HIIT is a form of exercise strategy in which intense bursts of activity is carried out for short fixed periods followed by brief rest periods repeatedly, until full exhaustion. For example, running for as fast as possible for 20 to 30 seconds with a rest time of 10 to 20 seconds for limited recovery.
There are two mechanisms that are needed in any program for results: stimulation and recovery. After stimulating the body, everyone must recover so they can work out again and make progress. There can be two situations: working out for an hour a day but not very hard and working out for twenty minutes a day, but very intensely. The first type of workout is low intensity, high volume. The workouts themselves are not very stimulating to the body so our body won’t change. The second workout is high intensity, but done too often so that there is not enough recovery for continued progress. The best scenario involves balancing the intensity of the workout with proper recovery time to avoid burnout and make consistent progress. HIIT workouts can be performed 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 bout where the body is restoring itself to pre-exercise levels, and thus using more energy. Because of the vigorous contractile nature of HIIT workouts, the EPOC generally tends to be modestly greater, adding about 6 to 15% more calories to the overall workout energy expenditure. HIIT training has been shown to improve:
- aerobic and anaerobic fitness
- boosting endurance
- increasing metabolism
- blood pressure
- cardiovascular health
- insulin sensitivity
- cholesterol profiles
- abdominal fat and body weight while maintaining muscle mass.
Tabata Training: Named after Japanese researcher Izumi Tabata, who has conducted extensive research on interval training, Tabata consists of performing an activity all-out for 20 seconds, resting for 10 seconds, and then repeating the on-off sequence for four minutes in total. One of Tabata’s most famous findings demonstrated that 20 seconds of all-out cycling followed by 10 seconds of low intensity cycling for four minutes was as beneficial for VO2 max (maximal aerobic capacity) as 45 minutes of long, slow cardio performed four times per week. Since VO2 max is generally considered the best indicator of an athlete’s cardiovascular fitness and aerobic endurance, this study was a game changer. It conclusively showed that positive health benefits derived from traditional aerobic training could be accomplished with high-intensity interval training.
Gibala regimen: Dr. Gibala, a professor of kinesiology at McMaster University in Hamilton, Ontario, tried to popularize the idea that we can rely on high-intensity intervals as our only exercise, and do very, very few of them while still improving our overall health and fitness. In 2010 study on students, he uses 3 minutes for warming up, then 60 seconds of intense exercise followed by 75 seconds of rest, repeated for 8–12 cycles. Subjects using this method training 3 times per week obtained gains similar to what would be expected from subjects who did steady state training five times per week. Dr. Gibala also proposed a gentler option for sedentary people who had done no exercise for over a year. It included 3 minutes of warm-up, 10 repetitions of 60-second bursts at 60% peak power each followed by 60 seconds of recovery, and then a 5-minute cool-down.
Zuniga Regimen: Assistant professor Dr. Jorge Zuniga of exercise science at Creighton University, carried out research to determine how to fit the highest volume of work and oxygen consumption into the smallest amount of time. He found that intervals of 30 seconds at 90% of maximum power output followed by 30 seconds of rest allowed for the highest VO2 consumption and the longest workout duration at specified intensity.
Vollard Regimen: Dr Niels Vollaard at the University of Stirling proposed a 10-minute exercise routine consisting of easy pedaling interspersed with two 20-second ‘all-out’ cycling sprints. He is of the opinion that when high-intensity intervals are done at ‘all-out’ intensities, associated health benefits plateau after performing 2 or 3 sprint repetitions. This concept led to the development of a meta-analysis which showed that common protocols with as many as 6 to 10 repetitions of 30-second ‘all-out’ sprints do not improve aerobic fitness more than the ‘2×20-s’ protocol.
Sprint 8 Protocol: Dr. David Braden of King’s Daughters Medical Center, Brookhaven, MS, USA proposed Sprint 8 protocol which requires HIIT for 20 minutes per bout, 3 times per week. The exercise starts with 2 to 3 minutes warm-up period which is done with slow pace, also known as the “active recovery pace” (ARP). Protocol starts with 30 seconds of full-sprint followed by an ARP for 1.5 minutes, completing first round. The sprint should be performed in an all out manner. The subject needs to carry out eight such rounds requiring 16 minutes. At the end, a 2 to 3 minutes cool down is carried out.
Pre-caution: Persons who have been living a sedentary lifestyle or period of physical inactivity may have an increased coronary disease risk to high intensity exercise. Family history, cigarette smoking, hypertension, diabetes (or pre-diabetes), abnormal cholesterol levels and obesity will increase this risk. Medical clearance from a physician may be an appropriate safety measure for anyone with these conditions before staring HIIT or any intense exercise training program. Prior to beginning HIIT training a person is encouraged to establish a foundational level of fitness through regular steady state exercise.