Biophysical and Anthropometric Determinants of Muscle Co-activation Patterns during Gait

Electromyogram (EMG) signals provide significant information about neuromuscular activation of gait patterns specifically with respect to the strength and order of recruitment of lower limb muscles during walking. The CoActivation Index (CAI) is an important parameter to examine the contribution of specific antagonist and agonist muscle pairs. In this study, the co-activation between knee extensors flexor pair and plantar flexors & dorsiflexors pairs for subjects of different gender, age groups and BMI were compared. The dataset consists of surface EMG signals obtained from Tibialis Anterior (TA), Plantar flexor (Soleus (S), Gastrocnemius medialis (G)), Biceps femoris (BF), Vastus Medialis (VM) from healthy participants between age groups of 6 and72 years. CAI was calculated for TA & S, TA & G and BF & VM muscle pairs. It was observed that CAI for young and old age groups were higher compared to middle age participants. Females were found to have higher CAI (BF & VM=58.9 ±13.2; TA & G= $43.2 \pm 10.0;$ TA & $S=49.7 \pm 13.7)$ than male (BF & VM=52.8 ±9.3; TA & G $=39.5 \pm 10.7$; TA & S $=43.8 \pm 9.9$). The influence of Body Mass Index (BMI) on CAI was manifested in both male and female with significant variation in CAI for female ($4.63 \pm 4.47$) than male $(1.59 \pm 1.11)$ participants. Also, the proposed study revealed that CAI corresponding to knee flexors and extensors (BF & VM) is always higher than the dorsiflexors and plantar flexors (TA & S, TA & G) reiterating the prominent role of knee articulators during walking. Therefore, the proposed study contributes to the understanding of the dynamics of CAI and its importance in gait analysis associated with different morphological and pathological conditions of human musculoskeletal system.