September 1, 2001
1- Featured Article:
The creatine-caffeine dilemma
This Month’s Featured Article:
The Creatine-Caffeine Dilemma
Obviously, creatine finds its way into skeletal muscle after being ingested. But, how is this actually accomplished?
From the blood stream creatine is transported into skeletal muscle via the action of transporter molecules distributed along the muscle surface. These are the molecular doors that allow creatine into muscle cells. Our physiological status determines how well these molecular doors work at letting in creatine. For example, sodium outside the muscle cell, the extramuscular sodium, regulates the activity of these transporter molecules. In this respect, an elevation of extramuscular sodium promotes creatine entry via these transporters.
Based on earlier studies showing that caffeine increases extramuscular sodium, it was proposed that caffeine should augment creatine transport into muscle cells and accentuate the benefits of creatine. Oddly, however, caffeine has the opposite effect than initially expected. Caffeine actually interferes with the enhancement of physical performance afforded by creatine. A possible explanation for this paradoxical finding is the topic of this month’s newsletter.
A recent study specifically looked at the consequences of caffeine consumption on the physical benefit normally afforded by creatine supplementation. The study consisted of a cross over design, which simply means that the subjects were divided into either experimental (caffeine and creatine) or control (creatine alone) groups, tested after a week, switched of conditions and then retested.
Nine males participated in the study. Their ages ranged between 20 and 23 years. Initially both groups were given 0.5 grams of creatine/kilogram of body weight for six days. This amount is slightly greater than the typically prescribed loading dose. In addition, the experimental group was also given 0.005 grams of caffeine per kilogram of body weight on days 4, 5 and 6. Therefore, for the last three days of supplementation the experimental group consumed both creatine and caffeine. On the seventh day their physical performance was tested using knee extension torque measurements. This is one entire day after the last dose caffeine.
After a washout period of 3 weeks the groups were switched, such that the experimentals (caffeine and creatine) became controls (creatine alone) and visa versa. Assuming that 3 weeks was enough time to completely reverse the effects of caffeine, the experiment was repeated. In this respect the effect of caffeine could be compared in each individual.
Caffeine consumption negated the physical benefit observed in the creatine group. Surprisingly, the effect of caffeine was observed one entire day after the last dose. This finding was at first paradoxical, because caffeine, at least initially, was proposed to increased creatine absorption into skeletal muscle via its effect on extramuscular sodium.
The amount of caffeine used in this study is equivalent to 2-3 strong cups of coffee for an average sized male, or 350 mg of caffeine for a 70 kilogram (154 pound) male. One important detail might be that caffeine was administered in the form of capsules.
Interestingly, caffeine did not interfere with the rise in muscular phosphocreatine associated with creatine loading. Remember that phosphocreatine is the biologically active form of creatine found within cells. In other words, caffeine neither decreased (nor increased, as expected) creatine transport at the muscle surface. Its inhibitory effect was felt after creatine had entered the cell and converted to phophocreatine.
A Possible Resolution
Coordinated movement is the result of opposing muscle groups contracting and relaxing in unison. For example, when performing a curl our biceps (front of arm) contract into a ball, whereas our triceps (back of arm) relax and lengthen. On the downward movement, the triceps contract and the biceps relax.
Another example is sprinting. A sprinter initiates a stride by contracting the front muscles and relaxing the back muscles of one leg. To move forward, however, he must then quickly relax the front muscles and contract the back muscles of that leg, so that his other leg can shoot forward. Therefore, muscle relaxation is part of coordinated movement and thus speed.
Calcium is what causes muscles to either contract or relax. A muscle contracts when calcium is released from storage sites deep inside the muscle. In other words, free calcium is the signal that tells a muscle to contract. Likewise, our muscles relax when calcium is reabsorbed into these internal storage sites. However, the restorage of calcium is an energetically expensive process and in this manner muscle relaxation cost us energy. The energy that pays for muscle relaxation comes from phosphocreatine!
Dr. Hepel’s group in Belgium has elegantly shown that phosphocreatine levels determine muscle relaxation rate. When our muscle phosphocreatine levels are high, as a result of supplementation, our muscles relax more rapidly. Conversely, when our phosphocreatine stores are low, muscle relaxation is slowed and our exercise performance drops.
Although caffeine doesn’t alter phosphocreatine levels, caffeine may nevertheless retard muscle relaxation by altering muscle calcium levels. Interestingly, caffeine is known to release calcium form internal stores. As outlined previously, this would slow muscle relaxation and jeopardize exercise performance, despite caffeine’s know stimulatory properties. Therefore, caffeine may negate creatine’s benefit by liberating internal calcium and thereby slowing muscle relaxation time.
Caffeine is a diuretic, meaning that it increases the excretion of water from the body in the urine. There are rumors that caffeine counteracts creatine by interfering with muscle volumizing. This is simply a false rumor and assumes that water retention by skeletal muscle is the source of strength. Although increasing the girth (volume) of our muscles, volumizing per se has no proven effect on strength. This was the topic of a recent newsletter. View it here.
If you pump up on caffeine prior to working out, while at the same time supplementing with creatine monohydrate to increase exercise performance, you could be wasting your time and money. Avoid this practice!
However, it must be mentioned that not all studies demonstrate an inhibitory effect of caffeine on the benefits afforded by creatine and may be a result of how creatine was administered, ie whether in liquid or tablet form.
Vandenberghe K, Gillis N, Van Leemputte M, Van Hecke P, Vanstapel F, Hespel P. (February 1996) Caffeine counteracts the ergogenic action of muscle creatine loading. Journal of Applied Physiology Volume 80:2: pages 452-457.
Van Leemputte M, Vandenberghe K, Hespel P. (March 1999). Shortening of muscle relaxation time after creatine loading. Journal of Applied Physiology Volume 86:3: pages 840-844.
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