Differences in self-selected and fastest-comfortable walking in post-stroke hemiparetic persons

Abstract

Post-stroke hemiparetic walking is typically asymmetric. Assessment of symmetry is often performed at either self-selected or fastest-comfortable walking speeds to gain insight into coordination deficits and compensatory mechanisms. However, how walking speed influences the level of asymmetry is unclear. This study analyzed relative changes in paretic and non-paretic leg symmetry to assess whether one speed is more effective at highlighting asymmetries in hemiparetic walking and whether there is a systematic effect of speed on asymmetry. Forty-six subjects with chronic hemiparesis walked at their self-selected and fastest-comfortable speeds on an instrumented split-belt treadmill. Relative proportions (paretic leg value/(paretic+non-paretic leg value)) were computed at each speed for step length (PSR), propulsion (PP), and joint moment impulses at the ankle and hip. Thirty-six subjects did not change their step length symmetry with speed, while three subjects changed their step length values toward increased asymmetry and seven changed toward increased symmetry. Propulsion symmetry did not change uniformly with speed for the group, with 15 subjects changing their propulsion values toward increased asymmetry while increasing speed from their self-selected to fastest-comfortable and 11 decreasing the asymmetry. Both step length and propulsion symmetry were correlated with ankle impulse proportion at self-selected and fastest-comfortable speed (cf., hip impulse proportion), but ratios (self-selected value/fastest-comfortable value) of the proportion measures (PSR and PP) showed that neither step length nor propulsion symmetry correlated with the ankle impulse proportions. Thus, the individual kinetic mechanisms used to increase speed could not be predicted from PSR or PP.

Figure 1

Change in walking speed (fastest-comfortable – self-selected) versus self-selected walking speed.

Figure 2

Propulsive symmetry Speed Ratio (PP at self-selected/PP at fastest-comfortable) versus Step length symmetry Speed Ratio (PSR at self-selected/PSR at fastest-comfortable). Shaded areas represent approximate symmetry between speeds (0.9 to 1.1). Speed ratios > 1.1 indicates greater relative paretic values at self-selected speeds. Speed Ratios Ratio < 0.9 indicates lesser relative paretic values at self-selected Speeds. Shaded regions (0.9 to 1.1) represent the relative symmetric region for Speed Ratios (i.e., little change in measures between self-selected and fastest-comfortable speed).

Figure 3

Ankle moment impulse proportion (AIP) Speed Ratio (AIP at self-selected / AIP at fastest-comfortable) versus A) step length symmetry (PSR) and B) propulsion symmetry (PP). Shaded areas represent approximate symmetry between speeds (0.9 to 1.1). Speed Ratios > 1.1 indicates greater relative paretic values at self-selected speeds. Speed Ratios < 0.9 indicates lesser relative paretic values at self-selected Speeds. Shaded regions (0.9 to 1.1) represent the relative symmetric region for speed ratios (i.e., little change in measures between self-selected and fastest-comfortable speed).