What is HIIT?
Many people ask me whether they should include High Intensity Interval Training in their program due to its highly promoted benefits. High intensity interval training (Commonly referred to as HIIT) involves alternating between high intensity and low intensity bouts of cardio. The popularity of this form of cardio has exploded in recent years and with good reason, with some fitness professionals unequivocally touting the benefits of HIIT without question. However, like any form of training HIIT has both its benefits and detriments that need to be considered when deciding whether or not to include it in your training program. In this article I’ll outline the pros and cons of HIIT and make recommendations about whether it should be a part of your exercise regime based on your fitness goals.
Benefits of HIIT
Recent research highlights that HIIT can be a more effective and efficient form of cardio when compared to traditional ‘steady-state’ cardio when it comes to fat loss.1 The reason for this is simple, HIIT burns more calories in less time per session (compared to steady state cardio). Perhaps even more impressive is the fact that HIIT has the potential to stimulate calorie burning post workout.2 This effect is also known as Excess post- exercise oxygen consumption (EPOC). This effect seems to be intensity dependent meaning that the harder you train the more calories you burn post workout. Some research suggests that this effect can last for up to 36 hours post workout which translates to approximately 150 additional calories burned per day. Finally, some studies have shown HIIT to potentially build muscle if the correct exercises are performed which further highlights the effectiveness of this form of cardio.3
While HIIT is an excellent fat burning tool there are several disadvantages of this form of cardio. Primarily, HIIT has the potential to deplete vital energy stores and your body’s central nervous system. The high intensity nature of this form of cardio is very similar to resistance training. Therefore, HIIT can make it somewhat challenging for you to train with the intensity required to build muscle, strength and/or power if done in conjunction with a regimented resistance training program. In addition, performing HIIT alongside a resistance training program puts you at an increased risk of overtraining. Overtraining is often characterised by increased fatigue, increased catabolic stress hormones (mainly cortisol), reduced testosterone levels and a compromised immune system. The result of this is that gains in strength and muscle are stunted.
With all this in mind, is it wise to make HIIT an integral part of your fitness program? If your goal is to maximise strength, power or muscle gains then I would recommend that you steer clear of this type of training. Instead, if you want to perform some form of cardio while attempting to build muscle then I would advocate a low-moderate steady state cardio approach in order to minimise the strain on your central nervous system. However, if you are attempting to maximise fat loss or want to simply improve your cardiovascular health and/or fitness then High Intensity Interval Training can be an extremely effective and time effective tool for doing so. As with everything, weigh up the positives, negatives and your goals to make an informed decision about whether to include it in your program.