I found a wonderful article at SportsScience (www.sportsci.org). It breaks down several studies detailing the effects of HIIT on endurance performance. The interesting thing about the study isn’t that it showed significant gains in performance among athletes participating in HIIT training, but that different intervals and rest periods seemed to show strikingly different results. Across the board there were significant improvements, but the groups who used either 30s intervals or 4 minute intervals experienced the most extreme improvements in performance.

The problem with the study is that not all factors were consistent. One variable tested was changing the length of time during which max effort was performed, but they also changed the amount of time during rest, as well as the amount of intervals performed. While this is good to get an overall sense of how different intervals techniques can effect true performance, it fails to truly suggest an absolute best training program. They absolutely recognize this and the article ends with this quote:

The studies discussed in this article have used high-intensity intermittent exercise as a training intervention. However, the protocols varied widely. Some work intervals last between 15 and 30 s, while rest periods span 10 s to 4.5 min. More research is needed to establish the most effective form of interval training required to improve endurance performance.

I see the five main variables in HIIT to be:

• Type of activity (sprinting, cycling, jump rope…)
• Length of time of maximum effort
• Length of time of rest period
• Quantity of intervals
• Change in interval quantity over time

My training program is 30 second maximum effort, followed by 60 seconds of rest. With the quantity of intervals increasing by one interval every three workouts until 15 total minutes of workout are reached. I plan on getting to this point and if I see any plateau in weight loss or muscle growth, I’ll shorten the rest periods incrementally until I get to 30 second rests for a total of 15 intervals. At that point, I feel that my workout is more than adequate, and I’ll only wonder if my body can take that kind of exertion over a long period of time.

The interesting thing about HIIT training is that not only does your cardiovascular fitness improve, but so does your ability to transport oxygen through your blood, which contributes to your cardiovascular ability. Meaning, you not only won’t get as tired at the same levels of exercise, but you’ll be capable of a higher level of exercise. The article also discusses several other benefits of interval training:

[HIIT saw] substantial increases in activity of citrate synthase (38%) and 3-hydroxyacyl-CoA dehydrogenase (60%). These changes in oxidative enzyme activity may increase the rate of fat oxidation and reduce carbohydrate oxidation. The subsequent reduction in the accumulation of hydrogen ions could improve endurance performance (Hawley et al., 1997)

The interesting thing that I see is that an increase in fat oxidation and reduction in carbohydrate oxidation occurred. This means that the body is using more of its fat stores as its energy source, and less of its carbohydrate stores. The good news from this is that increased fat consumption, while staying away from trans fats and saturated fats, won’t be as devastating to the goal of losing weight. And a lowered intake of carbohydrates (without cutting them out) seems to create a good diet that will feed muscle and burn fat, complimenting the body’s changed metabolism. Which means I can continue to feast on peanut butter. And I’ll feel a little better about my bacon cravings.

Related Posts

• My first HIIT session
• HIIT - A better way to burn fat?
• Friends may be mad at you if you encourage them to HIIT
• It’s not raining, I better take advantage