As a coach, I get this question with some frequency. It usually goes something like this…
“I’m training for a marathon and I don’t plan on running any faster than a 10 min/mile pace. So why do I need to do intervals?”
Fair question to be sure… and this question is the crux of the issue regarding the purpose of intervals/speedwork for endurance athletes. Additionally and slightly off topic, it’s important to note that what constitutes a ‘slow’ runner is subjective and is often a label given to one’s self.
There are two main reasons to perform high intensity intervals:
- To increase your speed
- To increase your aerobic capacity/lactate threshold
As you can see, both are correlated but they are often viewed as separate entities. There is an erroneous thought that only ‘fast’ runners need intervals. Therefore, the runner in the above example whose goal is to run a 10 min/mile pace would not need to do any intervals/speedwork.
PHYSIOLOGY
While this post will focus on intervals, speedwork is a fairly generic term for any type of workout that involves running fast. It could be tempo, intervals, fartleks, etc…
While intervals will increase one’s ability to run faster, the reason behind this is what’s important. In my humble opinion, interval training is perhaps the most important type of workout that can be done for endurance athletes. But why?
The basis of interval training is a hard effort, followed by some sort of recovery period – repeated ‘X’ number of times. The reason why I consider interval training to be so important is because during hard efforts, there is a large focus on increasing one’s lactate threshold and during the recovery period(s), there is a focus on aerobic development. Therefore, you get the most bang for your buck.
PSYCHOLOGY
Intervals are hard – no doubt about it. So often, coaches and athletes only look at training from the physical standpoint. The reality is that the physical and psychological aspects of training and racing are inexorably linked. No matter whether your goal is to run a marathon in 2:20 or 6:20, it will be hard and uncomfortable for some parts of it. By performing interval-based workouts, you are increasing your pain tolerance (not pain threshold), which is important regardless of your running speed.
RUNNING ECONOMY
Intervals, as well as other forms of speedwork and resistance training, increase the stiffness of muscles and connective tissue such as the Achilles tendon. So long as range of motion is not compromised, increasing the stiffness of muscles and connective tissue will increase one’s running economy. To visualize this, think of a two rubber bands that are stretched the same distance. Which rubber band will shoot farther – one that is harder to stretch or one that is easier? Of course the one that is harder to stretch (i.e., stiffer).
In respect to muscle stiffness, this is why recent research has shown that pre-stretching a muscle decreases it’s contractile forces, or more to the point, the degree to which a muscle can contract.
SUMMARY
Interval training and speedwork as a whole is not the exclusive domain of ‘fast’ runners. The science behind, and the benefits gained from interval training are applicable to all runners regardless of their speed or experience level.
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