Basic Research

 

modelframeworkOne of our primary goals is to discover the biomechanical determinants of locomotor energy cost. We approach this question from multiple directions including muscle-level analyses, gait analyses, and modelling.

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.

bloodflow

Our lab studies how the in vivo mechanics of muscles contribute to joint and limb locomotor function.  We are interested in how the muscle function is modulated when the  movement tasks is altered (e.g. speed, incline, surface, stability).  Recent work has focused on force-length and force-velocity characteristics of the muscle and how these are affected by gait and speed.

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)

birdInVivo

optimisation

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.

The biological diversity exhibited in limbed animals offers a wealth of information that can lead to major new, and often unpredicted, discoveries that are not possible from studying humans alone. In our lab we employ a research framework spanning both human and other terrestrial species.
GF

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

 

Associated Publications:

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).

Measuring muscle mechanics (e.g. muscle lengths, muscle forces) invasively is not generally feasible in humans and is often impractical in animal research. Computational modelling provides a means to estimate in vivo muscle mechanics non-invasively. We use custom human musculoskeletal models and have developed as several animal musculoskeletal models in OpenSim to estimate muscle mechanics and energetics during locomotion.

guineafowlGuinea fowl model (developed by Hardik Sanghvi, Jonas Rubenson, Melinda Cromie, Rich Marsh, Scott Delp)