Chapter 1: will outline provide the background and rationale for this work, through a comprehensive review of the literature as it pertains to homelessness and the health of people experiencing homelessness, addiction and mental health challenges, particularly physical health, and the physical function deficits and frailty which are evident in people who experience homelessness. It will conclude by highlighting the gaps in the evidence base and delineate the research question and the aims and objectives of this thesis.

Chapter 2: will describe the methodology in relation to the research design, the population of interest and the setting, the intervention and the data collection and analysis methodology. It will also provide an in-depth discussion on the outcome measures used in this thesis, including their validity and reliability.

Chapter 3: will discuss the results of the first PhD study, LEAP-II, a targeted pre-post intervention exercise intervention with post-intervention exit surveys delivered to a cohort of people who experienced homelessness, addiction and mental health challenges. Chapter 3 contains the following publications:
1. Kennedy F, Ní Cheallaigh C, Romero-Ortuno R, Doyle S, Broderick J. A study to explore the role of a low threshold, fitness focussed physical rehabilitation intervention with protein supplementation to target physical function and frailty in people with problematic substance use and homelessness: protocol for a single-arm pre-post intervention study. HRB Open Res. 2024 Oct 29:6:26. doi:10.12688/hrbopenres.13678.2. PMID: 39569024; PMC11576564.
2. Kennedy F, Ní Cheallaigh C, Romero-Ortuno R, Murray D, Broderick J. (2025). Acceptability and utility of a broad test battery to evaluate physical functioning and frailty in community-based settings for people experiencing homelessness and addiction–Findings from the LEAP trials. Physiotherapy. 2025 Mar;126:101449. doi: 10.1016/j.physio.2024.101449. Epub 2024 Nov 7. PMID: 39626407.”
3. Kennedy F, Ní Cheallaigh C, Romero-Ortuno R, Murray D, Behan, F.P., Broderick J. An exploration of frailty in a non-geriatric population with severe and multiple disadvantage using two geriatric frailty tools. (2025). Journal of Social Distress and Homelessness, 1-12. https://doi.org/10.1080/10530789.2025.2528272.
4. Kennedy F, Ní Cheallaigh C, Romero-Ortuno R, Murray D, and Broderick J. Impact of a physiotherapy-led low threshold exercise and protein supplementation intervention to optimise physical function and target frailty in people experiencing homelessness and addiction: The LEAP-II trial. Physiotherapy. Pre-proof. https://doi.org/10.1016/j.physio.2025.101873

Chapter 4: will discuss the results of the second study, the LEAP-W trial - a quantitative pre-post intervention study which provided a targeted exercise intervention to a cohort of women who experienced homelessness, addiction and mental health challenges. Chapter 4 contains the following publications:
1. Kennedy F, Murray D, Ní Cheallaigh C, Romero-Ortuno R, Broderick J. Evaluation of a Low-threshold Exercise And Protein supplementation intervention for Women (LEAP-W) experiencing homelessness and addiction: Protocol for a single-arm mixed methods feasibility study. PLoS One. 2025 Feb 6; 20(2):e0300412. Doi: 10.1371/journal.pone.0300412. PMID:39913349; PMCID: PMC11801605.
2. Kennedy F, Ní Cheallaigh C, Romero-Ortuno R, Murray D, Gavin, S. and Broderick J. Exploring the impact of targeted exercise intervention for women experiencing homelessness, addiction, and mental health challenges. A mixed-methods feasibility study. BMJ Open 2026;16:e103060. doi:10.1136/bmjopen-2025-103060.

Chapter 5: will discuss the results of the second part of the LEAP-W trial-the qualitative study, using semi-structured interviews and reflexive thematic analysis, which explored perspectives of 14 women who experienced homelessness, addiction and mental health challenges who participated in the targeted exercise intervention and six key stakeholders.

Chapter 6: will explore, critically reflect and interpret the overall findings of this work, including its strengths and limitations, future directions and implications for practice, policy and research. This chapter will also provide the present the concluding remarks.