Constraints on Stance-Phase Force Production during Overground Walking in Persons with Chronic Incomplete Spinal Cord Injury

Abstract

Persons with incomplete spinal cord injury (iSCI) face ongoing struggles with walking, including reduced speed and increased reliance on assistive devices (ADs). The forces underlying body weight support and gait, as measured by ground reaction forces (GRFs), are likely altered after iSCI because of weakness and AD dependence but have not been studied. The purpose of this study was to examine GRF production during overground walking after iSCI, because greater insight into GRF constraints is important for refining therapeutic interventions. Because of reduced and discoordinated motor output after iSCI, we hypothesized that persons with iSCI would exert smaller GRFs and altered GRF modifications to increased cadence compared with able-bodied (AB) persons, especially when using an AD. Fifteen persons with chronic iSCI, stratified into no AD (n = 7) and AD (n = 8) groups, walked across an instrumented walkway at self-selected and fast (115% self-selected) cadences. Fifteen age-matched AB controls walked at their own cadences and iSCI-matched conditions (cadence and AD). Results showed fore-aft GRFs are reduced in persons with iSCI compared with AB controls, with reductions greatest in persons dependent on an AD. When controlling for cadence and AD, propulsive forces were still lower in persons with iSCI. Compared with AB controls, persons with iSCI demonstrated altered GRF modifications to increased cadence. Persons with iSCI exhibit different stance-phase forces compared with AB controls, which are impacted further by AD use and slower walking speed. Minimizing AD use and/or providing propulsive biofeedback during walking could enhance GRF production after iSCI.

Keywords: assistive device; ground reaction forces; propulsion; spinal cord injury; walking.

Conflict of interest statement

Dr. Randy D. Trumbower has research support from the Wings for Life Foundation, the United States Department of Defense, and the National Institutes of Health. This study was funded by the NIH NICHD (R01 HD081274). The funding sources had no role in study design, collection, patient recruitment, or interpretation of data.

Denise Peters, Yann Thibaudier, Joan Deffeyes, Gila Baer, and Heather Hayes have no competing financial interests.

Figures

FIG. 1.

General methodology. (A) Depiction of measured fore-aft and (B) vertical (V) ground reaction forces.

FIG. 2.

Fore-aft ground reaction forces comparison between persons with incomplete spinal cord injury (iSCI) and able-bodied (AB) controls. Fore-aft ground reaction force data are shown for (A) persons with iSCI who ambulate without an assistive device (AD), and (B) persons with iSCI who ambulate with an AD (and their AB controls). A1 and B1 show representative fore-aft force profiles of a person with iSCI (iSCI01 and iSCI12 for A1 and B1, respectively) at self-selected cadence (gray line) and their AB control at their own self-selected cadence (solid black line), at matched cadence (black dashed line) and at matched cadence + AD (black dotted line). Group data are also shown for braking and propulsion area (A2–B2) and for inflection point (A3–B3). SSmet, self-selected cadence to a metronome. *p < 0.05

FIG. 3.

Fore-aft ground reaction force (GRF) modifications to increased cadence. Fore-aft GRF data are shown for persons with incomplete spinal cord injury (iSCI) (and their able-bodied [AB] controls) who ambulate without an assistive device (AD) (A) or with an AD (B). A1 and B1 show representative fore-aft traces of a person with iSCI (iSCI01 and iSCI12 for A1 and B1, respectively) (gray lines) and their AB control (black lines) under matched conditions at self-selected (SS, solid lines) and fast cadences (F, dashed lines; 115% of SS cadence). Group data are also shown for braking and propulsion area (A2-B2) and for transition point (A3-B3). SSmet, self-selected cadence to a metronome; SSmatch, matched conditions (cadence and AD) at self-selected cadence of person with iSCI; Fmet, fast cadence to a metronome; Fmatch, matched conditions (cadence and AD) at fast cadence of person with iSCI. *p < 0.05. Color image is available online at www.liebertpub.com/neu

FIG. 4.

Vertical ground reaction force (GRF) comparison between persons with incomplete spinal cord injury (iSCI) and able-bodied (AB) controls. Vertical GRF data are shown for (A) persons with iSCI who ambulate without an assistive device (AD), and (B) persons with iSCI who ambulate with an AD (and their AB controls). A1 and B1 show representative vertical force profiles of a person with iSCI (iSCI01 and iSCI12 for A1 and B1, respectively) at self-selected cadence (gray line) and their AB control at their own cadence (solid black line), at matched cadence (black dashed line) and at matched cadence + AD (black dotted line). Group data are also shown for V1Max (A2-B2), V2Max (A3-B3) and modulation (A4-B4). SSmet, self-selected cadence to a metronome. *p < 0.05

FIG. 5.

Vertical ground reaction force (GRF) modifications to increased cadence. Vertical GRF data are shown for persons with incomplete spinal cord injury (iSCI) (and their able-bodied [AB] controls) who ambulate without an assistive device (AD) (A) or with an AD (B). Both A1 and B1 show representative vertical traces of a person with iSCI (iSCI01 and iSCI12 for A1 and B1, respectively) (gray lines) and their AB control (black lines) under matched conditions at self-selected (SS, solid lines) and fast cadences (F, dashed lines; 115% of SS cadence). Group data are also shown for V1Max (A2-B2), V2Max (A3-B3), and modulation (A4-B4). SSmet, self-selected cadence to a metronome; SSmatch, matched conditions (cadence and AD) at self-selected cadence of person with iSCI; Fmet, fast cadence to a metronome; Fmatch, matched conditions (cadence and AD) at fast cadence of person with iSCI. *p < 0.05. Color image is available online at www.liebertpub.com/neu

FIG. 6.

Relationship between fore-aft and vertical ground reaction forces and clinical measures of walking ability, leg strength, and spasticity in persons with incomplete spinal cord injury (iSCI). Only statistically significant (p < 0.05) relationships are shown. Regression line and 95% confidence interval for the group are depicted; open circles represent the assistive device (AD) group, solid circles represent the no AD group. LEMS, Lower Extremity Motor Score; 10MWT, 10 Meter Walk Test; SCI-FAI, Spinal Cord Injury Functional Ambulation Inventory; SCATS, Spinal Cord Assessment Tool for Spastic Reflexes.