Low recruitment rates in clinical trials are a significant global challenge in SCI research [11, 24, 25]. By recognizing and addressing the multifaceted challenges of recruitment of persons with subacute SCI in rehabilitation hospitals, there can be improvement in research participation that can contribute to the development of effective treatments for persons with SCI. The objective is to balance clinical care with research demands; ensuring patients receive optimal support while advancing scientific knowledge.

In general, factors influencing successful recruitment include the presence of an existing research infrastructure, study design that minimizes participant burden, and the characteristics of both recruiters and participants [26]. Specifically, effective recruitment is enhanced by recruiters’ communication, empathy, cultural competence, and professionalism, as well as participants’ interest, trust, availability, cultural compatibility, and health literacy. A recruitment model grounded in ethical research principles is essential to minimize patient harm and risk. It is therefore important to offer individuals with SCI opportunities to learn about research voluntarily and ensure researchers can access potential participants without coercion.

Established barriers to participation in research, which have been identified in various study populations, include understanding of randomization, placebo assignments, possible adverse effects, complex protocols, financial burdens, transportation logistics, and mistrust in physicians [27]. For older adults, barriers also include complex consent forms, distrust of research, lack of understanding of study protocols, and family members acting as gatekeepers [28, 29]. In persons with SCI specifically, Anderson et al. [27], identified key facilitators for research participation, including the potential for functional improvement, better understanding of SCI, altruism, access to cutting-edge care, and the desire for greater independence. Peer recommendations were also a strong facilitator. Significant barriers included potential functional decline, side effects, and out-of-pocket expenses. These issues are important to keep in mind when designing and approaching individuals with new research opportunities.

A critically important aspect of clinical trials for persons with SCI is to involve persons with lived experiences in designing research study elements. Such individuals are often eager to participate [30,31,32], and their insights can enhance all aspects of a study, including the design, establishing meaningful outcome measures, and improving retention rates. The North American Spinal Cord Consortium (NASCIC) offers a free online course that focuses on how to meaningfully engage individuals with SCI as research partners, rather than merely as participants [33].

To enhance the success of research studies in a rehabilitation hospital during the subacute period post-injury, the following are recommendations (see Table 1).

To address the challenges posed by patient-related variability, it is essential to develop strategies that ensure the research process is both inclusive and effective. An example includes implementing stratified randomization methods to accommodate different levels and severities of injuries [34]. This can include varying the age range of inclusion criteria and including persons with incomplete injuries. Furthermore, participating in multicenter trials or extending collaboration to non-traditional centers such as LTACHs and rehabilitation centers without existing research infrastructures can enhance potential enrollment.

When designing studies, it is important to assess internal strengths, the volume of eligible participants, and competition for potential participants before initiating new study protocols. A system of communication to alert investigators of potential candidates for recruitment should be established. Determining the screening-to-recruitment ratio (S:R) will enable researchers to accurately estimate the time and resources needed for optimal participant recruitment within a predictable timeframe [35].

Educating persons with SCI admitted to rehabilitation facility about the potential benefits of research participation can enhance their motivation and willingness to take part. Disclosing all potential studies and ensuring their rights to be aware of their options should be prioritized over the labs’ needs. Researchers should coordinate their efforts to prevent overwhelming patients with multiple study requests. It is important to designate a limited number of individuals to present studies to facilitate enrollment and decrease the sense of pressure felt by potential participants. Although enrollment may take a few days, a mechanism to initiate the process as soon as the individual is ready is important, ideally shortly after admission.

Simplifying the informed consent process by providing clear and concise information will make it easier for patients to understand and agree to participate. Involving clinical team members trained in research suitability can be beneficial, but this approach has ethical implications. Studies have shown that inpatients may feel pressured to participate in research to please their healthcare providers, conflating the aims of research with clinical care [36, 37]. The potential for therapeutic misconception is significant, given the disabling nature of SCI and the hope that experimental interventions may be beneficial [24, 25, 38,39,40]. To address these issues, Craven et al. [26] recommend using a neutral third party, the Patient Research Liaison (PRL), to distinguish between clinical care and research participation and mitigate therapeutic misconception. This model, while potentially effective, may require substantial organizational resources to implement and each setting needs to determine what is feasible for their site.

Hiring the right personnel to describe studies and recruit participants is crucial, as personality can make a significant difference. Developing a clear process for approaching potential candidates and families about studies, supplemented by advice from persons with lived experience, will streamline recruitment. Hosting research question and answer sessions for inpatients and open forums for discussions with patients and families will promote engagement and transparency. Continuous collaboration with institutional review boards (IRBs) and ethics committees is necessary to assess and monitor the risk-benefit ratio of studies.

Involving a range of individuals, including clinicians, researchers, and persons with lived experience, in developing standardized protocols can help optimize the study and minimize the impact on schedules. Creating manuals of procedures (MOPs) that detail protocols in a step-by-step manner and rehearsing their execution will lead to more streamlined operation of these studies. Working directly with the clinical scheduler to integrate research activities into the rehabilitation schedule without disrupting essential medical and rehabilitation services is crucial. It is also advisable to establish direct communication with participants (or their families), to keep them informed, as they are often the best source of information about their schedules, including activities outside of therapy.

Utilizing shared resources and establishing a responsive system for scheduling research activities can ensure lab and personnel availability. Furthermore, maintaining a flexible and scalable research infrastructure will allow for adjustments in response to fluctuations in patient admissions. Consideration for designing shorter protocols with fewer outcome measures to streamline the study is recommended.

Addressing health status and medical complications requires thorough medical screening procedures before enrollment and on a daily basis. Study protocols should be flexible to accommodate the management of medical complications without compromising the integrity of the research. All team members should watch for signs of adjustment issues, such as changes in mood, anxiety, or disinterest in participating in activities. Consistent and close collaboration between research personnel and the primary clinical team is critical. A handoff before and after each research session should be documented and communicated to the clinical team, such as the primary nurse.

Choosing the right primary outcome measure is critical, with the goal of ensuring that the main research question is answered [11]. The addition of multiple secondary goals to a protocol may work against recruitment and retention by making the study less attractive to individuals considering participation. An excessively complex study may run out of time or money before being fully enrolled, or the burden on research staff and participants may lead to collection of incomplete or unreliable data. Any study, even a successful one, will usually leave the research team with more questions than answers [11].

Using validated and widely accepted clinical and outcome measurement tools that are appropriate for SCI research will enhance the reliability of outcomes. Employing clinically relevant outcome measures that align with patients’ real-life activities and challenges, and implementing longitudinal studies to capture long-term functional improvements and the impact of interventions over time, will ensure comprehensive and meaningful research outcomes.

To ensure continued participation and effective follow-up post-discharge, it is important to establish and implement a participant tracking system. Providing incentives, including compensation, and support, such as transportation assistance, or coordinating with local facilities to facilitate follow-up appointments and assessment, will further support participant engagement and retention. Developing comprehensive follow-up plans, which include telemedicine options and home visits, as well as communication with the outpatient clinical team, will help maintain contact. Lastly, making the follow-up atmosphere as welcoming as possible can increase the perceived value of follow-up and help participants understand that their contributions are essential and appreciated.