An introduction to interval training

It’s the fast way to build strength and boost endurance. If you're looking to take your running to the next level, it’s time to try intervals.

What is interval training?

Interval training is a type of training intended to test your limits at high speeds, but in short bursts, or intervals – hence the name. Each fast interval is followed by a rest period, then you go again. It’s the epitome of no pain, no gain training, and can deliver a huge payoff in performance.

Often referred to as HIIT (high-intensity interval training), interval training can be solely running, but can also refer to intense sets of other exercises, such as mountain climbers, burpees or press-ups. Also similar is “fartlek” training, from the Swedish meaning “speed play”, which incorporates intervals into your run with no fixed structure (sprinting to the next tree, the next traffic sign, etc.).

Why should I run intervals?

To level-up your running, intervals are the way to go. Shorter and more varied in pace than the traditional long run, many runners prefer intervals to slower sessions, embracing the intensity and efficiency. Hitting start on your watch for that first set is exhilarating, as you know you’re going to come out the other side a better runner. And there’s science to prove it.

Compared with continuous endurance exercise, interval training is better at increasing your VO2 max, which is the amount of oxygen your body can use during intense exercise. If you’re looking to get fitter, increasing VO2 max is the key – the more oxygen your body can process, the faster and further you can go before you feel exhausted.

Among many other benefits, interval training is even more effective than steady running for increasing the volume of blood your heart pumps when you’re approaching maximum exertion. Think of it as upgrading your engine; a turbo boost for the track or trail. The enhancements extend to the muscles too. Intervals are effective at increasing the size and number of mitochondria in your muscle cells. These tiny superheroes are the energy factories that help your muscles produce greater force for a longer period of time, making sure you’ve always got a kick for a sprint finish.

How do I start with interval training?

Sold on the benefits? Time to get started then. The good news is that a great interval session needs little more than some old-fashioned determination.

In terms of kit, you want gear that’ll keep you at your comfortable best both in the heat of the sprints and the cooler breaks in between. The On Long-T is ideal. It’s made to adapt to your body and the conditions, so you can focus on smashing out results. To feel sure your intervals remain uninterrupted if rain arrives, the On Weather Jacket and Weather Vest work well over the top as outer layers that are light enough to keep you at top speed.

Shoes that are built for pace are also ideal for intervals. The Cloudboom Echo 3 is engineered for fast running, offering a cushioned landing followed by an explosive takeoff.

You can run intervals on the road or trail, or even throw in some hills, but many runners choose the track. A full loop of 400 meters is a common interval set, so with a track you can see where you’re up to as you’re chasing down the distances.

You can divide your intervals by time or distance, so using a GPS running watch is ideal. If it has a heart-rate monitor, you could vary intervals based on heart rate zones too. If you’re new to intervals, 8 x 400 meters with the same distance as rest in-between is a good place to start. As you improve, you can increase the distances or shorten the recovery time. Recovery is usually active rather than full rest, transitioning from all-out exertion to an easy jog. What’s important is that the recovery is gentle enough that you’re ready to go again when your watch tells you it’s time.