Modulation of Hoffmann reflex excitability during action observation of walking with and without motor imagery

We measured H-reflex in the soleus muscle under the following conditions: (1) control, (2) AO, and (3) AO + MI. Posterior tibial nerve electrical stimulation, which induces H-reflex, was applied at the following four walking phases: 1) mid-stance, 2) terminal-stance, 3) early-swing, and 4) terminal-swing. Our results showed that AO + MI significantly increases H-reflex over AO alone, regardless of phase and that AO significantly modulates H-reflex depending on the observed phase. These findings suggested that spinal reflex excitability can be modulated during AO and AO + MI and that neural effects are different in AO and AO + MI.