PhD Student

Start date: October 2022 Mode: full-time

Supervisors: Dr Michael Newell, Dr Jeffrey Aldous, Mr Martyn Morris

Working thesis title

Fluid ingestion and sodium supplementation in endurance and ultra-endurance performers

Abstract

There is huge inter- and intra-individual variability in sweat rate and sweat sodium concentration (Baker, 2017), meaning sodium and fluid requirements during exercise vary between individuals. Exercise-associated hyponatraemia (defined as a plasma sodium concentration <132 mmol.L^-1) mainly occurs due to overconsuming fluid relative to sweat losses, but in rare cases may occur due to excessive sodium losses through sweat (Lewis et al., 2018). Sodium requirements also depend on fluid intake rate, whereby replacing a higher % of fluid lost in sweat will increase the likelihood of sodium supplementation being required (Pahnke et al., 2010). Recent modelling data has predicted the sodium intake required to maintain plasma sodium concentration during different sporting events for individuals with different sweat rates, sweat sodium losses and fluid intake strategies (McCubbin, 2022), but this has yet to be tested in experimental trials.

Dehydration resulting in a body mass loss >2% impairs endurance performance in the heat (James et al., 2019), however whether this extends to longer duration endurance events is debated, given the increased mass loss due to substrate oxidation (Hoffman, 2019).

Therefore, the first study of my PhD aims to determine the amount of sodium required to maintain plasma sodium concentration for different individuals and determine at which point dehydration begins to impair performance during longer duration endurance events in the heat. I hope that the findings of this study will improve the hydration and sodium intake recommendations for long duration endurance events in the heat.

Research questions

• Can a mathematical model be used to predict sodium requirements during prolonged endurance exercise in the heat?
• At what point does dehydration negatively impact endurance performance?
• What fluid volume can athletes tolerate at the level of the gut, alongside meeting carbohydrate recommendations?
• Can pre-exercise sodium and fluid intake affect endurance performance?
• Do the beliefs of athletes as to the importance of sodium ingestion affect their sodium intake?
• Can athletes successfully identify the causes of dehydration/hyponatraemia symptoms?
• How does sodium pre-loading with different doses of sodium affect endurance performance in the heat?

Get involved

I am recruiting trained male cyclists or triathletes for a study based on hydration status, sodium ingestion and endurance performance. Participants must have done at least 3 hours of endurance/cycling training for at least 3 years and be aged between 18 and 45. If you fit this criteria and want to get involved, please email me on sean.sage@study.beds.ac.uk

About me

My interest in exercise physiology began at school, where I played lots of sport and completed A levels in Biology, Chemistry and Physical Education. I then studied Physiology (BSc) at the University of Bristol and Exercise Physiology (MSc) at Loughborough University. At Loughborough I completed a project on the effect of dietary nitrate supplementation on intermittent exercise performance, which sparked an interest in nutritional interventions and sporting performance.

After my MSc, I worked as a sport science intern at a football academy whilst also tutoring students in Biology, Chemistry and Physical Education GCSE and A-Level. I then travelled around Australia in summer 2022, shortly before beginning my PhD.

Alongside my PhD this, I also work as part of the Human Performance Centre (HPC), performing a variety of physiological tests with athletes. My future ambition is to work with elite athletes in a consultancy manner whilst also contributing to sport science research and teaching.

Outside of work, I love playing sport (mainly football and cricket), running, lifting weights and going to live music events.

Contact information

Email: sean.sage@study.beds.ac.uk

Twitter: @sagesportsci