The Running Bug explains speed (or interval) and fartlek training, what the benefits are and how to do them properly.

Tip! Great for 5k and 10k training

What is it?
It's a cliché, but true: If you want to run faster, then you need to run faster. Speed sessions usually refer to short bursts of timed reps and intervals longer reps measured over distance. Try these 6 Tricks to Run Faster.

Many schedules use the track when planning the distance for interval sessions, i.e. 400m is once around a track, and is roughly .25 of a mile. But you can plan speed work to time if you prefer, (between 90 seconds and 2 minutes would be a typical 400m rep).

The Benefits
Speed work will make you a stronger more efficient and faster runner and you will notice a big difference to your fitness and speed in short period of time. It will help take you from a jogger to a runner. Fitness rewards are gained because running fast will increase type-two muscle fibres (the ones that help you run fast); strengthen quadriceps; improve the strength of the ventilatory muscles (which will help you breathe more efficiently); and prepare you mentally for racing - whatever the distance.

How to do it
You only need to work at a high intensity (at 85 to 95 percent of max heart rate, or eight nine out of 10 on a perceived rate of exertion, or one mile to 5k pace), over a series of short intervals to reap rewards. You will usually only need to do one or two sessions a week, and as these are high intensity, you must follow with an easy or recovery day.

Different types of speed work are designed to improve different aspects of running. Short sharp sprints will boost your leg turnover and anaerobic fitness, and with these you plan in a longer recovery, for example two to three minutes.

For marathon runners, who want to develop speed endurance, a general rule of thumb for planning interval training is to make the whole distance covered longer and the recoveries shorter. So for short 30-second bursts, you might do 20, with a 30-second recovery. You will also benefit from doing longer intervals.

Try some of the following speed sessions for marathon runners, making sure you warm up and cool down for 10 to 15 minutes either side:

• Pyramid: 400m, 800m, 1600m, and then work your way down 1600m, 800m, 400m, with recovery jogs of 1 minute between each burst.
• 4 to 6 x 1 mile at 10k pace, with 90 second recovery.
• 6 to 8 x 800m with 1 minute recovery.

Fartlek
This is Swedish for speed-play, a no-brainer speed session. You don't need GPS or a measured course, you simply run fast and slow - run between lamp-posts, or do timed bursts (30 seconds to 3 minutes). Or, try a pyramid fartlek session, for example, run hard five, four, three, two and one minute bursts with equal recovery time. This is a great way to run fast with no pressure and ideal when you're starting out.

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