Locomotion Laboratory

phone: 303-492-0926
fax: 303-492-4009

Research Interests

Graduate Student: Kristine Snyder, M.S.; Christopher Arellano, M.S.; Jason Franz, M.S.; Richard Ellis, Sc.B.

Collaborators: Jamie Bartlett, Ph.D., Navy Medical Center, San Diego; Ray Browning, Ph.D., Colorado State University; William Byrnes, Ph.D., University of Colorado at Boulder; Max Donelan, Ph.D., Simon Fraser University, Canada; Ellen Generaal, M.S., Free University of Amsterdam; Jinger Gottschall, Ph.D., Penn State University; Alena Grabowski, Ph.D., MIT; Hugh Herr, Ph.D., MIT; Wouter Hoogkamer, M.S., Free University of Amsterdam; William McDermott, Ph.D., The Orthopedic Specialty Hospital, Utah; Craig McGowan, Ph.D., University of Idaho.

(L to R): Rich Ellis, Jason Franz, Rodger Kram, Krissy Snyder, Chris Arellano

Biomechanical Basis for the Energetic Cost of Human Walking (Franz, Kram). Muscles must perform at least four functions during walking: (1) Generate muscular force to support body weight; (2) Perform mechanical work to redirect and restore the center of mass velocity during the step-to-step transition; (3) Swing the legs; and (4) Maintain stability. We are performing a series of experiments that manipulate one or more of these functions so as to quantify the cost of each function in normal healthy adults. In addition, we are investigating the greater energetic cost of walking by obese persons and the underlying mechanisms for the greater cost.

The Biomechanics of Uphill/Downhill Walking in Young and Elderly Adults (Franz, Kram). We are performing a series of experiments to understand the biomechanics of level, uphill and downhill walking at the individual leg, joint and muscle levels. Although most healthy elderly adults have little difficulty walking over level surfaces, walking uphill can lead to exhaustion. Accordingly, we are investigating how age-related changes in lower limb function during level walking affect uphill walking performance in the elderly.

Biomechanical Basis for the Energetic Cost of Human Running (Arellano, Hoogkamer, Kram). In running, our research shows that generating force to support body weight is the major biomechanical factor determining metabolic cost. However, we have found that generating forward propulsive forces comprises about 30% of the cost of running and leg swing appears to consume about 10%. We continue to refine these ideas as to how the cost changes with speed and grade.

Biomechanics and Energetics of Running by Amputee Athletes (Grabowski, Herr, McGowan, McDermott, Kram). We are studying the phenomenal performance of some of the world's fastest Paralympic athletes. The goals of this research include: helping the athletes to improve their performance, designing even better leg prostheses, enhancing our understanding of the fundamental factors that limit running performance in both amputee and non-amputee runners.

Biomechanics and Energetics of Cushioning During Running (Franz, Kram). We are investigating the biomechanical determinants of the metabolic energy cost of ÒcushioningÓ during running, where cushioning refers to both the shock absorbing properties of shoes as well as the actions of the leg muscles during landing. Traditionally, cushioning inherently involves the mass of running shoes. But, recently some have advocated barefoot running because it is purportedly Òmore efficientÓ. As part of this project we are investigating the energetic cost of barefoot running and how the effects of cushioning and shoe weight interact.

The Muscular Basis for the Energetic Cost of Human Standing (Generaal, Kram). The energetic cost of standing is small relative to locomotion, but people stand up for much of the day. We are investigating how much energy is required for weight support, cardiac work and balance. Further, we are determining which specific leg muscles contribute to balance.

Comparative Locomotion Biomechanics and Energetics (Kram, McGowan). We occasionally study different animal species that exhibit exceptional locomotion. For example, we are initiating a study of the locomotor abilities of pronghorn and the unique bipedal behavior of the gerenuk, an African antelope.

Passive Cycling Energetics (Byrnes, Kram). We have discovered that a person's metabolic rate can be substantially increased by passive movement of their legs on a stationary bicycle powered by an electric motor. We are exploring if passive cycling can aid the treatment/prevention of obesity, cardiovascular and metabolic syndrome

The requirements for undergraduate students who want a research experience in our Laboratory are:

For more information, contact Prof. Rodger Kram (rodger.kram@colorado.edu). Unfortunately, due to high demand, we cannnt accommodate all qualified students.

Browning RC, Kram R. Pound for pound: Working out how obesity influences the energetics of walking. Journal of Applied Physiology 106: 1755-1756, 2009.

Browning RC, McGowan CP, Kram R. Obesity does not increase mechanical work per kilogram body mass during walking. Journal of Biomechanics 42: 2273-2278, 2009.

Grabowski AM, McGowan CP, McDermott WJ, Beale MT, Kram, R, Herr HM. Running-specific prostheses limit ground-force during sprinting Biology Letters 6: 201-204, 2010

Kram R, Grabowski AM, McGowan CP, Brown MB, Herr HM. Counterpoint: Artificial limbs do not make artificially fast running speeds possible. Journal of Applied Physiology 108: 1012-1014, 2010

McGowan CP, Kram R, Neptune RR. Modulation of leg muscle function in response to altered demand for body support and forward propulsion during walking. Journal of Biomechanics 42: 850-856, 2009.