To HIIT or not to HIIT? (High Intensity Interval Training)

High intensity interval training, or HIIT; a term you may have heard buzzing around lately. Perhaps you’ve wondered what it is or if it’s something that could benefit you…or maybe not…but now you have! High intensity interval training is not a new concept, like many fitness trends, but this type of training has recently started to gain in popularity for many different types of training from weight loss and cardio training to sports training. While it is very demanding and not recommended for beginners, it can bring about a lot of benefits and make a good boost to your traditional cardio training.

HIIT is a specialized type of cardiovascular training that has many different variations. It consists of a circuit of high intensity exercise for a short time, followed by rest or low intensity exercise. The programs can vary in time, number of sessions and different levels of intensity during the low intensity interval. The key to HIIT is to reach max effort during the high intensity interval which is about 90% of your maximum heart rate (max HR). The time of the high intensity interval can also vary, anywhere from 6 seconds to 4 minutes, or sometimes longer. A few examples are 10 seconds max effort and 10 seconds rest or 1 minute max effort and 2 minutes rest, there is really no end to the time variations you can make. The session lengths typically last from only a couple of minutes and up to around 20 minutes, depending on your time ratios. The ratios generally used for the high intensity interval and low intensity interval are 1:3, 1:2, 1:1 or 2:1. You can also vary the type of exercise; sprints, rowing, cycling and swimming are just a few of your options.

This type of training is thought to have many benefits which include metabolic adaptations, an increase in caloric burn during and after your workout, improvements to endurance and a limit to muscle loss in comparison to traditional cardiovascular training of longer time periods. It also has the added benefit of shorter workout durations. However, there are several drawbacks as well; HIIT is not for beginners, there is a higher risk for injury, more recovery time between sessions is needed plus it is very demanding and is much easier to over-train. A warm-up and cool-down is especially important. When starting this type of program you will need to build up gradually so you do not injure yourself or overdo it. You also need to be able to exercise for at least 20-30 minutes at 70-85% of your max HR without exhausting yourself. If your heart rate does not drop back down to about 70% during the recovery phase, it is suggested that you may need to shorten the high intensity interval portion or lengthen your recovery interval.

Many studies done on HIIT have found that it awards you similar changes to your body that traditional endurance training offers. Studies have shown it to improve both the anaerobic and aerobic systems while traditional cardio training only improves the aerobic energy system. Ok, you may be wondering, why would I want to improve my anaerobic system…wait, what the heck is this anaerobic system? …Well, an explanation of this can get a bit complicated but basically you have two energy systems in your body, aerobic and anaerobic. Very simply put, aerobic exercise means your muscles use oxygen for fuel while, for anaerobic exercise, they do not. Your anaerobic energy system has a duration of about 2 minutes while the aerobic system is primarily used during activities that are greater than approximately 2 minutes. Both aerobic and anaerobic exercise is needed for balanced and healthy lifestyle. Aerobic exercise is great because it strengthens your cardiovascular system and brings with it many benefits, such as lower blood pressure and a lower risk of cardiovascular disease. Anaerobic exercise also has benefits of its own. It helps you become stronger, leaner and more powerful; weight lifting is a form of anaerobic exercise. HIIT is typically linked to sports that depend on the anaerobic energy systems and is thought to be less effective on the aerobic system, but recent studies have shown that high intensity interval training can help increase your VO2max more than traditional cardio training (VO2max is how we gauge a person’s cardiorespiratory endurance).

In inactive and recreationally active people, HIIT has been known to improve endurance performance more than traditional low to moderate cardio training alone and has shown to be beneficial improving endurance performance in athletes as well. Two or three sessions a week is enough to improve performance without causing too much stress on your body. Combining traditional low to moderate intensity training with careful use of this training seems to be best for developing endurance performance.

I see many claims that it can burn more calories than regular training but studies have shown differing results on EPOC (“excess post exercise oxygen consumption” or simply how many calories you burn after an exercise session). The research has shown that your caloric burn from HIIT training seems to equal that of traditional cardio training meaning that either type will benefit weight loss.

High intensity interval training can be a great change to your exercise routine and a good complement to your regular cardio training. Remember though, that when starting a HIIT program, just as any other, it’s important to start slow and build gradually. Try it for your next cardio session; just be warned, to say it’s just demanding is an understatement. If you have any questions about HIIT training please feel free to contact Seattle Athletic Club Downtown Fitness Director Jacob Galloway.

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