**3. Potential Contributions of This Study**

This study will fill an important research gap and may contribute to future intervention studies, having a direct and immediate impact on clinical practice in children with CZS. This study protocol will determine the feasibility of an intervention using powered mobility for young children with CZS, who present severe motor impairments. The acceptability of the intervention for young children with CZS and their families will be described. In addition, we will assess the effects of the intervention on mobility, social function and participation of children; the barriers and facilitators of the intervention will also be analyzed.

Feasibility studies are relevant as they use rigorous methods to access processes, resources, management and effects related of the intervention of interest [40]. The feasibility assessment includes data on the acceptability of the intervention and the perceived burden of the procedures. Feasibility studies may therefore contribute resources invested in larger trials that are the most likely to generate clinically significant results [41]. In this protocol, we propose an approach of mixed methods; the primary outcomes will be qualitative, which will allow a deeper understanding in terms of feasibility. The quantitative measures will enable a complementary analysis of the feasibility and contribute to answer the specific objectives of the study. Thus, data obtained in this study will be able to guide future clinical trials on powered mobility in children with CZS and benefit these children and their families. It is expected that this innovative study will contribute evidence for the adoption of low cost environmental early child interventions in Brazil and other low-and middle-income countries around the world.

**Author Contributions:** Conceptualization: E.L., S.W.L., A.C.D.C.; Project Administration: E.L.; Methodology: E.L., A.C.D.C., A.S.B., D.L.d.L.N.C., M.L.G.C., C.C., K.S.M., S.W.L.; Investigation: A.S.B., D.L.d.L.N.C., M.L.G.C., K.S.M.; Writing: Original draft preparation: E.W.L., A.C.d.C., S.W.L., K.S.M.; Writing: Review and editing: E.L., A.C.D.C., A.S.B., D.L.d.L.N.C., M.L.G.C., C.C., K.S.M., S.W.L.; Funding acquisition: E.L., A.C.D.C. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research is funded by PROPESQ/UFRN, grant number (05/2019) and REDE Brazil. This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001.

**Acknowledgments:** We acknowledge the support of Bonny Baker and Luiza Lourenço at The Global Health Network/REDe, for all the efforts made for this project to come true. We are also grateful for the families who provided valuable information regarding their preferences for the intervention. Additionally, we thank Klayton Galante Sousa and Nelci Adriana C.F. Rocha, for comments on the study design.

**Conflicts of Interest:** The authors declare no conflict of interest.
