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High Intensity Interval Training
HIIT is claimed to be a time-efficient way to achieve training goals such as increasing endurance capacity and reducing body fat
Introduction
High intensity interval training (HIIT) is an alternative, but increasingly popular method of exercise training used to bring about improvements in aerobic fitness and reductions in percentage body fat. In contrast with the long duration steady-state approach of traditional endurance-type exercise training, during HIIT, a short duration effort is completed at maximum or (near maximum) intensity. Following a single high intensity effort (or rep), a rest period is allowed, and the process is repeated for the prescribed number of repetitions. The duration and intensity of both the exercise activity and rest can be altered to adjust the physical demands of the training. A common protocol based on a series of experiments from Canada’s McMaster University consists of seven repetition of 30 second all-out sprints on a stationary bike, with each sprint separated by 4 minutes of low intensity pedalling as recovery.
HIIT is most commonly known as ‘interval training’ in sporting contexts, or as ‘Tabata training’ in the fat loss and fitness industry. The concept of interval training can be traced back to the 1930s when German coach Woldemar Gerschler put a formal structure to the variation of intensity and recovery period? of exercise programs. The current guise of interval training as ‘Tabata training’ dates from work in the mid-1990s by a Japanese exercise scientist Izumi Tabata who demonstrated the positive effects of short duration maximal high intensity training during studies with Japanese athletes.
Advantages/positive effects of HIIT
- Time-efficient
- Rapid improvements in aerobic fitness
- Improves cardiovascular health
- Increases fat loss
- Improved HDL cholesterol levele
Why do HIIT
HIIT is claimed to be a time-efficient way to achieve training goals such as increasing endurance capacity and reducing body fat. This has led to use of the epigram “train hard, not long” in support of its popularity. It can burn more calories in a given time period than steady-state exercise, accelerate weight loss, increase insulin sensitivity, and improve sports-specific endurance in comparison to traditional endurance training. The time demand of HIIT is generally quite low, typically, about 30-40 minutes. This is because of the fatiguing effect of high intensity exercise, and the difficulty associated with maintaining prolonged high intensity exercise. This makes it an ideal training method for people with time restrictions, but who want to maximise the benefit of workout time. It is worth noting that in the protocol described above, the amount of high intensity effort only equates to 3.5 minutes work out of an approximately 40 minute session.
How to do HIIT
There are a number of training variables that must be considered in designing HIIT training programs:
- The type of activity
- The intensity of the exercise
- Duration/distance of the interval
- Repetitions per set
- Sets per session
- The rest allowed between efforts
- The rest activity, active rest or complete rest
HIIT training can be implemented simply by picking a repeatable exercise that can be completed quickly at high intensity i.e. running, swimming, skipping, cycling or rowing. By choosing an exercise that fits these criteria you can adjust the intensity quite simply and quickly.
Tabata HIIT
Following exercise selection, the work: rest intervals must be set. The traditional Tabata method stipulates that the work period should be 20 seconds and the rest period should be 10 seconds. The total interval repetition goal in the Tabata format is set at 8 i.e. 4 minutes of total work for one exercise. For individuals who wish to increase the workload in this style of training, the goal repetitions can be increased and performed in one block, or the total repetitions can be increased and completed over two blocks with a rest period in between. This gives the following set/repetition configurations:
- Traditional: One set of 8 repetitions
- Increased single set workload: One set of 10/12 repetitions
- Increased multi-set workload: Two sets of 6-8 repetitions
Long/short HIIT
When using variable interval training, the first parameter that must be established is the intensity of the exercise. This will link closely to the energy system targeted or training goal (i.e. exercise at X % - Y % of VO2max/HRmax or at A time to complete B distance). The distances or times that the interval is performed over will depend largely on the requirement of the person’s sport. Team sport players who sprint for short distances during games will use short duration high intensity intervals. Track athletes may use intervals that are shorter than competition distances to improve the speed that they can compete at, but typically the distances used are 0.3-1.5 time the race distance.
The number of repetitions per set and the number of sets will be dependent on the needs of the sport (what distances are covered in competition) and the intensity of the activity. If the intensity of the interval is high and duration of the interval is short, more repetitions and sets can be prescribed. As the interval length increases, the intensity of the exercise will decrease and this should result in the repetition count and set count being lowered along with reduced recovery time between repetitions. The activity completed during the rest interval can be varied depending on the activity and intensity, such that when the intensity is near maximal, complete rest or light active rest can be prescribed between exercise efforts.
Sports HIIT
A new concept in interval training for team sports is the use of small-sided games (SSG) to enhance sport-specific endurance. Research has demonstrating the effectiveness of SSG has shown greater improvements in endurance compared to traditional straight-line intervals. This method of training also allows for the development technical and tactical aspects of the game in conjunction with physiological development. For athletes and coaches who are subject to squad training time demands, this represents an ideal way to develop many aspects of the athletes training needs with one method. However, the SSG training method is dependent on the athlete having the technical and tactical knowledge to implement the training; if they are not skilled enough to properly complete game tasks, the game intensity will be reduced. The coaching staff must have the specific knowledge of how to adapt training variables of small-sided games such as the number of players per team or the playing area size. When using SSG as a part of training, there must be sufficient numbers of coaching staff present to monitor its use as a key element of the SSG is the participation intensity of the athletes. The coaches must be vigilant in monitoring how much effort the athletes are putting into the SSG session. The rest section of the SSG allows for inclusion of low-intensity technical skill refinement that can be then reintegrated into the high-intensity SSG.
HIIT for health
HIIT training as a method of fat loss has been proven to deliver increased caloric expenditure per time unit of exercise in comparison to traditional steady-state exercise. The additional fat loss associated with HIIT is linked to the intensity of the exercise, i.e. the greater the intensity of the exercise, the greater the effect of the exercise session on fat loss, even for the same amount of calories expended. The additional time-efficiency of HIIT compared to traditional long-duration aerobic exercise makes it exceptionally viable for those individuals who cite a lack of time as a barrier to exercise participation. The effect of HIIT has been shown to extend beyond improved cardiovascular function and fat loss. A two week program of HIIT twice weekly can dramatically improve insulin sensitivity this can help improve the risk factors for people at risk of metabolic disease, but who will not commit to long duration health interventions.
HIIT can be an effective method of training for people with poor cholesterol profiles. The ratio of LDL (bad) cholesterol to HDL (good) cholesterol can be improved through high intensity training. The improvements in HDL brought about as a result of HIIT can further influence the risk profile of people at risk of metabolic disease: high ratios of HDL to LDL are desired as HDL acts to reverse cholesterol accumulation in the vascular system. It scavenges for LDL and removes it to the liver where it can be re-packaged and removed as bile.
Summary
HIIT is a training method that has many applications, from sporting to fat loss and an improved health profile. It is a time-efficient method of achieving positive results from exercise training. The Tabata model has, along with more traditional interval training, become a popular mainstream training method. The use of interval training can also be applied to team sports through small sided games. The use of SSG allows for concurrent tactical, technical and physiological training. However the use of SSG in team training places an extra demand on the players and coaches to maintain intensity during the training.