Thursday, February 28, 2008

Caffeine and exercise: metabolism, endurance and performance

In the news
I was recently interviewed by MC about graduate student life, exercise for busy people, nutrition on the go, home gym set up and much more!
Check it out here
Also check around her blog for some excellent info!

In the lab
I am working hard on a protocol for a new study in the lab, but in the process I found a review I've read in the past and probably one of the best on caffeine and exercise performance. The abstract is below and unfortunately there is not a free copy of the entire review, but if you are a student or university faculty you can probably get it through the library.

Mike N

Sports Med. 2001;31(11):785-807

Caffeine and exercise: metabolism, endurance and performance.
Graham TE.

Human Biology and Nutritional Sciences, University of Guelph, Ontario, Canada.

Caffeine is a common substance in the diets of most athletes and it is now appearing in many new products, including energy drinks, sport gels, alcoholic beverages and diet aids. It can be a powerful ergogenic aid at levels that are considerably lower than the acceptable limit of the International Olympic Committee and could be beneficial in training and in competition. Caffeine does not improve maximal oxygen capacity directly, but could permit the athlete to train at a greater power output and/or to train longer. It has also been shown to increase speed and/or power output in simulated race conditions. These effects have been found in activities that last as little as 60 seconds or as long as 2 hours. There is less information about the effects of caffeine on strength; however, recent work suggests no effect on maximal ability, but enhanced endurance or resistance to fatigue. There is no evidence that caffeine ingestion before exercise leads to dehydration, ion imbalance, or any other adverse effects. The ingestion of caffeine as coffee appears to be ineffective compared to doping with pure caffeine. Related compounds such as theophylline are also potent ergogenic aids. Caffeine may act synergistically with other drugs including ephedrine and anti-inflammatory agents. It appears that male and female athletes have similar caffeine pharmacokinetics, i.e., for a given dose of caffeine, the time course and absolute plasma concentrations of caffeine and its metabolites are the same. In addition, exercise or dehydration does not affect caffeine pharmacokinetics. The limited information available suggests that caffeine non-users and users respond similarly and that withdrawal from caffeine may not be important. The mechanism(s) by which caffeine elicits its ergogenic effects are unknown, but the popular theory that it enhances fat oxidation and spares muscle glycogen has very little support and is an incomplete explanation at best. Caffeine may work, in part, by creating a more favourable intracellular ionic environment in active muscle. This could facilitate force production by each motor unit.