The Physiological Benefits of HIIT Training
Everyone is familiar with conventional, steady-state cardiovascular training — spending long periods running, biking or swimming at a steady pace. But what if there’s a way to get the same results in less time?
That’s where high-intensity interval training comes in. Rather than plodding for hours at the same speed, HIIT demands brief sets of intense effort followed by short periods of recuperation. HIIT can help people to burn fat, break through training plateaus and improve performance quickly.
What Is HIIT?
HIIT is training method that demands quick, intense bursts of exercise at 100 percent effort followed by short recovery periods. This isn’t a training protocol for the faint of heart — if someone isn't gasping for breath at the end, then they're not doing it right.
The foundation of a typical HIIT workout is the work-to-rest ratio: This is the time you spend going all out relative to your rest periods. According to researchers Micah Zuhl and Len Kravitz at the University of New Mexico, a 1:1 ratio might consist of a 30-second burst, followed by 30 seconds of rest. A ratio of 1:2 would then be 30 seconds of work, followed by one minute of rest.
Results in Less Time
A study published in 2015 in the Journal of Sports Science Medicine found that HIIT training could produce simultaneous adaptations in both anaerobic and aerobic exercise capacity in an extremely short amount of time, when compared to steady-state training. While test subjects all improved their fitness markers as measured by VO2 max, the HIIT trainees did so with much less time spent working out.
This means that HIIT allows people to still enjoy the benefits of conventional training when there isn't much time available for a typical workout.
HIIT for Endurance
While short, intense bursts of effort seem to be as effective as conventional training for increased respiratory capacity, does it help to improve endurance?
A study in the January 2002 issue of Sports Medicine concluded that elite endurance athletes who no longer improved using conventional training methods managed to break through performance plateaus when they began using a HIIT training protocol.
The Afterburn Effect
People expect to look and feel better as a result of the time and effort spent sweating out a training session — and here’s where interval training shines.
Kravitz states that excess post-exercise oxygen consumption, or EPOC, is what makes HIIT such an efficient calorie burner even though you’re not training for very long. EPOC (also called "afterburn") is the increased rate of oxygen consumption after physically strenuous work. According to Kravitz, it’s the intensity of aerobic effort that has the most significant impact on EPOC and not duration.
What this means is that a short, intense interval training workout could raise the metabolic rate for hours after someone has stopped exercising.
How Safe Is It?
Interval training shouldn’t present any significant risks for people in reasonably good health as long as they avoid doing too much, too soon. However, anyone who has heart disease or high blood pressure should talk to their doctor before attempting an interval training program.
- Journal of Physiology: Short-term Sprint Interval versus Traditional Endurance Training; Martin J. Gibbala, et.al.; July 2006
- Journal of Strength and Conditioning Research: Influence of High-Intensity Interval Training on Adaptations in Well-Trained Cyclists: P. B. Laursen, et.al.; August 2005
- High-Intensity Interval Training in Patients With Heart Failure With Reduced Ejection Fraction; Ellingsen Ø, Halle M, Conraads V, Støylen A, Dalen H, Delagardelle C, Larsen AI, Hole T, Mezzani A, Van Craenenbroeck EM, Videm V, Beckers P2, Christle JW, Winzer E, Mangner N, Woitek F, Höllriegel R, Pressler A, Monk-Hansen T, Snoer M, Feiereisen P, Valborgland T, Kjekshus J, Hambrecht R, Gielen S, Karlsen T, Prescott E, Linke A; (2017)