Effects of One Versus Two Doses of a Multi-Ingredient Pre-Workout Supplement on Metabolic Factors and Perceived Exertion during Moderate-Intensity Running in Females

Abstract

The primary purpose of this study was to examine the acute effects of one versus two doses of a multi-ingredient pre-workout supplement on energy expenditure during moderate-intensity treadmill running. In addition, our second aim was to investigate the responses of associated metabolic factors (i.e., substrate utilization, measures of gas exchange), perceived exertion, and resting cardiovascular variables with one and two doses of the pre-workout supplement. Twelve females (mean ± SD: age = 25.3 ± 9.4 years; body mass = 61.2 ± 6.8 kg) completed three bouts of 30 min of treadmill running at 90% of their ventilatory threshold on separate days after consuming one dose of the pre-workout supplement (1-dose), two doses (2-dose), and a placebo. There were no differences among conditions for energy expenditure, fat or carbohydrate oxidation, respiratory exchange ratio, oxygen consumption, or heart rate across exercise time. The two-dose group, however, had lower (p = 0.036) ratings of perceived exertion (11.8 ± 1.7) than the one-dose (12.6 ± 1.7) and the placebo (12.3 ± 1.2) at the 20-min time point of exercise as well as greater resting systolic blood pressure (110 ± 10 mmHg) compared to the one-dose (106 ± 10 mmHg) and the placebo (104 ± 10 mmHg) conditions. Both the one-dose and two-dose conditions had greater increases in diastolic blood pressure compared to the placebo. Thus, our findings indicated that the present pre-workout supplement had no performance-enhancing benefits related to energy metabolism but did attenuate feelings of exertion.

Effects of a Multi-Ingredient Preworkout Supplement Versus Caffeine on Energy Expenditure and Feelings of Fatigue during Low-Intensity Treadmill Exercise in College-Aged Males

“…For example, 3 mg·kg -1 of caffeine has been shown [ 7 , 30 ] to have no effect compared to the 6 mg·kg -1 of caffeine used in the present study and other investigations [ 7 ] that demonstrated increases in energy expenditure. Collectively, these findings [ 7 , 23 , 24 , 27 , 28 , 29 ] suggested that other ingredients in the present preworkout supplement with moderate levels of caffeine (<260 mg or <3.1 mg·kg −1 ) may have provided a synergistic effect that increased energy expenditure.…”

“…These results were surprising given that the caffeine content (<260 mg or <3.1 mg·kg −1 ) of the preworkout supplement was approximately half of the caffeine condition (496 ± 52 mg or 6.0 mg·kg −1 ). Previous studies [ 23 , 27 , 28 , 29 ] have shown that preworkout supplements provide positive effects on resting energy expenditure across a wide range of caffeine content (150–340 mg), whereas preworkout supplements with these same doses (i.e., 150 and 300 mg caffeine) had no effect during moderate-intensity exercise [ 24 ]. The influence of caffeine supplements alone on energy expenditure, however, appears to be dependent on the size of the relative dose.…”

“…While there is limited research on the effects of preworkout supplementation on aerobic exercise, the results of the present study are inconsistent with those previously observed in regard to oxygen consumption. For example, Erickson and colleagues [ 24 ] reported no significant changes in 2 during 30-min treadmill running bouts at 90% of ventilatory threshold following the ingestion of one and two doses of a preworkout supplement containing caffeine (150 and 300 mg, respectively). In addition, the administration of 6 mg·kg −1 of caffeine alone has been shown to increase 2 during treadmill walking in females [ 7 ], whereas 3 mg·kg −1 of caffeine has resulted in no change [ 7 ].…”

“…Our findings for lack of change in RER under the preworkout and caffeine conditions can likely be explained by concurrent increases in 2 and CO 2 . Erickson and colleagues [ 24 ] also reported no effect on substrate utilization following the ingestion of a preworkout supplement in trained females during treadmill running. Similarly, Jung and colleagues [ 28 ] observed no change in RER in recreationally active males and females during resting metabolic rate tests following the ingestion of preworkout with p -synephrine.…”

“…Blood pressure was measured with an inflatable sphygmomanometer (Medline Industries, Inc., Northfield, IL, USA) and stethoscope (Littmann, 3M Company, Maplewood, MN, USA) prior to ingesting the supplement condition (PRE) and 5-min postexercise (POST). Gas analyzers and flow volume of the metabolic cart were calibrated as previously described [ 24 ]. Oxygen uptake ( 2 ), pulmonary ventilation ( E ), carbon dioxide output ( CO 2 ), respiratory exchange ratio (RER), and heart rate (HR) were recorded as 10-min averages throughout the test.…”