Creatine is useful for short, intense exercises (e.g., 100 m dash, lifting weights)
- Initially, during a weight lifting session for example, oxygen is supplied by myoglobin for a limited amount of time during aerobic respiration – this store is rapidly depleted (cue creatine!)
- Muscles meet most of ATP demand by borrowing phosphate groups (Pi) from other molecules & transferring them to ADP; **Two enzyme systems control these phosphate transfers
- Myokinase: transfers Pi from one ADP to another, converting the latter to ATP
- Creatine kinase: obtains Pi from a phosphate-storage molecule creatine-phosphate (CP)
- Both of these systems are fast-acting; they help maintain the ATP level while other ATP-generating mechanisms are being activated
- Creatine phosphate and ATP are naturally stored in muscle cells and provide nearly all energy used for short bursts of intense activity
- Taking oral creatine increases level of creatine phosphate in muscle tissue and increases speed of ATP regeneration. This is why people are able to increase their reps and overall strength when taking creatine.