vascular system could be also important in the interpretation of these grooves. These grooves might be partially related to levels of ambulatory activity, but we conclude that its presence cannot be used alone as a qualitative marker of mobility. Its use as a general indicator of overall lower limb muscle activity should be explored.