Abnormal coactivation of knee and ankle extensors is related to changes in heteronymous spinal pathways after stroke

Abstract

BackgroundAbnormal coactivation of leg extensors is often observed on the paretic side of stroke patients while they attempt to move. The mechanisms underlying this coactivation are not well understood. This study (1) compares the coactivation of leg extensors during static contractions in stroke and healthy individuals, and (2) assesses whether this coactivation is related to changes in intersegmental pathways between quadriceps and soleus (Sol) muscles after stroke.MethodsThirteen stroke patients and ten healthy individuals participated in the study. Levels of coactivation of knee extensors and ankle extensors were measured in sitting position, during two tasks: maximal isometric voluntary contractions in knee extension and in plantarflexion. The early facilitation and later inhibition of soleus voluntary EMG evoked by femoral nerve stimulation were assessed in the paretic leg of stroke participants and in one leg of healthy participants.ResultsCoactivation levels of ankle extensors (mean ± SEM: 56 ± 7% of Sol EMG max) and of knee extensors (52 ± 10% of vastus lateralis (VL) EMG max) during the knee extension and the ankle extension tasks respectively were significantly higher in the paretic leg of stroke participants than in healthy participants (26 ± 5% of Sol EMG max and 10 ± 3% of VL EMG max, respectively). Early heteronymous facilitation of Sol voluntary EMG in stroke participants (340 ± 62% of Sol unconditioned EMG) was significantly higher than in healthy participants (98 ± 34%). The later inhibition observed in all control participants was decreased in the paretic leg. Levels of coactivation of ankle extensors during the knee extension task were significantly correlated with both the increased facilitation (Pearson r = 0.59) and the reduced inhibition (r = 0.56) in the paretic leg. Measures of motor impairment were more consistently correlated with the levels of coactivation of biarticular muscles than those of monoarticular muscles.ConclusionThese results suggest that the heteronymous pathways linking quadriceps to soleus may participate in the abnormal coactivation of knee and ankle extensors on the paretic side of stroke patients. The motor impairment of the paretic leg is strongly associated with the abnormal coactivation of biarticular muscles.

Motor Function Evaluation of Hemiplegic Upper-Extremities Using Data Fusion from Wearable Inertial and Surface EMG Sensors

“…Subsequently, the normalized data segment consisting of 10 EMG channels, six accelerometer axes and six gyroscope axes was further normalized in time to 256 sample points, to alleviate time duration variation of task performance. Finally, the motion data profile was produced as a 22 × 256 data matrix for each data segment. Time duration : The time duration of each data segment was specifically calculated to reflect proficiency of task performance, while such information was not involved in the above MDP due to the normalization process. IMU extremum number : Within each data segment, the number of local minima and maxima was computed for each axis of both IMUs and then summed up as a feature as well. EMG power distribution : After the root mean square (RMS) of each surface EMG channel was computed, the percentage of one channel EMG RMS to summation of the RMS values from all 10 channels was subsequently obtained, thus producing a 10-element vector indicating EMG power distribution across channels [30]. …”

“…EMG power distribution : After the root mean square (RMS) of each surface EMG channel was computed, the percentage of one channel EMG RMS to summation of the RMS values from all 10 channels was subsequently obtained, thus producing a 10-element vector indicating EMG power distribution across channels [30]. …”

Rectus femoris hyperreflexia predicts knee flexion angle in Stiff-Knee gait after stroke

“…The modulation of H-reflexes in knee extensors and ankle extensors have been well documented (Dietz et al, 1990) and associated to joint angles of knee and ankle during gait (Larsen et al, 2006; Sinkjær et al, 1996). Enhanced intersegmental facilitation of soleus muscle from hyperactive quadriceps afferents has been revealed after stroke (Dyer et al, 2009; Dyer et al, 2011) and related to altered activation timings of knee and ankle extensors during gait following stroke (Dyer et al, 2014). However, altered reflex excitability in the targeted muscle is highly context-dependent.…”

Neuromusculoskeletal simulation reveals abnormal rectus femoris-gluteus medius reflex coupling in post-stroke gait

“…Following a stroke, individuals often experience significant impairments including muscle weakness, spasticity, increased tone, and abnormal coordination (Twitchell 1951), which often results in compensatory movements (Perry and Burnfield 1992). Abnormal coordination has been quantified in the upper limb (Dewald, Pope et al 1995),but only more recently in the lower limbs using joint torque measures (Cruz and Dhaher 2008, Neckel, Blonien et al 2008, Cruz, Lewek et al 2009, Sakuma, Ohata et al 2014, mechanical perturbations (Finley, Perreault et al 2008, Sakuma, Ohata et al 2014) and H-reflex stimulations (Marque, Simonetta-Moreau et al 2001, Maupas, Marque et al 2004, Dyer, Maupas et al 2009, Dyer, Maupas et al 2011). However, it is unclear whether such abnormal coordination has direct consequences on gait function.…”