Table 3.

Methodological problems in rehabilitation research (14).

Categories of issues	Type of issue
Control group	Difficulties in having a “placebo” group. For some interventions, it may be possible to reproduce the non-pharmacological intervention using a placebo device but, most of the time, the control group will receive no intervention. The placebo effect of the intervention could therefore not be assessed.
Blinding	Difficulties in blinding participants and personnel. Indeed, participants are aware of their group of appurtenances since, they will either receive the intervention or not. For the staff, it is a challenge to ensure that the person applying the treatment is not the same as the person carrying out the measurements.
Randomization	Limited participant's acceptance of randomization. Participants are often hesitant of being randomly assigned to one group and, particularly to the control group with no intervention offered. Patients are often in pain or suffer from important mobility issues/disabilities. Therefore, when they are included in the control group, they only need to perform the measurement at the entry and at the end of the study and they do not perceive any benefit from participating in the study.
Ethics	Unacceptability to use a control group that withholds or delays treatment. Patients assigned to the control group often receive no intervention and are required to not modify their current rehabilitation.
Eligibility	Existence of multiple comorbidities that restrict the inclusion of participants. Therefore, there is an insufficiency of eligible participants in one unique site of recruitment and multisite studies often have to be organized. Difficulties to recruit participants with pathologies that can be considered as similar on the phenotypic level.
Monitoring of interventions	Complexity of some interventions that makes it difficult to monitor their administration.
Confounding factors	The multifactorial rehabilitation of PRM patients that makes difficult to identify the true intervention effect and differentiate the aspects of natural recovery processes within the course of their rehabilitation.
Participant attrition	Interventions proposed in PRM research may be long in term of follow-up, which increases the risk of participant attrition.