Skip to main content
  • Poster presentation
  • Open access
  • Published:

Thermogenic and hemodynamic effects of ingesting a pre-workout supplement with and without synephrine


A number of nutritional strategies have been developed to optimize nutrient delivery prior to exercise. As a result, a number of pre-workout supplements have been developed to increase energy availability, promote vasodilation, and/or positively affect exercise capacity. The purpose of this study was to examine the acute effects of ingesting a pre-workout dietary supplement with and without synephrine on energy metabolism and cardiovascular hemodynamics.


In a double-blind, crossover, randomized and placebo-controlled manner; 25 apparently healthy and recreationally active men and women (21.76±3.00 yr, 15.24±5.26% fat, 25.09±3.03 kg/m2) volunteered to participate in this study and had resting blood pressure (BP), heart rate (HR), 12-lead electrocardiographs (ECG), and resting energy expenditure (REE) measured for 10 minutes. Participants then ingested in a randomized and counterbalanced manner a dextrose flavored placebo (P); a pre-workout supplement (PWS) containing 3.0 g beta alanine, 2 g creatine nitrate, 2 g arginine AKG, 300 mg of N-acetyl tyrosine, 270 mg caffeine, 15 mg of Mucuna pruriens; or, the PWS with 20 mg of synephrine (PWS+S). Metabolic changes were measured continuously while BP, HR, and ECG’s were obtained every 10 minutes during the REE test. Participants repeated the experiment after a one week washout period with the alternate supplements in a randomized and counterbalanced manner. Data were analyzed by repeated measure MANOVA and are presented as means ± SD or SEM from baseline. Consent to publish the results was obtained from all participants.


MANOVA analysis revealed a significant overall Wilks’ Lambda time (p<0.001) and time x group interactions (p<0.001) for oxygen uptake (VO2), carbon dioxide production (VCO2), minute ventilation (Ve), respiratory exchange ratio (RER), and REE values. MANOVA Greenhouse-Geisser univariate analysis revealed significant interactions among groups in VCO2 (p=0.003) and RER (p<0.001) with a trend toward significance in REE (p=0.098). Delta analysis revealed significant differences among groups in mean change in VO2 (P: 3.8±5.2; PWS: 15.4±5.2; PWS+S: 23.5±5.2 ml/min; p=0.03), VCO2 (P: 12.5±5.1; PWS: 31.8±5.1; PWS+S: 37.7±5.1 ml/min; p=0.002), RER (P: 0.033±0.009; PWS: 071±0.009; PWS+S: 0.071±0.009; p=0.005), and REE (P: 0.034±0.025; PWS: 0.095±0.025; PWS+S: 0.132±0.025 kcal/min; p=0.02) with significant differences observed among the P group and both supplemented groups. PWS-S ingestion promoted a more prominent increase in VO2, VCO2, and REE during the initial 5-10 minutes after ingestion with differences minimizing thereafter. Area under the curve (AUC) analysis of changes from baseline revealed that PWS+S and PWS supplementation resulted in significantly greater AUC values than P in VO2 (PWS+S: 1,034±584; PWS: 802±434; P: 684±376; p=0.01); VCO2 (PWS+S: 1,372±604; PWS: 1,151±604; P: 634±262; p<0.01); and RER (PWS+S: 2.79±0.89; PWS: 2.44±0.98; P: 1.46±0.66; p<0.01). There were no significant interaction effects for HR (p=0.77), SBP (p=0.35), or DBP (p=0.65) and there was no evidence of an increase in ECG assessed arrhythmias during the REE assessment.


Ingesting a PWS containing beta alanine, creatine nitrate, arginine AKG, N-Acetyl Tyrosine, caffeine, and Mucuna pruriens increased resting VO2, VCO2, RER, and tended to increase REE values in comparison to a placebo. Addition of 20 mg of synephrine to the PWS resulted in a greater increase in the metabolic response during the first 5-10 minutes after ingestion but differences were not as apparent thereafter and AUC values were not significantly different between the PWS and PWS+S groups. PWS and PWS+S ingestion did not result in a significantly different HR or BP responses during the REE test in comparison to P responses. Results indicate that ingestion of these pre-workout supplements promoted modest thermogenic response and that addition of 20 mg of synephrine to the PWC provided limited additional benefit.


Supported by Woodbolt International, Inc. (Bryan, TX)

Author information

Authors and Affiliations


Corresponding author

Correspondence to R Kreider.

Rights and permissions

Open Access  This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made.

The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.

To view a copy of this licence, visit

The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated in a credit line to the data.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Jung, Y., Goodenough, C., Cho, M. et al. Thermogenic and hemodynamic effects of ingesting a pre-workout supplement with and without synephrine. J Int Soc Sports Nutr 11 (Suppl 1), P35 (2014).

Download citation

  • Published:

  • DOI: