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.
Aged 18-45 years.
Minimum of 2 years of systematic HIFT/CrossFit/Hyrox training experience.
Performing >4 training sessions per week.
Ability to perform the HYROX Physical Fitness Test (P'F'T) and has participated in at least one official HYROX event.
Occurrence of acute musculoskeletal injury or trauma during the study period.
Any medical or health contraindications (including severe menstrual disorders, planned pregnancy, or breastfeeding).
Failure or refusal to strictly adhere to the dietary, supplementation, and exercise testing protocols.