Analysis of Ankle Muscle Activation Patterns During Self-Initiated Versus Motor-Induced Falls From Standing Height: A Pilot Study

Background: Falls represent a critical public health issue involving neuromuscular control strategies to execute appropriate motor plans.While self-initiated falls (SIF) and motor-induced falls (MIF) are common laboratory paradigms, the continuous temporal differences in their underlying neuromuscular strategies remain poorly understood. Objects:We conducted experiments to identify and compare the neuromuscular control strategies between SIF and MIF across three directions using continuous waveform analysis.Methods: Eight healthy young adults performed SIF and MIF in forward, backward, and sideways directions while surface electromyography was recorded from the bilateral tibialis anterior (TA), lateral gastrocnemius, and medial gastrocnemius.Data were normalized via maximum voluntary isometric contraction and reference voluntary contraction and analyzed using statistical non-parametric mapping over the entire fall duration (0%-100%).Results: Neuromuscular divergence was strategically concentrated within three critical windows: initial, mid-to-terminal, and terminal phases.For the TA, MIF elicited significantly higher activation during the initial phase of sideways falls (1%-5%, p < 0.05) and the mid-to-terminal phase of backward falls (62%-75%, p < 0.05).For the GCM, significantly higher activation in MIF was observed during the terminal phase of forward falls (70%-99%, p < 0.05), both early (1%-24%, p < 0.05), and late (58%-98%, p < 0.05) phases of sideways falls, and the initial response phase of backward falls (1%-5%, p < 0.05). Conclusion:The central nervous system is characterized by high-amplitude activation patterns, which may reflect a response to unpredictable threats (MIF) compared to planned descents (SIF).These findings suggest the potential importance of direction-specific and timesensitive neuromuscular training to better prepare for real-world falls.