Jem Arnold’s PhD Thesis Proposal

Title: Detection, Monitoring, and Management of Flow Limitations in the Iliac Arteries in Cyclists

Thesis Supervisor: Dr. Michael S. Koehle
Committee Members: Dr. David Taylor, Dr. Cameron Mitchell, Dr. Robert Boushel
Dr. David Wright

Abstract: Flow limitations in the iliac artery (FLIA) is a sport-related vascular condition that affects otherwise healthy endurance athletes. Awareness of this condition is emerging as a potential occupational hazard for professional cyclists. The major challenges in FLIA include diagnostic delays and lack of knowledge on effective conservative management.

The primary tools used for describing physiological responses in athletes with FLIA will include near-infrared spectroscopy (NIRS), systemic oxygen uptake (V̇O2), and pedal force measurement. NIRS is a non-invasive optical method of evaluating the balance of metabolic oxygen exchange directly in working muscle. This local indicator of metabolic load can be combined with external work measured at the pedals, and systemic V̇O2 measured from gas exchange at the mouth to describe global physiological responses between healthy athletes and patients, and within both affected and non-affected legs.

The purpose of this thesis project will be to develop the overall understanding of physiological responses to exercise in endurance athletes with FLIA to improve early detection and monitoring, and to evaluate treatment options. We hypothesise that muscle oxygenation will be lower relative to external workload and muscle reoxygenation kinetics will be slower in affected legs. When moving from a race position to a modified upright body position, FLIA patients will have a higher workload at the onset of symptoms, higher peak systemic V̇O2, and observe improvements to muscle oxygenation measures.

Study I will assess a large sample of FLIA patients and healthy athletes to rigorously evaluate a new gold-standard diagnostic procedure for FLIA. Two visits will be used to perform current standard-of-care evaluation, and a noval cycling protocol designed to investigate sensitivity for early detection. In Study II, patients suspected of having FLIA will be evaluated in their provocative race position and a modified upright position to monitor the effects of conservative management, compared to healthy athletes.

Study III will involve a comprehensive literature review of conservative management and post-operative rehabilitation guidelines in FLIA. A scoping review following PRISMA guidelines will be published to identify the breadth of existing recommendations and gaps in the current literature. An evidence-informed structured return to sport guideline will be proposed for FLIA patients based on available literature and clinical expertise.

The anticipated outcomes of this thesis project will improve our ability to detect and diagnose FLIA, and monitor physiological and performance changes non-invasively, outside of a vascular specialist clinic. Novel clinical tools will be developed including a provocative exercise test sensitive and specific to earlier stages of FLIA, an automated data analysis platform (e.g., a publicly available app) to analyse NIRS data collected for screening of FLIA, and guidelines for conservative management and post-operative return to sport as education material for athletes and care providers.