Effect of experimental muscle pain on the acquisition and retention of locomotor adaptation: different motor strategies for a similar performance

Background: As individuals with musculoskeletal disorders often experience motor impairments, contemporary rehabilitation relies heavily on the use of motor learning principles. However, motor impairments are often associated with pain. While there is substantial evidence that muscle pain interferes with motor control, much less is known on its impact on motor learning, especially on locomotor learning. The objective of the present study was to assess the effects of muscle pain on locomotor learning. Methods: Two groups (Pain and Control) of healthy participants performed a locomotor adaptation task (robotized ankle-foot orthosis perturbing ankle movements during swing) on two consecutive days. On Day 1 (acquisition), hypertonic saline was injected in the Tibialis Anterior (TA) muscle of the Pain group participants, while Control group participants were pain-free. All participants were pain-free on Day 2 (retention). Changes in movement errors caused by the perturbation were assessed as an indicator of mo...