Some of our studies explore how the different joints contribute to energy expenditure under different locomotor tasks. Others studies examine the energy cost of various muscle functions (e.g. work production, isometric force, co-contraction) .
We use both standard open-flow and flow-through respirometry, and have also adopted an injectable microsphere technique to assess muscle blood flow as a proxy for muscle-level energetics.
We use a combination of non-invasive techniques to assess the mechanical function of muscle in vivo in humans (e.g. dynamic ultrasound imaging of muscles, electromyography) and mode direct techniques in non-human animals (e.g. sonomicrometry, tendon force buckles)
One of the aims of our research is to understand the optimality criteria that govern locomotion in various locomotor tasks and environments. We are starting to study how energy cost, stability and cognition might each influence how a person moves. The example above is an experiment assessing whether the walk-to-run transition minimizes joint mechanical costs; Pires et al. 2014, J. Exp. Biol.
Birds are the only other taxa that have evolved habitual bipedalism, and are thus an excellent (albeit much less studied) source for probing the relationships between the morphology, biomechanics and physiology of moving on two legs. They may even teach us a thing or two about how to better engineer legged robots and prosthetics.
Emu running over force plate- Cal Poly, Pomona, CA. Video courtesy Rich Marsh and Don Hoyt
We have borrowed from human biomechanics techniques to study the detailed three-dimensional joint function in walking and running ostriches. 3D inverse dynamics techniques have helped reveal the features of limb structure related to economical running in this species (and possibly other cursorial animals).3D model of an ostrich running
Together with colleagues from the Royal Veterinary College, London (John Hutchinson, Alexis Wiktotowicz), The University of Queensland (Glen Lichtwark) and The University of Idaho (Craig McGowan) we have been studying the effect of body size on macropod locomotion and the scaling of limb mechanical advantage.Kangaroo motion capture
Rubenson, J., Heliams, B.D., Besier, T.F.,Lloyd, D.A., and Fournier, P.A. (2011) Adaptations for economical running: the effect of bipedal limb structure on 3-D joint mechanics. J. R. Soc. Interface. 8: 740-755. (PDF).
Watson, R.R., Rubenson, J., Coder, L., Hoyt, D.F., Propert, M.W.G. and Marsh, R.L. (2011) Gait-specific energetics contribues to economical walking and running in emus and ostriches. Proc. R. Soc. B. 278: 2040-2046. (PDF).
Rubenson, J., and Marsh, R.L. (2009) Mechanical efficiency of limb-swing during walking and running in guineafowl (Numida meleagris). J. Appl. Physiol. 106: 1618 – 1630. (PDF)
Rubenson, J., Besier, T.F., Heliams, B.D., Lloyd, D.G., and Fournier, P.A. (2007). Running in ostriches (Struthio camelus): three-dimensional joint axes alignment and joint kinematics. J. Exp. Biol. 210: 2548-2562 (PDF).
Rubenson, J., Henry, H.T., Dimoulas, P.M. and Marsh, R.L. (2006). The cost of running uphill: linking organismal and muscle energy use in guinea fowl Numida meleagris. J. Exp. Biol. 209: 2395-2408. (PDF).
Marsh, R.L., Ellerby, D.J., Henry, H.T. and Rubenson, J. (2006). The energetic cost of trunk and distal limb loading during walking and running in guinea fowl Numida meleagris. I. Organismal metabolism and biomechanics. J. Exp. Biol. 209: 2050-2063. (PDF).
Rubenson, J., Heliams, B.D., Lloyd, D.G., and Fournier, P.A. (2004). Gait selection in the ostrich: mechanical and metabolic characteristics of walking and running with and without an aerial phase. Proc. R. Soc. B. 271: 1091 – 1099. (PDF).