Lack of time is one of the most common barriers to exercise, but the good news is you can get an effective workout with as little as 10 minutes of exercise.
High Intensity Interval Training (HIIT) is a popular workout regime alternating between high intensity intervals and low intensity recovery periods. The idea is that short but challenging bursts of exercise will give you similar (or better!) results to a 30 minute moderate intensity cardio workout (e.g. jogging). It may sound too good to be true, but research shows there are many advantages to H.I.I.T training including saving you time throughout your busy week!
How intense is high intensity?
High intensity exercise means working at 80-95% of maximum exertion which is no stroll in the park! Depending on the exercise program, the total time of a H.I.I.T workout can vary between 4 to 30 minutes. High intensity intervals typically last between 20 seconds to 1 minute, followed by the recovery period (either low intensity or rest) which typically lasts anywhere from 30 seconds to 4 min.
Who can participate?
Anybody! H.I.I.T is easily modified for all fitness levels, populations, and activities. H.I.I.T can be applied to running, swimming, cycling, elliptical cross training, stair climbing, jumping, rowing, and body weight exercises. H.I.I.T can be done in a group setting or individually in the comfort of your own home. H.I.I.T has been shown to be effective for a number of chronic conditions such as diabetes, cardiovascular disease, and COPD without increasing disease risk. A study by Little et al. (2011) found that after 2 weeks of H.I.I.T at 85-90% of max heart rate, individuals with type 2 diabetes had improved blood glucose levels. In addition, a study by Gillen et al. (2013) found that women who completed 3 sessions of H.I.I.T for 6 weeks had decreased total body fat and increased fat-free mass (e.g. muscle).
What are the benefits of H.I.I.T?
Research shows there are a number of benefits to H.I.I.T. including:
Improved aerobic and anaerobic fitness
Improved blood pressure
Improved cardiovacular health
Increased Insulin sensitivity
Improved cholesterol levels
Decreased abdominal fat and body weight, while still maintaining muscle mass
Another beneficial aspect of H.I.I.T is the amount of calories you burn after the exercise, called EPOC (excess postexercise oxygen consumption). With both moderate intensity and H.I.I.T exercise there is a period of time after you stop exercising where your body continues to burn more calories compared to your usual resting state. Research has found that with H.I.I.T, individuals have a higher EPOC up to 24 hours after exercising. This means individuals continue to burn a higher amount of calories for up to 24 hours after they have stopped exercising!
Examples of HIIT program
Below are 2 examples of H.I.I.T programs that are commonly used in research and have been shown to provide the benefits explained above.
For any H.I.I.T workout, make sure you warm up beforehand, and cooldown at the end. During the recovery periods you want to keep moving but at a slow pace.
One simple way to confirm you are working at a high intensity is through the use of the borg scale, which estimates how hard an exercise is perceived to each individual. This scale runs from 6 (very, very light) to 19 (very, very hard). Aim to fall between 15-18 on the BORG scale during the high intensity intervals, and between 7-10 during the recovery period.
If instead you would like to exercise at your target heart rate, here is a simple way to calculate it. To calculate your Max heart rate use the following equation:
220 - your age = Max heart rate
Then, if you are working out at 90% of your max heart rate use the following equation to find your target HR:
0.90 x Max heart rate = target heart rate
The 10 minute workout
This first workout only lasts 10 minutes and requires you to work at 95-100% of your HR max (17-18 on the BORG scale) during the high intensity interval.
This workout begins with a 30 sec high intensity interval, followed by a 2 minute recovery at 45% of your HR max. Repeat cycle 4 times.
The 20 minute workout
With this 20 minute workout, you will be working at 85-90% of your HR max (15-16 on the BORG scale) during the high intensity interval.
This workout begins with 1 minute at high intensity, followed by 1 minute of recovery at 40-50% of your HR max. Repeat cycle 10 times.
Gillen, J.B., Gibala, M.J. (2013). Is high-intensity interval training a time-efficient exercise strategy to improve health and fitness? Applied Physiology, Nutrition, and Metabolism, vol. 39, pp. 409-412.
Gillen, J.B., Percival, M.E., Ludzki, A., Tarnopoisky, M.A., Gibala, M.J. (2013). Interval training in the fed or fasted states improves body composition and muscle oxidative capacity in overweight women. Obesity, vol. 21, no. 11, pp. 2249-2255.
Little, J.P., Gillen, J.B., Percival, M.E., Safdar, A., Tarnopolsky, M.A., Punthakee, Z., et al. (2011). Low-volume high-intensity interval training reduces hyperglycemia and increases muscle mitochondrial capacity in patients with type 2 diabetes. Journal of Applied Physiology, vol. 111, pp. 1554–1560.
Ross, L.M., Porter, R.R., Durstine, J.L. (2016). High intensity interval training (HIIT) for patients with chronic diseases. Journal of Sport and Health Science, vol. 5, pp. 139-144.
Skelly, L.E., Andrews, P.C., Gillen, J.B., Martin, B.J., Percival, M.E., Gibala, M.J. (2014). High-intensity interval exercise induces 24-h energy expenditure similar to traditional endurance exercise despite reduced time commitment. Applied Physiology, Nutrition, and Metabolism, vol. 39, pp. 845-848.