Acute Effects of Rhodiola Rosea and Caffeine on Mean Propulsive Velocity Loss in Resistance Training (Rhocaf2)

This study is a randomized, double-blind, placebo-controlled, four-arm crossover trial designed to investigate the acute neuromuscular and ergogenic effects of single and combined supplementation with Rhodiola rosea (1,000 mg) and caffeine (3 mg/kg) in advanced resistance-trained subjects.

Neuromuscular fatigue during heavy resistance training impairs movement velocity, power output, and overall volume performance. While caffeine is a central nervous system stimulant that enhances motor unit recruitment and reduces perceived exertion, Rhodiola rosea is an adaptogen proposed to modulate central monoamines and attenuate fatigue during high-intensity effort. This protocol evaluates whether co-ingestion provides a synergistic advantage over isolated administration or placebo in maintaining movement execution quality and accelerating acute recovery.

Study Procedures:

Familiarization Session: Prior to the experimental trials, participants complete a familiarization session to establish baseline measurements and estimate 1-repetition maximum (1RM) in the barbell back squat using a two-point load-velocity method (using loads corresponding to ~1.0 m/s and ~0.5 m/s) with a linear position transducer.

Experimental Trials (4 Visits): Participants complete four experimental testing visits in a randomized, counterbalanced order, separated by a 72-hour washout period.

During each of the 4 experimental visits, participants complete the following sequence:

Supplement Ingestion: Double-blind administration of the assigned treatment:

Rhodiola placebo consists of opaque cornstarch capsules. Caffeine placebo consists of a 60 mL liquid solution containing sweetener, 3 g of sugar, and 1 g of citric acid.

Active conditions consist of 1,000 mg of Rhodiola rosea and/or 3 mg/kg of caffeine.

Pre-Exercise Evaluation: Completion of baseline perceptual questionnaires. Velocity Determination: Identification of the exact load corresponding to a Mean Propulsive Velocity (MPV) of 1.0 ± 0.03 m/s in the back squat.

Acute Fatigue Protocol: Execution of 3 sets at 70% estimated 1RM in the back squat performed to muscular failure, recording total repetitions and velocity loss across sets.

Post-Fatigue Velocity Recovery: Re-assessment of MPV using the pre-determined 1.0 m/s load at exactly 1 minute and 2 minutes post-fatigue protocol to evaluate acute neuromuscular fatigue and velocity recovery.

Perceptual Evaluation: Rating of Perceived Exertion (RPE) recorded post-exercise.