Fig. 3

Modular NP system adapted for gait activity. (A) System components, how they are connected and the type of communication that is established. (B) Events and gait phases identified with the preset event detection algorithm and finite state machine used in open-loop control to assist the target muscle [61, 62]. The predefined assistance is marked in black. The example of two up and down ramps down is shown in grey. The down ramps are executed once the end of stimulation is detected. The up ramps, on the other hand, would be executed within the black band as the corresponding event is detected. (C) Target muscle groups of the lower limbs involved in gait. Abbreviations: heel contact (HC), toe off (TO), heel off (HO), maximum knee flexion in swing (K1), gluteus maximus (GM), tensor fasciae latae (TFL), quadriceps (Q), hamstrings (H), gastrocnemius (GS) and tibialis anterior (TA), time (t), left knee angle (αK_L), right knee angle (αK_R), left hip (H_L), left knee (K_L), left ankle (A_L), right hip (H_R), right knee (K_R) and right ankle (A_R)