The goal of this clinical trial is to determine whether a ketone supplement with carbohydrates extends time to fatigue during cycling compared with a carbohydrate-only supplement in healthy, trained cyclists aged 18-55. The main questions it aims to answer are:

Is the time to fatigue increased with ketone supplementation and carbohydrates compared to carbohydrates alone? Will ketone supplementation with carbohydrates produce lower blood lactate concentrations compared to carbohydrates alone?

Participants will:

• Perform a staged maximal cycling exercise test on a stationary bicycle.
• Finger prick to obtain a drop of blood for lactate measurements.
• Wear a mask connected to a metabolic cart to measure breath contents.
• Perform a cycling exercise test to fatigue for at least one hour.
• Consume either a ketone supplement with carbohydrates or a carbohydrate supplement during the exercise at least 4 times.
• Finger prick to obtain a drop of blood to measure blood lactate, ketones, and glucose.

The significance of this study is to address gaps in the literature by investigating the combined effects of R-1,3-Butanediol and carbohydrate supplementation on cycling performance during steady-state exercise above the lactate threshold. Participants include:

1. Trained cyclists ages 18-55

   1. ≥ 6 hours of cycle training per week.
   2. Above average VO2max for their age range per ACSM guidelines.

2. The sample is drawn from the University of Oklahoma, local cycling events in Oklahoma, and local bicycle shops.

There will be a total of three visits, lasting approximately one hour and separated by at least 7 days. The protocol begins with a familiarization visit, during which participants complete a maximal graded exercise test. They are instructed to be at least 4 hours postabsorptive and not complete strenuous exercise within 24 hours of the initial visit, and each participant signs an informed consent form, fills out a POMS questionnaire, and exercise history questionnaire (PAR-Q). Participants' height and weight were recorded, and their bicycles will be connected to the cycling trainer or will use the Zwift One stationary bicycle. To determine VO2 max and lactate threshold, a continuous incremental cycling test will be performed. The test begins at 1 watt per kilogram of body weight and increases 0.5 watts per kilogram of body weight every 3 minutes until two of the following were reached: volitional fatigue, inability to maintain cadence within 10 rpm of their preferred cadence, maximal heart rate within 10 bpm of age-predicted max heart rate, or respiratory exchange ratio greater than 1.10 The intent is to provide insights into metabolic and performance responses beyond traditional exercise intensities. The findings could inform endurance athletes and coaches on nutritional strategies for sustaining performance during high-intensity efforts.The study aims to investigate the performance effects of a ketone supplement (R-1,3-Butanediol) with carbohydrate supplementation on cycling performance above the lactate threshold. It aims to determine whether time to fatigue will be affected and if blood lactate concentrations will decrease due to ketone supplementation. Hypotheses include:

Time to fatigue is increased with ketone supplementation and carbohydrates compared to carbohydrates alone.

Ketone supplementation with carbohydrates will produce lower blood lactate concentrations compared to carbohydrates alone.

Inclusion Criteria:

• Highly trained males and females
• Ages 18-55
• Greater than or equal to six hours of cycling training per week
• Participants from the University of Oklahoma, Oklahoma cycling teams, and local cycling races in Oklahoma.

Exclusion Criteria:

• Cardiovascular disease
• Respiratory disease
• Gastrointestinal disease
• Metabolic disease
• Kidney disease
• Neurological disease
• Pregnancy