1.
ADOR2A C Allele Carriers Exhibit Ergogenic Responses to Caffeine Supplementation.
Grgic, J, Pickering, C, Bishop, DJ, Del Coso, J, Schoenfeld, BJ, Tinsley, GM, Pedisic, Z
Nutrients. 2020;(3)
Abstract
Caffeine's ergogenic effects on exercise performance are generally explained by its ability to bind to adenosine receptors. ADORA2A is the gene that encodes A2A subtypes of adenosine receptors. It has been suggested that ADORA2A gene polymorphisms may be responsible for the inter-individual variations in the effects of caffeine on exercise performance. In the only study that explored the influence of variation in ADORA2A-in this case, a common polymorphism (rs5751876)-on the ergogenic effects of caffeine on exercise performance, C allele carriers were identified as "non-responders" to caffeine. To explore if C allele carriers are true "non-responders" to the ergogenic effects of caffeine, in this randomized, double-blind study, we examined the acute effects of caffeine ingestion among a sample consisting exclusively of ADORA2A C allele carriers. Twenty resistance-trained men identified as ADORA2A C allele carriers (CC/CT genotype) were tested on two occasions, following the ingestion of caffeine (3 mg/kg) and a placebo. Exercise performance was evaluated with movement velocity, power output, and muscle endurance during the bench press exercise, countermovement jump height, and power output during a Wingate test. Out of the 25 analyzed variables, caffeine was ergogenic in 21 (effect size range: 0.14 to 0.96). In conclusion, ADORA2A (rs5751876) C allele carriers exhibited ergogenic responses to caffeine ingestion, with the magnitude of improvements similar to what was previously reported in the literature among samples that were not genotype-specific. Therefore, individuals with the CT/CC genotype may still consider supplementing with caffeine for acute improvements in performance.
2.
Effect of the MTHFR 677C/T polymorphism on homocysteinemia in response to creatine supplementation: a case study.
Petr, M, Steffl, M, Kohlíková, E
Physiological research. 2013;(6):721-9
Abstract
Creatine (Cr) is recommended as a dietary supplement especially for athletes but its therapeutic potential is also discussed. It is assumed that human body uses Cr for the formation of phosphocreatine, which is necessary for muscular work as a source of energy. Production of Cr in a body is closely connected to methionine cycle where guanidinoacetate (GAA) is in a final step methylated from S-adenosylmethionine (SAM). Increased availability of SAM for phosphatidylcholine (PC) and sarcosine synthesis can potentially stimulate endogenous production of betaine a thus methylation of homocysteine (HCy) to form methionine. Our subject who was methylenetetrahydrofolate reductase (MTHFR) 677TT homozygote lowered plasma HCy from 33.3 micromol/l to 17.1 micromol/l following one-month Cr supplementation (5 g/day) opposite to 677CC and CT genotypes whose HCy levels tended to increase (but still in normal ranges). We suppose that Cr supplementation stimulates pathways leading to production of sarcosine which can serve to regenerate tetrahydrofolate (THF) to form 5,10-methylene-THF. This could potentially increase MTHFR enzyme activity which may later result in increased HCy methylation. Cr supplementation significantly effects metabolism of one carbon unit and potentially lower body´s demands for methyl groups. This could be beneficial as in the case of reduced enzyme activity such as MTHFR 677C/T polymorphism.
3.
Carbohydrate-electrolyte drink ingestion and skill performance during and after 2 hr of indoor tennis match play.
McRae, KA, Galloway, SD
International journal of sport nutrition and exercise metabolism. 2012;(1):38-46
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Abstract
Twenty-two tennis players were individually studied on 2 occasions. They performed a prematch skill test, a 2-hr tennis match against an equally ranked opponent, and a postmatch skill test. A carbohydrate-electrolyte (CHO-E; Lucozade Sport) or flavor-matched placebo-electrolyte (PL) beverage was administered in a double-blind fashion. During the trials, heart-rate and movement intensity were monitored, and the match was recorded for performance analysis. There were no differences in skill-test scores pre- to postmatch or between trials (154±38 pre- and 160±35 postmatch on PL, 155±36 pre- and 165±33 postmatch on CHO-E). CHO-E ingestion elevated blood glucose concentration throughout the match, and participants reported feeling more energetic (general activation) and more tense (high activation) 1 hr into the match than at baseline (p<.05). Participants in the CHO-E trial spent more time in moderate-intensity activity and less time in low-intensity activity than on PL. Performance analysis revealed that CHO-E ingestion increased overall serve success (M±SD, 68%±7% for CHO-E vs. 66%±7% for PL; p<.05) and success of first serves (65%±9% for CHO-E, 61%±7% for PL; p<.01) and serves to the advantage side (70%±9% for CHO-E, 66%±7% for PL; p<.05). Return success was greater during the second set of the match (p<.05) in the CHO-E trial. Differences in serve and return success were not associated with blood glucose response to CHO or player ability.