Trunk Muscle Activation Patterns During Standing Turns in Patients With Stroke: An Electromyographic Analysis

Abstract

Recent evidence indicates that turning difficulty may correlate with trunk control; however, surface electromyography has not been used to explore trunk muscle activity during turning after stroke. This study investigated trunk muscle activation patterns during standing turns in healthy controls (HCs) and patients with stroke with turning difficulty (TD) and no TD (NTD). The participants with stroke were divided into two groups according to the 180° turning duration and number of steps to determine the presence of TD. The activation patterns of the bilateral external oblique and erector spinae muscles of all the participants were recorded during 90° standing turns. A total of 14 HCs, 14 patients with TD, and 14 patients with NTD were recruited. The duration and number of steps in the turning of the TD group were greater than those of the HCs, independent of the turning direction. However, the NTD group had a significantly longer turning duration than did the HC group only toward the paretic side. Their performance was similar when turning toward the non-paretic side; this result is consistent with electromyographic findings. Both TD and NTD groups demonstrated increased amplitudes of trunk muscles compared with the HC groups. Their trunk muscles failed to maintain consistent amplitudes during the entire movement of standing turns in the direction that they required more time or steps to turn toward (i.e., turning in either direction for the TD group and turning toward the paretic side for the NTD group). Patients with stroke had augmented activation of trunk muscles during turning. When patients with TD turned toward either direction and when patients with NTD turned toward the paretic side, the flexible adaptations and selective actions of trunk muscles observed in the HCs were absent. Such distinct activation patterns during turning may contribute to poor turning performance and elevate the risk of falling. Our findings provide insights into the contribution and importance of trunk muscles during turning and the association with TD after stroke. These findings may help guide the development of more effective rehabilitation therapies that target specific muscles for those with TD.

Keywords: electromyography; muscle activation patterns; stroke; trunk muscles; turning.

Figure 1

Placement of surface EMG electrodes. EO, external oblique muscle; ES, erector spinae.

Figure 2

Representative plots of trunk muscle amplitudes for participants with stroke with and without turning difficulty and healthy controls when performing standing 90° turn tasks toward both sides. EO, external oblique muscle; ES, erector spinae; TD, turning difficulty; NTD, no turning difficulty; P, paretic side; NP, non-paretic side.

Figure 3

Bilateral external oblique and erector spinae muscles amplitudes (% RVC) for stroke participants with and without turning difficulties and healthy controls during 90° standing turns toward paretic (left) and non-paretic sides (right). EO, external oblique muscle; ES, erector spinae; TD, turning difficulty; NTD, no turning difficulty; P, paretic side; NP, non-paretic side; HC, healthy control. *represents a significant difference compared with EO. ^†represents a significant difference compared with HCs.