Effects of handrail hold and light touch on energetics, step parameters, and neuromuscular activity during walking after stroke

Abstract

Background: Holding a handrail or using a cane may decrease the energy cost of walking in stroke survivors. However, the factors underlying this decrease have not yet been previously identified. The purpose of the current study was to fill this void by investigating the effect of physical support (through handrail hold) and/or somatosensory input (through light touch contact with a handrail) on energy cost and accompanying changes in both step parameters and neuromuscular activity. Elucidating these aspects may provide useful insights into gait recovery post stroke.

Methods: Fifteen stroke survivors participated in this study. Participants walked on a treadmill under three conditions: no handrail contact, light touch of the handrail, and firm handrail hold. During the trials we recorded oxygen consumption, center of pressure profiles, and bilateral activation of eight lower limb muscles. Effects of the three conditions on energy cost, step parameters and neuromuscular activation were compared statistically using conventional ANOVAs with repeated measures. In order to examine to which extent energy cost and step parameters/muscle activity are associated, we further employed a partial least squares regression analysis.

Results: Handrail hold resulted in a significant reduction in energy cost, whereas light touch contact did not. With handrail hold subjects took longer steps with smaller step width and improved step length symmetry, whereas light touch contact only resulted in a small but significant decrease in step width. The EMG analysis indicated a global drop in muscle activity, accompanied by an increased constancy in the timing of this activity, and a decreased co-activation with handrail hold, but not with light touch. The regression analysis revealed that increased stride time and length, improved step length symmetry, and decreased muscle activity were closely associated with the decreased energy cost during handrail hold.

Conclusion: Handrail hold, but not light touch, altered step parameters and was accompanied by a global reduction in muscle activity, with improved timing constancy. This suggests that the use of a handrail allows for a more economic step pattern that requires less muscular activation without resulting in substantial neuromuscular re-organization. Handrail use may thus have beneficial effects on gait economy after stroke, which cannot be accomplished through enhanced somatosensory input alone.

Fig. 1

a. Effect of light touch and handrail hold on the net energy cost of walking. b. boxplot of the difference between Touch and Normal, and Hold and Normal. The central mark is the median, the edges of the box are the 25th (q¹) and 75th (q³) percentiles. Whiskers extend to the last datapoint > q ¹ − 1.5(q ³ − q ¹) or < q ³ + 1.5(q ³ − q ¹). Datapoints outside this range are shown as a red cross. * = significantly different from NORM at p < .05

Fig. 2

Effects of light touch and handrail hold on spatiotemporal step parameters. * = p < .05

Fig. 3

Eigenvalue spectrum λ_j (left panel), projections Y _k^(j) (central panels) and eigenvectors v ^(j) = (v ₁^(j), …, v _n^(j), …, v ₁₆^(j)) (right panels) for the first three modes (j). Gait cycle for the central panel starts and ends with initial contact of the nonparetic leg

Fig. 4

Reconstructed time normalized EMG patterns (dimensionless) of paretic (upper row) and non-paretic (lower row) leg, based on the three modes for each condition, averaged over strides and participants. Using the time courses Y _k^(j) we reconstructed signals as superposition $X_{m,k}\approx {\tilde{X}}_{m,k}={\sum }_{j=1}^J{v}_m^{\left(j\right)}{Y}_k^{\left(j\right)}$. We further added the DC-values of the original EMGs to these time courses to generate EMG-like patterns. Solid lines indicate averages, shaded areas indicate SD over participants. Stride cycle starts and ends with initial contact of the nonparetic leg. GM = m. Gastrocnemius medialis; TA = m. Tibialis anterior; PL = m. Peroneus longus; RF = m. Rectus femoris; VL = m. Vastus lateralis; ST = m. Semitendinosus GL = m. Gluteus medius; TF = m. Tensor fascia latae

Fig. 5

Changes in muscle activation patterns based on PCA analysis. Left column: root mean squared value (RMS ^(j)) for first three modes for each condition averaged over subjects. Right column: Relative phase distribution plot (∆φ), for relative phase between mode 1 and 2, and variance (V) in relative phase between mode 1 and 2. As can be seen, the relative phase between mode 1 and 2 is centered between 240 and 300 (or: −60 and −100) degrees