Is HIIT training for you? Pros and Cons

Due to the recent pandemic HIIT became a go to training method for all the home training workouts and videos floating around.

A bonus for HIIT was the confirmation that even though results in body composition change were similar, it can be achieved in more time-efficient manner than moderate intensity, continuous training.

So I will give you few points and you can decide for yourself if it’s suitable for You!


It makes you younger

Research at the Mayo Clinic suggested that HIIT can actually reverse the signs of ageing at a cellular level. This was found to be due to improved mitochondrial function, a decline of which is common in older adults and improved protein synthesis that enhanced energetic function and led to hypertrophy, thereby countering the impact of sarcopenia.

Robinson et al, Enhanced Protein Translation Underlies Improved Metabolic and Physical Adaptations to Different Exercise Training Modes in Young and Old Humans, Cell Metabolism March 2017

Short bursts of HIIT (85% of maximum working heart rate) improve cholesterol and blood sugar among type 2 diabetes patients more significantly than continuous low intensity exercise (working at 65%). This is somewhat revolutionary as, historically, diabetes management programs have focused primarily on low intensity exercise.

Researchers were unclear why shorter bursts of high intensity exercise lead to more significant improvements compared with continuous low intensity exercise other than to suggest that high intensity exercise uses energy in a different way.

Francois and Little, Effectiveness and Safety of High Intensity Interval Training in Patients with Type 2 Diabetes, American Diabetes Association, January 2015


The feel-good factor

HIIT results in increased endorphin release in the brain, which plays a role in dampening physical and emotional stress. Comparing moderate and high intensity exercise, researchers have identified that HIIT significantly increases the release of endorphins and other opioid peptides in the brain areas controlling pain and emotion.

It is suggested this exercise-induced endorphin release determines whether we maintain motivation during exercise, pushing ourselves to continue working out despite exhaustion, thereby predisposing better results.

As opposed to continuous exercise, HIIT offers a sense of accomplishment after each bout of effort, and the recovery bout allows a moment to reflect positively on the work done, but also acts as something to look forward to going into the next effort bout. The end result is that the protocol is perceived as being more pleasant.

Saanijoki et al, Opioid Release after High-Intensity Interval Training in Healthy Human Subjects. Neuropsychopharmacology, July 2017


Beat the cheat meal

Cardiovascular diseases, such as heart attacks and strokes, are one the leading cause of death worldwide, and it’s known the foundations of these conditions are formed during youth. An impairment in the function of blood vessels is thought to be the earliest event in this process, and this is known to occur in the hours immediately after consuming a high fat meal. However, the good news is, HIIT before a high fat meal can potentially offer a preventive quality.

Researchers compared HIIT against continuous moderate intensity exercise on blood vessel function in adolescent subjects after they had a high fat milkshake. It showed that approximately 25 minutes of moderate intensity cycling prevented the fall in blood vessel function after the high fat meal, but just 8 minutes of high intensity cycling not only prevented this fall, but improved blood vessel function.

Bond et al, Exercise Intensity and the Protection from Postprandial Vascular Dysfunction in Adolescents, American Journal of Physiology – Heart and Circulatory Physiology, March 2015





Could be too challenging

Dr Paul Bedford, an internationally renowned retention specialist, says the harder you work some clients, the sooner they’ll leave you. Unless managed carefully, HIIT workouts could have a negative impact on the likelihood of them sticking to an exercise regime, particularly those new to exercise. Gym floor surveys by a multi-site operator established that members who’d been exercising for some time were keen to step up and try HIIT, but new exercisers who thought it looked fun, discovered the discomfort they experienced was so great, many only did it once.

Abigail Harris, Pain Response, Health Club Management, June 2019

Risk of injury

A study that shows there has been an increase in the number of injuries since 2007 links the increase with the growing popularity of HIIT. A team analyzed records in the National Electronic Injury Surveillance System from 2007 to 2016, noting a total of nearly 4 million injuries. They found a steady increase in gym injuries (60,000 per year), which mirrored the growth in the number of people doing HIIT workouts.

In its conclusion, the report states that given increases in injuries related to HIIT workouts, participants should be educated on how to minimize them. Since knee and ankle sprains are most common, pre-strengthening and technique focus sessions would be of great value to new clients.

In addition, since it’s suggested that just one extreme indoor cycling class can be enough to trigger rhabdomyolysis, where muscle fibers break down and their contents leak into the bloodstream and can in turn lead to kidney failure, it’s important that participants understand the difference between ‘high’ and ‘dangerously high’.

Rynecki et al, Department of Orthopedics, Rutgers New Jersey Medical School, Injuries sustained during high intensity interval training: are modern fitness trends contributing to increased injury rates? The Journal of Sports Medicine and Physical Fitness, Feb 2019

Too much of a good thing

If HIIT produces great results, then surely more frequent workouts will lead to even better results? Seems logical but it’s not the case according to recent research that suggests any more than 40 minutes of HIIT in a maximum training zone, per week, can reduce performance and potentially result in a greater risk of injury.

The study measured effects of HIIT by examining cortisol and testosterone concentrations in saliva samples and it appears those who do more than 40 minutes of HIIT per week are unable to produce a positive stress response.

Gottschall, Penn State University, 2018 American College of Sports Medicine Annual Meeting


Not suitable for Complete Beginners and Elite athletes

Following HIIT workouts, beginners showed fragmentation of the ryanodine receptor, which leads to impairment of the muscle cell’s ability to contract. However, the cells react to this stress by increasing their endurance capacity, making them better able to withstand the next bout of HIIT.

Unfortunately, endurance athletes don’t get the same benefits due to having developed a more effective antioxidant system that dampens this effect. It’s true to say that some elite athletes might be too fit for HIIT.

Place et al, Ryanodine receptor fragmentation and sarcoplasmic reticulum Ca2+ leak after one Proceedings of the National Academy of Sciences, November 2015


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