The study will examine the impact of the Nuun Sport tablets, as compared to water only, on heart rate, perceived exertion, and related outcomes in male and female runners, during and following the performance of a 60-minute treadmill run.

As discussed in our prior applications (protocol FY2020-327 and FY2021-96), maintaining adequate hydration is essential to optimal health (Perrier, 2017), as well as athletic performance (Nuccio et al., 2017). When individuals exercise (in particular in a warm environment), they can lose excessive amounts of fluids through sweating, along with necessary electrolytes (e.g., sodium, potassium, chloride). With dehydration, individuals may feel sluggish and can experience impaired physical performance. (Kenefick, 2018)

Many attempts have been made to improve and measure the hydration status of active individuals (Love et al., 2018). This typically involves the ingestion of fluids leading up to activity (typically plain water), as well as the ingestion of fluids during the activity itself (water, along with a diluted carbohydrate/electrolyte beverage).

During aerobic exercise, the shift in fluid (intake versus losses) can affect electrolyte balance, with dehydration and potential adverse effects on performance and health (Perrier et al., 2021; Armstrong et al. 2021). A better understanding of rehydration methods and resultant efficacy would permit selection by an athlete of the optimal method for preventing dehydration to optimize physical performance and reduce potential deleterious effects.

It is well-accepted that electrolyte replenishment is of importance, both during and following exercise-to aid in rehydration for subsequent bouts. Electrolytes (sodium in particular) have been used for decades to aid athlete hydration and this has led to the development of various sport drinks-which also include small amounts of carbohydrate (e.g., Gatorade, Powerade).

The present study will examine the impact of the Nuun Sport tablets, as compared to water only, on heart rate, perceived exertion, and related outcomes: changes in body mass, changes in plasma volume, post-exercise urine volume, and changes in urine specific gravity in male and female runners, during and/or following the performance of a 60-minute treadmill run.

Inclusion Criteria:

• body mass index (BMI) between 18-29.9 kg/m2 (not obese)
• be able to fast overnight (>8 hrs)
• consuming a minimum of two liters of water per day, on a regular basis
• distance runners: run ≥ 15 miles/week, ≥ 3 runs/week, for at least the past 6 months
• have completed a run of 60 minutes or more at least once per month for the past 6 months
• normal resting blood pressure (systolic < 140 mmHg, diastolic < 90 mmHg) and heart rate (40-80bpm)
• a negative verbal pre-study drug screen (alcohol abuse, amphetamines, benzodiazepines, cocaine, opioids, phencyclidine, barbiturates, cotinine) and no history of use of illicit drugs or other substances of abuse within 12 months of the screening visit

Exclusion Criteria:

• tobacco user
• if female, pregnant
• history of known cardiovascular disease
• more than 400mg caffeine intake per day
• self-reported active infection or illness of any kind
• consumption of alcohol-containing beverages within 48 hours of testing
• consumption of caffeine-containing beverages within 48 hours of testing
• strenuous exercise within 48 hours of testing