Run fast for a short distance, slow down for a bit to recover. Do it all again. Interval training boils down to this simple formula – and offers runners a route to continuous improvement.
‘Interval training is going to increase your level of fitness faster than pretty much any other type of running,’ says running coach Jeff Gaudette. Giving yourself a breather between segments of fast running allows you to handle more of it, delivering a greater stimulus to your heart, lungs and muscles.
And despite fast running’s reputation for causing injuries, half marathoners who incorporated intervals into their training were less likely to get hurt than those who didn’t, according to a recent study. Though this may have something to do with mileage and experience level – advanced runners tend to both do more intervals and have a lower injury risk – there’s also evidence that running form may improve at quicker paces, says Gaudette. Provided that you begin with a fitness base and allow ample time between hard workouts for recovery, ‘short, hard bursts can teach your body a more efficient way to run, which ideally transitions into the rest of your training’, says Gaudette.
Tweak the reps and rest and you can create an infinite number of workouts, each with its own benefits. Whether you’re targeting a half or full marathon, your first (or fastest) 5K, or just the ability to run stronger or longer this autumn, here are the interval sessions that can get you there.
1/ Finish your first 5K
Steady, consistent running will carry you across the finish line of your first 5K. But if you can already comfortably complete an easy 5K, adding surges of speed will make a faster-than-usual pace come naturally on race day. Plus, mixing things up with a weekly speedy run adds fun to your training routine, says coach Rebekah Mayer.
The workout: Try a fartlek run – the term means ‘speed play’ in Swedish. After a 10-minute warm-up, choose a landmark between 30 seconds and three minutes ahead. Run at a comfortably tough pace – you should be able to speak only a word or two at a time – until you reach it. Jog slowly for the same amount of time to recover. Repeat for 10-15 minutes before a 10-minute cool-down.
2/ Nail a short race
The biggest barrier to a faster 5K or 10K comes from the waste products that build up in your muscles when you pick up the pace, says Gaudette. Intervals at these race paces train your body to process these substances while also increasing the rate at which oxygen travels to your muscles, allowing you to run faster for longer. ‘You’re getting an opportunity to practise the pain, mental stress and fatigue that come with running at that pace,’ says coach Carl Leivers.
The workout: After a 10-minute warm-up, run 12 x 400m repeats at your 5K pace (if that’s your goal distance), with 30 seconds of easy running in between. Targeting a 10K? Do 16 x 400m at 10K pace instead. The first few reps should feel relatively easy – the second half should be where it gets tough, says Gaudette.
3/ Build strength
Age and/or neglect can rob your muscles of their fast-twitch fibres, eventually sapping your speed, power and strength. Fortunately, you can fight back with short, super-fast intervals. Summoning fast-twitch fibres to propel you at full tilt trains your brain to recruit them more quickly at any speed – while you might associate these fibres only with fast running, your body can also use them to keep you moving forward when slow-twitch fibres are fatigued, says Mayer. These workouts can even convert some flexible muscle fibres into the fastest-twitch type, says Gaudette, which results in a fluid, more efficient stride.
The workout: After a long warm-up – two to four miles – run the following series of repeats as fast as you can without feeling out of control: 3 x 100m, 3 x 150m, 3 x 100m. Take two to three minutes of standing or walking rest to recover between each rep. As you sprint, focus on leaning forward slightly and pawing backward with your hamstrings and glutes. Supplement these workouts with two to three weekly strength sessions for your hips, core and glutes; lower-body weakness can lead to injury at top speed, says Gaudette.
4/ Increase endurance
Intervals can boost your efficiency in ways that help you run longer than ever – whether you’re aiming to increase from 5K to 10K or all the way up to a half or full marathon. ‘The more efficient you can be, the less energy you’ll use to run a given pace,’ says Gaudette. ‘That allows you to potentially go a lot farther before you start to break down.’
The workout: Warm up for 10 minutes, then run half-mile or mile repeat s at a comfortably challenging pace (you might be able to speak a few words, but not quote scenes from Shakespeare, says Gaudette). Recover by jogging for half the time the rep takes. Start with three miles or six half miles, and increase every two to three weeks until you’re logging five miles or 10 half miles of fast running.
What you do between hard intervals depends on the purpose of your workout
Standing: This alleviates stress and impact between short, fast reps when you’re building speed and strength. Avoid dropping your hands to your knees, as this could cause light-headedness.
Walking: Newer runners benefit most from walking between repeats of at least 400m – it brings your heart rate down but, crucially, keeps blood flowing to clear waste products.
Jogging: It keeps your heart rate elevated, extends the distance of your workout and simulates late-race fatigue. It is good recovery for most workouts carried out at less than all-out effort.
Related: How to recover between intervals