Background: People who are homeless are more likely to experience poor mental health and addiction as well as suffering from non-communicable diseases. There is evidence of frailty and accelerated physical ageing among people experiencing homelessness. Appropriate physical rehabilitation and nutritional supplementation strategies can stabilize or reverse frailty and general physical decline, but it is not known how this type of intervention would work in practice in this population.

Aim: To evaluate the feasibility and preliminary efficacy of a physical rehabilitation drop in intervention with protein supplementation to target physical functioning and frailty in people with problematic substance use who are experiencing homelessness.

Methods: The intervention will consist of a 12-week low threshold physical rehabilitation program with protein supplementation. Participants will be service users of the Advance Ballyfermot Project, a day services center for people who are homeless and have active addiction issues. Primary outcomes will be feasibility including numbers recruited, retention of participants and number of repeat visits. Any adverse events will be recorded. Secondary outcomes will be strength and muscular mass, physical performance and lower extremity physical function, pain, frailty and nutritional status.

This single arm feasibility cohort study is taking place in the Advance Ballyfermot Project, located in Dublin. This centre provides a 5-day a week meal service as well as drug related services for people with active addiction issues who are temporarily housed or homeless. A dedicated exercise room has been allocated for the duration of the intervention period. This study has received ethical approval from the Faculty of Health Sciences REC at Trinity College Dublin (Ethical Approval Reference Number: 211202).

The aim of the study is to be as low threshold as possible. This means that minimal constraints are put in place to access the intervention. In order to be as pragmatic as possible in terms of inclusion criteria, all clients (>18 years) accessing services from The Advance Ballyfermot Project who consent to study participation can be included in this study. Only participants with acute problematic behavioral issues or confusion, are in an agitated state or have major physical problems ,(medical or orthopedic) which would preclude ability to safely participate in the exercise class will be excluded from study participation. Participants with a confirmed pregnancy will also be excluded.

The intervention will consist of a twice weekly (for 12 weeks, from November 2022 to February 2023) exercise class with nutritional intervention and a once weekly 'Park Walk'. The intervention will be fully supervised and delivered by two research physiotherapists.

Each session will commence with a warm-up and stretch of the major muscles and will end with cool-down and stretch. The intensity of the workout will be managed by using the Borg Perceived Rate of Exertion (RPE) scale where participants will be advised to exercise at a rate of between 11 and 13 on the PRE scale, ie. between 'fairly light' to 'somewhat hard', where they find it hard to have a conversation but can comfortably continue to exercise.

In an attempt to build sustainability beyond the life cycle of the project, participants will also be educated about exercise and available local resources where possible. Clients will be invited and encouraged to return weekly to continue with the exercise intervention.

The service provided will be low threshold to facilitate adherence and compliance. The research physiotherapists will make every effort to be flexible and accommodating to participants who do not need to make repeat appointments and may turn up on the day of the intervention. Adherence to the program will be measured by the uptake, compliance and number of repeat visits to the drop-in program. Demographic information will include biological sex and current homeless status.

Demographic details, including age, and named General Practitioner (GP) of participants will be collected. A letter will be sent to the GP to inform them of study participation. Questions around current addiction status will be guided by Section 1 of the Treatment Outcome Profile (TOP).

Analytic Plan Our study is very much feasibility focused and not hypothesis driven so formal power calculations are not directly applicable. Prospectively, potential participants that meet the study eligibility criteria will be invited to participate. Descriptive statistics will summarize participant demographics and feasibility measures such as attendance rates. Nominal or ordinal variables will be reported as frequencies and percentages. Continuous variables will be summarized as mean and standard deviation if normally distributed and median and inter-quartile range if non-normally distributed. Data will be tested for normality using the Kolmogorov-Smirnov test and will be compared across timepoints using the general linear model procedure (normally distributed data) and the Friedman's test (non-normally distributed data). As participants will be heterogeneous, data will be sub-stratified and participants will be grouped meaningfully. Free text responses from subjective questions will be reported and organized into topic areas.

Inclusion criteria:

• Any person (>18 years) accessing services in Ballyfermot Advance

Exclusion criteria:

• Any person with acute problematic behavioural issues, confusion or major physical problems
• Females with confirmed pregnancy

Clients accessing services in the Advance Ballyfermot Project (Dublin)