Center of Mass Acceleration as a Surrogate for Force Production After Spinal Cord Injury Effects of Inclined Treadmill Walking Mark G. Bowden, PhD, PT Research Health Scientist, Ralph H. Johnson VA Medical Center Assistant Professor, Department of Health Science and Research and Division of Physical Therapy SCIRF 10-003
Traditional Walking Outcomes speed, walking independence (WISCI- II), balance (BBT, DGI) strength, sensation (ASIA evaluation) amount of community walking (SAM) Patient perspective Quality of life WHAT DO THESE TELL US ABOUT THE FACTORS THAT CONTRIBUTE TO IMPAIRED WALKING?
Advanced Measurement Tools EMG for analyses of muscle activation Motion capture to determine body positioning and movement (kinematics) and force requirements (kinetics)
Force Production 100 Pp (%) 50 0 1 2 3 Bowden, et al, 2006
Non-paretic Paretic Week 1 Week 4 Week 7 Week 10 Week 13 Longitudinal assessment of propulsion. Notice the steady improvement in leg performance from Session 1 to session 13, reflecting an improvement in weaker leg contribution to propulsion from 3.8% to 32.9%.
Overall Purpose of Research Program Utilize the framework that has been developed from previous experiences studying walking in people with stroke in order to: 1. Understand the mechanisms by which walking is impaired in those individuals with incomplete spinal cord injury 2. Develop interventions to address those mechanisms specifically in improve walking ability (and performance).
Complicated math for PTs: F=ma Control Acceleration in m/s 2 1.5 1 0.5 0-0.5-1 1 9 17 25 33 41 49 57 65 73 81 89 97 Summed GRF COM Acceleration -1.5 % of gait cycle Plots of summed ground reactions forces (GRFs) and COM acceleration. Calculated COMa measures are very similar to data collected directly from force plates on an instrumented treadmill, implying that COMa is a valid surrogate for laboratory-collected ground reaction forces. The ability for measures to equate to theoretically identical outcomes is critical to link laboratory measures to portable measurement tools. Acceleration in m/s 2 0.8 0.6 0.4 0.2 0-0.2-0.4-0.6 Person with Paresis 1 11 21 31 41 51 61 71 81 91 101 % of gait cycle Summed GRF COM Acceleration
Using COMa as an Outcome Measure 1.5 1 Acceleration in m/s 2 0.5 0-0.5 1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69 73 77 81 85 89 93 97 101 Pre Post Control -1-1.5 Pre- and post-training accelerations of individuals participating in a locomotor training intervention. While COMa increases, it does not approach normative values, particularly in the critical phase 3 and 4 period of the gait cycle, implying specific therapies need to target specific mechanistic elements of the walking pattern.
Can COMa be Trained?
COMa in m/s 2 0.6 0.4 0.2 0-0.2-0.4-0.6-0.8 COMa before (blue line) and 2 minutes after (red line) incline training. A brief (5 minute) period of adaptation training yielded a 48% increase in both peak COMa and the time integral of the COMa curve in phase 3 and 4. The x-axis represents percentage of the gait cycle. Hip Extension Angle: Peak hip extension increased by 1.8 degrees in the weaker leg and by 2.1 degrees in the stronger leg. These increases were maintained at the end of 2-minutes (increases over baseline were 1.8 degrees in the weaker leg and 1.7 degrees in the stronger leg). Propulsive (Anterior) GRF: The peak GRF increased in the weaker leg by 12.3% (36.1N/kg to 40.6 N/kg) and did not change in the stronger leg (48.1 to 47.9 N/kg). The increase in the weaker leg persisted at the end of two minutes (41.3 N/kg). Propulsive impulse (area under the positive portion of the anterior/posterior GRF curve) responded similarly: the weaker leg increased by 10.5% and the stronger leg had a minor decrease of 3.8%.
Final Enrollment
Manuscripts Gregory CM, Embry AE, Perry LA, and Bowden MG. Quantifying human movement across the continuum of care: from lab to clinic to community. J Neuro Methods. 231: 18-21, 2014. DiPiro D, Bowden MG, Embry AE, Perry LA, and Gregory CM. Intensity Matters: A multimodal exercise program improves strength and gait speed after incomplete SCI. Topics in Spinal Cord Injury Rehabilitation (in press). Bowden MB, Embry AE, Gregory CM. COM acceleration as a surrogate for force production after incomplete SCI: impact of incline training. (in progress).
Conference Presentations DiPiro ND, Bowden MG, Embry AE, Perry LA, and Gregory CM. Intensity Matters: A multimodal exercise program improves strength and gait speed after incomplete SCI. American College of Sports Medicine Annual Meeting, Indianapolis, IN, 2013. Phadke C, Nair P, Madhavan S, Bowden MG, Thompson F, Behrman AL. Soleus H-reflex modulation after motor incomplete spinal cord injury: Effects of locomotor training. American Physical Therapy Association Combined Sections Meeting, January 21-24, 2013, San Diego, CA. Bowden MG, Gregory C and Kautz S. Center of mass acceleration as a surrogate for force production after neurological Injury: Effects of inclined treadmill walking. Poster presentation at the Society for Neuroscience Annual Meeting. October, 2012; New Orleans, LA. Bowden MG, Behrman AL, Gregory C, Patten C, Kautz S. Translational niomechanics: development of portable quantitative measurement. American Physical Therapy Association-Combined Sections Meeting, New Orleans, LA, 2011.
Research Coordinators: Brian Cence 792-8198 cence@musc.edu Christina Thompson 792-6313 thompch@musc.edu Research Physical Therapists: Aaron Embry, DPT, MSCR 792-8198 embry@musc.edu Stephanie Pudlik, DPT 792-3362 pudlik@musc.edu Collaborating Investigators: Chris Gregory, PT, PhD 792-1078 gregoryc@musc.edu Steve Kautz, PhD Professor and Chair, Department of Health Science and Research kautz@musc.edu Jim Krause, PhD Associate Dean of Research College of Health Professions krause@musc.edu