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

Area of Science:

• Biomechanics
• Gerontology
• Neurology

Background:

• Elderly individuals often display increased co-contraction (CC) during gait, leading to diminished movement smoothness.
• Jerk, a measure of the rate of change of acceleration, is a recognized quantitative indicator of movement smoothness.

Purpose of the Study:

• To investigate the relationship between lower-leg jerk and lower-extremity co-contraction (CC) during gait in middle-aged and elderly individuals.
• To determine if lower-leg jerk is a significant factor influencing CC during gait, especially in older adults.

Main Methods:

• Participants: 30 healthy middle-aged and elderly individuals.
• Measurements: Surface electromyography (EMG) of lower-extremity muscles (tibialis anterior, gastrocnemius lateralis, vastus lateralis, biceps femoris) and lower-leg motion using an inertial measurement unit (IMU).
• Analysis: Calculation of jerk from IMU data, quantification of CC using the percent co-contraction index (CCI), and multiple regression analysis to correlate jerk and CCI, adjusting for age and gait speed.

Main Results:

• Co-contraction index (CCI) of the vastus lateralis and gastrocnemius lateralis (VLGL) increased with higher lower-leg jerk during the latter half of the stance phase.
• VLGL CCI was also found to increase with declining gait speed and with advancing age.
• Multiple regression analysis confirmed a significant relationship between lower-leg jerks and VLGL CCI, even after adjusting for age and gait speed.

Conclusions:

• Lower-leg jerk is a key factor associated with lower-extremity co-contraction (CC) during gait in the elderly.
• The findings suggest that increased lower-leg jerk contributes to altered gait patterns and reduced smoothness in older adults.
• Understanding this relationship may inform interventions aimed at improving gait stability and reducing fall risk in the aging population.