The combined effects of a pre-workout supplement and three weeks of high-intensity interval training on critical velocity, anaerobic running capacity, training volume, and body composition in men and women

Methods Twenty-five well-trained recreational athletes (mean ± SD age = 21 ± 2 yrs; stature = 172 ± 9 cm; body mass = 66 ± 12 kg, VO2max = 48 ± 9 ml·kg-1·min-1, percent body fat = 19 ± 7%) were assigned to either the active supplement (n = 12) or placebo (PL, n = 11) group. The active supplement (Game Time®, GT, Corr-Jensen Laboratories Inc., Aurora, CO) was 18 g of powder, 40 kcals, and consisted of a proprietary blend including whey protein, cordyceps sinensis, arginine, creatine, citrulline, ginseng, and caffeine. The PL was also 18 g of power, 40 kcals, and consisted of only maltodextrin, natural and artificial flavors and colors. Thirty minutes prior to all testing and training sessions, participants consumed their respective supplements mixed with 8–10 oz of water. Both groups participated in a three week HIIT program three days per week, and testing was conducted before and after the training. Cardiovascular fitness (VO2max) was assessed using closed circuit spirometry (Parvo Medics TrueOne® 2400 Metabolic Measurement System, Sandy, UT) during graded exercise tests on a treadmill (Woodway, Pro Series, Waukesha, WI). Also, four high-speed runs to exhaustion were conducted at 110, 105, 100, and 90% of the treadmill velocity recorded during VO2max, and the distances achieved were plotted over the times-to-exhaustion. Linear regression was used to determine the slopes (critical velocity, CV) and Y-intercepts (anaerobic running capacity, ARC) of these relationships to assess aerobic and anaerobic performances, respectively. Training volumes were tracked by summing the distances achieved during each training session for each subject. Percent body fat (%BF) and fat-free mass (FFM) were assessed with air-displacement plethysmography (BOD POD®, Life Measurement, Inc., Concord, CA).