If you want to improve your cardio fitness or running speed, incorporating sessions focused on intervals is important. While running intervals on a track or at a park outdoors are good places to workout, they not be conveniently located or the conditions may not be in your favour. In these cases, the treadmill can be a great alternative option.

HIIT, or "High-Intensity Interval Training", is a type of training which focuses on repeated short bursts of exercises performed at a high intensity followed by a period of rest. The aim is to work at your maximum capacity during your work intervals, tapping into your anaerobic energy reserves. This type of training is often used to improve cardiovascular conditioning.

For this article we'll be referring to "High-Intensity Interval Training" as a loose term to refer to "sprint intervals" and look at how you can do do this on a treadmill in the gym.

As HIIT exerts a lot of effort, it can only be carried for a short amount of time. This means HIIT workouts are short and therefore can be a great option if you're short on time. By sprinting flat out for 20 seconds, reducing your pace to a jog for the next minute, then repeating the circuit for 10-15 minutes, you can get a lot within a short amount of time.

A key requirement of HIIT is sprinting flat out, with maximum exertion during each sprint window. To successfully pull this off outside, you'll need access to a long, even stretch of land where you won't have to worry about colliding with any children, cars, or shoppers who happen to step out in front of you. Performing HIIT on a treadmill can help you to work on your speed in the convenience of gym if you don't have access to a track or suitable location outdoors to do this. One of the great benefits of using a treadmill for your HIIT workouts is that it will allow you to scale the difficulty of your training session more easily than training outdoors. Just make sure to familiarise yourself with how to use a treadmill and how to safely get on and off it.

HIIT has been shown to improve cardiovascular function, blood pressure, insulin sensitivity, and increase VO2 max (how much oxygen you can use during exercise).

Finally, HIIT has been shown to have a dramatic effect on increasing muscular endurance. Even a single workout triggers changes in your muscles which lead to an increased ability to perform work under tension for longer periods of time. With sprint training the bulk of that effect will be in the muscles of the lower body -- the calf muscles, quadriceps, hamstrings, and glutes. The muscles of the lower back also benefit indirectly.

The key to triggering these benefits is forcing your muscles to contract as hard as possible in a short space of time. This is the same basic principle behind generating power in any sport or physical activity. It just so happens that there's research to suggest that doing hill sprints conditions your hips to generate greater power under tension. Therein lies another key benefit of doing HIIT on a treadmill. The different settings available allow you to subtly modify the focus of your workout in ways which your immediate environment may not.

For example, you could alter the workout back and forth between more muscle fatiguing hill sprints, and flat sprints which allow you to perform at your max speed.

There are some things to consider when doing HIIT treadmill workouts. The first step is to familiarise yourself with the treadmill at your gym. If you're not sure how to use it, you can check our guide on how to use the treadmill , watch the treadmill interval guide below, or ask a personal trainer at your gym.

The next step is to wear the right kit. Wear running shoes that fit you well. You probably want to wear fabric that is breathable to help wick sweat off and keep you comfortable while running.

Plan your workout ahead of time so you know what intervals you'll be doing. See below for example HIIT treadmill workout ideas.

Before you start your HIIT workout on the treadmill, make sure to warm up properly. Check out our Warm up for runners guide for ideas. 

When running on the treadmill, try to maintain good running form and adjust the speed to suit your level. 

After you've completed your workout, remember to take some time to cool down by walking on the treadmill at a relaxed pace and performing some stretches targeting your legs, for example a standing hamstring stretch.

A HIIT treadmill workout should take no longer than 15 minutes.

Working at an high intensity can be very demanding so it's important to make sure that you are not overtraining, get adequate rest and sleep and are fueling your body properly, as this can result in burnout and lead to injuries.

Here are some examples of HIIT treadmill workouts:

1. Eight all-out, 20-second sprints, with one minute of rest in between.

2. Six all-out 15 seconds sprints, with 45 seconds rest in between.

3. Five all-out 30-second sprints, with one minute and a half rest in between

4. Five all-out 15 seconds sprints, with 45 seconds rest in between. With each round, increase the incline by 1%.

Make sure to take the time to warm up before and cool down after your workout.

You can also try these intervals with other pieces of kit in the gym such as a ski erg or rower. 

For more HIIT workout ideas, check out our free workouts guide packed with a variety of different interval workouts and the free PureGym app to get access to over 600 workouts. For a low impact HIIT workout, try this HIIT rowing machine workouts guide.

References:

https://www.unm.edu/~lkravitz/Article%20folder/HIITvsCardio.html

https://link.springer.com/article/10.1007/s40279-017-0727-x

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2991639/

http://www.pnas.org/content/112/50/15492.abstract

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2808749/