[quote]Safety Dyck wrote:
HIIT vs LI
Layne Norton has addressed this a few times, here’s 1 of the quotes:
Quote:
High-intensity cardio seems to be more muscle sparing. Several studies have shown that high-intensity interval training (aka HIT) burns less calories when compared to continuous lower intensity cardio. However, the skinfold losses were greater with the HIT group than in the continuous intensity group. This means not only did the HIT group lose more fat, they also spared more muscle tissue by burning less overall calories .
Some relevant studies:
Two studies done by the same researchers, were published in Int J Obes Relat Metab Disord. 2001 Mar;25(3):332-9. The first study was done on two groups of 352 total men, those who did High intensity activities regularly and those who did not. The study showed that men who were more likely to be in high intensity activities not only had lower bodyfat and subcutaneous fat, but even when they ate more than the sedentary group.
The 2nd study was more direct, measuring the effects after a high intensity excercise. They found that oxygen consumption and fat oxidation increased afterwards. They also found that the oxygen consumption effect was much greater in the high intensity group compared to low intensity. In other words, the high intensity group not only had increased metabolism and fat loss abilities for hours post excercise, but the metabolism increasing effect was much higher over the low intensity group.
Interesting part is they found these effects to stop with the addition of propranolol, researchers concluded that beta adrenergic stimulation, may be the major role in the after effects from high intensity excercise.
Another study published in Metabolism. 1994 Jul;43(7):814-8 They compared a group (8 women 9 men) doing 20-week endurance-training compared to a group (5 men 5 women) doing HIIT. The decrease in subcutaneous skinfolds when adjusted for energy expedenture were 9 times greater than the endurance group! Researchers concluded that higher intensity, was not only superior for metabolism and fat burning effects, but also for skeletal muscle adaptions.
The study published in (J Appl Physiol (December 14, 2006). doi:10.1152/japplphysiol.01098.2006) done on moderately active women for 2 weeks. Results showed increased capacity in fat burning in muscles and whole body, during HIIT cardio sessions.
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This is a good article, and Layne is an amazing bodybuilder - probably much better than I ever could be.
However, the non-weight lifting activities you do to burn fat also depend on what you’re doing in weight training. Lonnie Lowery once wrote that he only does steady-state cardio because he’s constantly bordering on overtraining with the weights because he destroys himself in the gym - a la Dorian Yates.
The type of activity also depends on weight. 250+ pound bodybuilders aren’t running sprints and it would be injury-prone for them to do so. Not to mention their form and endurance for sprint workouts would be abysmal.