Tuesday, April 7, 2015

Maximizing Excess Post-Exercise Oxygen Consumption aka EPOC | Run, Don't Cycle, Split Your Training Session in Two Intervals Instead of Doing One Long Session a Day!

Bring the heart rate up with exercises that involve the whole body and do workout short, intense and frequent to maximize the excess post-exercise oxygen consumption, but don't fall for the falls believe that this alone would be enough to get you shredded.
It's pretty straight logical and with the publication of the accepted manuscript of a recent study from the Institute of Physical Education and Sports at the Laboratory of Physical Activity and Health Promotion of the University of Rio de Janeiro State it's scientifically proven, splitting your cardio training in two sessions kicks cardio's (=medium to high intensity steady state exercise's) ass, when it comes to maximizing the Excess Post-Exercise Oxygen Consumption (EPOC).

As Cunha et al. point out in the intoduction of their latest paper, "previous research investigating the effects of intermittent vs. continuous exercise upon EPOC superficially matched the exercise bouts for external work (same intensity and duration), the exercise volume was not matched by the actual EE [energy expenditure]" (Cunha. 2015).
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In other words, you if you want a fair comparison you have to make sure that the intra-workout energy expenditure is identical and cannot compare 10 minutes of steady state exercise to 2x5 minutes of steady state exercise, because it's not a given that the workload will be absolutely identical: Only if you standardize the workout volume by measuring the energy expenditure and make sure that the the exercise intensity and cardiorespiratory fitness levels of your subjects are taking into account you will be able to objectively compare the effects of continuous and intermittent exercise on the magnitude of EPOC.

In their latest study Cunha et al. tried to do just that, when they had ten healthy men, aged 23 to 34 yr, performed six bouts of exercise
  • firstly, two maximal cardiopulmonary exercise tests for running and cycling to determine exercise modality-specific peak oxygen uptake (VO2peak); and
  • secondly, four isocaloric exercise bouts (two continuous bouts expending 400 kcal and two intermittent bouts split into 2 x 200 kcal) performed at 75% of the running and cycling oxygen uptake reserve.
This means, the subjects expended the same 400kcal, but in one trial they did it in a single session, while in the other, they burned 200kcal in session 1 and 200kcal in session 2, exactly 1h later.
Beware! This is not a HIIT vs. LISS study! At first I thought that this would be another HIIT vs. LISS comparison, but this is not the case. It's a comparison of two forms of steady state exercise, where one is classic, i.e. training for roughly 30 minutes, while the other was designed to consume the exact same amount of energy, albeit in two sessions seperated by 1h of rest.
The exercise bouts were separated by 72 h and performed in a randomized, counter-balanced order. The VO2 was monitored for 60-min postexercise and for 60-min during a control non-exercise day.
Figure 1: It's quite obvious - the more muscle you train, the higher your EPOC is going to be. Plus: If you do interval training, your total EPOC will exceed the amount of fat burned after isocaloric continuous exercise (Cunha. 2015).
As it was to be expected, the VO2 was significantly greater in all exercise conditions compared to the control session (P < 0.001). More importantly, however, the combined magnitude of the EPOC from the two intermittent bouts was significantly greater than that of the continuous cycling (mean difference = 3.5 L, P=0.001) and running (mean difference = 6.4 L, P <0.001).

In the end, both, the exercise type (cycling = less muscle vs. running = more muscle) and modality (continuous vs. intermittent) both had a significant effect on net EPOC, where running elicited a higher net EPOC than cycling (mean difference = 2.2 L, P <0.001).
If you are training for max. EPOC, only, you are a fool | more.
In the end, the study does therefore provide convincing evidence that what most of you will probably already have assumed is in fact the case: "Intermittent exercise increased the EPOC compared to a continuous exercise bout of equivalent energy expenditure. Furthermore, the magnitude of EPOC was influenced by exercise modality, with the greatest EPOC occurring with isocaloric exercise involving larger muscle mass (i.e., treadmill running vs. cycling)" - or, as the title of today's SuppVersity article suggests: 'If a maximal EPOC is your goal, select an exercise that involves a maximal amount of muscles and split your X minutes of working out in two intervals.'

Whether that's something you must do, however, depends on how convinced you are that EPOC matters. In previous SuppVersity articles I have already dissected the myth that burning a few extra-calories from fat after the workouts will make the difference between being flubby and being jacked. In case you can't remember the result, i.e. that it probably doesn't make much of a difference, I suggest you take another look at the respective article | Comment on Facebook!
  • Cunha, Felipe A., et al. "Effect of continuous and intermittent bouts of isocaloric cycling and running exercise on excess postexercise oxygen consumption." Journal of Science and Medicine in Sport (2015).