How do the Jennis HIIT Run sessions actually work?

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These brand-new running sessions, designed by Jess Ennis-Hill, use the principles of Fartlek to make you faster and stronger – and they're also quick and fun. Here, we look at the science of how they get results and find out how you can incorporate them into your fitness week...

The perceived wisdom is that to get faster at running, you need to spend your time pounding the pavements. But, the reality is that if you run at the same pace and the same distance over and over, you won't see improvements.

To up your strength, stamina and pace, the key is to include variety in your runs, with the goal being to feature different periods of pace, rest and intensity. Sound tricky? Then Jess Ennis-Hill's guided audio HIIT runs will do all the thinking for you.

What is a Jennis audio HIIT Run session?

Taking inspration from Jess's professional training career, the Jennis audio HIIT Run sessions guide you through short bursts of intense exercise performed at speed, followed by slower rest periods.

There are Beginner, Intermediate and Advanced sessions, and you don’t need any equipment or a timer, as Jess will talk you through when you need to run and when to reduce your pace.

The Jennis HIIT Run sessions in detail

BEGINNER

Total time = 18 minutes or 23 minutes 40

3 or 4 x sets, with a longer 3-minute rest in between

2-minute warm up

Set 1 (2 minutes 40 seconds)- 40-second run- 30-second rest- 30-second run- 20-second rest- 20-second sprint- 10-second rest- 10-second sprint

3-minute rest

Set 2 (2 minutes 40 seconds)- 40-second run- 30-second rest- 30-second run- 20-second rest- 20-second sprint- 10-second rest- 10-second sprint

3-minute rest

Set 3 (2 minutes 40 seconds)- 40-second run- 30-second rest- 30-second run- 20-second rest- 20-second sprint- 10-second rest- 10-second sprint

3-minute rest

Set 4 (2 minutes 40 seconds)- 40-second run- 30-second rest- 30-second run- 20-second rest- 20-second sprint- 10-second rest- 10-second sprint

2-minute recovery rest

INTERMEDIATE

Total time = 22 minutes 30 or 28 minutes 40

3 or 4 x sets, with a longer 3-minute rest in between

2-minute warm-up

Set 1 (4 minutes 10 seconds long)- 50-second run- 40-second rest- 40-second run- 30-second rest- 30-second run- 20-second rest- 20-second sprint- 10-second rest- 10-second sprint

3-minute rest

Set 2 (4 minutes 10 seconds long)- 50-second run- 40-second rest- 40-second run- 30-second rest- 30-second run- 20-second rest- 20-second sprint- 10-second rest- 10-second sprint

3-minute rest

Set 3 (4 minutes 10 seconds long)- 50-second run- 40-second rest- 40-second run- 30-second rest- 30-second run- 20-second rest- 20-second sprint- 10-second rest- 10-second sprint

3-minute rest

Set 4 (4 minutes 10 seconds long)- 50-second run- 40-second rest- 40-second run- 30-second rest- 30-second run- 20-second rest- 20-second sprint- 10-second rest- 10-second sprint

2-minute recovery rest

It’s only during the final runs of 20 seconds and 10 seconds in length that you should really push yourself to 100 per cent effort. These are proper sprints – so leg it as fast as you can!

ADVANCED

Total time = 28 minutes or 37 minutes

3 or 4 x sets, with a longer 3-minute rest in between

2-minute warm-up

Set 1 (6 minutes long)- 60-second run- 50-second rest- 50-second run- 40-second rest- 40-second run- 30-second rest- 30-second run- 20-second rest- 20-second sprint- 10-second rest- 10-second sprint

3-minute rest

Set 2 (6 minutes long)- 60-second run- 50-second rest- 50-second run- 40-second rest- 40-second run- 30-second rest- 30-second run- 20-second rest- 20-second sprint- 10-second rest- 10-second sprint

3-minute rest

Set 3 (6 minutes long)- 60-second run- 50-second rest- 50-second run- 40-second rest- 40-second run- 30-second rest- 30-second run- 20-second rest- 20-second sprint- 10-second rest- 10-second sprint

3-minute rest

Set 4 (6 minutes long)- 60-second run- 50-second rest- 50-second run- 40-second rest- 40-second run- 30-second rest- 30-second run- 20-second rest- 20-second sprint- 10-second rest- 10-second sprint

2-minute recovery rest

How do Jennis HIIT Runs help you get fitter?

All exercise activates biological reactions that help you get fitter and improve your cell health. However, the more intense workouts involved in HIIT and HIIT Runs fast-track these reactions , so you improve your fitness in less time.

The reason for this is that when you do a high-intensity workout, your body can’t supply blood and oxygen fast enough to the muscles, which means it has to rely on its anaerobic system for energy (tapping into the glucose available for energy in the muscles).

Then, during the rest periods, the body switches back to its aerobic system, which releases fat stores for energy. Eventually, your body relies less on the anaerobic system, improving efficiency all round .

The rest periods are a vital part of the workout, giving your body time to recover for the next high-intensity burst of exercise. They also help your heart to adapt between the sprint and recovery periods, so it becomes more efficient at transporting oxygen around the body. 

How fast do you run in a Jennis HIIT Run session?

When it comes to the hard runs, you shouldn’t go full gas or you'll burn out too quickly. Instead, aim for 70 per cent of your maximum effort, so that you definitely get your heart rate up but you don’t go so hard that you have nothing left. This is particularly important for the 60, 50, 40 and 30-second run efforts.

It’s only during the final runs of 20 seconds and 10 seconds that you should really push yourself to 100 per cent effort. These are proper sprints – so leg it as fast as you can. If you can speak during one of these, you need to go faster…

You don’t need any equipment or a timer, as Jess will talk you through when you need to run and when you need to reduce your pace

Can you walk in the rest periods?

In an ideal world, you’d jog gently through your rest periods to make it more of a workout. But if you’re really struggling and need a break, walking is good, too. A 2014 study in the Journal of Sports Medicine and Physical Fitness reported that active rest – which includes walking as well as jogging – is more effective at clearing lactate, a waste produced during intense exercise, from the blood.

After your workout

Just as you would with an indoor workout, it’s important to take the time to cool down and stretch after a Jennis HIIT Run. Lacking in inspo? Check out Jennis Fitness Extras on the app for Jessica Ennis-Hill's cool-down stretches.

Map your training to your menstrual cycle with Jennis CycleMapping.  Download the app

Read what  Refinery 29  had to say about the programme

Try Jennis Training for  iPhone  and  Android

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