Why High Intensity Interval Training Works

Are you tired of ordinary cardio exercises?  Fueled by endurance running plateaus and supported by evidence, a new type of training emerged: high intensity interval training (HIIT).  HIIT can be a complimentary exercise for those who dread cardio workouts, want to improve their success in endurance events, or only have time for a short workout.
 
The Science Behind The Phenomenon
High intensity interval training (HIIT) is defined as “brief to moderate duration intervals with high intensity (above anaerobic threshold) separated by brief periods of low intensity exercise or rest to allow for some but not full recovery.” For example, instead of jogging for 45 minutes at a steady pace, a standard HIIT session involves sprinting for 30 seconds, then lightly jogging for 1 minute, before repeating the sprint for a total of 15 minutes. The time frame is considerably shorter, but the aerobic workload is comparable. A 2008 study by Gibala et al proved 2.5 hours of sprint interval training produced similar biochemical muscle changes to 10.5 hours of endurance training and similar endurance performance benefits. 

Success with HIIT revolves around the ability to exceed your anaerobic threshold - the point at which lactic acid begins to accumulate in the bloodstream. Consistently training at high intensities, such as during HIIT, improves your anaerobic threshold. When you improve your anaerobic threshold, you train the body to recycle lactic acid allowing you to work harder, for longer. This translates to improved aerobic endurance by improving the ability to buffer lactic acid over the long term. Other than improved training performance for both aerobic and anaerobic activities, HIIT training has been shown to increase resting metabolic rate (King 2010). For the weight conscious adult, this means that you will residually burn more calories following a workout.

In 2010, Dr. Nybo concluded “SIT [HIIT] may induce similar improvements in cardiorespiratory fitness and skeletal muscle oxidative capacity as prolonged training.” This suggests that the same benefits seen in extended training times could be replaced by HIIT style workouts. 
 
Apply High Intensity Interval Training Today!
Is this method practical for the general population? As a health care practitioners, we do not typically release people to exercise at maximal intensities unless they are cleared from medical care. Our recommendation is to perform interval training to YOUR level of intensity. Instead of training at 90-100% of your capabilities, scale down the intensity interval to 80% of your maximal output. Then next time push your body and intervals a little further. Remember, we use HIIT to challenge our cardio system, improve endurance results, and maximize efficiency under time constraints.

High intensity interval training can be performed with any type of exercise: running, on the elliptical, or with circuit training. Incorporating different variations like HIIT into your workout routine is a simple way to challenge the body to help you reach your fitness goals.

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References:
1. Gibala, Martin J; Jonathan P. Little, Martin van Essen, Geoffrey P. Wilkin, Kirsten A. Burgomaster, Adeel Safdar, Sandeep Raha and Mark A. Tarnopolsky (September 15, 2006)     
2. King, Jeffrey W. A Comparison of the Effects of Interval Training vs. Continuous Training on Weight Loss and Body Composition in Obese Pre-Menopausal Women (M.A. thesis). East Tennessee State University.
3. Laursen, P.B. and Jenkins, D.G. (2002b) The scientific basis for high- intensity interval training: optimizing training programs and maximizing performance in highly trained endurance athletes. Sports Medicine 32(1), 53-73
4. Nybo, Lars, Emil Sundstrup, Markus D. Jakobsen, Magni Mohr, Therese Hornstrup, Lene Simonsen, Jens Bülow, Morten B. Randers, Jens J. Nielsen, Per Aagaard, and Peter Krustrup. "High-Intensity Training versus Traditional Exercise Interventions for Promoting Health." Medicine & Science in Sports & Exercise 42.10 (2010): 1951-958. Web. <http://www.ncbi.nlm.nih.gov/pubmed/20195181>.