Adaptation of motor control strategies and physiological arousal during repeated blocks of split-belt walking

Physiological arousal, mediated by the autonomic nervous system (ANS), is known to co-modulate with adaptation of motor control strategies, governed by the central nervous system (CNS), in response to repeated standing perturbations. However, adaptation of the ANS physiological arousal response during repeat exposure to walking challenges remains unknown. This study examines the physiological arousal response (electrodermal activation, EDA) and motor control strategy of gait during a single session of repeated exposure to blocks of split-belt walking. Twenty young adults completed three repeated blocks (3.5 min each) of split-belt walking (2:1 speed ratio) alternating with three blocks of tied-belt walking. Step length symmetry (SLS), EDA, bilateral tibialis anterior (TA) and gastrocnemius medialis (GM) muscle activation and ground reaction forces (GRFs) were measured. For each walking block, the first (early) and last (late) 15 strides were analyzed. A linear mixed-effects model (LMM) tested the effect of repeated blocks and phases (early/late) on SLS. Statistical parametric mapping (SPM) examined patterns of within-block changes in EDA, muscle activation, and GRFs. The greatest within-block adaptation of SLS occurred during first exposure to split-belt walking (S1; p<.001). Similarly, the largest magnitude of within-block adaptation in muscle activation, GRFs, and EDA occurred during S1 (p<.05). Attenuated EDA responses together with lower magnitude of motor adaptation in subsequent split blocks 2 and 3 were observed, indicating savings across the ANS and CNS. Taken together, these findings demonstrate that the ANS-mediated physiological arousal response modulates alongside the CNS-driven locomotor adaptation to repeated exposure to blocks of split-belt walking.