[silver_pilate]

Fifteen years old should be old enough to avoid any negative effects from weight lifting. The epiphysis of the bones will take a good amount of stress without effecting your growth. However, if you start experiencing bone pain...and I'm not talking about the delayed onset muscle soreness you're going to feel...ease off for a while.

At your age, your metabolism is likely pretty high as it is. Working out is going to increase that metaboic rate. Eating sufficiently (and balanced) is going to be important. I remember at your age when I was lifting, I had to eat to keep from loosing weight.

I dont' recommend Creatine phosphate supplementation...especially not at your age if at any. You receive all the creatine your body needs from your diet, especially from red meats.

FYI:

Supplementing with creatine is intended to increase the amount of creatine stored in the muscles thus increasing the length of time one can sustain maximal activities during short duration exercises before entering into an oxygen deficit.

Adenosine triphosphate (ATP) is the primary fuel used by the body to produce energy. One of the phosphates is enzymatically broken off, releasing energy and forming Adenosine diphosphate (ADP).

ATP is produced via three pathways. The first to be utilized is the ATP-PCr (creatine phosphate) system. PCr is not used directly to produce energy, but rather, it is broken down by creatine kinase in a similar manner that ATP is broken by ATPase. When one of the phosphates is cleaved from PCr, energy is released. This energy is utilized to add a phosphate back to ADP, forming ATP (rephosphorilation). A phosphate is then cleaved from ATP via ATPase to yield energy. This form of respiration occurs very rapidly to supply energy for short-term, high intensity exercise. However, the body's supply of PCr is rapidly depleated. Creatine loading theoretically slightly increases the bodies stores of PCr, thus allowing one to work in a high intensity exercise for a longer period of time. This is especially beneficial for those in power lifting and training.

However, as I said before, the body has a sufficient supply of PCr in reserve. As soon as PCr is depleted, the anaerobic pathways of glycolysis take over, followed shortly by the oxidative respiration and electron transport chain in the mitochondria. Most of the ingested PCr is excreted in the urine, while only a small portion of it is stored in the muscles. This can place a heavy load on the kidneys, and there have been instances in which the kidneys shut down completely when the cycling periods were not followed. Also, there are no long-term studies on the effects of supplementation on health.

Wow, I actaully remembered some stuff from my classes....

--nathan