The Effect of Manipulating Hydration Status During Cycling in the Heat on Acute Kidney Injury Biomarkers

The Effect of Manipulating Hydration Status During Cycling in the Heat on Acute Kidney Injury Biomarkers

Acute Kidney Injury (AKI) is common in prolonged endurance events. Risk factors for exercise-associated AKI include: the exercise itself, heat, hypohydration, muscle breakdown and non-steroidal anti-inflammatory drug (NSAID) use. Prior research from our laboratory showed the hypohydration during high-intensity running increased a biomarker of AKI (urine osmolality-corrected kidney injury molecule 1). Therefore, the current study will now investigate the effect of manipulating hydration status during cycling on biomarkers of AKI.

Participants will be required to restrict their water intake during cycling in the heat (90-120 minutes at 35°C), in order to achieve a body mass loss of approximately 3%.

Participants will be provided with water intake that matches their sweat losses during cycling in the heat (90-120 minutes at 35°C)

Water intake will be manipulated in both arms to create a hypohydrated state and a euhydrated state, post-exercise

Changes in urinary Kidney Injury Molecule 1 (uKIM-1) (uncorrected/raw values and urine osmolality-corrected values)

Changes in urinary neutrophil gelatinase-associated lipocalin (uNGAL) (uncorrected/raw values and urine osmolality-corrected values)

Pre-exercise (baseline) and post-exercise (immediately after the intervention), as well as all urine produced from post-exercise until 24 hours post-baseline

pre-exercise (baseline), throughout exercise, post-exercise (immediately after the intervention), 24 hours post-baseline

Ad libitum energy (Kj), carbohydrate (g), sugar (g), protein (g), fat (g), saturated fat (g), sodium (g) and water intake (g).

Participants will complete a weighed food and fluid diary, using a set of food scales and a diary, to record all food and fluid that they ingest. This data will then be analysed using dietary analysis software (e.g. Nutritics)

Participants will be asked to rate their headache on a scale of 0-10, with higher scores meaning a worse outcome .

pre-exercise (baseline), every 30 minutes during exercise (30, 60,90 and 120 minutes), post-exercise (immediately after the intervention) and 24 hours post-baseline

Participants will be asked to rate their nausea on a scale of 0-10, with higher scores meaning a worse outcome .

pre-exercise (baseline), every 30 minutes during exercise (30, 60,90 and 120 minutes), post-exercise (immediately after the intervention) and 24 hours post-baseline

Participants will be asked to rate their dizziness on a scale of 0-10, with higher scores meaning a worse outcome .

pre-exercise (baseline), every 30 minutes during exercise (30, 60,90 and 120 minutes), post-exercise (immediately after the intervention) and 24 hours post-baseline

Participants will be asked to rate their thirst on a scale of 0-10, with higher scores meaning a worse outcome .

pre-exercise (baseline), every 30 minutes during exercise (30, 60,90 and 120 minutes), post-exercise (immediately after the intervention) and 24 hours post-baseline

Participants will be asked to rate their thermal comfort on a scale of -10 to 10, with -10 being cold impossible to bear and 10 being heat impossible to bear

pre-exercise (baseline), every 30 minutes during exercise (30, 60,90 and 120 minutes), post-exercise (immediately after the intervention) and 24 hours post-baseline

Participants will be asked to rate their gastrointestinal comfort on a scale of 0-10, with higher scores meaning a worse outcome .

pre-exercise (baseline), every 30 minutes during exercise (30, 60,90 and 120 minutes), post-exercise (immediately after the intervention) and 24 hours post-baseline

Participants will be asked to rate their stomach fullness on a scale of 0-10, with higher scores meaning a worse outcome .

pre-exercise (baseline), every 30 minutes during exercise (30, 60,90 and 120 minutes), post-exercise (immediately after the intervention) and 24 hours post-baseline

Participants will be asked to rate their stomach bloatedness on a scale of 0-10, with higher scores meaning a worse outcome .

pre-exercise (baseline), every 30 minutes during exercise (30, 60,90 and 120 minutes), post-exercise (immediately after the intervention) and 24 hours post-baseline

Participants will be asked to rate their urge to vomit on a scale of 0-10, with higher scores meaning a worse outcome .

pre-exercise (baseline), every 30 minutes during exercise (30, 60,90 and 120 minutes), post-exercise (immediately after the intervention) and 24 hours post-baseline

pre-exercise (baseline), post-exercise (immediately after the intervention) and 24 hours post-baseline

Will be monitored throughout the exercise intervention, at 15 minute intervals (15 minutes, 30 minutes, 45 minutes, 60 minutes, 75 minutes, 90 minutes, 105 minutes and 120 minutes)

Will be monitored throughout the exercise intervention, at 30 minute intervals (30 minutes, 60 minutes, 90 minutes and 120 minutes)

Will be determined immediately prior to the exercise intervention (at rest) and then throughout the exercise intervention at 15 minute intervals (15 minutes, 30 minutes, 45 minutes, 60 minutes, 75 minutes, 90 minutes, 105 minutes and 120 minutes)

Inclusion Criteria: Healthy recreationally active Exclusion Criteria: Smoker/vaper regular use of anti-inflammatory medications (e.g. ibuprofen) history of kidney disease or diabetes