What Is Short-Duration HIIT?
If you have yet to read my article on HIIT then you might want to do this first.
There does not appear to be an exact cut-off point at which high intensity interval training becomes short-duration high intensity training. Nevertheless, by short duration, they really do mean short duration! Obviously, with the duration of exercise efforts becoming shorter, the intensity of these bouts of exertion become way more intense. Importantly though, as with any high intensity interval training there needs to be a mix of adenosine triphosphate (ATP) derived energy from both aerobic and anaerobic energy systems.
The Wingate Model For Short Duration High Intensity Interval Training
The Wingate test consists of 30 seconds of ‘all out absolute maximum intensity exertion against resistance (e.g. bicycle) Wingate test, followed by 4 minutes of rest. The idea is to repeat this cycle 8 times, though some have decided that a 6 cycle Wingate is more than sufficient! The only potential drawback of the Wingate is that it might be unsafe for people with certain diseases (e.g. cardiac problems or obesity). Modified short-duration HIIT models have been designed for these populations.
Dr Tabata’s Short Duration HIIT Workout
Dr Tabata created this exercise regime after observing the Japanese speed skating team. His routine involves 20 seconds of all-out effort, followed by 10 seconds of rest, with the athlete repeating this cycle 8 times.
Thus his entire exercise routine takes a mere 4 minutes!
Let me quickly qualify this by mentioning that you should ALWAYS warm up before exercising, and particularly if you are going to be going at 100% immediately. Otherwise, the chance of injury is extremely high. So take a few minutes at the beginning to just turn over the peddles in advance.
So how can we increase fitness through a 4 minute routine, repeated 2-3 times a week? The key clearly is intensity. If we average 2 and a half sessions a week, that would mean doing a mere 10 minutes of exercise per week!
Of those 10 minutes though 6 minutes and 40 seconds is at maximum performance, where you are wringing every last ounce of torque out of that bicycle!
How Often Should I Do High Intensity Short Duration Interval Training?
So if twice a week HIIT is good then 6x a week HIIT must be even better!?
In fact, it appears that less is more!
Our bodies need a couple of days to recover from high intensity workouts, so doing them more frequently can actually just damage our system. If you are feeling the urge to do High Intensity Interval Training more than 3x a week then you need to question whether you are actually going all out for those 100% of peak performance intervals. Since this whole methodology revolves around intensity, you really need to give this your all.
Of course, nothing stops you from doing something like strength training on some other days if you feel compulsively drawn to the gym. Just make sure that you aren’t utilising any of the key muscle groupings that you are using for the HIIT. Upper body training and stomach exercises would be the logical choice.
Generally speaking, although we activate many upper body muscle groups during HIIT we are not putting them under the same kind of strain that our gluteal muscles, quadriceps, hamstrings and calf muscles are under if we are doing high intensity interval training on a bike.
So Is This For Real? Does 10 Minutes Of Exercise Per Week Actually Achieve Anything?
Research to date has answered with an emphatic ‘Yes!’
Research Confirming That Less Is More For Short Duration High Intensity Interval Training
Tabata’s IE1 Protocol
One study studied an experimental group following Dr Tabata’s program 4 times per week for 6 weeks (this is above the recommended maximum weekly amount if you are using the same muscle groups e.g. cycling, but possibly okay if you are doing circuit training and alternating muscle groups). This would amount to16 minutes of exercise a week for 6 weeks, amounting to a total of 96 minutes of exercise.
This group was compared to a control group, who trained in a normal, constant effort aerobic way and spent 1 hour on a bike 5 days a week, for 6 weeks. This would amount to 30 hours (1800 minutes) of exercise.
At the end of the 6 week period the HIIT group had increased their anaerobic capacity by 28%, as well as increasing their maximum aerobic power (VO2 max) by 15%. In contrast the control group did not improve their anaerobic capacity at all, and their aerobic power (VO2 max) increased by only 10%.
The 4×4 Study
This particular study compared two groups that were both following variations of the 4-minute Tabata protocol. The first group merely completed the 4-minute interval at 90% of maximum heart rate (HRmax), 3 x per week. The second group completed 4 minute intervals of high intensity exercise (90% HRmax), followed by 3 minutes of active recovery (So more gentle exercise – 70% HRmax). They would repeat this 7 minute circuit 4 times – which is why it is sometimes called 4×4 training – also 3x per week.
At the end of a 10 week period the shorter duration group increased VO2max by 10% compared to 13% in the longer duration group.
So the extra training did lead to slightly superior effects over the short term. The only problem though is whether the longer duration group’s bodies might start to show greater strain over a longer period of time than just 10 weeks.
The shorter duration group actually showed GREATER decreases in blood pressure than the longer one, for both systolic and diastolic measures!
National Health And Nutrition Examination Survey (NHANES)
This study collected health and nutritional data, and also gave participants accelerometers to wear to track physical activity levels. Participants included 2202 women and 2309 men between the ages of 18 and 64 that were randomly drawn from the database. It broke exercise down into 4 groupings, higher versus lower intensity, and longer versus shorter bouts.
Results showed that high intensity was by far the largest predictor of weight loss, as opposed to duration. They found that on average each daily minute spent in higher-intensity short bouts of exercise was correlated with a decrease of 0.07 of their body mass index (BMI).
BMI is a measure of body fat, which also takes height into account.
BMI = Height (m)2
Therefore, BMI = weight in kilometres over the square of the height in meters.
Now if we run with this, each daily minute of high intensity exercise equates to a loss of 0.186 kg (0.41 pounds).
The authors give the example that ‘when comparing two 5′ 5″ women, the woman who regularly adds a minute of brisk activity to her day will weigh nearly a half-pound less’.
Results for men were very similar. Most importantly, each daily minute of higher-intensity activity lowered the odds of obesity by 5% for women and 2% for men.
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