Ankle muscles co-activation patterns during normal gait: An amplitude evaluation

The objective of this work was to quantify co-activations of ankle muscles during able-bodied walking, in terms of amplitude values of surface electromyographic signal (sEMG). Gastrocnemius lateralis (GL) was analyzed as representative muscles for plantar-flexion. Tibialis anterior (TA) was analyzed as representative muscles for dorsi-flexion. Rudolph’s dynamic co-activation index was computed on the sEMG acquired from 182 strides, with the aim of quantifying the ankle-muscles co-contraction amplitude. Four different co-activations between GL and TA were observed during Heel strike (HS), Foot contact (FC), Push-off (PO), and Swing (SW), respectively. No differences were detected in time-duration of co-contractions detected in the different phases (p<0.05). TA/GL co-contraction activity is more intense in stance phase (especially during HS and FC), where a more intensive muscular control is needed for weight-support and Center of pressure (COP) progression. Co-contractions in swing phase are more frequent but milder. SW co-contraction in adults was pointed out only recently; to our knowledge, the present work is the first that quantifies it in terms of absolute and comparative amplitude. PO seems to be a transitory phase between high-level (HS and FC) and low-level (SW) co-contraction intensity regions. Present findings could be useful for deepening the physiological interpretation of ankle muscles co-activity during walking.