Anatomically asymmetrical runners move in an asymmetrical way at the same metabolic cost

We hypothesized that, as occurring in cars, body structural asymmetries could generate asymmetry in the kinematics/dynamics of locomotion, ending up in a higher metabolic cost of transport (C), i.e. more 'fuel' needed to travel a given distance. Previous studies found asymmetries in horses' body negatively correlated with galloping performance. We analyzed anatomical differences between the right and left lower limbs by designing a software implementing the 3D Cross-Correlation of images from Magnetic Resonance undertook by 19 male runners, clustered as Occasional, Skilled and Top Runners. Running kinematics of their body centre of mass (BCoM) were obtained from body segments coordinates measured by a 3D motion capture system at incremental running speeds on a treadmill. A recent mathematical procedure quantified the asymmetry of the 3D BCoM trajectory between the two steps. During the same sessions, runners' metabolism was measured to estimate C. No correlations were found between anatomical/kinematic variables and C, regardless of the skill level. However, anatomical symmetry significantly correlated to the running kinematic symmetry, and the Top Runners showed the highest level of symmetry. Also, anatomical symmetry negatively correlated with subjects' age. Results suggest that despite the effects of anatomical asymmetry on kinematics, either those changes are too small or some plastic compensation in the locomotor system mitigates the expected negative effects on C.