What Is High Intensity Interval Training (HIIT)

High Intensity Interval Training (HIIT)

As we know that obesity is the imbalance between energy intake and energy expenditure. Work-out is an encouraging exercise for weight loss as it does increase energy expenditure. For overweight and obese individuals, low to moderate intensity exercise is usually recommended to promote fat oxidation. Low to moderate intensity exercise are utilised to avoid injury and to improve exercise tolerance. Another reason for low intensity exercise may be to make sure that overweight/ obese individuals can keep up with the life long exercise sessions.

High Intensity Interval Training (HIIT)
High Intensity Interval Training (HIIT)
Mostly, exercise protocols to induce weight loss are focused on regular fixed exercise such as walking and jogging at low to moderate intensity. However, exercise protocols which can reduce body fat effectively and which can be carried out by obese, overweight, or people with sedentary life style are required.

While some overweight/ obese individuals may have difficulty keeping non-stop high intensity exercise, however it is very effective to develop metabolic adaptations like improved skeletal muscle fat oxidation and improved blood sugar levels tolerance.

What is a high intensity interval training workout? 

High-intensity intermittent exercise (HIIE) or High-intensity intermittent training (HIIT) is of short duration and performed above the lactate threshold, close to maximal oxygen consumption (VO2max), and with intermittent periods of rest, allowing sedentary overweight/obese individuals sufficient time to recover and perform additional high-intensity bouts. HIIT is based on the Wingate test where an “all out” effort is performed; individuals start with 3 to 5 minutes of warm-up and then cycle for 30 seconds at maximum effort against a supra-maximal workload.

Let me try to simplify it. High-intensity interval training (HIIT) has three phases

  1. Vigorous Exercise to maximum tolerable level for a short duration for example 2-3 minutes
  2. Followed by brief period of rest to recover for example 30 seconds to 1 minute
  3. Additional high-intensity exercise.
There are many evidences and studies which show that impaired utilization of free fatty acid in the skeletal muscle in obese persons is thought to be a main causative factor to the aetiology of obesity and weight gain. 

Although limited studies have been done on the effectiveness of HIIT yet, HIIT encourage metabolic adaptation of skeletal muscle and develop the skeletal muscle capability of lipid oxidization in overweight/obese people.

Studies show that HIIT is responsible for increase level of catecholamines, cortisol, and growth hormones. Catecholamine response is a significant characteristic of HIIT as catecholamines, especially epinephrine, are mainly responsible for subcutaneous and intramuscular fat release by enhancing lypolysis. 

Interestingly,  abdominal fat are shown to have more β-adrenergic receptors as compared to subcutaneous fat suggesting that HIIT may have the potential to lower abdominal fat stores.  A possible explanation for the HIIT-induced fat loss may be due to increased fat oxidation during exercise and post exercise and decreased post exercise appetite. 

Regular HIIT has been shown to increase both aerobic and anaerobic fitness considerably and HIIT also significantly lowers insulin resistance and results in increases in skeletal muscle capacity for fatty acid oxidation and glycolytic enzyme content. However, minimal dose of HIIT for the maximum health benefit remains a challenge so far.

So, what should be the intensity and duration of HIIT or how many times a week should you do HIIT?

Growing research suggests that high-intensity interval training (HIIT) is a time-efficient exercise strategy to improve cardiorespiratory and metabolic health. Only 3 HIIT sessions (30 min per session) per week have demonstrated an ability to improve aerobic capacity, skeletal muscle oxidative capacity and markers of disease risk. 

Additional research is warranted, as studies conducted have been relatively short-term, with a limited number of measurements performed on small groups of subjects. Although "lack of the time" remains probably one of the most commonly cited barriers to regular physical exercise participation, time efficient HIIT is an encouraging technique for attaining maximised performance and maximizing health advantages.

Is there any specific exercise which is only for HIIT? 

What is the best high-intensity interval training? This is a very common question which individuals face while planning for HIIT. So here are some examples of HIIT activities. This is not an all inclusive list.

  • Treadmill Exercise
    Treadmill Exercise
  • Jogging,
  • Jumping jacks,
  • Push ups
  • Skipping rope,
  • Stair climbing,
  • Uphill walking
  • Cycling
  • Swimming etc.

The principle remains the same - Start with warm up and reach up to maximum threshold then take a short period of rest and then again intensify the activity.

The intensity and duration of exercise mainly depends on your over all health condition, underlying disease and level of exercise tolerance etc,


  • Safe and tolerable
  • Reported to be more enjoyable than the traditional exercise regimes
  • Time-efficient
  • Cost effective and economical
  • Enhance cardiorespiratory fitness
  • Reduce metabolic risk factors
  • Optimize fat oxidation


We have seen and discussed how HIIT is beneficial for health especially in weight loss and fat reduction. However, there are some disadvantages also.

  • HIIT may be difficult to perform for person suffering from any systemic disease.
  • HIIT may cause severe fatigue.
  • Excessive load of exercise may result in over training which increases the risk of injury.


  • It is highly advisable to consult your physician before starting HIIT regime especially if you have history of any systemic disease or disorder such as heart, lungs or kidney disease etc.
  • Always go with your tolerance level. Intensify your HIIT without causing any harm to you.
  • Take proper rest and allow time for recovery during and after HIIT to avoid fatigue and over training
  • Excessive load of exercise may result in over training which increases the risk of injury.


HIIT is beneficial in weight loss program as it helps in burning calories. HIIT is great approach for building muscle. HIIT is helpful in reducing blood pressure and blood sugar. Another benefit of HIIT is that promotes brain health by improving mental health and memory. HIIT is cost effective and economical and usually does not require expensive or highly sophisticated gym equipment. It is time efficient and its activities are enjoyable as compared to other traditional exercise. All these factors make HIIT a popular exercise for physical fitness and for weight loss program.

Also Read:

Is Exercise The Most Important Factor When Treating Obesity?

1 comment:

  1. I love a foot HIIT workout!!! Great information!!!


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