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Two half-hour jogging sessions more effective than one whole hour

If you're into not too intensive cardio sessions you'll burn more fat by splitting them into two. Japanese sports scientists came to this conclusion in a human study which was published in the Journal of Applied Physiology. Two half-hour sessions of cycling burn more fat than one hour of continuous cycling.

3-Hydroxybutyric acid
Some time ago we wrote about a study done 25 years ago, which showed that you burn more fat if you split running sessions into two. This effect is the result of a higher total post-exercise energy burning, EPOC.

Looking at the research done 8 years ago at the Japanese University of Tsukuba, then the effect of split-up cardio training may be even bigger than the 1990 research suggested. In the latter study the researchers did not look at the EPOC, but at the calorie burning during the sessions and not at how much, but where the energy was derived from.

The researchers did a trial with 8 male students, with an average age of 25. On one occasion the students cycled for an hour at 60 percent of their VO2max. [Single] In the figures shown below they started at t=20 minutes. On the other occasion the students cycled twice for half an hour. [Repeated] In these figures the students started cycling at t=0 minutes. They stopped at t=30 minutes, rested for 20 minutes and at t=50 got back on their bikes.

The figure below shows that the quantity of free fatty acids [FFA] in the blood increased by more when the second procedure was followed.

Two half-hour jogging sessions more effective than one whole hour

It's likely that the free fatty acids came from the fat reserves. The amount of glycerol in the blood also rose. A fat molecule looks a bit like a paperclip with three rubber bands attached. The paperclip is the glycerol, and the rubber bands are fatty acids. If you find high amounts of glycerol and free fatty acids in the blood, it indicates that the fat cells are releasing their contents into the blood.

The figure below shows how a cardio session split into two results in more fat burning. The graph shows the concentration of the pep hormone adrenalin. This increases by more if you train twice in fairly rapid succession. Adrenalin forces fat cells to release fatty acids into the bloodstream.

Two half-hour jogging sessions more effective than one whole hour

If the body burns more fatty acids the amount of ketones in the blood goes up. The compound 3-hydroxybutyric acid [structural formula shown above] is one of these ketones. The figure below shows that the body does actually burn more fatty acids as a result of splitting a cardio session up.

Two half-hour jogging sessions more effective than one whole hour

So if you want to lose fat, and you've got plenty of time on your hands - try splitting up your cardio sessions.

J Appl Physiol. 2007 Jun; 102(6): 2158-64.

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