Harris-Love ML, Forrester LW, Macko RF, Smith GV; University of Maryland - Baltimore, Baltimore, Maryland, USA. Mharris-love@som.umaryland.edu.

PURPOSE: To determine whether vastus lateralis (VL) activation differs between velocity-matched treadmill (TM) and overground (OG) walking in participants with chronic stroke. SUBJECTS: 19 volunteers (age 62.9 ± 9.8 years, 13 males), 41.1 (± 31.0) months post-stroke. METHODS: VL activation patterns were compared using bilateral surface electromyography (EMG) during OG and TM walking at matched velocities. EMG was analyzed as an ensemble average of at least 10 gait cycles, time-normalized to the non-paretic (NP) gait cycle. Variables included burst onset and offset times (% cycle), burst duration (% cycle), integrated amplitude (mV · % cycle), and EMG onset relative to footstrike (% cycle). ANALYSES: Paired t-tests. RESULTS: OG and TM conditions differed for the following variables: paretic (P) VL onset time (OG: 47.1%, TM: 41.9%, p=0.01); NP VL onset time (OG: 85.2%, TM: 87.6%, p=0.09), offset time (OG: 54.7%, TM: 47.8%, p=0.03), duration (OG: 69.1%, TM: 61.2%, p=0.01), and integrated amplitude (OG: 14.1, TM: 10.6, p=0.05). In addition, P VL onset occurred 5.1% before P footstrike OG, and 8.6% before footstrike on the TM (p=0.01); similarly, NP VL onset occurred 14.8% before NP footstrike OG and 12.4% before footstrike on the TM (p=0.09). CONCLUSIONS: TM-walking induces immediate changes in the temporal and amplitude characteristics of VL activation patterns. The P burst onset occurs earlier and NP burst onset occurs later in the gait cycle. In addition, the TM induces earlier P burst onset relative to P stance onset. These alterations suggest that over the course of long-term TM training, neural adaptations in individuals with chronic stroke may be promoted. FUNDING SOURCE: This study was supported by the National Stroke Association (LWF), National Institutes of Health grant R29AG14487-01 (RFM), and the Baltimore Veterans Affairs Medical Center (LWF, RFM).

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