What Is HIIT?
While “hard work, short rests” is the essence of HIIT, there are five main variables that can change the nature of your HIIT workout massively. The first two are your work and rest durations. Working for 40 seconds and resting for 20 is significantly different to resting for 40 and working for 20, with longer work periods generally being better for improving endurance and shorter ones better for power.
Then there’s the intensity of the work periods. With HIIT you need to be pushing hard to get the most benefit from it, and it’s also important to try and maintain a consistent level of effort across the work periods. That means it’s not just about going all-out, because you won’t be able to sustain it across the workout.
“You need to know your target heart rate or understand the rating of perceived exertion (RPE),” says Philippe Ndongmo, a personal trainer at Dolphin Square Fitness Club in London. Rate the latter out of ten and try to keep the effort constant across every interval.
The fourth variable is the type of rest you do – are you stopping completely or engaging in active recovery, like pedalling slowly on an exercise bike? The latter can help flush out lactic acid ahead of your next work period.
Lastly there’s total volume, as in how many intervals you do. It’s easy to do too much with HIIT, which ends up being of no real benefit because by the end of the workout you’re unable to maintain the intensity. As a rule, start with low volume and go as hard as possible. When it feels easy, add a round or two, but drop the RPE slightly.
That’s just about it. There aren’t any hard and fast rules when it comes to HIIT in terms of the type of exercise you do. It can be done with bodyweight moves, cycling, running or weights, just as long as you’re able to do it at a high intensity. That makes some disciplines more suitable than others. Rattling out efforts on an exercise bike is significantly less dangerous than trying to do heavy barbell squats at a furious pace (please don’t do heavy barbell squats at a furious pace).
You can cycle through a circuit of different exercises for your HIIT session, or stick to one or two for all of your reps. The latter makes it easy to hit your time targets because you don’t have to switch exercise equipment during your rest periods, but doing a circuit containing a variety of moves means you can target more muscle groups during your workout.
The Benefits Of HIIT Workouts
Let’s start with the calories you’ll burn, which are many, not only during the workout but also in the hours afterwards. The latter comes from the excess post-exercise oxygen consumption (EPOC) effect, where your body burns more calories as it returns to its normal resting state after a workout and adapts to the exercise you’ve done. The EPOC effect increases with the intensity of the exercise you do, which is why HIIT is such an effective fat burner.
HIIT also increase your VO2 max, which is the amount of oxygen your body can use and is an indicator of cardio fitness. This is why any running or cycling training plan worth its salt has some form of interval training in it. Increasing your VO2 max is key to working harder for longer, helping you log a 5K personal best, for example.
There are also logistical benefits to HIIT, like the fact your workout takes less time so you can fit it into a lunch break. And while it’s tremendously hard work, the short, sharp challenge of HIIT ensures you’ll never get bored with your training.
When To Avoid High-Intensity Circuit Training
If you’re feeling worn down in the first place, HIIT isn’t the session to go for. “A common mistake with HIIT is the assumption that it trumps steady-state cardio at all times, which isn’t true,” says David Jordan from personal training gym The Fitting Rooms.
“HIIT is highly effective because it requires less time and burns calories during recovery. However, to reap the benefits of HIIT you need to attack it with a lot of energy. On days when you’re feeling less than 100% or, more importantly, you’re sore from your previous workout and are at risk of pulling a muscle, then steady-state cardio is probably more effective – and safer.”
Finally, it’s important to consider how often you can do “real” HIIT. “It’s true that HIIT can trigger protein synthesis but it also causes protein breakdown,” says Jordan. “Doing several HIIT sessions a week would be catabolic so while you’d lose weight overall, some of that loss would be muscle mass.
“If building muscle is a goal, proper weight training still needs to be your primary focus with HIIT as a supplement. A training split of two weights sessions and two HIIT a sessions a week would keep you lean, while making sure you aren’t overtrained.”
Remember: it’s supposed to be short, intense and infrequent, not an everyday effort. Recovery days are vital both for avoiding injury and for ensuring you can actually work at the intensity required for effective HIIT. Simply put, if you’re doing four or five HIIT sessions a week, it probably isn’t real HIIT, and you’re probably going to get injured.
Types Of HIIT Workouts
Beginner: Timmons Method
Developed by a team at Loughborough University, this one’s entry-level. Do 20 seconds of all-out work, followed by two minutes of active recovery (walking/freewheeling will do) or complete rest. Repeat three times, and you’re done.
Intermediate: 10-20
Also known as “reverse Tabata”, this doubles the rest and reduces the work intervals to shift the focus to anaerobic fitness. Use it if you’re aiming for power production, or if you don’t have the fitness for an all-out Tabata (explained below). Warm up for ten minutes, then do six to eight rounds.
Advanced: 10-20-30
Now things get complicated. In this plan, you’ll do five “blocks” of work, made up of 30 seconds at 30% intensity, 20 seconds at 60% and ten seconds all-out. Result? Lots of volume, at manageable intensity.
Nasty: Tabata
The most famous HIIT protocol is ideal for increasing VO2 max – as long as you do it right. Twenty seconds of all-out work, followed by ten seconds of rest, repeated eight times, improved endurance by as much as 30 minutes of steady-state cardio in a Queen’s University study. The key is keeping intensity high – if you can talk during the session, you’re getting it wrong.
