All of the participants continued their usual caffeine intakes (100–300 mg per day).

Resistance exercise was performed 3 times per week. Fifteen minutes before each workout, the participants ingested 60 calories from either maltodextrin (15 grams of carbohydrate) or a multi-ingredient preworkout supplement, which contained 5 grams of carbohydrate, 2.5 grams of citrulline malate, 2 grams of betaine, 1.3 grams of acetyl L-carnitine, 1 gram of taurine, 1 gram of tyrosine, 406 milligrams of caffeine, and essential amino acids.

Changes in body composition, vastus lateralis and elbow flexor muscle thickness, maximal isometric mid-thigh pull, jump height, medicine ball throw, and muscular endurance were similar between groups.

The manufacturer of the preworkout supplement funded the study.

Carbohydrates vs. preworkout supplement: Which should you take before the gym? Original paper