Separating the wheat from the chaff on the current fitness industry hot topic
The recent rapid and wide-spread growth of the boutique fitness sector has been greatly attributed to High Intensity Interval Training (HIIT) and it appears no trainer is worth his or her salt unless deploying this, reportedly, most fashionable of fitness trends. According to the American College of Sports Medicine, HIIT has featured in the top 3 most popular workout modes for the last 6 years, as a result of which the mainstream media have jumped on it, reporting with varying degrees of accuracy regarding what it is, what are the benefits and why it works.
For me, education is empowerment. So reminding yourself of the basics and then sharing this information with your clients not only enhances your reputation as a knowledgeable professional, but helps them to understand your modus operandi and to value it above the claims from the mavericks in our midst who promise unrealistic results in impossibly short time periods, usually with little effort.
HIIT - 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
MYTH - just for Gen Y and Gen Z
A program of high intensity resistance training (85–90% 1RM) demonstrated that elderly men can not only tolerate these workloads but will exhibit muscular changes similar to their younger counterparts. The suggestion is that high intensity resistance training can be practiced by healthy ageing men and can be safely incorporated as part of a fitness plan for this population.
Hikida et al, Effects of High Intensity Resistance Training on Untrained Older Men - Muscle Fibre Characteristics and Nucleo-Cytoplasmic Relationships, The Journals of Gerontology, July 2000
HIIT - ideal for tackling diabetes
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
MYTH - helps improve exercise adherence
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
HIIT - 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
MYTH - no injury risk
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
HIIT - beat the cheat meal
Cardiovascular diseases, such as heart attacks and strokes, are the leading cause of death in the UK, 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
MYTH - 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
HIIT - fusion workouts with bite
In the never-ending search for stimulating exercise formats, HIIT has infiltrated way beyond treadmills, rowers, bikes and burpees, and has given birth to some challenging combination workouts.
HIIT YOGA provides a workout for both the body and mind, boosts the metabolism, deepens stretches and gets the endorphins going. The HIIT element of the workout is a combination of bodyweight movements lasting 20 minutes and then the yoga postures are practiced to practice balance and promote recovery.
LIFTED is a workout combining HIIT with meditation, the selling point being that it mimics the rhythm of real life where we aren’t always in the perfect place to meditate. Rather, we’re more often running around and breathless. The workout begins with guided meditation followed by mindful movement and culminates in an intense finisher.
SWIM HIIT uses moves from martial arts, yoga and Pilates, as well as weights and deep stretches, to supercharge the aquatic exercise experience. Driven by the fact that water is more resistant than air and reduces pressure on the joints, people can work harder without worrying about aches and pains.
MYTH - it’s a new trend
It’s well documented that Finnish runners Hannes Kolehmainen and Paavo Nurmi utilised HIIT in preparing for the Olympics in 1912 and 1924, respectively. More famously, Franz Stampfl made HIIT a key ingredient in preparing Roger Bannister to break the 4-minute mile in 1954, a landmark many experts at the time thought was beyond the capability of the human body.
HIIT - for a new heart
Survival rates for recipients of heart transplants have grown in recent years, furthering a desire for researchers to look at how to maximize the benefits of exercise in improving quality of life.
HIIT has been proven to be of benefit to heart transplant recipients with workouts helping to increase exercise capacity, maintain control of blood pressure and improve resting heart rates.
Researchers also found that HIIT increased maximum oxygen uptake by 17% compared to just 10% in the moderate intensity group.
Dall et al, Effect of High Intensity Training Versus Moderate Training on Peak Oxygen Uptake and Chronotropic Response in Heart Transplant Recipients, American Journal of Transplantation, August 2014
MYTH - it’s the perfect workout for beginners and elite
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
HIIT & MYTH - best route to fat loss
A meta-analysis of 36 studies revealed that HIIT is no better than moderate intensity continuous training in terms of body fat percentage reduction, both showing similar results. However, HIIT showed a greater reduction in total absolute fat mass. This difference was attributed to several factors, including supervision of exercise, walking/running as the exercise modality and age.
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.
Viana, et al, Is interval training the magic bullet for fat loss? A systematic review and meta-analysis comparing moderate-intensity continuous training with high-intensity interval training, British Journal of Sports Medicine, May 2019
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