Every day we are facing uneven terrains like forest trails, cobblestones, sand, meadow and so on. And humans are able to adapt to these terrain conditions perfectly. Still there is little understanding of how humans adapt to uneven terrain as nearly all biomechanical analysis of human locomotion have been done on even surfaces. To understand the adjustments in locomotion on uneven terrain can provide useful insights why for example elderly or disabled people have difficulties on uneven terrain and can provide information for the construction of robotic orthoses and prostheses.

In previous studies it has been found that walking on uneven terrain increases the overall net metabolic energy expenditure. When looking for the causes of this increase it was found that the variability of the step width and step length increased on uneven terrain. Furthermore an increased mechanical work at the knee and hip joint could be observed [1, 2]. These finding might partially but not totally explain the rise in energy expenditure.

Up to now only the biomechanics of the lower body have been analyzed in this context. The contribution of the upper body to the raise energy expenditure remains unclear.

Thus the particular subject matter of our project was to analyze and compare the upper body motion in walking on uneven and even terrain.

In the following podcast you can see how we approached the following questions:

• How does an uneven surface effect the trunk motion in walking?
• How can we define trunk motion?

In summary we found that uneven terrain results in greater range of motions in the frontal and sagittal plane. These additional movements might partially account for the elevated energy expenditure on uneven terrain.

As only the data of three subjects has been analyzed these finding cannot be generalized and should be validated with a larger group of subjects.

During the project phase we sighted a lot of literature concerning biomechanical analysis of upper body motion. We were not able to find an example of upper body reconstruction based on a more or less equal marker set as the one used for our data collection. For further work on this topic we would suggest to use a maker set for the 3D motion analysis which allows a more detailed reconstruction of the upper body and it movements.

A common approach in the literature was to calculate trunk angles relative to the global coordinate system and relative to the pelvis. We tried to account for the latter by calculating the angle between a normal vector on the pelvis plane and the trunk segment. Until the end of our project the results from this calculations did not seem plausible to us. Therefore additional work has to be done on the calculations of the trunk motion relative to the pelvis in frontal and sagittal plane.

As we finalized the Matlab routine for angle calculations it is possible to use this routine as well for the analysis of trunk motion in running.

[1] Voloshina, A. S., Kuo, A. D., Daley, M. A. & Ferris, D. P. (2013). Biomechanics and energetics of walking on uneven terrain. The Journal of Experimental Biology, 216, 3963-3970.

[2] Voloshina, A. S. & Ferris, D. P. (2015). Biomechanics and energetics of running on uneven terrain. The Journal of Experimental Biology, 218, 711-719.