Training with Intensity: The Physiological and Biomechanical Benefits
When starting out on a new exercise regime, many beginner athletes will experience a stark increase in their performance. They will feel better when exercising, be able to complete bigger distances, and their running times will come down. They will be on cloud nine because they are reaping the benefits of their new hobby. However, as time goes on, these 'beginners gains' start to diminish, and their performance plateaus. Why? Well, let's face it - whatever you give a beginner to do is going to result in improvement, but it's what comes after that's more important. So why do they drop off? Perhaps they get injured? After all, in the past I have talked at length about the dangers of just simply increasing mileage while neglecting to ensure that ALL of your body's key muscle groups are strong enough to do what you are expecting of it... But you can read my other blog posts for more information on that subject. Injuries withstanding, there is another key reason why performance tends to plateau off, and that is the fact we just don't run fast enough!
What is the VO2 Max?
One of the main determinants regarded by sports scientists in improving endurance performance is what is known as the VO2 Max. This is the maximum amount of oxygen that can be taken in and utilised by the muscles when exercising. In fact, it is believed that up to 70% of differences in performance between runners results from variation between their VO2 Max scores. Some of the VO2 Max is determined by genetics, but is also largely decided by what training you do. When you first start training, your VO2 Max will start to increase just from doing your long, slow, sub-maximal jogs. However, it will eventually reach the point where this no longer cuts it, so you have to adapt and do different types of training instead - as it would be ridiculous to continually do the same thing and expect different results...
"One of the main determinants regarded by sports scientists in improving endurance performance is what is known as the VO2 Max.This is the maximum amount of oxygen that can be taken in and utilised by the muscles when exercising."
There are various ways in which training can be manipulated to make it easier or harder, and these are known as the 'F.I.T.' principles. These stand for 'Frequency' (training more or less often), 'Intensity', (increasing or decreasing the oxygen demand of the muscle), and 'Time' (increasing or decreasing duration). As most runners almost entirely focus on increasing frequency and time, I am going to focus on intensity, which is most often neglected.
First of all, let's examine the physiological and performance benefits of running faster. Let's say that your goal is to run 8 minute miles in a 6 mile race. A lot of your training therefore will go into running longer distances at a much slower pace (perhaps determined by a heart rate zone, which seems to be all the rage at the moment). After all, these longer slower sessions are great for general health, and muscular endurance and strength. However, there is a physiological issue with this. Firstly, there is a difference between HEALTH and FITNESS. Going back to my example of the plateauing runner earlier - if you don't test your body by gradually overloading yourself, then no further improvement will occur. In sum, going out for slow jogs may be great at reducing the risk of illnesses such as heart disease, and type 2 diabetes, but because your body is used to it, its maximum capacity (i.e. your fitness) is not going to change. This is shown by the fact that your VO2 Max will experience a greater improvement when you increase the intensity of your training. Essentially, if you never run 8 minute miles in training, then how is your body ever going to be able to do this in a race? It's going to be an alien thing, because you are expecting your body to use a completely different energy system, one which you haven't trained!
"if you never run 8 minute miles in training, then how is your body ever going to be able to do this in a race?"
So What is this Energy System and how does it Work?
When exercising at a greater intensity, energy demand increases, and this energy to fuel the muscles has to be provided much faster. As such, the usual energy system that would be used predominantly on a long, slow run (the Aerobic System) would not be suitable here. This pathway has too many chemical reactions taking place, slowing the delivery of this energy, when it is required much faster - no good then for quicker running. Therefore, when running faster, there are other energy systems available to meet this swift energy demand. These are known as the anaerobic energy systems (meaning energy is provided without oxygen, whereas aerobic is with oxygen). Without the presence of oxygen, a process called anaerobic glycolysis takes place to provide energy. This process is faster than the Aerobic System, but as a drawback, lactic acid is produced as a by-product, fatiguing the muscles and causing that 'burn'.
It is through training where the body's tolerance to lactic acid build-up is increased. In fact, lactic acid is usually thought of as the enemy, but in reality, it doesn't actually exist in the muscles for very long, as it immediately dissociates into 'lactate' and hydrogen ions. It is only the hydrogen ions that cause the acidity and the denaturing of the body's enzymes, whereas the 'lactate' part is actually quite useful, as this substance can be recycled back into the glycolysis process and used again to keep the energy demand going. This process is of course made more efficient through training.
"lactic acid is usually thought of as the enemy, but in reality, it doesn't actually exist in the muscles for very long, as it immediately dissociates into 'lactate' and hydrogen ions.It is only the hydrogen ions that cause the acidity and the denaturing of the body's enzymes, whereas the 'lactate' part is actually quite useful"
What is the Relevance of Anaerobic Energy Production in Endurance Activity?
As mentioned earlier, an increase in the level of VO2 Max is more effectively achieved via a training programme which includes higher intensity training. Now, it is important to note here that despite the fact that anaerobic systems are primarily used in disciplines requiring a great deal of speed and power, it doesn't mean to say that they aren't important in endurance sports as well. It is vital to understand that ALL the energy systems (aerobic and anaerobic) contribute to meet the energy demand at ALL times. It is merely a question of which is working the most predominantly at any given time. So when running endurance, although the majority of your energy will be provided aerobically, there is still a significant amount that is supplied via anaerobic means, even during a marathon. This is what the term 'anaerobic endurance' refers to; the ability to continuously manage and buffer the production of lactic acid over an extended period. Your body will not likely have to cope with a significant amount of lactic acid on your slow and steady jogs, but when you are running a race it will have to! This therefore is one of the things that separates the best from the rest - you need to train intensity so that when in a race, your body is better able to tolerate lactic acid when it starts to increase in quantity in the muscles and bloodstream (research 'lactate threshold' for more information on this). In sum, even as a marathon runner, speed should not be neglected, and this is one of the biggest things runners need to do to improve their plateauing performance, as their ability to run at speed is usually very poor.
"when running endurance, although the majority of your energy will be provided aerobically, there is still a significant amount that is supplied via anaerobic means, even during a marathon. This is what the term 'anaerobic endurance' refers to... ...This therefore is one of the things that separates the best from the rest - you need to train intensity so that when in a race, your body is better able to tolerate lactic acid when it starts to increase in quantity in the muscles and bloodstream"
What kind of sessions should I do to increase my VO2 Max?
Let's not overcomplicate things. Anything that involves running faster is going to improve your anaerobic ability, things like:
☑️ Intervals/sprints/fartlek sessions
☑️ Hill reps
☑️ Tempo runs (running at approx. 25-30 secs slower than your 5K race pace, or about 90%)
One thing to consider is when doing intervals, sprints, track sessions and hill reps, the length of your recovery between reps and sets determines what sort of energy system you will be targeting. This in turn should be dictated by what you are trying to achieve according to your chosen discipline. For instance, 6 minute recoveries between reps would be commonplace for a sprinter in order to maintain maximal speed, whereas if you are targeting more 'speed endurance', then much shorter recoveries (e.g. 90 secs) are more suitable. My advice would be to chose the appropriate duration of recovery, based on your intended session outcome, stick to it. Being strict with your recovery will make sure you are getting the most from your session.
What are the Biomechanical Benefits?
It's not just the physiological side of things that provide benefits either. As I say to many of my clients, running faster is a vital way to make sure that your body stays nice and balanced. This is because of the different way you utilise your muscles when running fast compared to running slow. When simply steadily jogging along, you don't use your muscles through their full range of motion. In fact, on a regular basis when I see runners training on the streets, I can tell from a distance what muscles they are using, for example there is often no point at which I see their trail leg fully extended, without at least a small amount of bend in the knee. If this is the case, what are the chances they are actually using their glutes instead of just hamstrings? How much are they using their hip flexors when their feet are literally barely clearing the ground? The list could go on...
These runners are so used to running at the same slow pace all the while that it results in chronic muscle imbalances whereby some muscles don't get a turn. Each muscle group has its own job when it comes to performance enhancement and injury prevention, but to summarise, not using certain muscle groups on a regular basis results in biomechanical dysfunction and misalignment of the body, so too much of the same thing is bad for you...
If however quicker running is introduced, it will help to utilise and strengthen these neglected muscles, as when sprinting, the trail leg should extend more, making it easier to activate the glutes. When sprinting, the runner's knee lift should also be higher, forcing you to use the hip flexors through a greater range of motion to increase stride length.
"When simply steadily jogging along, you don't use your muscles through their full range of motion."