Introduction: The plantar flexors (PFs) are crucial for ankle push-off during gait, providing forward propulsion and controlling foot movement during the stance phase. In stroke survivors, reduced activation of the PFs leads to difficulty with propulsion and toe clearance, contributing to abnormal gait patterns known as hemiplegic gait. This issue is often exacerbated by decreased weight bearing (WB) on the paretic limb and adaptive shortening on the paretic PFs, as PF activation is highly dependent on loading input for balance and gait. Purpose and Hypothesis: This study investigates whether simultaneously increasing paretic WB and PF muscle length can enhance paretic PF muscle activation during a dynamic skateboarding task. We hypothesize that this combination will significantly increase paretic PF activation. Methods: This study was a single-session, randomized controlled trial. We recruited 15 individuals with chronic stroke and measured the activations of their paretic plantar flexors using surface electromyography (EMG). Measurements were taken under six randomized conditions: three paretic limb loadings (50%, 75%, and 90% of BW) paired with two surface configurations (level and incline). During each condition, participants were instructed to roll a skateboard forward and backward for three cycles using their unaffected limbs, all while maintaining the targeted WB level on their paretic limbs. A high-speed camera system recorded foot trajectories to define the onsets of the forward and backward cycles during the skateboarding motions.PF muscle activation was calculated by integrating the EMG signal within a cycle and then normalized to 50% BW on the level condition. Results: The results showed increasing paretic BW loading resulted in significant increases in paretic PF activation. The normalized paretic PF activation was significantly higher during 75% BW and 90% BW loading compared to 50% (p =0.04 and 0.01 respectively). There was a trend of increasing PF activation on the incline surface compared to the level surface, however, this difference was not statistically different. Discussion and Conclusion: These findings suggest greater paretic PF activation is associated with increasing paretic WB. Locomotor exercises should aim to increase WB on the paretic limb to enhance paretic PF activation, which may improve gait and standing balance. Further studies with subacute stroke populations and a larger sample size are needed to generalize these results.
Locha et al. (Thu,) studied this question.