In the last two posts about energy systems, I explained how ATP production is the end game of your metabolic processes. In order to fuel your daily activity; whether it be laying on the couch watching football all day or actually playing football, your body uses ATP for the energy to do so.
In addition, I inquired as to why a 300 lb defensive linemen would be forced to run a series of 300 yard sprints when during regular football game he would never run more than fifteen yards over seven seconds. The way his body would produce and use ATP over seven seconds of maximum effort is completely different than the way it would produce and use ATP over a 300 yard run.
The first way would incorporate the short term ATP/CP system, which provides ATP for very short periods of time but provides for maximal intensity.
The second way would be a mix of intermediate and long term systems which provide ATP, and thus muscular contraction, for extended periods of time but necessitates less intensity due to how long it takes to break down nutrients to produce ATP.
I’m really only interested in energy systems as it pertains to weightlifting. I couldn’t care less about endurance exercise which is why I rarely write about it. The two main systems which provide ATP during weightlifting are:
-ATP/CP system which provides energy for maximal intensity for up to seven seconds but makes steadily declining contributions for up to 30 seconds.
- The Intermediate system which increasingly fuels muscular contraction from about the 6-30 second mark. After that, although it still contributes to ATP production, it’s contribution declines as the long term system begins to take over most of the ATP production.
Remember that energy production isn’t an either/or proposition. All three energy systems are contributing at all times. Instead, the systems are intensity dependent. The higher the intensity, e.g., the faster you are running, the heavier you are lifting, the greater the contribution of the ATP/CP system. But the ATP/CP system is dependent on stored ATP and creatine phosphate. Once those stores are depleted, the intensity of your exercise can’t be sustained because the intermediate system takes longer to provide ATP due to its complex system of ATP production.
In weight lifting terms this means that sets of heavy lifting lasting no longer than 10 seconds will utilize mainly the ATP/CP system. As the duration of the set increases, the intermediate system starts to take over the ATP production responsibilities and maximal intensity is no longer possible. The effect of the exercise on muscle becomes more endurance based. But keep in mind that if you are handling a heavy weight that can only be lifted for 5-8 reps, it’ll be much more strength based than endurance based.
Theoretically, if you could increase the levels of stored ATP/CP within the muscles, you could maintain maximal effort for a while longer. This would lead to increased strength and muscle because you’ll be able to exercise at a higher intensity for a longer period of time. So instead of getting 225 pounds on the bench press for five reps, maybe you’ll be able to get seven or eight reps.
Storage of ATP and CP is increased as a natural adaptation to strength training, but we have no way of artificially boosting ATP beyond what our body allows. However, you can increase the storage of CP in the muscles by using creatine supplements. The simple explanation as to why it works is:
ATP (three phosphate molecules) is broken down into ADP (two phosphate molecules) and the energy released is used by the body. Creatine phosphate then attaches to the ADP so that it now becomes ATP again. The process continues until the CP is depleted or so drastically reduced that high intensity exercise can no longer be continued. Increasing the creatine in the muscle means that high intensity exercise, like lifting heavy weights, can be sustained longer.
As I mentioned, none of this is extremely important to know unless you need to explain to the “know-it-all” meathead at the gym why creatine works. It’s more “behind the scenes” information than anything else. But if you find the info interesting and makes you want to know more about how the human body functions, all the better.