Assessing muscle activity is essential for diagnosis and treatment of neuromuscular disorders such as spasticity and dystonia. While muscle functional magnetic resonance imaging (MRI) enables non-invasive imaging of muscle activation, conventional methods rely on comparisons between rest and activity, which are unsuitable for patients with sustained muscle contractions. This pilot study introduces a novel resting-state fMRI (rs-fMRI) approach using regional homogeneity (ReHo) to evaluate muscle activity without requiring activation paradigms. Eight healthy male participants performed separate isometric plantar and dorsal foot flexion tasks during 3T MRI scanning. rs-fMRI data were analyzed using ReHo to assess local synchronization of BOLD signal. Calf muscle activation was quantified using z-transformed ReHo values and activation thresholds were derived via ROC analysis. Statistical differences in activation between tasks were assessed using the Wilcoxon signed-rank test. Significant ReHo differences were observed between active and inactive muscles during both tasks. This study demonstrates the potential of rs-fMRI combined with ReHo analysis as a non-invasive method for detecting muscle activity using one series of volumes. Further research in larger cohorts is warranted to validate and expand this approach.

The authors have declared no competing interest.

This study was supported by the National Institute for Neurological Research (Programme EXCELES, ID project no. LX22NPO5107) - Funded by the European Union - Next Generation EU.

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:

Ethics committee of General University Hospital in Prague gave ethical approval for this work.

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the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

All data produced in the present study are available upon reasonable request to the authors.