Great research, bro! I really enjoyed your writing style, too.
Absolutely, higher intensity exercise will increase EPOC to a greater extent. But the issue we proposed in our articles, is that either way, EPOC is only going to increase by a small amount no matter what you do. So most of the calories you metabolize will be during exercise itself. To quote one section of our article here, http://www.abcbodybuilding.com/Nutri...ningpart41.php
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First, HIIT training is normally purported to take less time than lower intensity sessions. However, to control variables Laforgia et al. (1997) examined the effect of intensity on EPOC, while matching total work performed in each session. Participants consisted of eight male middle distance runners, who performed 30 minutes of 70 % V02 max treadmill running in condition one, and interval training in condition two. Interval training consisted of 20, one minute sprints at 105 % of V02 max. The session lasted 60 minutes, as sprints were interspersed with 2 minute intervals in which participants performed active recovery. It was found that the 70 % V02 max condition metabolized 31 extra calories over the entire nine hours following exercise, while the high intensity condition metabolized 64 extra calories as extrapolated by EPOC. This equates to a negligible 33 extra calories for the high intensity condition. Laforgia et al. (1997) suggests that a comparison of the excess calories above moderate intensity exercise ‘for the interval treatment is of little physiological significance to the energy balance of athletes because this amount of energy is equivalent to the kilojoules in only 75 ml of orange juice (1/3rd cup).’ They further conclude that ‘the major contribution of both treatments to weight loss was via the energy expended during the actual exercise. The excess post exercise energy expenditure is therefore of negligible physiological significance as far as weight loss is concerned.’
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So by doing 45-60 minutes of moderate intensity cardio, I will metabolize a greater amount of calories than someone who does 20 minutes of HIIT; including EPOC and caloric expenditure during the routine.
Further, results show that the percentage of fat utilized will be optimal around the 65% VO2 max range.
Say someone exercises for 20 minutes at 25, 65, and 85% VO2 max. And say that the total amount of calories metabolized were 100, 250, and 300 for the 25, 65, and 85% VO2 max conditions, respectively. Based on research, during the 25% VO2 max condition, 85% of the fuel probably came from fat, which would mean the person metabolized 85 calories from fat. For the 85% VO2 max condition, of the 300 calories metabolized, 75 calories of fat were also metabolized, but an additional 225 calories from carbohydrates were also metabolized. Finally, in the 65% vo2 max condition, a whopping 125 calories were metabolized from fat during the same period of exercise. This is 40% more total fat than both the high and low intensity conditions.
Overall, the main point Prez and I make is that EPOC is not going to be the determining factor for calories metabolized. Rather, what you do during your workout will be.
So does that mean that bodybuilders should not do HIT? No. We think a combination of both is optimal.
HIT has many benefits. It will improve mitochondria, VO2 max, vascularity, and other aspects to a greater extent than lower intensity cardio. So it should be included in a bodybuilders routine.
One method we suggest is to do both at the same time. High intensity training may prove beneficial if used properly. For example, its potent stimulation of whole body lipolysis during exercise leads to a rapid influx of plasma free fatty acids after intensity is lowered. In this context, it is postulated that performing a notably short, high intensity session, followed by a long duration, low to moderate intensity workout, may optimize lipid oxidation.
Great study on the low rest period times!
One issue I have with that study that is always quoted on HIT being superior to low intensity cardio, is that bodybuilders don’t just do low intensity cardio. In fact, bodybuilders are primarily high intensity athletes. So we receive the benefits that are associated with high intensity exercise.
Low intensity exercise is just meant to supplement our program. It is a great way to get rid of fat, while minimizing glycogen depletion and muscular damage.
SO WHAT IS BEST?!?
Again, I say a combo of both.
Let me know your thoughts!