Updated: Apr 30
INTERVAL TRAINING FOR AEROBIC CAPACITY
In a previous article I talked about the importance of steady state continuous training (long slow distance, or LSD) for improving cardiovascular endurance (you can read the article here). I have mentioned that there are certain adaptations (such as eccentric cardiac hypertrophy) that can only be achieved through this type of training and no amount of HIIT (high intensity interval training) can replace the famous roadwork.
However, this doesn't mean that high intensity training is any less important. It only means that the cardiac adaptations induced by the different training methods are not the same. Once you build a strong aerobic foundation by focusing more on long slow distance training, it is time to turn up the intensity and get your conditioning to the next level.
DIFFERENT TYPES OF INTERVAL TRAINING
There are countless definitions of high intensity interval training. The main difference between HIIT and LSD is that you are not working continuously for a certain amount of time, but rather working at a higher intensity for a shorter interval, followed by a rest interval, repeating the sequence for the given number of repetitions. The intervals can be as short as 10 seconds (or less), or as long as 15 minutes. Different durations (and different rest periods) will facilitate different adaptations.
1. Long intervals = central adaptations
Longer intervals of 4 minutes and above target the heart and the blood vessels (central adaptation), causing them to deliver oxygen more efficiently to the muscle cells. These adaptations take time, but with consistent training you can achieve significant increases in VO2 max (the most common indicator of aerobic capacity - the maximum amount of oxygen your body can take in, transport through the blood and utilise to produce energy). Now, these are not easy 4 minute jogs. The aim is to spend a great amount of time in the so called red zone (HR equal to or higher than 90% of maximum, or, on a scale of 1-10, that would be between 8.5 and 9, where 10 is your all out, absolute this is the best I can do maximum). Only at this intensity you can force the heart to operate at its maximum pumping capacity long enough to cause the desired adaptations.
The simplest way of doing this would be to perform 4 x 4 minutes of high intensity work with 2 minutes rest in between (this can be hard running or any other type of exercises that will keep your heart rate up in the red zone). The fun part is, you can break this up into smaller chunks (or even make it into a pyramid, yayy) with shorter rest periods that will allow you to catch your breath quickly, without letting your heart rate drop too much. A good example of this is Tabata training. I'm sure you've heard of it before: 20 seconds on, 10 seconds off. Repeat this 8 times and you have your 4 minutes. Rest for 2-3 minutes and do 3 more rounds. You can do different exercises in each round, or even mix it up within the round, as long as you keep it intense.
2. Medium length intervals = muscle buffering
Intervals that last for about 2 minutes are mainly aimed at improving the buffering ability of the muscles. What is buffering, you ask? In simple terms muscle buffering is clearing out the lactate and hydrogen ions from the blood, which accumulate as a consequence of a prolonged high intensity work (and anaerobic energy production). This is what causes the burning feeling in your muscles, and forces you to stop after a certain time. This is normal, and it cannot be avoided. However, you can increase the body's ability to tolerate lactate (embrace the pain), as well as the ability to clear out the lactate more efficiently. And that is called muscle buffering.
I'm not gonna lie to you, it's gonna be painful. 2 minutes of torture, working at your near maximum, followed by 3 minutes of recovery. Repeat it 6 to 8 times and you will hate me, the treadmill, the road and everyone else around you. Sorry. So why would you do it? That's a great question you didn't ask! Well, if you're an athlete in a sport that requires you to perform repetitive high intensity bouts (as in most combat sports), you will want to recover from those bouts as quickly as possible, so you can perform them over and over again, for 3-12 rounds. The more the hydrogen ions build up in your muscles, the harder it is going to be for you to perform, even at lower intensities. So a good buffering capacity will definitely come in handy in the ring.
3. Short intervals = peripheral adaptations
Short intervals (30 seconds or less) are also called sprint intervals. Even if you're not actually running, the term sprint is supposed to suggest an all out 10 out of 10 effort, performed for a very short period of time, followed by long recovery. These intervals, though might not seem like much, are excellent for inducing peripheral adaptations (increase the ability of the muscles to extract and utilise the oxygen from the blood). Since the work interval is very short, maximum intensity is crucial when performing this type of training. Exercises such as hill sprints, maximum sprints on a curved treadmill or an assault bike are the best to achieve the required intensity in a short time period. As the muscles get better at utilising the oxygen from the blood, you will be able to work at higher intensities for longer.
Perform a 30 second all out, as fast as you can go, as hard as you can go (intent is very important here) sprint, preferably on a hill or a curved treadmill, or a normal treadmill with a big incline, or the machine of my nightmares: the assault bike, then rest for 3-4 minutes to allow for full recovery. This is so you can give your absolute maximum on all the following reps, too. Perform 4-6 repetitions and that's it for the day. That's pretty much 2-3 minutes exercise in total. As I said, it doesn't seem like much, but it is effective.
So these are the three main types of intervals you can do for improving your aerobic capacity. Combining all three in a well-programmed conditioning plan will give you the best results. Of course, if you just wish to mix up your training, you can do countless other variations of intervals,. Be creative and the sky is your limit.
Here's one more of my favourite running intervals:
Even though it might seem like a medium length interval (2 minutes), this actually falls into the first category. Rather than running as hard as you can for 2 minutes then taking a long rest (like you would for a buffering session), you do 2 minutes, with 1 minute rest and then 2 minutes again. That's your interval. Give it a go and let me know how you like it. Remember, keep that heart rate up in the sky!
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