Annabel investigates….

Can doing too much High Intensity Interval Training (HIIT) be doing more damage than good….


The physical activity guidelines recommend completing at least 150 minutes of moderate to high intensity aerobic exercise each week. But making sure you aren’t overtraining is a key component to your exercise regime. Ensuring that you have the right balance between aerobic, resistance and mobility training is key to higher performance. Today, Annabel and the Longevity Exercise Physiology teams at Drummoyne, EdgecliffMarrickvilleBella VistaRandwick, PymbleBalmain and Neutral Bay discuss the benefits and possible consequences of adding excessive HIIT training sessions to your exercise program.


What exactly are HIIT training sessions?

This type of training is specific in building an individual’s strength as well as being able to spike your heart rate to high intensities. They consist of repeated periods of high-intensity work, followed by periods of recovery. For example, completing 30 seconds of running on the treadmill followed by 30 seconds resting and repeating this for several minutes, is an example of a typical HIIT session. These sessions can be effective for those who are time poor, as a 20-minute session can still be very effective. The benefits of completing HIIT training consist of higher and more efficient fat burning and building muscle power in a short amount of time. HIIT was originally developed to improve the aerobic capacity of athletes, and individuals of similar aerobic capacity dominated sports such as running and swimming. HIIT training can also be used within high volume strength training, aimed at improving endurance and performance longer term.

Although much of social media may be leading you to believe that HIIT is the most efficient training method, doing too much may be doing your body a disservice. Completing over the recommended amount can lead to exhaustion, disrupt your sleep patterns, and leave you more prone to injury and having greater mood swings. While there are many benefits to completing a single HIIT workout the analysis on the benefits of completing frequent higher intensity workouts and whether the benefits decrease if you do this training too often have not been well studied. We are here today to sift through the information and determine the benefits and the consequences of performing too many HIIT workouts.

One article by Mikael Flockhart, noted that in individuals completing HIIT training, in the shorter term, it improved performance, as this led to greater development of mitochondria within the body. Mitochondria helps convert the energy we take from food into energy that the cell can use. But over the longer term, adding in more high intensity aerobic sessions, fitness gains and mitochondrial function started to depreciate. The effects were a greater disturbance in blood sugar levels, decreased mental health and poorer levels of sleep (Flockhart et al., 2021). Additionally, the specific exercises that are usually involved in HIIT sessions, place large pressure on the joints, due to the jumping nature of these exercises, and can pose risk to the individual.

Associate professor of Kinesiology at Penn State University, Jinger Gottschall, conducted some research around individuals performing HIIT training, in which she noted that those who completed higher volumes of this type of training were unable to reach their maximum heart rate regularly and complained of symptoms related to overtraining. When you begin to exercise, your body uses up the sugar within your body and once that has been depleted, your body uses glycogen which is an energy source stored in your muscles and liver. These glycogen stores are replenished when the body is recovering/resting. During HIIT workouts your body does not have the adequate time to rest, causing the glycogen stores to not be fully replenished. This causes the body to feel slower and weaker during your workouts and can negatively effect the way your body recovers from exercise (Mackenzie, 2021).


“Those who completed higher volumes of this type of training (HIIT training) were unable to reach their maximum heart rate regularly and complained of symptoms related to overtraining.”

The studies have concluded that about 90 minutes a week is a safe amount of HIIT for healthy people, according to a new study. The individuals who completed this amount of training over time, were able to generate more power during the workout and had better stamina. They also showed improvements to their mitochondria and decreased rates of injuries. It is essential to balance out this type of training with lower intensity exercise, to ensure that you do not damage your mental and physical health. It is important to be aware, that if you have not undertaken this type of training before, studies strongly suggest that anyone interested in high-intensity interval training start will small HIIT durations.


If you are looking for an individualised exercise program, to ensure you are getting the right balance of resistance, aerobic and mobility training within your week, give Longevity Exercise Physiology Edgecliff, Pymble, Marrickville, Randwick, Drummoyne, Balmain, Bella Vista, and Neutral Bay a call on 1300 964 002 to book in a session today!


Written by Annabel Bergman



Flockhart, M., Nilsson, L., Tais, S., Ekblom, B., Apró, W., & Larsen, F. (2021). Excessive exercise training causes mitochondrial functional impairment and decreases glucose tolerance in healthy volunteers. Cell Metabolism33(5), 957-970.e6. doi: 10.1016/j.cmet.2021.02.017

Mackenzie, M. (2021). Is It Possible to Do Too Much HIIT? A New Study Says Yes. Shape.