Metabolic and Mechanical Energy Saving Mechanisms in Barefoot vs. Shod Human Running Leslie Fischer Honors Program and Division of Kinesiology and Health Advisor: Dr. Matthew W. Bundle Spring 2010

Background

Metabolic energy use during running Loaded Metabolic Energy Running Speed

Muscle Function During Running No muscle length change during stance Therefore muscles perform little, to no, work during the stance phase The job of the active muscle is to provide force for weight support Roberts et al., 1997

Muscle force production and metabolism The force generation step in muscle requires ATP hydrolysis (the energy currency of the cell) This provides for a link between rates of muscle force production and cellular energy release Metabolic Energy α 1/tc Kram & Taylor, 1990

Spring-like function of the human leg During the stance phase of running the leg is under compression and is shortest at mid-stance Since muscle is isometric, this length change occurs in the tendons, and connective tissue This allows for the temporary storage and release of elastic energy within the large tendons of our legs

Foot strike patterns and collision forces in habitually barefoot versus shod runners Foot can collide with the ground in three ways: Rear-foot strike (RFS) Mid-foot strike (MFS) Fore-foot strike (FFS) Evidence showing that barefoot runners and minimally shod runners avoid RFS Barefoot or minimally shod runners are likely to be resistant to injury Lieberman et al., 2010

Cost of transport on average is 1.41% less for barefoot running Metabolic Energy Cost of transport on average is 1.41% less for barefoot running Squadrone & Gallozzi, 2009

Contact Time Divert et al. 2005 and Squadrone & Gallozzi 2009

Electromyography Speed was at 3.33 m/s Divert et al., 2005

Variables During Running Expectations Results Energy Expended Same Contact Time EMG Less in Barefoot Less in Barefoot Greater in Barefoot

Question: Why is it in-expensive to run barefoot?

Hypotheses: 1.) Massiveness of Limb 2.) Leg Stiffness 3.) Effective Mechanical Advantage (EMA)

1.) Massiveness of the limb Constant Speed at 3.33m/s Percent Differences: 0.50 kg thighs: 1.66% 1.00 kg thighs: 3.53% 0.50 kg feet: 3.34% 1.00 kg feet: 7.16% Martin,1985

1.) Massiveness of the limb Frederick, 1985

Metabolic Energy

2.) Leg Springs The tendons, ligaments, and muscles in our legs function like springs The stiffness of the leg spring kleg = Force Δl can change in response surface and shoe compliance

2.) Stiffness Lieberman et al., 2010

3.) Effective mechanical advantage (EMA)

Conclusion

References Burkett, L.N., Kohrt, W.M., & Buchbinder, R. (1985). Effects of shoes and foot orthotics on VO2 and selected frontal plane kinematics. Med Sci Sports Exerc, 17(1): 158-63. De Wit, B., De Clercq, D., & Aerts, P. (2000). Biomechanical analysis of the stance phase during barefoot and shoe running. J Biomech, 33(2):269-78. Divert, C., Mornieux, G., Mayer F., & Belli, A. (2005) Mechanical comparison of barefoot and shod running. Int J Sports Med, 26(7):593-8. Frederick, E.C. (1983). A model of the energy cost of load carriage on the feet during running. Nike Sport Research Laboratory, Exeter, New Hampshire, U.S.A. Karm ,R. & Taylor, R. (1990). Energetics of running a new perspective. Nature, 346:265-267. Martin, P.E. (1985). Mechanical and physiological responses to lower extremity loading during running. Med Sci Sports Exerc, 17(4): 427-22. Roberts, T.J., March, R.L., Weyand, P.G., Taylor, C.R. (1997). Muscular force in running turkey: the economy of minimizing work. Science, 275:1113-1115, Squadrone, R. and Gallozzi, C. (2009). Biomechanical and physiological comparison of barefoot and two shod conditions in experienced barefoot runners. J Sports Med Phys Fitness, 49(1):6-13.