Effect of caffeine and citrulline malate on resistance exercise and jumping performance: a randomized double-blind placebo-controlled crossover study

INTERVENTION: Study design A randomized, double‐blind, placebo‐controlled, crossover trial is being used to investigate the isolated and combined effects of caffeine and CitMal on countermovement jump (CMJ) performance, maximal strength, muscular endurance, and pain perception. In the first session, the participants are being familiarized with the testing protocol, which will then be repeated for all the experimental sessions. The experimental sessions involve four testing trials where the participants will receive either placebo (zero‐calorie drink), 5 mg/kg caffeine, 12 g of CitMal, or the respective dosages of caffeine and CitMal combined, mixed in 500 mL non‐caloric cordial. In all four conditions, supplementation is provided 60 minutes before the start of the testing protocol. All testing trials are separated by a minimum of 72 hours and a maximum of seven days to ensure treatment washout and sufficient recovery. The participants are instructed to refrain from caffeine, alcohol, and training 24 hours prior to every testing session. All participants are recording a 24‐hour diet log the day prior to testing and a weekly caffeine log. The participants are instructed to replicate the food log before every trial to reduce variation in energy intake and hydration level. The order of the trials is counterbalanced and randomized using Microsoft Excel (Version 2205, 64‐bit). Participants A total of 40 healthy resistance‐trained males (n=20) and females (n=20) with no known medical condition, injuries, or any other health limitation are being recruited. The study is being performed in accordance with the Helsinki Declaration and approved by the Norwegian Center for Research Data (NSD) (project nr: 445723) and by the local e CONDITION: Sports‐related outcomes ; Nutritional, Metabolic, Endocrine PRIMARY OUTCOME: ; 1. Jump height (cm) measured using a force plate at every trial before the strength test and after warmup; 2. Maximal power (W) measured using a force plate at every trial before the strength test and after warmup; 3. Rate of force development (kN/s) measured using a force plate at every trial before the strength test and after warmup; 4. Peak force (N/kg) measured using a force plate at every trial before the strength test and after warmup; 5. Maximal strength measured using a barbell and plates for loading at every trial after the jump test; 6. Number of repetitions to failure with barbell and plates for loading on every trial after the jump test; SECONDARY OUTCOME: Pain perception measured using a numerical rating scale straight after the number of repetitions to failure test for both bench press and back squat INCLUSION CRITERIA: 1. Aged between 18 and 45 years old 2. A minimum of 12 months of resistance training experience 3. Currently performing resistance training at least two times per week 4. Able to perform the barbell back squat and bench press with 120% and 100% of body mass for males and 100% and 70% of body mass for females