Analysis of center of mass acceleration and muscle activation in hemiplegic paralysis during quiet standing

Abstract

Hemiplegic paralysis after stroke may augment postural instability and decrease the balance control ability for standing. The center of mass acceleration (COMacc) is considered to be an effective indicator of postural stability for standing balance control. However, it is less studied how the COMacc could be affected by the muscle activities on lower-limbs in post-stroke hemiplegic patients. This study aimed to examine the effects of hemiplegic paralysis in post-stroke individuals on the amplitude and structural variabilities of COMacc and surface electromyography (sEMG) signals during quiet standing. Eleven post-stroke hemiplegic patients and the same number of gender- and age-matched healthy volunteers participated in the experiment. The sEMG signals of tibialis anterior (TA) and lateral gastrocnemius (LG) muscles of the both limbs, and the COMacc in the anterior-posterior direction with and without visual feedback (VF vs. NVF) were recorded simultaneously during quiet standing. The sEMG and COMacc were analyzed using root mean square (RMS) or standard deviation (SD), and a modified detrended fluctuation analysis based on empirical mode decomposition (EMD-DFA). Results showed that the SD and the scale exponent α of EMD-DFA of the COMacc from the patients were significantly higher than the values from the controls under both VF (p < 0.01) and NVF (p < 0.001) conditions. The RMSs of TA and LG on the non-paretic limbs were significantly higher than those on paretic limbs (p < 0.05) for both the patients and controls (p < 0.05). The TA of both the paretic and non-paretic limbs of the patients showed augmented α values than the TA of the controls (p < 0.05). The α of the TA and LG of non-paretic limbs, and the α of COMacc were significantly increased after removing visual feedback in patients (p < 0.05). These results suggested an increased amplitude variability but decreased structural variability of COMacc, associated with asymmetric muscle contraction between the paretic and the non-paretic limbs in hemiplegic paralysis, revealing a deficiency in integration of sensorimotor information and a loss of flexibility of postural control due to stroke.

Analysis of Vertical Micro Acceleration While Standing Reveals Age-Related Changes

“…Previous studies also investigated the amplitude and structural variabilities of apCOMacc and EMG, showing an enhanced relationship between postural variability and responsible muscle activation [ 49 ] Similarly, this study also evaluated the relationship between the sagittal plane COM and the calf muscles, while a different correlation was found between vCOMacc and calf muscle. Thus, it is possible that vCOMacc allows the observation of different aspects of balance control.…”

Biomechanical and Physiological Evaluation of Biologically-Inspired Hip Assistance With Belt-Type Soft Exosuits

“…c) Acceleration of the COM Vertical acceleration of the COM was calculated using the resultant vertical GRF (minus body weight) of both legs divided by the body mass. Horizontal acceleration of the COM was equal to the resultant horizontal GRF divided by the body mass [40].…”

A Hidden Markov Model Based Detecting Solution for Detecting the Situation of Balance During Unsupported Standing Using the Electromyography of Ankle Muscles

“…18 Furthermore, electromyography has been used for examining the effect of postural sway, the difficulty of the postural control tasks, paralysis, augmented visual feedback of the CoP, balance exercises, muscle fatigue, and wearing the prosthesis during standing on muscle activation dynamics. 16,[19][20][21][22][23][24][25][26][27][28] Despite valuable studies done, using electromyography for the real-time detection of stability level during unsupported standing has not been addressed profoundly. Therefore, in the current research, a hidden Markov model-based detecting solution has been proposed and evaluated for online determination of standing balance situation based on electromyography of ankle gastrocnemius muscles.…”