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.


Associated publications:

Stearne, S.M., McDonald, K.A., North, I, Oxnard, C.E., Alderson, J.A., and Rubenson, J. (2016). The foot’s arch and the energetics of human locomotion. Nature Scientific Reports. 6:19403, 1-10. (PDF)

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. Journal of the Royal Society, Interface. 8: 740-55. (PDF)

Umberger, B.R. and Rubenson, J. (2011). Understanding muscle energetics in locomotion: New modeling and experimental approaches Exerc. Sport Sci. Rev. 39: 59-67. (PDF)

Watson, R.R., Rubenson, J., Coder, L., Hoyt, D.F., Propert, M.W.G., and Marsh, R.L. (2011). Gait specific energetics contribute to economical walking and running in emus and ostriches. Proc. R. Soc. Lond. B. 278: 2040-6. (PDF)

Rubenson, J. and Marsh, R.L. (2009). Mechanical efficiency of limb swing during walking and running in guinea fowl (Numida meleagris). J. Appl. Physiol. 106: 1618–30. (PDF)

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).


Associated publications:

Panizzolo, F.A., Maiorana, A.J., Naylor, L.H., Dembo, L., Lloyd, D.G., Green, D.J., Rubenson, J. (2016). Muscle size explains low passive skeletal muscle force in heart failure patients. PeerJ. Sep 15;4:e2447. (PDF)

McDonald, K.A., Stearne, S.M., Pires, N.J., North, I, Alderson, J.A., and Rubenson, J. (2016). The role of arch compression and metatarsophalangeal joint dynamics in modulating plantar fascia strain in running. PLoS ONE. Apr 7;11(4):e0152602. (PDF)

Panizzolo, F.A., Green, D.J., Lloyd, D.G., Maiorana, A.J. and Rubenson, J. (2013) Soleus fascicle length changes are conserved between young and old adults at their preferred walking speed. Gait and Posture. 38: 764-9. (PDF)

Rubenson, J., Pires, N.J., Loi, H.O., Pinniger, G.J., and Shannon, D. (2012). On the ascent: the soleus operating length is conserved to the ascending limb of the force length curve across gait mechanics in humans. J. Exp. Biol. 215: 3539-51. (PDF)

Carr, J.A., Ellerby, D.J., Rubenson, J., and Marsh, R.L. (2011). Mechanisms producing coordinated function across the breadth of a large biarticular thigh muscle. J. Exp. Biol. 114: 3396 – 404. (PDF)


One of the aims of our research is to understand the optimality criteria that govern locomotion in various locomotor tasks and environments. We are particularly interested in how energy cost might each influence how a person moves, and when energy or other criteria (e.g. stability, fatigue) are prioritized. The example above is an experiment assessing whether the walk-to-run transition minimizes joint mechanical costs; Pires et al. 2014, J. Exp. Biol.

Associated publications:

McDonald, K.A., Devaprakash, D., Rubenson, J. Is conservation of center of mass a priority in human walking? Insights from leg length asymmetry experiments. (2019). J. Exp. Biol. 222: doi: 10.1242/jeb.195172. (PDF)

McDonald, K.A., Cusumano, J.P., Peeling, P., Rubenson, J. Multi-objective control in human walking: insights gained through simultaneous degradation of energetic and motor regulation systems. (2019). J. R. Soc. Interface. 16: doi: 10.1098/rsif.2019.0227. (PDF)

Pires, N.J, Lay, B., Rubenson, J. (2018). Modulation of joint and limb mechanical work in walk-to-run transition steps in humans. J. Exp. Biol. 221: 1-13. (PDF)

Pires, N.J., Lay, B. and Rubenson, J. (2014). Joint-level mechanical triggers for the walk-to-run transition in humans. J. Exp. Biol. 217: 3519-27. (PDF)

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.

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.

Guinea fowl running wearing a passive-elastic exo-tendon. Video courtesy S.M. Cox.

Associated Publications:

Cox, S.M., Rubenson, J., Sawicki, G.S. (2018). A soft-exosuit enables multi-scale analysis of wearable robotics in a bipedal animal model.  IEEE Intelligent Robots and Systems IROS. (PDF)

Bishop PJ, Graham DF, Lamas LP, Hutchinson JR, Rubenson J, Hancock JA, Wilson RS, Hocknull SA, Barrett RS, Lloyd DG, Clemente CJ. (2018). The influence of speed and size on avian terrestrial locomotor biomechanics: Predicting locomotion in extinct theropod dinosaurs. PLoS One. 21;13(2):e0192172. (PDF)

Bishop PJ, Clemente CJ, Weems RE, Graham DF, Lamas LP, Hutchinson JR, Rubenson J, Wilson RS, Hocknull SA, Barrett RS, Lloyd DG. (2017). Using step width to compare locomotor biomechanics between extinct, non-avian theropod dinosaurs and modern obligate bipeds. J R Soc Interface. 14(132). (PDF)

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 Suzanne Cox, Jonas Rubenson, Katrina Easton, Melinda Cromie, Rich Marsh, Scott Delp)

Associated publications:

Cox, S., Easton, K, Cromie, M., Marsh, R., Delp, S.,Rubenson, J.  The interaction of compliance and activation on the force-length operating range and force generating capacity of skeletal muscle: a computational study using a guinea fowl musculoskeletal model (2019). Integrative Organismal Biology, obz022, (PDF)

Rankin, J.W., Rubenson, J. and Hutchinson, J.R. (2016) Inferring muscle functional roles of the ostrich pelvic limb during walking and running using computer optimization. R. Soc. Lond. Interface. May;13(118). pii: 20160035. (PDF)

Hutchinson J.R., Rankin J.W., Rubenson J., Rosenbluth K.H., Siston R.A., Delp S.L. (2015). Musculoskeletal modelling of an ostrich (Struthio camelus) pelvic limb: influence of limb orientation on muscular capacity during locomotion. PeerJ 3:e1001 (PDF)