Northwestern University Feinberg School of Medicine

Northwestern University Prosthetics-Orthotics Center

Preliminary Quantitative Gait Analysis of Reciprocating Gait Orthosis (RGO) Users

Principal Investigator: Steven Gard, PhD

Student Investigator: William Brett Johnson, MS

Co-Investigator: Stefania Fatone, PhD

Funded by: National Institute on Disability Research and Rehabilitation (NIDRR)

Status: Completed

PurposePediatric RGO.

This project studies the motions and associated energy consumption of Reciprocating Gait Orthosis (RGO) (see figure) users. The energy cost of walking in an RGO is very high, and we wish to find ways to reduce this cost. Very little has been published on the motion of RGO users; so, we quantified their gait in an attempt to identify the causes of the high energy cost.


We measured the motion of five RGO users using a marker-based video motion capture system, the kinetics of their gait using force plates, their muscle activation patterns using electromyography, and their energy consumption using a COSMED portable spirometer. We used this data to calculate the net forces and moments acting on RGO users' hips and shoulders as well as the mechanical and metabolic energy used to walk with a RGO.


We found that RGO users walk with a flexed trunk throughout the gait cycle. The RGO users flexed their trunks during periods of double support and extended their trunks during periods of single support. We also found that RGO users bore less than 40% of their body weight through their stance leg and more than 50% through their arms during portions of the single support phase. Bearing weight through the arms may be a source of high energy expenditure. We theorize that the flexed trunk posture encourages weight bearing through the arms during single support. With a flexed trunk, forces borne through the arms were shown to encourage trunk extension while forces borne through the stance leg encouraged trunk flexion. Therefore, to achieve the trunk extension observed during the single support phase, forces born through the arms increased and forces born through the stance leg decreased.

We also found that RGO users extended their swing hip at the beginning of swing. This motion is counterproductive to the forward advancement of the swing leg and may also be caused in part by the flexed trunk posture of RGO users and compliance within the RGO's reciprocal link. For the rest of the swing phase, however, we observed small net flexion moments at the hip. We also calculated that the rate of work done by the net moment at the hip during swing was less than the rate of work done by the net force acting at the hip. Since many of our subjects lacked active hip flexors we assumed that the moments at the hip were generated by the RGO's reciprocal link. The small moments, the low rate of work, and information from other studies concerning the reciprocal link lead us to conclude that the reciprocal link contributes little to advancing the leg forward during swing. The reciprocal link appears to be under utilized. If the link was used more during swing, then it may help reduce energy expenditure.

Finally, we observed poor conservation of mechanical energy at the RGO users' trunks. Poor mechanical energy conservation could be another source of high energy expenditure because more work may have to be done to maintain steady state walking. We theorize that this poor conservation is caused by a deceleration of the body during the latter half of single support, as indicated by posteriorly directed forces acting on the stance foot and walking aides of the RGO users.

Related Presentations and Publications

Johnson WB and Fatone S. (2006) Dynamic Analysis of an ARGO User. The Academy Today. American Academy of Orthotists and Prosthetists, Virginia, IL, USA.

Johnson WB and Gard S. (2006) Preliminary Findings from Quantitative Gait Analyses of RGO Users. BMES Annual Fall Meeting, Chicago, IL, October 11-14.

Johnson WB, Fatone S, Gard S. (2006) Preliminary Findings for a Pilot Study on the Mechanics of RGO Gait. 15th Annual Visiting Professor Symposium, Motion Analysis Center, Children's Memorial Hospital, November 10, Chicago, IL.

Johnson WB, Fatone S, Gard S. (2007) Preliminary Results for a Dynamic Analysis of RGO Users. Gait and Clinical Motion Analysis Society, April 11-14, Springfield, Massachusetts (poster).

Johnson WB. (2007) Preliminary Findings for a Study of the Dynamics of RGO Gait. Capabilities, 15(2):3. Northwestern University, Chicago, Illinois.

Johnson WB. (2008) Dynamic Analysis of RGO Users. Paper presented at: Midwest Chapter Meeting of the American Academy of Orthotists and Prosthetists; June 27-28, Joliet, IL.

Johnson WB. (2008) Preliminary Quantitative Gait Analysis of Reciprocating Gait Orthosis (RGO) Users. MS Thesis, Biomedical Engineering, Northwestern University.

Johnson WB, Fatone S, Gard SA. (2009) Walking mechanics of persons who use reciprocating gait orthoses. J Rehabil Res Dev. 2009; 46(3):435-446. 

Johnson W, Fatone S, Gard S. (2009) Dynamic analyses of the gait of RGO users. Paper presented at: Annual Meeting and Scientific Symposium of the American Academy of Orthotists and Prosthetists; March 4-7, 2009; Atlanta, GA. 

Johnson WB, Fatone S, Gard S. (2010) Dynamics of Reciprocating Gait Orthosis (RGO) assisted gait. World Congress of the International Society for Prosthetics and Orthotics, May 10-15, Leipzig, Germany.

Johnson WB, Fatone S, Gard S. (2011) Investigating the effects of hip joint stiffness on RGO assisted gait with a lower limb paralysis simulator. Invited Speaker, Midwest Chapter of the American Academy of Orthotists and Prosthetists, June 3-4, Grand Geneva Resort, Wisconsin.

Johnson WB, Fatone S, Gard SA (2011) Modeling the walking patterns of reciprocating gait orthosis users with a novel lower limb paralysis simulator. Conference Proceedings IEEE Engineering Medicine Biology and Society, Aug:7841-7844.

Johnson WB, Fatone S, Gard SA. (2013) Modeling the effects of sagittal-plane hip joint stiffness on Reciprocating Gait Orthosis Assisted gait. Journal of Rehabilitation Research and Development, 50(10):1449-1456.