Sprint and Anaerobic Training
There are two systems that supply us with energy anaerobically. They are called the phosphocreatine (aka phosphagen or ATP-PCr) and glycolytic systems. Compared to our aerobic system they are both simpler processes which allow them to provide us with higher and shorter term bursts of energy. Our aerobic system will get us to the finish line. Our anaerobic system will allow us to attack and sprint. Two important pieces to the puzzle.
Phosphocreatine (ATP-PCr) System
Our phosphocreatine system (I’ll call it PCr) supplies us with maximum sprint power for up to ten to fifteen seconds. The goal of all our energy systems is to create Adenosine Triphosphate (ATP). When ATP is broken down into adenosine diphosphate (ADP) and phosphate it releases the energy our muscles use to contract. Phosphocreatine can quickly donate one of its phosphates to adenosine diphosphate (ADP) to recreate adenosine triphosphate (ATP). This resynthesized ATP can then break down again to create more energy for the muscles. There is only so much phosphocreatine that can be stored in the muscle and it is mostly depleted after ten to fifteen seconds.
Improving Our PCr System
There are a couple of ways that we might not normally think of to improve our PCr system. One is to increase the number and size of our fast twitch muscle fibers. We can achieve this by maximally sprinting. Another way that might work even better is by strength training. More fast twitch muscle means more phosphocreatine stores and more force production. When we are in season we probably want to choose sprinting since it is very hard to gain muscle when we are cardio cycling so much. It’s better to put more energy into the gym in the off season when we have it to give. In season is time for gym strength maintenance.
Another way different athletes improve their PCr system is with creatine supplementation. Although I am a personal trainer and would love to strength train with you, I am not suggesting you supplement with creatine without consulting your doctor and/or registered dietitian. It is safe to say that creatine supplementation has been studied and shown to improve sprint power. Supplementing with creatine increases the amount of phosphocreatine in the muscle. More phosphocreatine will obviously improve this energy system. One negative to supplementation is that it can potentially increase our body weight through fluid retention.
Many experts will say that this energy system is the hardest to improve through training, especially if that training doesn’t include lifting weights. That doesn’t mean it’s impossible. It might mean that it will take a little longer to notice improvements. It’s important to remember that it is not the only factor that goes into our sprint power.
Some Other Factors
Our muscles need energy to contract but that isn’t the full picture. This is why I decided to include “sprint” in the title. Inside our muscles we have different muscle fiber types. As we know from previous reading some are slow twitch and produce their energy aerobically and some are fast twitch and produce their energy anaerobically. Some are a hybrid and can do a little of both. What kind and how much of each muscle fiber type we have depends on our genetics. We may never be able to be a sprint champion if we were born with mostly slow twitch muscle fibers but that doesn’t mean that we can’t improve our sprint. When we train our sprint regularly our fast twitch muscle fibers increase in number and size. This will increase our sprint power.
Another factor that is especially important for sprinting is our neuromuscular system. The law of orderly recruitment tells us that the more maximal a muscle contraction is the more motor units are recruited. A maximum sprint will use the maximum amount of muscle. A muscle can have hundreds of motor units. Each motor unit can control hundreds of individual muscle fibers. This requires a lot of coordination! Even more complicated is that our synergist (helper) muscles have to coordinate with our agonist (main) muscle. Then, not only do we have muscles that need to contract, we have muscles that need to relax. Our glutes contract on the downstroke to push the pedals down. Our hip flexors can contract on the upstroke to pull the pedals up. While our glutes are contracting we want our opposite muscle (antagonist), the hip flexors, to relax. If our hip flexors don’t relax at the right time then they will be working against our glutes on the downstroke. This leads to inefficiency. This is also one way injuries can happen in the muscles.
So we need agonists and synergists to fire together and we need our antagonists to relax. This coordination and neuromuscular efficiency is important all the time but especially with sprinting. As we increase our rpm’s and amount of muscle fibers we are recruiting this gets more challenging for our neuromuscular system. When we practice our sprint our muscles will learn how to fire properly and become more efficient. This is coordination is a major contributor to improving our sprint power.
Out of all these factors it’s probably most important to understand how our PCr system works for two reasons. One is so we know how to structure our training intervals and two is so we know how to use this system to its fullest potential in a race situation. It will take about thirty seconds after a maximum sprint for our PCr system to return to 70%. It will take three to five minutes for it to return to 100%. Of course these time frames will vary between individuals, our fitness, and with training. If we are in a race and we throw down a big sprint attack in the last couple of minutes then we should be prepared to not have our maximum sprint power for the finish line if we are caught. In training if we are training our maximum power output we are going to want at least three to five minutes in between each interval.
Glycolysis
Glycolysis is our other anaerobic energy system. This system uses carbohydrates to produce energy. It also produces hydrogen ions and something called pyruvate. At lower intensities these two things are used by the aerobic system to produce even more energy. This is why you may have heard “fat burns in a carbohydrate flame.” Glycolysis is used as a flame to ignite aerobic metabolism. Glycolysis is always happening, even at rest. When we start to exercise more vigorously eventually we reach a point where we ask our glycolytic system to produce so much energy that our aerobic system can’t keep up. The hydrogen ions start to build up. This brings the acidity in our muscles up and makes our muscles burn. This increase in acidity causes enzymes, which are responsible for both anaerobic and aerobic metabolism, to not function properly. Our energy production decreases and our power drops. The power output where the hydrogen ions build up is sometimes called the anaerobic threshold. So this is one reason why our aerobic system is so important. It makes use of the byproducts of glycolysis so they do not build up. A stronger aerobic system will lead to a stronger anaerobic system.
Glycolysis will do the bulk of the work from thirty to ninety seconds so these are the most common interval lengths to train this system. Some experts advise a work to rest ratio of 1:3 to 1:5. If you performed a one minute interval you would rest between three and five minutes before the next interval. Just like with the recommended recovery interval for sprint training this will vary between individuals and with aerobic fitness.
Lactate Tolerance
Lactate, lactic acid, and hydrogen ions are words that sometimes describe the same thing, the cause of the burning in our muscles. Lactate tolerance is the most common name that describes our ability to tolerate the burning in our muscles caused by hydrogen ions. Remember our enzymes that produce the energy in our muscles can’t work well in acidic environments. We can train our enzymes/muscles to be able to tolerate that acidity a little better. So with training we can push a little harder or last a little longer during anaerobic efforts when we are feeling the burn. If we are looking to train our PCr or glycolytic systems to the maximum then we would want our longer recovery intervals. If we want to train our body to be able to tolerate “lactic acid” we would train anaerobically with little rest. This is one benefit to the classic 40/20 or Tabata intervals.
Training
These are some of the basics about anaerobic metabolism. We have our PCr system for short sprints (<10-15 seconds) which is distinct from our longer glycolytic efforts. If we are looking to train each system’s maximum output we want to have the proper recovery time. If we are looking to train our body to tolerate the acidity that glycolysis can produce then we would reduce our recovery times. If we are looking to increase the number and size of our fast twitch muscle fibers we may sprint train at a lower rpm with more muscle force. If we are looking to improve our neuromuscular efficiency we may sprint at a higher rpm.
RPM’s For Sprinting
A quick note on rpm’s for sprinting. Power is basically the combination of how forcefully we can push on the pedals and how many rpm’s we can turn. If we push harder on the pedals, increase our rpm’s, or both then our power will increase. The consensus is that most riders will see their best sprint power between 110-140 rpms. That’s a pretty big range. One reason for this wide range is due to muscle fiber type. If you have more slow twitch muscle fibers you will probably notice you have your best sprint power at a lower rpm. If you have more fast twitch fibers you will probably see higher power at a higher cadence. Because of this variation it is important to try different rpms to see what is the best for you.
Trainingpeaks Program
Here is a one month program covering all these bases. This program is best if you have some fitness built up and you are looking to add that top end power a few weeks out from an event. As always feel free to email for a special discount price.
