Stroke often results in compensatory movement strategies that combine use of trunk movements with nonuse of the affected upper extremity, which is considered detrimental to recovery. In this study, we investigate whether compensation and nonuse can be more than a suboptimal counterpart to recovery. We explore the influence of neuromechanics on nonuse and compensation in 22 stroke survivors and 22 controls. We asked seated participants to reach a target under two nonuse conditions (spontaneous or with minimized trunk compensation) and under three arm weight conditions (control, lightened and weighted). We replicated the findings that stroke induces more trunk compensation, more anterior deltoid activation and greater effort. We found that, in stroke patients, reduced arm weight decreased nonuse, while in controls, increased arm weight induced trunk compensation similar to what is observed after stroke. Furthermore, reaching with nonuse after stroke required less effort and preserved a force reserve at the shoulder. Our results show that both poststroke and healthy individuals engage in similar nonuse and compensation in the face of their neuromechanical limitations, as predicted by an optimal control policy aiming to succeed at the task while keeping a force reserve at each joint. We derive two theoretical predictions for future clinical research. First, patients whose nonuse yields few functional gains should benefit most from interventions to reduce compensation. Second, improving shoulder strength after stroke should reduce relative muscle activation, thereby decreasing trunk compensation and upper extremity nonuse. Clinical Trial: NCT04747587

The authors have declared no competing interest.

NCT04747587

This study was supported by Nimes University Hospital (ID-RCB: 2020-A02695-34) and the LabEx NUMEV (ANR-10-LABX-0020) within the I-SITE MUSE.

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

The Ethics Committee of Nimes University Hospital gave ethical approval for this work (ID-RCB: 2020-A02695-34). All participants provided written informed consent. This study adhered to the 1964 Declaration of Helsinki. Clinical Trial Registration: NCT04747587.

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Yes