T Nation

Scientific Reference for Cardio After a Workout.

A friend of mine is a gym teacher, and while discussin today, she was interested in what I was saying regarding advantage of doing cardio training (HIIT) after a weight lifting workout as opposed to before.

What I explained to her was that carbohydrates is the main fuel source while lifting weight, therefore the need not to use it up before one engages in lifting weights.

Then, after you’re done with the muscle building part of your workout, you’ve already burned up much carbs calories, so when you hit cardio training, you’ll soon start burning fat calories for fuel since you’re likely carb depleted by then (unless you fueled your glycogen stores back up after you were done lifting)

I can’t seem to recall where I read that from, BUT I do know it was from a reliable source.

Anyone can point me to a study stating the above in scientific terms ? My gym teacher wants me to be provide her with that info.

Any help would you be greatly appreciated.

Well a muscle full of glycogen is stronger than one depleted. So doing weights before will mean that you will be stronger which will lead to a more productive workout.

Cardio doesn’t take much, so a muscle depleted of glycogen is easier to use for cardion instead of lifting.

Since she should understand weights are more important than cardio that would be my way of convincing her. More than likely she doesn’t understand this and that’s why your in the predicament your in today. lol

Sorry no references there…

DG

There are loads of articles on Pub Med, most of which are completely boring to read. I have a stack of 30 articles for some thesis I am writing.

Just type in “substrate utilization exercise” into Pub Med. This might help.

Be prepared to read a lot of annoying shit.

Certainly the logic of doing weights before cardio in most situations, including weight loss, is correct because it can help burn fat. But that applies mainly to steady state cardio.

The issue is that the primary fuel for HIIT cardio is carbs, which is also the primary fuel for the weights, so the argument that you will burn carbs by doing weights and then fat by doing HIIT is not as sound, you will either have a crappy HIIT workout (due to low glycogen) or start burning muscle in place of the glucose.

If you wanted to do HIIT and weights on the same day I would spread them out by at least a few hours (ideal) with some food inbetween, make them both short enough so you don’t run out of glycogen (under 60 min total as a super general guideline), or do whichever one has the least negative impact on the other first.

Thanks all, especially bricknyce. I’ll print her couple of Pubmed abstracts–however the fact remains that it’s funny for her not to already know about this like someone posted.

Thanks Tim–sorry I’ve just noticed you posting–makes much sense I must say.

Yeah this is like the basic stuff in the nutrition and exercise world. She should know how this works and also everything it has to do with cell respiration and that.

HIIT leads to EPOC(Excess Post Exercise Oxygen Consumption) which is basically oxygen debt, which is fast glycolyisis, which is the utilization of carbohydrate for energy without oxygen, which has a byproduct of lactic acid; add in glycogen depletion and minor creatine phosphate depletion and you have an environment that is less conducive to a productive weight training workout.