The Effects of Acute Nitrate and Caffeine Co-ingestion on Discipline-Specific Exercise Performance.

Condition(s) studied

Investigational drug(s) / intervention(s)

Caffeine: Anhydrous caffeine administered orally in a hard gelatine capsule. To address the unique physiological profiles of the two cohorts, a highly specific, differentiated dosing protocol is implemented: Cohort A (adult functional fitness athletes) will receive a high-performance dose of 6 mg/kg body mass, while Cohort B (elite junior swimmers) will receive a safe, youth-adapted dose of 3 mg/kg body mass. In all experimental trials, the capsule is ingested exactly 60 minutes prior to the onset of the discipline-specific exercise test to match peak plasma caffeine concentration.

Dietary Nitrate (Beetroot Juice): Concentrated beetroot juice (BJ) administered as a single, acute organic shot of 70 mL (Beet It Sport, James White Drinks Ltd., Ipswich, UK). Each active shot contains approximately 400 mg (equivalent to \~6.4 mmol) of inorganic nitrate. In contrast to chronic loading designs, this study evaluates purely acute effects; the shot is ingested exactly 3 hours (180 minutes) prior to the physical performance test to align with peak systemic concentration of plasma nitrite.

Placebo (Maltodextrin Capsule): Placebo capsule containing inert maltodextrin powder. The capsule is identical in size, shape, weight, color (opaque), and texture to the active caffeine capsule to ensure robust blinding. It is administered at the exact same time point (60 minutes pre-exercise) according to the identical body-mass-adjusted dosing scheme (simulating either 3 mg/kg or 6 mg/kg).

Placebo (Nitrate-Depleted Beetroot Juice): Nitrate-depleted beetroot juice (Beet It, James White Drinks Ltd., Ipswich, UK) administered as a 70 mL shot. This placebo is identical in taste, smell, appearance, packaging, and viscosity to the active concentrated shot, but has been selectively filtered to contain negligible nitrate levels (\<0.4 mmol / \~25 mg of nitrates). It is ingested exactly 3 hours prior to the exercise test.

Study summary

The purpose of this study is to investigate the acute, separate, and combined ergogenic effects of dietary nitrate (beetroot juice, BJ) and caffeine (CAF) supplementation on discipline-specific athletic performance. The project employs a double-blind, randomized, placebo-controlled, four-arm crossover design. It evaluates two highly distinct, heterogeneous populations of athletes: (A) adult high-intensity functional training (HIFT/CrossFit/Hyrox) competitors performing the standardized Hyrox Physical Fitness Test (P'F'T), and (B) elite junior competitive swimmers (National Team members) performing a progressive 8 × 100 m swimming test. The study will assess physical performance, lactate kinetics, subjective exertion, biochemical indices, psychological metrics, and gastrointestinal tolerance.

Eligibility

Primary outcome measure(s)

• Exercise Performance Time (minutes and seconds, Cohort A - Hyrox P'F'T) — At each experimental visit (Visits T1-T4), with visits conducted at 7-day intervals following the baseline/familiarization visit (T0).
  Total time (in minutes and seconds) required to complete the standardized HYROX Physical Fitness Test (P'F'T) consisting of 6 specific functional exercises.
• Swimming Performance (minutes and seconds, Cohort B - 8x100m Step-Test) — At each experimental visit (Visits T1-T4), with visits conducted at 7-day intervals following the baseline/familiarization visit (T0).
  Swimming performance will be assessed using the completion time (seconds and milliseconds) for each 100-m repetition of the standardized 8 × 100-m step test, including the maximal-effort repetition performed during the fifth stage.

Trial sites (1)

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