Oral supplementation with glycine-arginine-α-ketoisocaproic acid (GAKIC) has previously been shown to improve exhaustive high-intensity exercise performance. There are no controlled studies involving GAKIC supplementation in well-trained subjects. The aim of the current study was to examine the effects of GAKIC supplementation on fatigue during high-intensity, repeated cycle sprints in trained cyclists. After at least 2 familiarization trials, 10 well-trained male cyclists completed 2 supramaximal sprint tests each involving 10 sprints of 10 s separated by 50-s rest intervals on an electrically braked cycle ergometer. Subjects ingested 11.2 g of GAKIC or placebo (Pl) during a period of 45 min before the 2 experimental trials, administered in a randomized and double-blind fashion. Peak power declined from the 1st sprint (M ± SD; Pl 1,332 ± 307 W, GAKIC 1,367 ± 342 W) to the 10th sprint (Pl 1,091 ± 229 W, GAKIC 1,061 ± 272 W) and did not differ between conditions (p = .88). Mean power declined from the 1st sprint (Pl 892 ± 151 W, GAKIC 892 ± 153 W) to the 10th sprint (Pl 766 ± 120 W, GAKIC 752 ± 138 W) and did not differ between conditions (p = .96). The fatigue index remained at ~38% throughout the series of sprints and did not differ between conditions (p = .99). Heart rate and ratings of perceived exertion increased from the 1st sprint to the 10th sprint and did not differ between conditions (p = .11 and p = .83, respectively). In contrast to previous studies in untrained individuals, these results suggest that GAKIC has no ergogenic effect on repeated bouts of high-intensity exercise in trained individuals.
Lukas Beis, Yaser Mohammad, Chris Easton and Yannis P. Pitsiladis
Andrew E. Kilding, Claire Overton and Jonathan Gleave
To determine the effects of ingesting caffeine (CAFF) and sodium bicarbonate (SB), taken individually and simultaneously, on 3-km cycling time-trial (TT) performance.
Ten well-trained cyclists, age 24.2 ± 5.4 yr, participated in this acute-treatment, double-blind, crossover study that involved four 3-km cycling TTs performed on separate days. Before each TT, participants ingested either 3 mg/kg body mass (BM) of CAFF, 0.3 g · kg−1 · BM−1 of SB, a combination of the two (CAFF+SB), or a placebo (PLAC). They completed each 3-km TT on a laboratory-based cycle ergometer, during which physiological, perceptual, and performance measurements were determined. For statistical analysis, the minimal worthwhile difference was considered ~1% based on previous research.
Pretrial pH and HCO3 were higher in SB and CAFF+SB than in the CAFF and PLAC trials. Differences across treatments for perceived exertion and gastric discomfort were mostly unclear. Compared with PLAC, mean power output during the 3-km TT was higher in CAFF, SB, and CAFF+SB trials (2.4%, 2.6%, 2.7% respectively), resulting in faster performance times (–0.9, –1.2, –1.2% respectively). Effect sizes for all trials were small (0.21–0.24).
When ingested individually, both CAFF and SB enhance high-intensity cycling TT performance in trained cyclists. However, the ergogenic effect of these 2 popular supplements was not additive, bringing into question the efficacy of coingesting the 2 supplements before short-duration high-intensity exercise. In this study there were no negative effects of combining CAFF and SB, 2 relatively inexpensive and safe supplements.
Robyn F. Madden, Kelly A. Erdman, Jane Shearer, Lawrence L. Spriet, Reed Ferber, Ash T. Kolstad, Jessica L. Bigg, Alexander S.D. Gamble and Lauren C. Benson
-point shooting performance. 6 Further investigation is needed to evaluate the effects of caffeine on performance metrics and the ability to execute sport-specific skills without committing errors. Recent investigations have considered the ergogenic effect of low doses of caffeine (∼3 mg/kg body mass
Priscilla M. Clarkson
Priscilla M. Clarkson
Melvin H. Williams
Alan D. Rogol
Most hormonal agents used for nonmedical purposes in athletes have legitimate medical uses. This review introduces each compound by its pharmacology, clinical pharmacology, and legitimate medical use and reviews information on its abuse. Human growth hormone is presently available in virtually unlimited quantities due to its production by recombinant DNA technology. Its use in athletes is considered for its muscle-building, fat-depleting properties. Erythropoietin is a kidney hormone that increases red cell mass. It is used for renal dialysis patients to avoid blood transfusions. Its use in athletes is to raise red blood cell mass in an attempt to augment maximal oxygen capacity and the ability to do endurance work. Human chorionic gonadotropin has the biological activity of luteinizing hormone to increase testosterone synthesis and to maintain (partially) testicular volume when exogenous androgens are taken. Clenbuterol is a beta2 adrenergic agonist with muscle-building properties that are seemingly specific to striated muscle; clenbuterol may cause reduction in body fat.
Craig A. Horswill
As a result of exercise-induced sweating, athletes and trained individuals can lose up to 3 L of fluid per hour. Fluid replacement is required to maintain hydration and allow the athlete to continue to perform. Inadequate fluid intake will adversely affect temperature regulation, cardiovascular function, and muscle metabolism. To maximize fluid intake and effectively replace fluid, athletes must employ behavioral strategies. Athletes can also select beverages with characteristics that complement their behavioral efforts. Palatability, rapid absorption, retention of the fluid, and ergogenicity are the major attributes to consider for enhancing hydration during training and physical activity.
Joelle Leonie Flueck, Martina Lienert, Fabienne Schaufelberger, Jörg Krebs and Claudio Perret
The aim of our study was to investigate the effect of caffeine supplementation on 3-min all-out arm crank exercise performance in paraplegic (P) and tetraplegic (T) compared with able-bodied (AB) participants. A placebo-controlled, randomized, crossover, and double-blind study design was chosen to investigate the differences between caffeine (CAF) and placebo (PLC). In total, 34 healthy, trained participants were tested. Seventeen were AB (median [minimum; maximum] VO2peak: 33.9 mL/min/kg [23.6; 57.6]), 10 were P (VO2peak: 34.4 mL/min/kg [19.5; 48.8]), and 7 were T (VO2peak: 13.6 mL/min/kg [8.6; 16.3]). All participants performed two 3-min all-out tests on an arm crank ergometer following the ingestion of either PLC or CAF. Power output parameters, plasma caffeine (PC), epinephrine (EPI), and norepinephrine (NOR) concentrations were assessed. CAF significantly increased average power over the first 30 s (p = .028) and 60 s (p = .005) in P, but not in T (p = .61; p = .87) nor in AB (p = .25; p = .44). Peak power was increased in the CAF trial in AB (+46 W) as well as in P (+21 W) but was not significantly different from PLC (AB: p = .10; P: p = .17). PC significantly increased in all groups (AB: p = .002; P: p = .005; T: p = .018) whereas EPI showed a significant increase only in AB (p = .002) and in P (p = .018). NOR increased significantly in AB (p = .018) but did not increase in the other groups. Caffeine seems to enhance short-duration exercise performance in P. In contrast, T showed a high interindividual variability and overall no ergogenic effect was detected in this group.