Effects of Pre-Workout PRO ST on Performance in Active Adults

Dr. Fernando Naclerio

Professor of Strength Training and Sports Nutrition.
Director: Centre for Exercise Activity and Rehabilitation
Institute for Lifecourse Development
School of Human Sciences
University of Greenwich

Introduction

Multi-ingredient supplements ingested before training “preworkout” (PREW) are designed to optimize performance during exercise. These formulations include caffeine combined with amino acids and other nutrients with ergogenic properties (Naclerio, 2023). Caffeine (administered in doses of 3–6 mg·kg−1) works by antagonizing adenosine receptors and thus, reducing the perception of effort and increasing the mobilization of fatty acids; frequently, the formulations add amino acids such as citrulline/arginine (precursors of nitric oxide), betaine, taurine, and tyrosine which increase blood flow, hydration, and cognitive aspects (Guest et al., 2021; Trexler et al., 2019).

In the scientific projects on sports nutrition that we are carrying out at the University of Greenwich (Centre for Exercise Activity and Rehabilitation), UK, we have evaluated “preworkout” products marketed by the company Crown Sport Nutrition (CSN). On this occasion, I will comment on the results of two randomized, double-blind, controlled studies, in adults over 40 years old, physically active. The company CSN provided the supplements evaluated, PREW and carbohydrates (COMP), both with the same number of calories, identical format, flavor, and texture.

In physically active middle-aged adults, the intake of PREW with caffeine combined with proteins/amino acids and slow-release carbohydrates, such as isomaltulose, acutely increased the weekly strength training volume and promoted fat oxidation during low-intensity aerobic exercise compared to the intake of an isocaloric control supplement providing only carbohydrates (Puente-Fernández et al., 2020). However, it is not so clear whether these short-term observed benefits translate into superior long-term adaptations measured over longer periods (e.g., 6 weeks). In a randomized 6-week trial with strength training carried out three times per week, the intake of the same PREW or the COMP produced similar improvements in the reduction of body fat, the increase of lean mass, muscle mass, strength, and muscular endurance; only waist circumference showed a modest reduction that favored the group that consumed the PREW (Puente-Fernández et al., 2025).

This brief commentary summarizes the procedures and results of the two studies conducted, emphasizing the effects on training volume, substrate oxidation, body composition, and muscle function. In addition, practical recommendations are provided for the efficient use of multi-ingredient supplements to be taken before training (PREW) in physically active adults.

Study 1 (Puente-Fernández et al., 2020) – Training microcycle of 5 days

Randomized, double-blind, crossover trial that tested the short-term effects of pre-workout intake of a multi-ingredient (PREW) compared to an isocaloric control providing only carbohydrates (COMP) over a microcycle of 5 days of training and evaluation in 14 middle-aged adults (7 women; ~49 years) in two counterbalanced phases separated by a two-week period during which no supplements were ingested and no exhaustive exercises were performed. The participants ingested the assigned supplement 15 minutes before training and completed three strength training sessions that included 8 full-body exercises performed in a circuit format in sets of ~16 maximum repetitions for each exercise. These sessions were alternated with two 30-minute cycling sessions at individual intensity where fat utilization was maximized (Fat Max).

Supplementation:

• PREW (40 g; ~100 kcal) contained 16 g of carbohydrates (predominantly isomaltulose), 9 g of protein/amino acids, including branched-chain amino acids, 400 mg of caffeine, and 300 mg of yerba mate.

• COMP: 27 g of carbohydrates (maltodextrin); ~102 kcal.

The diet remained unchanged throughout the duration of the study.

Results of the main variables:

• Strength training volume: When participants ingested the PREW supplement, a significant increase in the weight lifted per session (p<0.05) and across the full week (p = 0.001, d = 1.26) was observed compared to when they ingested only carbohydrates (COMP). Despite the higher workload performed, the subjective perception of effort measured at the end of each session did not differ between the two conditions.

• Substrate oxidation: During resistance sessions, compared to the COMP condition, PREW caused greater fat oxidation (p = 0.046) with a concomitant (non-significant) reduction in carbohydrate oxidation (trend p = 0.07).

Results of the secondary variables:

• Muscle function measured at the end of strength training: The decrease in medicine ball throw distance after the second strength session was smaller in the PREW condition (p = 0.001 vs. COMP). The drop in maximal isometric strength after the third strength training session was also smaller with PREW consumption (p = 0.007 vs. COMP). Vertical jump showed no differences between conditions.
• Neuromuscular measures: The variables of involuntary muscle function (tensiomyography) showed no relevant changes or differences between conditions.
• Subjective answers: Pre-workout energy/focus and perceived effort measured at the end of the training sessions were similar between conditions.
  

Interpretation:

In physically active middle-aged adults, the intake of a pre-workout supplement (PREW) with caffeine and enriched with amino acids increased strength training volume and promoted fat oxidation during low-intensity aerobic endurance exercise. These changes did not cause an increase in the subjective perception of effort compared to when only carbohydrates were consumed (COMP). PREW also attenuated performance declines measured at the end of strength training sessions. No effects were observed on jumping, tensiomyography, or subjective feelings of effort. These findings support the consumption of PREW vs. the intake of only carbohydrates, to optimize short-term performance during microcycles of training in which multiple strength and aerobic endurance training sessions are performed.

Study 2 (Puente-Fernández et al., 2025): Training and supplementation intervention during 6 weeks

In this study, a randomized controlled, parallel, double-blind trial was conducted for 6 weeks of intervention, which compared the effects of consuming a multi-ingredient supplement (PREW) before training with an isocaloric supplement that provided only carbohydrates (COMP). The participants were 43 physically active middle-aged adults (26 women, 17 men; ~53 ± 5 years). All completed supervised strength training three times per week with progressive overload. Fifteen minutes before each session, the participants ingested 30 g of the assigned supplement. PREW (~60 kcal) was a vegan formula that provided protein (9 g of protein/amino acids), 406 mg of caffeine, 300 mg of yerba mate, 2.5 g of citrulline malate, 2 g of betaine, and 1.3 g of acetyl-L-carnitine and 5 g of carbohydrates (maltodextrin). COMP (~60 kcal) included 15 g of carbohydrates (maltodextrin) without added protein/actives. Both supplements had a citrus flavor and were indistinguishable to preserve blinding. Usual dietary intake was monitored at the beginning and at the end of the intervention, with no substantial changes observed nor differences between the compared groups (PREW vs. COMP).

Results of the main variables:
Body composition and muscle thickness. Both groups reduced fat mass and increased lean mass, with no differences observed between groups. The muscle thickness of the lateral vastus of the quadriceps and the elbow flexors increased modestly and similarly in both groups. The results are summarized in Table 1.

Table 1. Changes in body composition and muscle thickness after 6 weeks of training and supplementation [Pre-Workout (PREW) vs. Carbohydrates (COMP)]. The values indicate the mean changes measured at the end of the intervention period (mean ± SD). Asterisks indicate significant intragroup improvements. No differences were observed between groups for these results.

(*p < 0.05 within that group. "n.s." = not significant. The comparisons between groups were n.s. for all measures.).

The only measure with a notable intragroup effect that favored the PREW group was waist circumference. This decreased significantly (−1.8 ± 1.8 cm; p < 0.01 vs. baseline). The COMP group showed a smaller and non-significant decrease (−1.0 ± 1.5 cm). However, the comparison between groups for waist circumference did not reach statistical significance, indicating that PREW did not outperform COMP in reducing central adiposity.

Results of the secondary variables:
Performance and training dose. Both groups improved isometric strength, vertical jump height, distance in the medicine ball throw, and repetitions in 30 s in the sit-to-stand and bench press tests (training-induced gains), with no significant differences between groups after adjusting for baseline value. Throughout the intervention, the total training volume (accumulated load lifted in kg) increased comparably in both groups (PREW and COMP). In addition, the subjective perception of effort measured 20 minutes post-training was similar. These results suggest that the multi-ingredient (PREW) did not systematically alter perceived effort. It is important to highlight that performing a greater volume (number of exercises, sets, and repetitions) of training was not allowed within the intervention program carried out.

Interpretation:

When training volume and energy intake are matched, consuming a multi-ingredient pre-workout (PREW) did not confer additional long-term benefits compared to an isocaloric carbohydrate-only supplement in physically active middle-aged adults. Both strategies supported meaningful improvements in body composition and performance after 6 weeks. The only distinctive finding for PREW was an intragroup reduction in waist circumference that did not translate into a between-group advantage. These results emphasize that the training stimulus, with adequate nutrition, was the main factor driving changes in this population.

Discussion and recommendations

In the two studies conducted on physically active middle-aged adults, multi-ingredient supplementation consumed before training (PREW) showed a clear short-term performance-enhancing effect (a microcycle of 5 days of training), but no additional long-term advantage compared to the consumption of an isocaloric comparator (COMP) that provided only carbohydrates. These results were observed with training-matched designs in both conditions or intervention groups.

In the short-term study (a microcycle), the intake of PREW 15 min before training increased the weight lifted in strength workouts across the three sessions of the week and shifted substrate use toward greater fat oxidation during low-intensity cycling (Fat Max), without raising the perceived effort level. PREW also attenuated post-session declines in medicine ball throw and isometric strength compared to when only carbohydrates were consumed (with equal energy). These findings support the use of PREW as a short-term aid to sustain performance and manage fatigue in microcycles with multiple training sessions.

In the study of 6 weeks of intervention, which included a supervised strength training program three times per week and the consumption, before training, of a multi-ingredient supplement (PREW) or an isocaloric comparator (COMP) (carbohydrates only), both the PREW and COMP groups produced similar improvements in fat mass (~−1.0 to −1.4 kg), lean mass (~+0.8 to +0.9 kg), muscle thickness (lateral quadriceps and elbow flexors), maximal isometric strength, vertical jump, medicine ball throw, and muscular endurance tests of 30 s. Waist circumference decreased significantly within the PREW group (~−1.8 ± 1.8 cm), but the difference between groups was not significant. This suggests that there was no confirmed superiority in the reduction of central adiposity in favor of the PREW group. The total training volume and the subjective perception of effort progressed similarly in both groups, suggesting that PREW did not increase the dose performed within this program.

Context Analysis

The short-term benefits are consistent with the antagonistic effect of caffeine on adenosine receptors (lower perceived effort, increased activation) and its lipolytic/thermogenic actions (3–6 mg·kg−1 is typically ergogenic when ingested ~30–60 min before exercise, with interindividual variability) (Guest et al., 2021). Additional components of PREW (e.g., citrulline/arginine as precursors of nitric oxide synthesis, betaine, and taurine) may enhance blood flow, hydration, and resistance to fatigue. Current evidence shows small but significant benefits of citrulline intake in high-intensity strength/power tasks (Trexler et al., 2019). In the study of 6 weeks of intervention, however, any short-term advantage (one week) probably did not translate into accumulated effect because the training was prescribed and matched in number of exercises, sets, and repetitions; the main factor of adaptation was the training stimulus supported by adequate energy and protein intake.

Practical recommendations

• Strategic use: Use PREW to maximize performance in demanding training sessions (e.g., demanding microcycles, days with little sleep/low motivation, or when high volumes of work are scheduled). Expect more repetitions at a given intensity and greater total load at the same perceived effort; this could be very useful if your plan allows for accumulating that additional work.
• Long-term expectations: Do not expect chronic superior results compared to an isocaloric pre-workout drink containing only carbohydrates unless the PREW helps you consistently sustain greater volume or intensity with well-managed recovery.
• Dose/time: Start with ~3 up to 6 mg·kg−1 of caffeine 30–60 min before training; increase only if the dose is tolerated. Avoid its use in the hours before going to sleep (to protect sleep); consider periodizing/cycling its use to avoid becoming accustomed (Guest et al., 2021).
• Safety/individualization: Consider sensitivity to caffeine, hypertension, arrhythmias, pregnancy, and drug interactions. For athletes who avoid stimulants, the consumption of pre-workout supplements containing only carbohydrates or even proteins, but without caffeine, is a valid alternative (Puente-Fernández et al., 2025).
• Prioritize the fundamentals: Training with progressive overload, sufficient daily high-quality protein (1.6–2 g·kg−1·day−1) (Naclerio & Seijo, 2019) and adequate energy intake, sleep, and recovery practices will be the aspects most related to the observed results; supplements are complements, not substitutes.
• Conclusion: In active middle-aged individuals and older adults, the consumption of multi-ingredient supplements (e.g., PREW) before training is an effective short-term aid, but not a guarantee of superior chronic adaptations when energy and training design are matched.

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References

Guest, N. S., VanDusseldorp, T. A., Nelson, M. T., Grgic, J., Schoenfeld, B. J., Jenkins, N. D. M., Arent, S. M., Antonio, J., Stout, J. R., Trexler, E. T., Smith-Ryan, A. E., Goldstein, E. R., Kalman, D. S., & Campbell, B. I. (2021). International society of sports nutrition position stand: caffeine and exercise performance. Journal of the International Society of Sports Nutrition, 18(1), 1–37. https://doi.org/10.1186/s12970-020-00383-4

Naclerio, F. (2023). Supplementation with Multi-Ingredients for Physically Active Individuals. Iberoamerican Journal of Physical Activity and Sport Sciences, 12(3), 42–51. https://doi.org/10.24310/riccafd.12.3.2023.17761

Naclerio, F., & Seijo, M. (2019). Whey protein supplementation and muscle mass: current perspectives. Nutrition and Dietary Supplements, 11, 37–48. https://doi.org/10.2147/nds.s166195

Puente-Fernández, J., Larumbe-Zabala, E., Roberts, J., & Naclerio, F. (2025). Pre-workout multi-ingredients or carbohydrate alone promote similar resistance training outcomes in middle-aged adults: a double-blind, randomized controlled trial. Journal of the International Society of Sports Nutrition, 22(1). https://doi.org/10.1080/15502783.2025.2519515

Puente-Fernández, J., Seijo, M., Larumbe-Zabala, E., Jiménez, A., Liguori, G., Rossato, C. J. L., Mayo, X., & Naclerio, F. (2020). Effects of multi-ingredient preworkout supplementation across a five-day resistance and endurance training microcycle in middle-aged adults. Nutrients, 12(12), 1–19. https://doi.org/10.3390/nu12123778

Trexler, E. T., Persky, A. M., Ryan, E. D., Schwartz, T. A., Stoner, L., & Smith-Ryan, A. E. (2019). Acute Effects of Citrulline Supplementation on High-Intensity Strength and Power Performance: A Systematic Review and Meta-Analysis. Sports Medicine, 49(5), 707–718. https://doi.org/10.1007/s40279-019-01091-z