Soleus Loading Response During Walking

Completed · Not applicable

Conditions studied: Healthy, Spastic Hemiparesis, Stroke

In brief

Stroke survivors experience motor deficits, weak voluntary muscle activations, and low weight-bearing capacity that impair ambulation. Restoring motor function is a priority for people post-stroke, whose gait patterns are slow, and metabolically inefficient. The role of the ankle is crucial for locomotion because it stores mechanical energy throughout the stance phase, leading to a large activation of plantarflexor muscles during push-off for propulsion. After a stroke, paretic plantarflexors undergo changes in their mechanics and activation patterns that yield diminished ankle power, propulsion, and gait speed. Recovery of lost plantarflexor function can increase propulsion and mitigate unnatural gait compensations that occur during hemiparetic walking. In the stance phase, dorsiflexion is imposed at the ankle and the plantarflexors are loaded, which results in excitation of group Ia and II afferents, and group Ib afferents. Load sensing Ib afferents are active in mid-late stance, and through spinal excitatory pathways, reinforces the activation of plantarflexors and propulsive force generation at the ankle. Targeting the excitability of the load sensitive Ib excitatory pathway, propulsive soleus activity and resulting force generation (and thereby gait speed) can be improved after stroke. The long-term research goal is to develop a novel hybrid gait paradigm integrating operant conditioning and powered wearable devices to advance neuro-behavioral training and enhance locomotor ability after stroke. The overall objectives are to 1) modulate the soleus muscle loading response within the stance phase, and 2) develop a dynamic protocol to operantly condition the soleus response in stroke survivors. The central hypothesis is that enhancing the soleus loading response in mid-late stance phase through operant up-conditioning can increase plantarflexor power and forward propulsion after stroke. In working towards attaining the research objective and testing the central hypothesis, the objective of this pilot study is to modulate the soleus loading response in the stance phase during treadmill walking. The specific aims in this study are to 1) apply ankle perturbations in mid-late stance phase combining a control algorithm and a powered device to characterize the changes in soleus EMG between perturbed and unperturbed (i.e., when no perturbations are applied) step cycles in 15 able-bodied individuals; and 2) determine the feasibility of the wearable ankle device and its algorithm in 5 participants with hemiparesis and gait deficits due to a stroke. The testing of the device and its algorithm will provide foundational evidence to adjust the soleus stimuli continuously and reliably, and develop the new walking operant conditioning protocol for stroke survivors. An expected outcome in this pilot is to lay the groundwork to develop the soleus up-conditioning protocol as a potential strategy to improve paretic leg function. If successfully developed, this new protocol proposed in a subsequent study will be the first neurobehavioral training method that targets spinal load-sensitive pathways to improve ankle plantarflexor power and forward propulsion after stroke.

Key facts

Study ID

NCT05436366

Run by

Victor H. Duenas

People needed

10

Starts

2022-09-30

Expected to finish

2024-08-31

Last updated by the study team

2024-11-29

Who can join

Age: 18 and older. Sex: any. Healthy volunteers: accepted.

You may qualify if…

• For able-bodied individuals, the inclusion criterion is adults with no known neurological conditions or history of orthopedic injuries.
• For individuals after stroke, inclusion criteria include participants who are neurologically stable for >6 months (and >1 year post stroke) and have medical clearance to participate in the study (with the expectation that current medication will be maintained without change for at least 4 months); ability to ambulate with or without an assistive device at least 10 m; and unilateral ankle extensor spasticity (hemiparesis); and able to wear the robotic ankle device, provide written informed consent and follow instructions.

You may not qualify if…

• For able-bodied individuals, the exclusion criteria are motoneuron injury; a cardiac condition (history of myocardial infarct, pacemaker use); an unstable medical condition; and inability to provide written informed consent.
• For individuals after stroke, the exclusion criteria are are a cardiac condition (history of myocardial infarction or congestive heart failure, pacemaker use); motoneuron injury (i.e., the neurons that give rise to the axons innervating the muscles); ambulation velocity of >1.2 m/s; a medically unstable condition (e.g., unstable angina, shortness of breath without exertion); musculoskeletal disorders that limit ambulation; and inability to provide informed consent.

Where it is running

• Syracuse University — Syracuse, New York, United States

Full record on ClinicalTrials.gov

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