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)