Center for Functional Anatomy and Evolution, Johns Hopkins University School of Medicine
Saturday Afternoon, Ballroom C
The consequences of limb length proportions on the locomotor economy of fossil hominins have been widely discussed. Studies relating limb length proportions to locomotor efficiency have focused on movement over flat surfaces. However, natural terrain is not flat and the geographic ranges of many fossil hominins contained sloped terrain. Theoretical models suggest that changes in terrain slope may have major effects on the relationship between limb proportions and gait kinematics (step length, joint excursion), and by extension, locomotor efficiency. These models predict that, unlike on level surfaces, locomotor cost will increase during uphill walking with a relatively longer distal lower limb segment and during downhill walking with an increase in total lower limb length.
This study tests these models using experimental methods applied to a sample of human subjects (n = 10). Metabolic energy expenditure (Jkg-1m-1) was evaluated during level, uphill, and downhill treadmill walking using a range of speeds for each condition and a ParvoMedics TrueOne2400. Results support the models and suggest 1) a significant relationship between relative distal lower limb segment length and uphill walking cost, and 2) a near-significant relationship between total lower limb length and downhill walking cost. Additionally, total lower limb length was positively correlated with uphill walking cost, and total lower limb length and limb proportions were found to have little effect on locomotor cost during level walking. These results suggest that the effect of limb length proportions on locomotor efficiency differs considerably on level and non-level surfaces.