High-Intensity Interval Training (HIIT)

       Jenny doing burpees

                                

I just don’t have the time. This is often cited as the number one excuse for not exercising. Depending on the source, the amount of weekly exercise required to improve cardiovascular health and decrease risks of type 2 diabetes and obesity varies. Some recommend at least 20-minutes per day for 3-5 days per week while others recommend at least 150 minutes per week.

With high-intensity interval training (HIIT), you can achieve similar health benefits in a fraction of the time. When performing HIIT, you go all out for short periods of time, followed by periods of rest. Rather than pushing yourself moderately for 30-60 minutes during a workout, you push yourself to the max in half the time.

HIIT isn’t for everyone, though. Since this requires high-intensity movements, it can be impractical for those with bad knees, arthritis, or those with poor form when it comes to simple exercises. The usual disclaimer: consult your doctor before starting any new physical activity.

There are a number of types of HIIT regimens (see our Tabata page for example), and we plan to report on other types over time, but for now here is an example of a sprinting HIIT as well as some other studies that show the robust health benefits of HIIT.

Sprinting HIIT

Perform an all-out sprint for 30 seconds, then rest for 4 minutes. Repeat 4-6 times. Sound too easy? Jenny and I have tried this, and it is much harder than it sounds. Four minutes of rest sounds like a long time, but you will wish you had more time by the 4^th sprint. It’s important that for each sprint you really go ALL OUT.

The science:

A study in 2011 showed that performing all-out run sprints was equivalent or better compared to moderate continuous exercise in terms of improving aerobic capacity and burning fat. For each group, participants performed the designed exercise 3 times per week.

For the continuous exercise group, participants performed 30 minutes of treadmill running (at 65% oxygen output) for weeks 1-2, 45 minutes of treadmill running for weeks 3-4, and 60 minutes treadmill running for weeks 5-6.

The HIIT group performed all-out running sprints for 30 seconds followed by 4 minutes of recovery. This was performed four times for each workout in weeks 1-2, five times for each workout in weeks 3-4, and six times for each workout in weeks 5-6.

So group 1 spent 60 minutes on the treadmill while group 2 spent 27 minutes on the treadmill for each workout during the final weeks, and for group 2, only 3 of those 27 minutes required effort.

After six weeks, there was no significant difference between the two groups in terms of body mass. However, fat mass decreased in both groups, 12.4% in the HIIT group and 5.8% in the moderate continuous exercise group.

Both groups improved slightly when measuring a 2000-m run time trial.

Both groups improved VO₂ max (maximal aerobic capacity), but no difference between the two groups.

However, maximal cardiac output did not increase with the HIIT group but did increase with the moderate continuous exercise group.[1]

HIIT decreases hunger in obese men

Many people work out to lose weight, but by exercising, you often stimulate your metabolism and increase hunger. This can lead to overeating which nullifies the calories expended during exercise. A study was conducted to determine the effects of hunger and desire to eat (for obese men) in response to moderate intensity interval training (MIIT) and high intensity interval training (HIIT). The study determined that hunger and desire to eat decreased significantly after HIIT compared to MIIT and that fat intake decreased by 16% after HIIT while fat intake increased by 38% after MIIT.[2]

HIIT can lower blood pressure and decrease risk of type 2 diabetes

A study in 2014 demonstrated that young healthy adults who performed HIIT for 6 weeks achieved decreased systolic and diastolic blood pressure as well as beneficial changes in blood lipid and blood glucose levels for most participants. Therefore, HIIT (which requires far less time than traditional moderate exercise) can potentially be used as an alternative to the proposed 150 minutes physical activity per week in order to improve cardiovascular health and decrease risk of type 2 diabetes and cardiovascular disease.[3]

Some HIIT exercises. 
Example # 1: 
Perform all of these exercises with a two minute break in between. Remember to go all out as hard as you can. 
Jumping squats for 30 seconds
Rest
Burpees for 30 seconds
Rest
Jumping Squats for 30 seconds
Rest
Burpees for 30 seconds
Rest
Jumping Jacks for 1 minute
Rest
Plank for 1 minute
Example # 2: Longer workout
Jumping Jacks for one minute
Tricep Dips for one minute
Burpees for one minute
Lunges for one minute
Mountain Climbers for one minute
Running in Place for one minute
Rest for two-four minutes
Repeat whole sequence again. For advanced people repeat it two more times.
Example # 3: 
Jumping Jacks for one minute
Tricep Dips for one minute
Burpees for one minute
Lunges for one minute
Mountain Climbers for one minute
Running in Place for one minute
Rest for two-four minutes
Repeat whole sequence again. For advanced people repeat it two more times.

 It's important to see how well you can improve with these exercises. I recommend timing yourself with these last two to see what time you finish. You should not go over the time cap though. 
Example # 4: AMRAP (As many reps as you can in 20 minutes) 
Run 400 m
15 burpees
15 air squats
10 hand release pushups or normal pushups
Example # 5: AMRAP (As many reps as you can in 20 minutes) 
150 jump ropes or 150 jumping jacks
100 mountain climbers
15 air squats
10 hand release pushups or normal pushups
Example # 6: Equipment needed
Each minute perform each action. Workout should be performed for 15 minutes
Minute 1: Run 200 m or do 60 jump ropes
Minute 2: 15 wall balls (squat and throw the ball at a target on the wall)
Minute 3: 15 burpees
Example # 7: Equipment needed
Complete five rounds of these exercises. Workout should be performed for 17 minutes.
Run 200 m with a weighted ball overhead
15 box jumps
15 dumb bell snatches

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[1] Macpherson et al. Med Sci Sports Exerc. 2011; 43 (1): 115-22.

[2] Alkahtani et al. Int J Sport Nutr Exerc Metab. 2014 Mar 25. [Epub ahead of print]

[3] Higgins et al. Clin Hemorheol Microcirc. 2014 Jul 7. [Epub ahead of print]