Aim 2: Quantify metabolic cost as well as muscle mechanical energy expenditure during walking in persons with chronic post-stroke hemiparesis and neurologically healthy individuals. Post-stroke hemiparesis is associated with a variety of motor control problems that include abnormal synergistic organization of movement as well as altered temporal sequencing of muscle activity 5,10,11. Since muscle excitation during normal walking is believed to be very efficient 8,9,33 it is likely that altered muscle coordination post-stroke, reflected in increased mechanical work, is one factor contributing to the increased metabolic cost of walking. We hypothesize that the metabolic cost of walking post-stroke will be elevated relative to controls at matched speeds. Additionally, a measure of mechanical work, muscle mechanical energy expenditure (MMEE), will be elevated post-stroke, reflective of mechanically inefficient movement strategies and causal to a portion of the increased metabolic cost of walking.