Abstract
BackgroundWe compared Glycine Propionyl-L-Carnitine (GlycoCarn®) and three different pre-workout nutritional supplements on measures of skeletal muscle oxygen saturation (StO2), blood nitrate/nitrite (NOx), lactate (HLa), malondialdehyde (MDA), and exercise performance in men.MethodsUsing a randomized, double-blind, cross-over design, 19 resistance trained men performed tests of muscular power (bench press throws) and endurance (10 sets of bench press to muscular failure). A placebo, GlycoCarn®, or one of three dietary supplements (SUPP1, SUPP2, SUPP3) was consumed prior to exercise, with one week separating conditions. Blood was collected before receiving the condition and immediately after exercise. StO2 was measured during the endurance test using Near Infrared Spectroscopy. Heart rate (HR) and rating of perceived exertion (RPE) were determined at the end of each set.ResultsA condition effect was noted for StO2 at the start of exercise (p = 0.02), with GlycoCarn® higher than SUPP2. A condition effect was also noted for StO2 at the end of exercise (p = 0.003), with SUPP1 lower than all other conditions. No statistically significant interaction, condition, or time effects were noted for NOx or MDA (p > 0.05); however, MDA decreased 13.7% with GlycoCarn® and increased in all other conditions. Only a time effect was noted for HLa (p < 0.0001), with values increasing from pre- to post-exercise. No effects were noted for HR, RPE, or for any exercise performance variables (p > 0.05); however, GlycoCarn® resulted in a statistically insignificant greater total volume load compared to the placebo (3.3%), SUPP1 (4.2%), SUPP2 (2.5%), and SUPP3 (4.6%).ConclusionNone of the products tested resulted in favorable changes in our chosen outcome measures, with the exception of GlycoCarn® in terms of higher StO2 at the start of exercise. GlycoCarn® resulted in a 13.7% decrease in MDA from pre- to post-exercise and yielded a non-significant but greater total volume load compared to all other conditions. These data indicate that 1) a single ingredient (GlycoCarn®) can provide similar practical benefit than finished products containing multiple ingredients, and 2) while we do not have data in relation to post-exercise recovery parameters, the tested products are ineffective in terms of increasing blood flow and improving acute upper body exercise performance.
Highlights
We compared Glycine Propionyl-L-Carnitine (GlycoCarn®) and three different pre-workout nutritional supplements on measures of skeletal muscle oxygen saturation (StO2), blood nitrate/nitrite (NOx), lactate (HLa), malondialdehyde (MDA), and exercise performance in men
Performance Measures No statistically significant differences were noted between conditions for bench press power (p = 0.93), reps performed during the first set (p = 0.99), total reps performed (p = 0.98), mean reps performed (p = 0.98), total volume load (p = 0.99), mean volume load (p = 0.99), mean heart rate over the 10 sets (p = 0.56), or mean perceived exertion over the 10 sets (p = 0.98)
The following are noted: SUPP1 resulted in the greatest power output during the bench press throws, with values higher than the placebo (5.8%), GlycoCarn® (2.5%), SUPP2 (0.4%), and SUPP3 (1.5%)
Summary
We compared Glycine Propionyl-L-Carnitine (GlycoCarn®) and three different pre-workout nutritional supplements on measures of skeletal muscle oxygen saturation (StO2), blood nitrate/nitrite (NOx), lactate (HLa), malondialdehyde (MDA), and exercise performance in men. The category of sport supplements known as the "pre-workout" class appears to be a staple in the regimen of many athletes, bodybuilders and strength athletes in particular These products typically contain a combination of several (30+) ingredients, and usually contain stimulants (e.g., caffeine), energy-producing agents (e.g., creatine), agents that act as hydrogen ion buffers (e.g., beta alanine), protein recovery nutrients (e.g., amino acids), antioxidants, and nitric oxide precursors (e.g., arginine). In relation to the latter, an entire class of sport supplement ("nitric oxide boosters") has been built around the theoretical increase in nitric oxide following intake of L-arginine, and the supposed but unsubstantiated correlation between increased circulating nitric oxide and improved exercise performance and recovery [2]. Companies developing and selling such products boldly claim that a single use of the product will rapidly and dramatically increase circulating nitric oxide and result in an improvement in blood flow, muscle "pump", and exercise performance
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