The most trainable and important facet of your distance running training is development of your aerobic system. From distances as short as 5k and through to the Marathon, your aerobic system is far more important than speed.
So why do many distance runners simply overlook or not target this key component?
The simple answer is that it’s not ‘sexy’. There doesn’t need to be a lot of toys such as heart rate monitors, step counters or new power meters. It cannot be bought, or given to you. Aerobic conditioning takes time, discipline and most importantly controlling your competitive nature. Due to all of these reasons, most try to find an easier route, rather than getting down to work. Often all it takes is a simple tweak to your training and you’ll be absolutely crushing your next race.
Before we dive into specifics, it’s important to understand the aerobic system, how it works and most importantly, how to target it in training. So why is aerobic development important?
Let’s start the conversation as to ‘why aerobic development is so critical to distance running’ by breaking down how a body uses energy over a given number of distance.
Even for a “short” event like the mile, over 60% of the energy required to run the race is produced via aerobic metabolism. Looking at the research and the scientific data, we now know that the aerobic system is extremely important to distance running.
So how can slow running not only help build your aerobic capacity but also allows you to run faster?
The answer lies in how our body converts fuel to energy. Aerobic training and racing requires our body to break down sugar and convert it to glycogen so it can be used as energy or fuel. When we have enough oxygen, the body utilizes the aerobic system, also known as aerobic glycolysis, to energy that enables a sustained pace. In the aerobic system, energy ATP is produced through Pyruvic Acid and Lipid/Protein fragments entering the Kreb Cycle and the Electron Transport Cycle. Simply speaking, during aerobic respiration, you breathe in, the body efficiently uses all the oxygen it needs to power the body and then you exhale.
When you are running in an ‘aerobic state’ often this can be quite easy, your muscles have enough oxygen to produce all the energy they need to perform. Therefore, by focusing improving your capacity to transport and efficiently utilize available oxygen to produce energy will enable you to race faster, since this makes up 85-99% of the energy needed to race.
Let us reiterate; running easy is the best way to train the aerobic system!
So by running in an aerobic state, let’s take a look at the specific physiological adaptions that occur:
Benefit 1 – Capillary Development
Capillaries are the smallest of the body’s blood vessels and they help deliver oxygen and nutrients to the muscle tissues while shuttling waste products out. The greater the number of capillaries you have surrounding each muscle fiber, the faster you can transport oxygen and carbohydrate into your muscles. Aerobic training specifically increases the number of capillaries per muscle fiber. It also improves how efficiently you can deliver oxygen to fuel your working muscles and how quickly they can clear waste products such as lactic acid.
Benefit 2: Increase Myoglobin Content Of Muscle Fibers
Myoglobin is a special protein in your muscles that binds the oxygen that enters the muscle fiber. When oxygen becomes restricted due to exercise, myoglobin releases the oxygen to the mitochondria to produce more energy. The more myoglobin you have in your muscle fibers, the more oxygen you can sequester to the muscle under aerobic strain. This specifically applies in race situations. Aerobic training increases the myoglobin content of your muscle fibers.
Benefit 3: Mitochondria Development
Mitochondria are microscopic organelle found in your muscles cells that assist in the production of ATP (energy). In the presence of oxygen, mitochondria breakdown carbohydrate, fat, and protein into usable energy. So it’s a given, the more mitochondria you have and the greater their density, the more energy you can generate during exercise. Aerobic training increases both the number and the size of the mitochondria in your muscle fibers.
There are other physiological benefits to aerobic training, but the three major factors above are the primary contributors. Given this, aerobic development is the single most important factor to long-term development for distance runners and athletes. There is a time and place for track workouts, VO2max sessions and tempo runs however, nothing will consistently help you improve like developing your aerobic system.
So why doesn’t running faster on easy days develop the aerobic system more rapidly?
Not only will running faster result in diminished aerobic development, but it increases the chances of injury and overtraining. Easy days are easy, for the simple reason your need to recover from a heavy load. This is the single biggest mistake runners of all experience levels make in their training.
So how do we get to optimal aerobic development pace?
Scientific research as been able to identify exactly how the aerobic system responds and adapts to certain training paces. Physiologically, we know:
- Capillary development appears to peak at between 60 and 75 percent of 5k pace.
- Research has shown that maximum stimulation of myoglobin in Type I muscle fiber occurs at about 63-77 percent of VO2max. 63-77 percent of VO2max is about 55-75 percent of 5k pace.
- Two researchers, Holloszy (1967) and Dudley (1982) published some of the defining research on ideal distance and pace for mitochondrial development. In short, Holloszy found that maximum mitochondrial development when running at 50-75 percent of V02max. Likewise, Dudley found that the best strategy for slow-twitch, mitochondria enhancement was running for 90 minutes per outing at 70 to 75 per cent V02 max.
The body of evidence is clear: your optimal easy run pace for aerobic development is between 55 and 75 percent of your 5k pace, with the average pace being about 65 percent.
Specifically, for your long runs, the research indicates running 50-55 percent of 5k pace is provides near optimal physiological aerobic adaptation. But there are two huge bonuses for training at this pace:
- 1.You decrease the risk of injury and have less muscle tissue damage
- 2.Running slower means you most likely can handle more volume!
By showing self-control and containing your running pace in training, specifically on sessions are keys to developing your aerobic system.
