Does variation in fibular robusticity reflect variation in mobility patterns?

The fibula is rarely considered in studies of morphological variation. This may be due to the presumption of its relatively minor role in carrying mechanical loads. Differences in relative fibular diaphyseal robusticity have however been found within hominoidea, and relate to variation in positional behaviour (Marchi, 2007). Nevertheless, whether variation in fibular robusticity is influenced by habitual activity patterns in hominins remains uncertain. This study examines cross-sectional geometric properties of the tibia and fibula at mid-shaft across a sample (N=53) of male varsity cross-country runners, field hockey players, and sedentary controls. Fibular robusticity (relative to tibial robusticity) is compared between groups. Runners display low relative fibular robusticity compared to the other groups, while hockey players display significantly greater relative fibular robusticity (P < 0.05) compared to runners. Values for the control sample fall between these two groups. Differences between the runners and hockey players appear to correspond with athletic history. Generally, cross-country running requires the athlete to proceed in a relatively straight line. In contrast, movement patterns associated with field hockey require repeated directional changes. The more robust fibulae of hockey players may be a consequence of a training regime requiring profound mediolateral biomechanical loading of the lower limb, which would induce fibular loading more so than would uni-directional cross-country running. These results (1) provide support for the use of variation in fibular robusticity to infer locomotor patterns in living hominoids and, (2) present an additional tool for inferring hominin mobility patterns from skeletal and fossil remains.