Relationship Between Lower-Extremity Co-Contraction and Jerk During Gait

Abstract

The elderly exhibit increased co-contraction (CC) during gait, reducing movement smoothness. The jerk has been used to quantitatively smoothness. This study aimed to investigate the relationship between lower-leg jerk and lower-extremity CC during gait. Participants were 30 healthy middle-aged and elderly people. Surface electromyography (EMG) was measured from the tibialis anterior (TA), gastrocnemius lateralis (GL), vastus lateralis (VL), and biceps femoris (BF). An inertial measurement unit was attached to the lower-leg. Jerk was calculated from inertial measurement unit (IMU) acceleration data, and CC was quantified as the percent co-contraction index (CCI) for TAGL, VLBF, and VLGL. To examine the correlation between CCI and jerk, the part with the highest correlation between jerk and CC during gait was used as the dependent variable, and a multiple regression analysis was performed to obtain the estimated CC values (p < 0.05). VLGL CCI increased with higher jerk during the second half of the stance phase and also increased as gait speed declined. The CCI of the VLGL in-creased with age. The multiple regression analysis adjusted for age and gait speed revealed a relationship between jerks and CCI. The CCI of the VLGL is most closely related to lower-leg jerks, which affect the gait of the elderly.

Keywords: IMU; co-contraction; elderly; gait.

Figure 1

Electromyogram electrode position and IMU location. Surface EMG signal were recorded on the tibialis anterior (TA), gastrocnemius lateralis (GL), vastus lateralis (VL), and biceps femoris (BF) using a 4-channel using the Wave COMETA EMG system (2000 Hz. Milan, Italy). The electrodes were positioned on the participants’ according to the EMG for the Non-invasive Assessment of Muscles guidelines. An IMU (Cometa slr, Milano, Italia, 143 Hz) was attached to the fibular head of the lower leg to measure acceleration waveform data (three axes defined as; Ax: vertical, Ay: anterior–posterior, Az: mediolateral axes). The IMU was mounted on and fixed to the fibular head of the lower leg using double-sided tap.

Figure 2

Lower-extremity muscle activity and CCI during gait cycle. (A) shank part (TAGL), (B) thigh part (VLBF), (C) thigh-shank part (VLGL). The percent CCI was calculated as the percentage of CC between the agonist/an tangoist muscles in the shank part (TAGL), thigh part (VLBF), and thigh-shank parts (VLGL). Each CCI was obtained and defined as the entire stance phase (gait cycle: 0–62%), the first half of the stance phase (gait cycle: 0–31%), and the second half of the stance phase (gait cycle: 32–62%). Each CCI was averaged over five trials acquired per participant.

Figure 3

Lower-leg jerk during gait cycle. The stance phase of the gait cycle was divided into the first half of the stance phase and the second half of the stance phase. The difference value between the minimum and maximum values of each three axes jerk were calculated for each stance phase.

Figure 4

CCI of VLGL in different age strata. This figure was presented among the five different age strata of cases. GL activity decreases with age, VLGL (the second half of stance phase) CCI relatively increases with age (Figure 4). Gait speed, VL/GL (second half of stance phase). (gait speed, CCI of VLGL; (A): 1.46 m/s, 41.6% (B): 1.43 m/s, 44.1% (C): 1.55 m/s, 65.1% (D): 1.12 m/s, 72.7% (E): 0.93 m/s, 81.3%).