When you go out and do any kind of anything, your muscles contract so that you can move. For your muscles to contract, you need the energy to do it. That’s pretty easy to understand, right? No energy = No do anything. Our bodies are very detailed machines and I think it is the coolest thing to look at these details and see how it is that God has made things to work. As Spock would say, it’s “Fascinating.”
There are three different pathways of energy that your body will utilize to make your muscles contract when you exercise. I want to look at these three different pathways and hopefully explain them.
- THE ATP/CP ENERGY PATHWAY – This pathway is where everything starts. This begins the muscle contraction you need to do whatever is you are about to do. ATP is a molecule that stores energy for muscle contractions. It stands for “adenosine triphosphate.” One thing about ATP to understand is that it is the energy source for all human movement. The problem with ATP is that there isn’t very much of it stored in your muscle cells. This is where the “CP” comes in. It stands for “Creatine Phosphate.” When ATP is broken down for energy, it loses a phosphate. It becomes ADP, which stands for “adenoside diphosphate.” In order to be restored back to ATP, it needs another phosphate. That is where the creatine phospate comes in. It lends its phosphate to complete the ATP so it can be ready to help the muscle to contract. The biggest thing to know about this pathway is that it doesn’t last very long…maybe 10 seconds (give or take a few). So what happens when this pathway isn’t able to keep up with the activity you’re doing? When the creatine phosphate has been depleted and it can no longer supply the phosphate to turn the ADP into ATP? This is where the next pathway takes over: the glycolytic pathway.
- THE GLYCOLYTIC PATHWAY – When your body has used up all its creatine storage, it then moves to another source to turn ADP into ATP. This new source is glycogen that is stored in your muscles, as well as glucose that is in your blood. Now the glucose and the glycogen will be used to convert ADP into ATP. As your body is replenishing ATP, a waste product is being made: lactic acid. I mentioned this a little bit in my “Jean-Claude Van DOMS” blooooog. Eventually, lactic acid builds up in the muscle faster than it can be removed. When this happens, your muscles fatigue and you can’t get that last rep out. At that point you have reached what’s called “the anaerobic threshold.” You have to stop your exercise or slow down so your body can get rid of the lactic acid. The lactic acid is removed from the muscle and converted to a form that is less toxic. This form is called lactate and is used to produce more glucose for your muscles to use. While your body is now too busy dealing with lactic acid, it can no longer use glucose and glycogen to replenish ATP. This is where the third pathway for energy kicks in, the oxidative pathway.
- THE OXIDATIVE PATHWAY – The ATP/CP path requires creatine to make ATP, the glycolytic path requires glucose and stored glycogen to make ATP, and the oxidative path requires oxygen to make ATP. It requires oxygen because oxygen starts a cycle known as the krebs cycle in the mitochondria. Without a whole lot of science mambo-jumbo, the krebs cycle is a lot of reactions and electrons and things and stuff and processes and transporting and citric acids and pyruvate and cycles and glycolysis and lions and tigers and bears that is taking place…..with the end result being that ATP is produced. Just remember that without oxygen, this pathway doesn’t happen. It’s kinda like oxygen to a fire. Take that away and the fire stops. This pathway makes more ATP than the other two pathways, but it takes longer. This is why it is used for long endurance type of events….things like distance running, marathons, etc. It requires oxygen to happen, but it also uses glucose, glycogen, and fatty acids during the process. What it uses depends on the intensity: For high intensity endurance like HIIT cardio, it will use glucose and glycogen. For lower intensity endurance like distance running or elliptical machines, it uses fatty acids. So for those of you who are runners, get those fats in. They are your energy source for long runs. You folks that are 400m sprinters may want to focus more on carbs for your energy.
PUTTING THIS ALL TOGETHER
When I think of this stuff, I think of driving a car with a manual transmission….or an automatic transmission too, i guess. It doesn’t matter. It’s more about the car changing gears as you’re driving. When you’re at a complete stop and then start to accelerate, the car is in first gear for a few seconds, then the car goes into second gear to get more rpm’s, then it goes into third gear to get more rpm’s, then fourth gear, etc. You get the idea. The ATP/CP pathway is the first gear of your exercise to get you started on muscle contractions. The glycolytic pathway is that second and third gear to continue your muscle contractions for your exercise. The oxidative pathway is that fourth gear for your muscle contractions to continue your exercise. These pathways, or “gears,” as I like to think of them, can overlap and mix together at the begining and end of each other to keep you going. For some people, their ATP/CP pathway can go for 10 seconds, and for others it may be a few seconds longer before the glycolytic pathway takes over. It will then last for about another 90 seconds until the oxidative pathway takes over for the rest of the way.
Here’s another way of looking at it using an example of an exercise and how these exercises use the pathways to give you energy to perform them:
- short immediate intense power like shot-put or throwing a pitch – this will utilize the ATP/CP pathway
- a set of 10 to 12 bicep curls – this will utilize the ATP/CP pathway and then the GLYCOLYTIC pathway
- running a 5K – this will utilize the ATP/CP pathway and then the GLYCOLYTIC pathway and then the OXIDATIVE pathway
Well, that was fun. Hopefully this helps to understand just how cool and how detailed the body is and how God created it. If you have any questions or have anything to add to the conversation, please feel free to do so in the comments. Also, feel free to click “like” or “share” or do a back flip.
Until next time,