High-intensity interval training (HIIT) is one of the biggest buzzwords in the fitness industry because of its potential to torch maximum calories in a minimum amount of time.
The basic idea to do short periods of all-out work followed by short periods of active rest to make the body work harder (and burn more calories) than it might during extended steady-state cardio.
Of course, while most people who’ve been in a gym recently probably know what HIIT is, very few actually do it in a way that will maximize fat loss. In addition, most don’t apply the principle of progressive overload to their routines which eventually leads them to a strength and fat-loss plateau and prevents them from reaching the low levels of body fat they’re aiming for.
Let’s explore the 3 most important variables of HIIT: the best exercises for preserving strength and burning fat during HIIT, the optimal intensity for work intervals, and how to progressively overload to reach your goal levels of body fat.
Studies have shown that “the more a cardio exercise mimics the movements used in muscle-building movements, the less it hinders strength and muscle growth”. In other words, you should be performing forms of HIIT that highly mimic weightlifting movements in order to preserve muscle mass during a cut. The 3 best exercises for this reason are rowing, cycling, and sprinting since they highly mimic movements such as the squat and seated row.
Studies have shown that in order to reap the maximum benefits from HIIT (EPOC, hormonal response and increased fatty acid oxidation), you need to reach between 85%-95% of your max heart rate during the work intervals. You can tell if you’re at this level of intensity if you’re breathing so hard that you’re unable to maintain a normal conversation with someone. This is where most people fail in doing HIIT effectively; they simply aren’t pushing hard enough to reap the benefits of HIIT.
A good starting point is to perform 20s of HIIT at 80% max intensity with a 40s rest interval (work:rest ratio of 1:2). If you’re already a HIIT veteran, bump the intensity up to around 90-95%. Research has shown that it’s more effective to perform HIIT intervals with a lower duration (e.g. 30 seconds) as opposed to longer intervals with less intensity. Stick to a lower duration intervals and push hard.
Although many people don’t think about applying progressive overload to HIIT (or cardio in general), it’s the key to avoiding fat loss plateaus and achieving low body fat goals. There are 5 variables you can adjust to overload your workouts:
- Increase the intensity of your work interval.
- Increase the duration of your work interval.
- Decrease the duration of your rest interval.
- Increase the number of cycles performed.
- Increase the frequency of your workouts.
Progressively overload your workouts using one (or more) of the variables whenever you feel too comfortable with your workouts or when your fat loss has plateaued (which usually happens every 2-3 weeks).
Keep in mind that you should perform HIIT in conjunction with a weightlifting routine for the best results, and you can also incorporate steady-state cardio during rest days or days where you feel you need a break from HIIT.
The Bottom Line
- Cycling, rowing, and sprinting are the best forms of HIIT to preserve muscle mass while losing fat
- You need to reach ~85-95% of your max heart rate during the work intervals in order to reap the majority of benefits from HIIT
- Apply progressive overload every 2-3 weeks using the 5 variables to avoid reaching fat loss plateaus
Ramos JS, Dalleck LC, Tjonna AE, Beetham KS, Coombes JS. The impact of high-intensity interval training versus moderate-intensity continuous training on vascular function: a systematic review and meta-analysis. Sports Med. 2015 May;45(5):679-92.
Gergley JC. Comparison of two lower-body modes of endurance training on lower-body strength development while concurrently training. J Strength Cond Res. 2009 May;23(3):979-87.