Abstract Background In critically ill patients admitted to the intensive care unit (ICU), early nutritional therapy and mobilization rehabilitation are considered important interventions; however, when applied independently, neither approach has consistently demonstrated clear benefits in improving clinical outcomes. To date, no study has specifically examined the potential synergistic effects of combining high-protein nutrition with early mobilization. Therefore, this trial aims to investigate whether combining these interventions can promote physical and functional recovery after ICU discharge. Methods This single-center, prospective, participant- and assessor-blinded randomized controlled trial with a planned sample size of 92 critically ill patients will be conducted in the ICU of a tertiary emergency care facility. Mechanically ventilated adult patients in the ICU will be eligible. Participants will be randomly assigned to either a “usual-protein group” (1. 2 g/kg/day) or a “high-protein group” (1. 8 g/kg/day). In both groups, early mobilization will be delivered according to a standardized protocol using a mobile patient lift, enabling patients to achieve standing or higher-level activities early in the ICU course. The primary outcome will be the motor score of the Functional Independence Measure (FIM) at hospital discharge. Secondary outcomes will include the Cognitive subscale of the Functional Independence Measure, Brief Pain Inventory score, ICU length of stay, hospital length of stay, and discharge disposition. Written informed consent will be obtained from participants or their legally authorized representatives prior to enrollment. Discussion This trial will be the first to evaluate the potential synergistic effects of high-protein nutrition and standardized early high-intensity mobilization in ICU patients. By focusing on protein dose as the sole intervention variable and using a mobile patient lift to ensure uniform mobilization intensity, the study is designed to provide robust evidence regarding the role of high-protein nutrition during intensive rehabilitation. This trial is conducted in accordance with the SPIRIT guidelines. The findings are expected to inform future multicenter trials and contribute to the development of clinically relevant strategies to improve post-ICU functional recovery. Trial registration University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR), UMIN000059233. Registered on September 29, 2025. https: //center6. umin. ac. jp/cgi-open-bin/ctrₑ/ctrₕisₗist. cgi? recptno=R000067751.
Suzuki et al. (Sat,) studied this question.