Effect of the Combination of Nitrate and Caffeine on Critical Power In Trained Male Cyclists

Dietary nitrate and caffeine are among the most commonly used ergogenic aids in endurance and high-intensity exercise. Nitrate supplementation has been shown to improve exercise efficiency and tolerance to severe-intensity work, potentially through enhanced nitric oxide availability and improved oxygen delivery and utilization. Caffeine, primarily acting through central nervous system stimulation, has been associated with reduced perceived exertion and enhanced performance across a range of exercise modalities. Despite substantial evidence supporting their independent effects, limited research has examined the combined impact of nitrate and caffeine supplementation on exercise performance.

The present study aims to investigate both the independent and combined effects of acute dietary nitrate and caffeine supplementation on performance outcomes derived from a 3-minute all-out cycling test (3MT), a validated method for estimating critical power and W'. Trained male cyclists will complete four experimental trials in a randomized, double-blind, placebo-controlled, crossover design. Experimental conditions include nitrate-rich beetroot juice with caffeine (BR + CAF), nitrate-rich beetroot juice with placebo (BR), nitrate-depleted beetroot juice with caffeine (CAF), and nitrate-depleted beetroot juice with placebo (PLA).

Participants will consume dietary nitrate 3 hours prior to exercise and caffeine (5 mg/kg body mass) 60 minutes prior to testing. Following a standardized protocol, participants will perform a 3-minute all-out cycling test on an electronically braked cycle ergometer. Primary outcome measures include end power (EP) and work performed above end power (WEP), with secondary outcomes including peak power, mean power, and time-specific power output.

This study aims to determine whether co-ingestion of nitrate and caffeine produces additive or synergistic effects on severe-intensity exercise performance, and to evaluate the extent to which these commonly used ergogenic aids influence performance outcomes associated with critical power in trained individuals.

Inclusion criteria

• Males between the ages of 18 and 40 years of age
• All participants must be trained cyclists, having participated in structured cycling training consisting of at least 2-3 sessions per week for at least 30-60 min each session during the past 12 months.
• All participants must possess a relative max power output (Wmax) of 4.0 W/kg or greater OR a maximal oxygen consumption (VO2max) of 50 ml/kg/min.
• All participants must be healthy and free of any disease as determined through the completion of a medical history questionnaire.
• Body mass index (BMI) between 18.5 - 30 kg/m^2 OR bodyfat percentage <30%

Exclusion criteria

• All females
• Males who are younger than 18 years and older than 40 years of age
• Individuals who have a VO2max below 50 ml/kg/min and a relative Wmax below 4.0 W/kg
• Individuals who fail to meet the minimum training requirements of 2-3 sessions per week of structured cycling training for at least 30-60 min per session during the past 12 months.
• Any individual currently diagnosed with or being treated for any cardiovascular, renal, pulmonary, orthopedic, immunological, psychological or musculoskeletal disorder.
• Any individual who is currently supplementing with a known or purported ergogenic aid (nitrates, caffeine, beta-alanine, bicarbonate, creative, Cordyceps) will be required to refrain from their use for 30 days before beginning the study.
• Individuals who regularly smoke or have quit smoking within the last 6 months.