Substratmetabolism under träning med koffein och kolhydrat.

[King Grub]

PURPOSE:: 1) To investigate the effect of caffeine on exogenous carbohydrate (CHO) oxidation and glucose kinetics during exercise; and 2) to determine whether combined ingestion of caffeine and CHO enhanced cycling performance compared with CHO alone.

METHODS:: Ten endurance-trained cyclists performed three experimental trials consisting of 105 min steady-state (SS) cycling at 62% V O2max followed by a time trial (TT) lasting approximately 45 min. During exercise, subjects ingested either of the following: a 6.4% glucose solution (GLU), a 6.4% glucose plus caffeine solution providing 5.3 mg.kg of caffeine (GLU + CAF), or a placebo (PLA). Glucose solutions contained a trace amount of 'U-C'glucose, and eight subjects received a primed continuous '6,6-H2'glucose infusion.

RESULTS:: Peak exogenous CHO oxidation rates were not significantly different between GLU and GLU + CAF trials (52.6 +/- 2.7 and 49.1 +/- 2.1 mumol.kg.min, respectively). Rates of appearance (Ra) and disappearance (R d ) of glucose were significantly higher with CHO ingestion than PLA (P < 0.01) but were not significantly different between GLU and GLU + CAF trials. Performance times were 43.45 +/- 0.86, 45.45 +/- 1.07, and 47.40 +/- 1.30 min for GLU + CAF, GLU, and PLA, respectively. Therefore, GLU + CAF ingestion enhanced TT performance by 4.6% (P < 0.05) compared with GLU and 9% (P < 0.05) compared with PLA.

CONCLUSION:: The coingestion of caffeine (5.3 mg.kg) with CHO during exercise enhanced TT performance by 4.6% compared with CHO and 9.0% compared with water placebo. However, caffeine did not influence exogenous CHO oxidation or glucose kinetics during SS exercise.

Med Sci Sports Exerc. 2008 Oct 31. Substrate Metabolism and Exercise Performance with Caffeine and Carbohydrate Intake.

[Fearstrike]

Har du lust att förklara lite kort på Svenska vad det handlar om och vad resultatet blev? Tack.

[Eddie Vedder]

Har du lust att förklara lite kort på Svenska vad det handlar om och vad resultatet blev? Tack.

Den exogena kolhydratoxidationen påverkades inte signifikant av tillförsel av glukos tillsammans med koffein (jämfört med enbart glukos eller placebo i form av vatten), dock en förbättring av prestationsförmågan. Försökspersonerna var 10 stycken cyklister som genomförde tre 105-minuterspass vid ca 62% av VO2max.

Jag undrar hur många gånger King Grub ska behöva påpeka att han inte är engelskalärare, det verkar inte gå in riktigt.

[z_bumbi]

Kolhydrat + koffein 4,6% bättre än kolhydrat och 9% bättre än vatten räknat på tidsresultat.
Kolhydratanvändande ökade däremot inte av intagande av koffein.

[Langster]

Kolhydratanvändande ökade däremot inte av intagande av koffein.

Vilket borde bero på ökad användning av fett som energi? Någonstans måste ju den energin som ger den ökade prestationsförmågan tas ifrån.

[A.Steinbach]

Vilket borde bero på ökad användning av fett som energi? Någonstans måste ju den energin som ger den ökade prestationsförmågan tas ifrån.

Den exogena kolhydratoxidationen ökade inte med koffein men det är ju inget som säger att den endogena kolhydratoxidationen var högre i koffeingruppen.

Svårt att säga något utifrån abstraktet.

Dock så ökar ju koffeinintag utsöndringen av katekolaminer och skulle då kunna öka användandet av fett som energisubstrat.

En del av koffeinets ergogena effekt tros bero på att det binder till receptorer i det centrala nervsystemet och därmed minskar trötthetssymptomen.

One of the earlier attempts to explain the ergogenic effects of caffeine on endurance exercise proposes that caffeine enhances lipid oxidation so that glycogen stores may be spared and used to extend the limits of endurance [34]. Most studies report that caffeine elevates the level of adrenaline in the circulation (at rest as well as during exercise) and many also note increased levels of nonesterified fatty acids [34a]. A variety of studies have supported [34] and detracted from this ‘glycogen-sparing’ hypothesis [35]. The majority of the most recent studies report a lack of consistent and/or signifi cant results to lend support [16,36]. If caffeine is operating by ‘glycogen-sparing’ it should be observed that it switches fuel use from carbohydrate to lipid oxidation. The measurement of the RER (respiratory exchange ratio) is interpreted to refl ect the predominant fuel substrate that is being utilized. The fact that the studies conducted by Graham et al. [36] failed to show any change in RER values after caffeine ingestion contributed to their conclusion that the glycogen-sparing mechanism could not be responsible for the ergogenic effects of caffeine that have been reported.
The effects of caffeine on short periods of activity, e.g. sprinting, as discussed earlier, are inconclusive but there is some support for caffeine being
ergogenic in certain types of high-intensity short term (up to several minutes
in duration) exercise (where >100% V.o2max is achieved) [37]. Clearly, mechanisms of action other than ‘glycogen-sparing’ must be operating in these cases and Doherty et al. [37] propose that caffeine may exert its effect by lowering the subject’s perception of effort and thus ameliorating their feeling of fatigue. This explanation is consistent with the highly researched effects that caffeine has been shown to have on higher functions of the central nervous system [31,38] via its ability to bind to adenosine receptors.
The Authors Journal compilation © 2008 Biochemical Society
Caffeine and other sympathomimetic stimulants: modes of action and effects on sports performance

[Fredrik_S]

Vilket borde bero på ökad användning av fett som energi? Någonstans måste ju den energin som ger den ökade prestationsförmågan tas ifrån.

Ökad motivation pga pigghet. Lättare att pressa ytterligare lite extra om man är pigg?

[KniveN]

Ökad motivation pga pigghet. Lättare att pressa ytterligare lite extra om man är pigg?

De han undrar över är vart energin kommer ifrån. Att vara pigg ger inte energi, den måste tas från något.

[King Grub]

This study examined the effects of 6 mgxkg(-1) caffeine ingestion in team-sport players (N.=10) on repeated-sprint running performance (5 sets of 6 x 20 m) and reaction times, 60 min after caffeine or placebo ingestion. METHODS: Best single sprint and total set sprint times, blood lactate and simple and choice reaction times (RT) were measured.

Total sprint times across sets 1, 3 and 5 (departure every 25 s) were significantly faster after caffeine (85.49+/-5.55 s) than placebo (86.98+/-5.78 s) (P<0.05). Similarly, total sprint times across sets 2 and 4 (departure every 60 s), were significantly faster after caffeine (55.99+/-3.64 s) than placebo (56.77+/-3.74 s) (P<0.05). Significantly higher blood lactates were recorded in caffeine compared to placebo after set 3 (13.1+/-1.2 vs 10.3+/-1.4 mmolxL(-1)) (P<0.05) and set 5 (13.1+/-1.3 vs 10.3+/-1.6 mmolxL(-1)) (P<0.01). There were no significant effects on simple or choice RT, although effect sizes suggested improved post-exercise times after caffeine.

Caffeine ingestion 60 min prior to exercise can enhance repeated sprint running performance and is not detrimental to reaction times.

J Sports Med Phys Fitness. 2008 Dec;48(4):472-8. Effect of caffeine supplementation on repeated sprint running performance.

[Scratch89]

Nu kommer jag troligen inte åt fullängdaren eftersom jag inte sitter i skolan, men hur vana var testpersonerna med koffein? Jag antar att kaffeknarkare, eller de som äter koffeintabletter i vanliga fall, inte skulle få samma effekt. En ökning på 9 % (som i första studien) är väldigt mycket.

[King Grub]

Kroniskt koffeinbruk avtrubbar inte den ergogena effekten av akut intag.