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1.
J Strength Cond Res ; 30(8): 2354-60, 2016 Aug.
Article in English | MEDLINE | ID: mdl-26808856

ABSTRACT

Ribeiro, BG, Morales, AP, Sampaio-Jorge, F, Barth, T, de Oliveira, MBC, Coelho, GMdO, and Leite, TC. Caffeine attenuates decreases in leg power without increased muscle damage. J Strength Cond Res 30(8): 2354-2360, 2016-Caffeine ingestion has been shown to be an effective ergogenic aid in several sports. Caffeine administration may increase exercise capacity, which could lead to a greater degree of muscle damage after exercise. This was a randomized, double-blind, placebo-controlled crossover study. Six male handball athletes ingested placebo (PLA) or caffeine (CAF) (6 mg·kg body mass) capsules on 2 different occasions. Sixty minutes after ingestion of the capsules, serum CAF levels were evaluated. Thereafter, all participants performed a protocol of vertical jumps (VJs). The protocol consisted of 4 sets of 30 seconds of continuous VJs with 60 seconds of recovery between sets. Blood lactate (LAC) and creatine kinase (CK) levels were determined before and after the protocol. We found significant differences in serum CAF levels between PLA (0.09 ± 0.18 µg·ml) vs. CAF (6.59 ± 4.44 µg·ml) (p < 0.001). Caffeine elicited a 5.23% (p ≤ 0.05) improvement in the leg power compared with PLA. The CAF trial displayed higher LAC (p ≤ 0.05) compared with PLA (6.26 ± 2.01 vs. 4.39 ± 2.42 mmol·L, respectively) after protocol of VJs, whereas no difference in CK was observed between trials (p > 0.05). These results indicate that immediate ingestion of CAF (6 mg·kg body weight) can reduce the level of muscle fatigue and preserve leg power during the test, possibly resulting in increase in LAC. There was no increase in muscle damage, which indicates that immediate administration of (6 mg·kg body weight) CAF is safe. Thus, nutritional interventions with CAF could help athletes withstand a greater physiological overload during high-intensity training sessions. The results of this study would be applicable to sports and activities that require repetitive leg power.


Subject(s)
Caffeine/administration & dosage , Central Nervous System Stimulants/administration & dosage , Exercise/physiology , Muscle Fatigue/drug effects , Muscle, Skeletal/drug effects , Adult , Athletes , Caffeine/blood , Creatine Kinase/blood , Cross-Over Studies , Double-Blind Method , Humans , Lactic Acid/blood , Leg/physiology , Male , Muscle Fatigue/physiology , Muscle Strength/drug effects , Muscle Strength/physiology , Muscle, Skeletal/physiology , Young Adult
2.
FEBS Lett ; 585(1): 92-8, 2011 Jan 03.
Article in English | MEDLINE | ID: mdl-21074528

ABSTRACT

We examined the effects of lactate on the enzymatic activity of hexokinase (HK), phosphofructokinase (PFK) and pyruvate kinase (PK) in various mouse tissues. Our results showed that lactate inhibited PFK activity in all the analyzed tissues. This inhibitory effect was observed in skeletal muscle even in the presence of insulin. Lactate directly inhibited the phosphorylation of PFK tyrosine residues in skeletal muscle, an important mechanism of the enzyme activation. Moreover, lactate indirectly inhibited HK activity, which resulted from its cellular redistribution, here attributed to alterations of HK structure. PK activity was not affected by lactate. The activity of HK and PFK is directly related to glucose metabolism. Thus, it is conceivable that lactate exposure can induce inhibition of glucose consumption in tissues.


Subject(s)
Down-Regulation/drug effects , Hexokinase/metabolism , Lactic Acid/pharmacology , Phosphofructokinases/metabolism , Animals , Blotting, Western , Fructosediphosphates/pharmacology , Heart/drug effects , Hypoglycemic Agents/pharmacology , Insulin/pharmacology , Kidney/drug effects , Kidney/enzymology , Liver/drug effects , Liver/enzymology , Male , Mice , Muscle, Skeletal/drug effects , Muscle, Skeletal/enzymology , Myocardium/enzymology , Phosphorylation/drug effects , Tyrosine/metabolism
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