5 benefits of HIIT to lose weight and improve physical appearance

Are you already thinking about how to improve your physique for your next holiday or an upcoming event? Among the many workout programmes offered by magazines, the web and fitness centers, HIIT - High Intensity Interval training was a well-established trend in 2018 and seems to be going no-where in 2019! In this article, we explain what HIIT really is and compare this to the many programmes often promoted as HIIT workout. We’ll also review the latest research and give you the skinny on which method is best for fat loss – HIIT or steady state workout.

What is HIIT?

Boy runs on the stairs in the beach
High-Intensity Interval Workout - HIIT is a specific type of interval workout that uses short periods of very high-intensity work, alternating with very short periods of active or passive recovery. HIIT workout is always a type of interval workout BUT not all interval workout is HIIT workout. An important distinction that is often not appreciated among the lay press or fitness professionals wanting to jump on the latest bandwagon.
Scientific studies show that this type of workout can have an important influence on weight loss and increased athletic performance of those who practice it. The most widely promoted benefit of this type of workout is the increase in basal metabolic rate in the hours following the workout, known as Excess post-exercise oxygen consumption (EPOC). This effect causes a series of biochemical processes that increase oxygen consumption (and therefore energy expenditure) in the post-workout period.
Another benefit of HIIT may be the effect of intense muscular effort, which causes important physiological and metabolic adaptations at the cellular level, such as increased insulin sensitivity with positive repercussions on fat metabolism. The ability of HIIT to reshape skeletal muscle (photo skeletal muscle) is related to the need to recruit the larger muscle fibers (especially type II fibers) as well as the smaller ones.
Foam roller training
Moreover, this type of workout places the aerobic energy system under heavy strain and stimulates a need to increase the mitochondrial capacity of the body. Mitochondria are organelles responsible for producing energy aerobically in cells, an increase in their number and function will be reflected in an improvement in the ability to produce energy via the aerobic energy system.

Mitochondria and fat metabolism

To eliminate excess body fat, the human organism must use fatty acids as an energy source, and this happens within the mitochondria. Mitochondria are organelles present in the cells and are responsible for the breakdown of fatty acids using oxygen known as the aerobic energy system. Imagine mitochondria as power stations in the cells, the more and larger the mitochondria the more energy can be produced, and the more fuel used. In this case, the fuel will be a mixture of fatty acids and glucose/glycogen.
Girl runs around Omnia
In order to develop number and size, high-intensity workout is without a doubt the fastest and most successful method. The other choice would be long-lasting, time-consuming and monotonous aerobic activities.

To burn one gram of fat, you need two liters of oxygen.

Our metabolic furnaces

The number and volume of mitochondria vary across the population dependent on genetics and the type of activity practiced by the individual. Mitochondria are mainly located in the type 1 muscle fibers. Losing this type of muscle mass typically means reducing the number of mitochondrial power stations and reducing the ability to metabolize fatty acids as fuel.

HIIT can eliminate the problem of reduced muscle mass that can occur from spending countless hours performing moderate-intensity aerobic exercise because the higher intensity stimulates a simultaneous increase in muscle mass and mitochondrial capacity. Many scientific studies have shown that HIIT has a great effect on (PGC)-1α, a receptor that is considered the main regulator of mitochondrial biogenesis in skeletal muscle.

Repeating on steps is a high potential aerobic activity

Why HIIT and not steady state workout?

With low-intensity steady state workout, there is a risk of not improving body composition. It is true that exercises such as running are an effective way to expend calories, in twenty minutes you can burn about 300 at a steady pace, but the additional benefit of performing a HIIT workout is the effect of muscular conditioning.
HIIT workouts activate metabolism in a different way than low-intensity steady state workouts. A greater amount of muscle mass and fiber types are stimulated during HIIT workout than by working at a lower intensity in a single repetitive movement pattern. Over time this can lead to an increase in muscle mass and the associated increase in resting metabolism.

It is not a useful comparison to simply calculate the calories burned during each type of workout, because this is not the same as the total energy expenditure resulting from the workout once the post-workout energy consumption (EPOC) is accounted for and does not consider the increase in muscle mass possible by performing HIIT workout regularly over time.

Not only aesthetic benefits but also health benefits

Jumping rope
Aerobic activity at a moderate to vigorous intensity has long been recommended for all people of all ages as it provides better health of the heart, circulation and respiratory systems.
The same benefits can also be achieved through HIIT. HIIT is commonly used both in sports to increase endurance and aerobic power and in non-specific activities aimed at promoting well-being. It has been demonstrated that 4-minute sessions, carried out at high intensity and repeated 3-4 times consecutively, can have the same results as longer-duration sessions at lower intensities (using primarily aerobic metabolism) as regards the workout of athletes of a level.
Running on stairs

5 benefits of HIIT training

By summarizing the training Hiit allows you to get a lot of results:

  • Increasing muscle glycogen content at rest
  • Increasing the ability to use fatty acids
  • Improved peripheral vascular structure and function
  • Performance improvement
  • Improvement of the maximum oxygen uptake

What is the best HIIT protocol for fat loss/ weight loss?

There are several research-based HIIT protocols.  From the well-known Tabata method (Tabata, 1997), which provides for the repetition of the same exercise for 6-7 times alternating 20" of high intensity work with 10" of recovery, to circuit workout, from the EMOM method to the classic interval method, from Timmons, Johnathan Little and Martin Gibala to Craig Ballantyne etc.
High skip with rope
It is the intensity achieved that makes the workout effective, as opposed to the exercise selection. The necessary intensity will be easier to achieve with some movements than others, but the most whole body or lower body compound movements can be used to achieve an effective workload. To raise the heart rate and increase or reduce the workout load, key variables can be used to progress or regress an exercise:

  1. Range of movement
  2. Speed of movement
  3. The complexity of the exercise
  4. Load added to the exercise (e.g. from a free body squat to one with the rocker arm)
  5. TUT (Time under tension)
  6. Amount of muscle mass used in the exercise (e.g. progression from a bodyweight squat to an overhead squat)

How long does a HIIT session need to be to get results?

Running in the city
There are many articles that present HIIT programs of about 20 minutes duration to get results, but is it necessary?

In part, yes, 20 minutes of high-intensity workout contributes significantly to the consumption of fat mass, if it is accompanied by a correct and personalized dietary program. The central part of the workout cannot have a long duration (> 30-40 minutes) because of it impossible to maintain a sufficiently high intensity to be considered HIIT for this duration. If prolonged, this type of workout can lead to a reduction in the quality of exercise technique with a consequent increase in the risk of injury and potentially reduced recovery adaptations following workouts.

20 minutes of high-intensity work contribute significantly to the consumption of fat mass, provided that it is accompanied by a correct and personalised dietary programme.

Many studies have been carried out showing that 20 minutes of activity per day led to a significant reduction in fat mass after one month and an increase in lean mass.

Warm up and cool down

One clarification must be made regarding HIIT workout session structure. To achieve the best possible results during a HIIT workout session, a thorough warm-up is necessary to prepare the body for the intense exercise and an enough cooldown phase should be included after the main session for safety.
Jumps to the steps
The warm-up phase is essential for injury prevention. In addition to preparing the body for the activity, this phase starts the metabolic processes for energy production. If done properly, the warm-up allows you to have a proper energy consumption at the end of the workout will weigh on the calculation of calorie expenditure.
After 20-25 minutes of high-intensity workout, our body has a good number of fats ready to be used for energy purposes. It would be a shame not to take advantage of this moment and benefit from it. For this reason, the advice is to continue workout after the main session with less intense activity and keep it for about 15 minutes.

Example HIIT workout session plan

Here's a brief outline of high-intensity training:

  • Warm up (10'): Start the workout by performing multi-joint exercises alternating with locomotion exercises (running, walking, jumping, jumping forward, etc.) to mobilize joints, take muscles through a full range of motion, and raise heart rate gradually.
  •  Main session (20-25'): The choice is vast: For example, Circuits of 6-8 exercises alternating 20-30" of work with 10-15" of rest, or 8 rounds of the same exercise doing 20" of work and 10" of recovery or, a classic interval where you can alternate exercises to run, rowing, jumping rope.
  • Cool down (10-15’): Initially continue the workout with a low impact activity. Jogging on the spot may be a choice or even continue the previous circuit at a significantly decreased intensity. Always leave 5' for stretching and relaxation exercises at the end of the workout.
The warm up phase also has a very important function. In addition to preparing the body for the next activity, this phase also initiates metabolic processes for energy production. If done properly, the warm up allows you to have a proper energy consumption that at the end of the workout will weigh on the calculation of calorie expenditure.

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