Associations between lower-limb muscle activation and knee flexion in post-stroke individuals: A study on the stance-to-swing phases of gait

PLOS ONE, Nov 2019

Reduced knee flexion is a leading feature of post-stroke gait, but the causes have not been well understood. The purpose of this study was to investigate the relationship between the knee flexion and the lower-limb muscle activation within the stance-to-swing phases of gait cycle in the post-stroke hemiplegic patients. Ten stroke patients and 10 age- and gender-matched healthy subjects participated in the experiment. The lower-limb kinematic signals and the surface electromyography (sEMG) signals of the left and right rectus femoris (RF), biceps femoris (BF) and lateral gastrocnemius (GS) were recorded during walking. The angle range (AR) of knee flexion, the root mean square (RMS) and the mean frequency (MNF) of sEMG signals were calculated from the terminal stance (TSt) to the initial swing (ISw) phases of gait cycle. Stroke patients showed lower bilateral AR of knee flexion and lower RMS of GS on the paretic side, but higher MNF of RF on the non-paretic side compared with the controls. Within the stroke patients, significant differences were found between their paretic and non-paretic limbs in the AR of knee flexion, as well as in the RMS and MNF of GS (p < 0.05). Regression analysis showed that the RMS of BF, MNF of BF and MNF of GS explained 82.1% of variations in AR of knee flexion on paretic side (r2 = 0.821). But the RMS and MNF of all the muscles (including the RF, GS and BF) could explain 65.6% of AR of knee flexion variations on the non-paretic side (r2 = 0.656), and 45.2% of variations for the healthy subjects (r2 = 0.452). The reduced knee flexion during gait was associated with altered magnitude and frequency of muscle contractions and with simplified muscle synergy in the post-stroke hemiplegic patients. Identifying the muscles that are responsible for knee stiffness may facilitate improvement of rehabilitation strategy for post-stroke gait.

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Associations between lower-limb muscle activation and knee flexion in post-stroke individuals: A study on the stance-to-swing phases of gait

September Associations between lower-limb muscle activation and knee flexion in post-stroke individuals: A study on the stance-to-swing phases of gait Wei Wang 0 1 Ke Li 0 1 Shouwei Yue 1 Cuiping Yin 1 Na Wei 1 0 Laboratory of Motor Control and Rehabilitation, Institute of Biomedical Engineering, School of Control Science and Engineering, Shandong University , Jinan , China , 2 Department of Physical Medicine and Rehabilitation, Qilu Hospital, Shandong University , Jinan , China , 3 Department of Geriatrics, Qilu Hospital, Shandong University , Jinan , China 1 Editor: Riccardo Di Giminiani, University of L'Aquila , ITALY - Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Reduced knee flexion is a leading feature of post-stroke gait, but the causes have not been well understood. The purpose of this study was to investigate the relationship between the knee flexion and the lower-limb muscle activation within the stance-to-swing phases of gait cycle in the post-stroke hemiplegic patients. Ten stroke patients and 10 age- and gendermatched healthy subjects participated in the experiment. The lower-limb kinematic signals and the surface electromyography (sEMG) signals of the left and right rectus femoris (RF), biceps femoris (BF) and lateral gastrocnemius (GS) were recorded during walking. The angle range (AR) of knee flexion, the root mean square (RMS) and the mean frequency (MNF) of sEMG signals were calculated from the terminal stance (TSt) to the initial swing (ISw) phases of gait cycle. Stroke patients showed lower bilateral AR of knee flexion and lower RMS of GS on the paretic side, but higher MNF of RF on the non-paretic side compared with the controls. Within the stroke patients, significant differences were found between their paretic and non-paretic limbs in the AR of knee flexion, as well as in the RMS and MNF of GS (p < 0.05). Regression analysis showed that the RMS of BF, MNF of BF and MNF of GS explained 82.1% of variations in AR of knee flexion on paretic side (r2 = 0.821). But the RMS and MNF of all the muscles (including the RF, GS and BF) could explain 65.6% of AR of knee flexion variations on the non-paretic side (r2 = 0.656), and 45.2% of variations for the healthy subjects (r2 = 0.452). The reduced knee flexion during gait was associated with altered magnitude and frequency of muscle contractions and with simplified muscle synergy in the post-stroke hemiplegic patients. Identifying the muscles that are responsible for knee stiffness may facilitate improvement of rehabilitation strategy for poststroke gait. sdhrss.gov.cn/, Postdoctoral Innovation Foundation of Shandong Province, KL NA, http:// www.sdu.edu.cn, Young Scholars Program of Shandong University, KL. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Introduction Recovery of locomotion ability is a primary goal of post-stroke hemiparesis rehabilitation. The abnormal gait after stroke is characterized by reductions in stride length, movement speed, muscle power and joint range of motion [1±3]. Although all the lower-limb joints could be affected by stroke, the knee would be more vulnerable than the others. The peak knee flexion in the swing phase of gait usually drops off, recognized as the stiff-knee gait, which is a common abnormality associated with stroke. No consensus has been reached regarding the pathophysiology of stiff-knee gait. Over-activation of quadriceps muscle during the swing phase has often been mentioned [ 4 ]; while other factors, such as the hip flexor weakness and ankle plantar flexor hyperactivity at the terminal stance phase, may also make a contribution [ 5 ]. Identifying the contributors to the stiff knee may facilitate to find more efficient rehabilitation strategy for post-stroke gait. Among the muscles surrounding the knee, the rectus femoris (RF), gastrocnemius (GS) and biceps femoris (BF) are representative muscles responsible for generating appropriate range of motion. The RF prevents excessive knee flexion, and the BF and GS contribute to the knee flexion during swing of healthy gait. However, roles of these muscles in the post-stroke stiff knee are still controversial. Abnormal excessive activation of RF has been extensively observed in the post-stroke hemiparesis patients and is considered as a primary cause of stiff knee [ 6 ]. Some other studies showed that a transfer surgery or a botulinum toxin injection could lower the over-activity of RF, accompanied by the knee flexion improvement during swing [ 7, 8 ]. However, Knuppe et al reported that the RF activity during swing phase was not associated with stiff knee after nerve injury [9]. Decreased GS contraction has been found on the pre-swing stage of post-stroke gait, suggesting lowered muscle activation at the initiation of knee flexion during walking [ 10 ]. Studies on turning walking in post-stroke p (...truncated)


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Wei Wang, Ke Li, Shouwei Yue, Cuiping Yin, Na Wei. Associations between lower-limb muscle activation and knee flexion in post-stroke individuals: A study on the stance-to-swing phases of gait, PLOS ONE, 2017, Volume 12, Issue 9, DOI: 10.1371/journal.pone.0183865