Influence of speed on walking economy poststroke

Abstract

Background and objective: Walking speed influences energy cost in healthy adults, but its influence when walking is impaired due to stroke is not clear. This study investigated the effect of manipulating walking speed on the energy economy of walking poststroke.

Methods: Sixteen persons with chronic stroke underwent a clinical examination, including several lower extremity impairment measures. consumption (VO(2)) was measured as they walked at their self-selected speed (Free), 20% slower (Slow), their fastest possible speed (Fastest), and 2 speeds between Free and Fastest speeds. VO(2) was normalized to body mass and speed, resulting in energy cost per meter walked (CW).

Results: A main effect for speed was observed (P = .00001), with faster than self-selected speeds showing greater relative economy as a whole. However, for 5 subjects with the fastest walking speeds (>1.2 m/s), there was a trend toward decreasing relative economy at speeds higher than self-selected speed (P = .18). There was a negative correlation between improvement in CW at the most economical speed and (a) Free speed (r = -.857; P < .0001) and (b) lower extremity Fugl-Meyer scores (r = -.653; P = .006).

Conclusions: For those poststroke whose fastest walking speed after stroke is below 1.2 m/s, walking economy improves when speed is increased above the self-selected walking speed. The results suggest that for persons poststroke with very slow self-selected walking speeds, improvements in walking speed could be accompanied by improvements in walking economy if faster walking speeds can be attained through intervention.

Figures

Figure 1. Average Energy Cost per Meter Walked Across Subjects at Each Speed

Note: Error bars represent ±1 standard error of the mean. †P < .05 between the Slow speed and speed indicated; *P = .05 between the Free speed and speed indicated.

Figure 2. Average Energy Cost per Meter Walked for All Subjects at Their Free Speed and Speed of Energy Minimum

Note: Black bars represent energy cost per meter walked at subject’s Free speed and gray bars at their speed of energy minimum. Error bars represent ±1 standard error. CW indicates cost of walking.

Figure 3. Correlations Between Change in Energy Economy and Walking Speed and Lower Extremity Impairment

Note: A, Scatterplot of Free speed versus energy difference (CWfree – CWmin). B, Scatterplot of Fugl-Meyer Score versus energy difference (CWfree – CWmin). Each circle represents data from an individual subject. CW indicates cost of walking.

Figure 4. Energy Cost per Meter Walked Averaged for 2 Subgroups at Each Speed

Note: Black lines represent the average for the subjects whose Fastest speed is less than 1.2 m/s (n = 11). Gray lines represent the average for subjects whose Fastest speed is greater than 1.2 m/s (n = 5). The left y-axis shows energy cost per meter walked for the slower group and the right y-axis is for the faster group. Error bars represent ±1 standard error.