First, a basic look at creatine and its function. ATP is the muscle's gasoline, its what gives your pecs the energy for a 300 pound bench press. ATP is made in little powerplants inside your muscle called mitochondria. These powerplants aren't always running full steam though, there's no need for them to be pumping out massive amounts of energy when your laying in bed or watching TV. In this case, mitochondria enough ATP to fill the reserve tanks and then shut down.
The reserve tank is creatine. ATP is attached to creatine and stored like a battery, in case you need to throw a punch or jump away from a predator. The consensus is that most muscles have about 3-5 seconds of ATP-creatine, which is all they need because by that time the mitochondria have ramped up and are providing all the ATP that the muscle needs.
Here is where most people are confused about how creatine supplements work. More creatine must mean a bigger reserve, which has to let your muscles work longer right? Well there are two problems with that line of reasoning. The first is that muscles don't need more creatine because they have enough to cover the small time interval before the mitochondria ramp back up. It would be like trying to run a car via the battery once the engine is turning - its not necessary.
The second problem is that increasing the amount of creatine does not actually increase the supply of energy to a muscle. It seems that if the amount of creatine was increased, then the amount of ATP attached to creatine would increase and therefore a muscle would have more reserve, right? Unfortunately, that is not how things work out. Get ready to put your nerd pants on.
The chemical reaction were talking about is governed by something called Gibbs free energy:
Where K = [ATP][Cr] /[ADP]*[P-Cr].
The math looks really complex but most of the variables are constants. When we clean up the equation and keep whats relevant to us, it actually says something more like this:
Rate of ATP synthesis =(ATP/used ATP)* (creatine/ATP bound creatine)
For an in-depth look at how this was derived, check the comments.
What this means is that the amount of ATP synthesized is determined not by the amount of ATP bound to creatine, but the ratio of ATP bound creatine versus free creatine. This ratio does not change when you take supplements so neither does the energy output.
Debunking is fun, but at the end of the day the empirical data shows that creatine does help performance in "burst" type activities like sprinting and weight lifting. There is no certainty to the mechanism behind this effect, but the general consensus is that its osmotic. While the previously mentioned ratio doesn't change, the amount of creatine in the muscle does increase. The increased load causes other substances like water, nutrients, and electrolytes to move into the muscle - accounting for the swollen look the muscles acquire after supplementation. As far as I have read, there is no definite culprit to what is causing the increased performance, just that more "stuff" is getting to the muscles.
Would I recommend creatine to someone looking for gains in strength/performance? Absolutely. Its cheap, effective, and has stood the test of time. Safety-wise, it is completely harmless. There has been some worry as to kidney issues due to people confusing creatine with its metabolite creatinine - a measure of kidney function. Creatinine is used as a marker for kidney failure, not to be confused with a cause of kidney failure. I personally use creatine when I'm bulking and consider a worthwhile supplement.
The B.S. in this article has little to do with bachelors.
ReplyDeleteYour claim is equivalent to saying, "So you strapped 2 batteries together in parallel? Well, the total energy hasn't increased over 1 battery! You see, the voltage is STILL THE SAME!"
Seriously, if you even bothered to do a unit analysis, you'd see that R*T*ln(ratio) has units of Joules PER MOL. Double the number of moles, double the amount of energy.
That is, of course, assuming that the reaction in the body is as simple as CR-ATP <-> ATP + CR
Yet another demonstration of WHY you should get your science with citations folks.
Am I being trolled?
You're not being trolled, you are correct. I have fixed it. The end result is the same.
ReplyDeleteHere is what is occuring:
(Pi: phosphate, P-Cr: phosphocreatine, ADP: adenosinediphosphate, ATP)
Pi + Cr -> P-Cr
ADP + Pi -> ATP
Therefore P-Cr+ADP -> ATP + Cr
Keq = [ATP][Cr]/[ADP][P-Cr]
or
Keq = [ATP]/[ADP] * [Cr]/[P-Cr]
ATP synthesis is controlled by ATPsynthase, an enzyme that is activated by the [ATP]/[ADP] ratio. Since [Cr]/[P-Cr] does not vary with supplementation, you can see that supplementation would not have an effect on ATP synthesis. Even as the muscle is fatigued, the [Cr]/[P-Cr] ratio is maintained by the cell so the size of the creating pool does not matter.
Thank you for pointing that out. I must have had my brain on backwards.
Disclaimer: I'm speaking out of my depth. I know nothing about biology, I'm speaking just from some chemistry knowledge.
ReplyDeleteGibbs free energy gives the amount of energy produced per mol of reacted reactants.
Suppose Keq is such that the reaction is irreversible. Then, if ATP is not limiting, supplementing Cr will allow more ATP to react, leading to more energy production. If ATP is limiting, then adding Cr won't have any effect at all, since essentially all the ATP will have reacted.
Suppose the reaction is reversible. Then, adding more Cr will drive the reaction towards completion, meaning more ATP consumption, meaning more energy.
What's really important here is energy production, right? Which means, what we really care about is ATP consumption and how creatine supplementation affects that. Your statements about creatine supplementation seem to suggest that since the heat of fusion doesn't change, the amount of energy produced won't either. I think I've shown that that's patently false, unless both the reactions in our body that produce energy are irreversible, and ATP is the limiting factor in that reaction(which could easily be the case. I don't know enough about biochemistry to say one way or the other, which is why I stick to commenting, instead of posting my own articles)
I also have no idea how other reactions in the body play into this! I seem to recall that there is some method in the body for converting ADP-PCr back into ATP and Cr, but I don't know how that's going to play into the conversation.
On the same token, I think you are a bit better at PChem than I am so bear with me - I'm going to try an analogy.
ReplyDeleteATP synthesis is done by ATP synthase, a very unique enzyme. Energetically, its uncoupled from the P-Cr+ADP -> ATP+Cr reaction (uncoupled may be the wrong word here but you'll know what I mean in a second). It works like a dam, where H+ ions flow through a protein rotor like water through a turbine.
The ratio of ATP/ADP is how the dam measures if its output is adequate, call this our voltage sensor. If the voltage dips, the flood gates open and more ATP is produced.
So if you look at the creatine reaction:
Keq = [ATP]/[ADP] * [Cr]/[P-Cr]
You can see that if the Creatine/phosphocreatine ratio does not change, it does not affect ATP/ADP ratio and thus doesn't change the signal to ATP synthase.
What occurs in the muscle as its used is a flood of ADP is released into the system, quickly changing the signal to ATP synthase and telling it to open the flood gates. These flood gates stay open until enough ADP has been converted to ATP to reach the proper ratio again. This enzyme is very fast.
During this process, the Cr/PCr ratio does not change appreciably because the vast majority of ATP synthesis is coming from ATP synthase and not from the consumption of phosphocreatine.
In summary, the large flux in ADP with muscle use is from ADP being added into the system and the ATP correction is from ATP being added into the system. The system being the equilibrium reaction. This is why the [Cr]/[P-Cr] ratio does not appreciably change in a cell.