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High Intensity Interval Training

The popularity of high intensity interval

training is all the time increasing. High intensity interval training sessions are usually called HIIT workouts. This type of training comprises of repetitive stints of high intensity effort followed by various recovery times.


The intense work periods may range from 5 seconds to 8 minutes, and are performed at 80% to 95% of the individual’s theoretical maximum heart rate. The recovery periods may last equally as long as the work periods and are usually performed at 40% to 50% of a person’s theoretical maximal heart rate. The workout continues with interchanging between work and relief periods totalling 20 to 60 minutes.


What are the benefits of HIIT?

HIIT training has been shown to improve:

  • Aerobic and anaerobic fitness

  • Blood pressure

  • Cardiovascular health

  • Insulin sensitivity (which helps the active muscles more readily use glucose for fuel to make energy)

  • Cholesterol profiles

  • Abdominal fat and body weight while maintaining muscle mass.

Why is HIIT Training so Popular?


 HIIT training can easily be adapted for people of all fitness levels and special conditions, such as overweight and diabetes. HIIT workouts can be carried out on all exercise modes, including cycling, walking, swimming, aqua training, elliptical cross-training, and in many group exercise classes. HIIT workouts provide similar fitness benefits as continuous endurance workouts, but in shorter periods of time. This is because HIIT workouts tend to burn more calories than traditional workouts, especially after the workout.


The post-exercise period is called “EPOC”, which stands for excess post-exercise oxygen consumption. This is generally about a 2-hour period after an exercise session where the body is restoring itself to pre-exercise levels, and therefore using more energy. Because of the vigorous contractile nature of HIIT workouts, the EPOC generally tends to be modestly better, adding about 6 to 15% more calories to the overall workout energy expenditure.


How do You Develop a HIIT Exercise Program?


When planning a HIIT program, consider the duration, intensity, and frequency of the work intervals and the length of the recovery intervals. Intensity during the high intensity work interval should range ≥ 80% of your theoretical maximal heart rate. As a good subjective indicator, the work interval should feel like you are exercising “hard” to “very hard”. Using the talk test as your guide, it would be like carrying on a conversation, with difficulty. The intensity of the recovery interval should be 40-50% of your estimated maximal heart rate. This would be a physical activity that feels very comfortable; in order to aid you recover and prepare for your next work interval.


The relationship of the work and recovery interval is important. Many studies use a specific ratio of exercise to recovery to improve the different energy systems of the body. For example, a ratio of 1:1 might be a 3-minute hard work (or high intensity) stint followed by a 3-minute recovery (or low intensity) stint. These 1:1 interval workouts often range about 3, 4, or 5 minutes followed by an equal time in recovery.


Another popular HIIT training protocol is called the “sprint interval training method”. With this type of program the individual does about 30 seconds of ‘sprint or near full-out effort’, which is followed by 4 to 4.5 minutes of recovery. This combination of exercise can be repeated 3 to 5 times. These higher intensity work efforts are typically shorter bouts (30 seconds with sprint interval training).

What are the Safety Issues with HIIT Training?


Persons who have been living rather sedentary lifestyles or periods of physical inactivity may have an increased risk of coronary disease from engaging in high intensity exercise. Family history, cigarette smoking, hypertension, diabetes (or pre-diabetes), abnormal cholesterol levels and obesity are all factors that might increase this risk. Medical clearance from a doctor may be an appropriate safety measure for anyone with these conditions before staring HIIT or any exercise training.


Before beginning HIIT training a person is encouraged to establish a “base fitness level”. A base fitness level is consistent aerobic training (3 to 5 times a week for 20 to 60 min per session at a somewhat hard intensity) for several weeks that produces muscular adaptations, which improve oxygen transport to the muscles.


Establishing appropriate exercise form and muscle strength are important prior to engaging in regular HIIT to reduce the risk of musculoskeletal damage. Regardless of age, gender and fitness level, one of the keys to safe participation of HIIT training is for all people to modify the intensity of the work interval to a preferred challenging level. Safety in participation should always be top priority, and people should focus more on finding their own optimal training intensities as opposed to keeping up with others.


What is the recommended frequency for HIIT Workouts?


HIIT workouts are more exhaustive then steady state endurance workouts. Consequently, a longer recovery period is often needed. Perhaps start with one HIIT training workout a week, with your other workouts being steady state workouts. As you feel ready for more challenge, add a second HIIT workout a week, making sure you spread the HIIT workouts throughout the week.


Bottom line


Interval training has been an integral part of athletic training programs for many years because a variety of sport and recreational activities require short bursts of movement at high intensity. Interval training is becoming an increasingly recognised and well-liked method of training. The integration of interval training into a general conditioning program will optimise the development of cardiorespiratory fitness as well as many other health benefits.


I recommend you give HIIT a try but don’t forget that before beginning any exercise program, you should seek medical evaluation and clearance to engage in activity. Not all exercise programs are suitable for everyone, and some programs may result in injury. Activities should be carried out at a pace that is comfortable for the participant. Participants should stop partaking in any exercise activity that causes pain or discomfort. In such event, medical consultation should be immediately sought

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