Why the 'interference effect' is half true

Will cardio kill your gains?

It might, but it doesn't have to.

This idea, known as the "interference effect," has hung around the fitness world for decades.

it's essentially the idea that cardio is counterproductive for building muscle and building muscle is counterproductive for improving endurance.

About 10-15 years ago, this idea was taken as unquestionable truth.

Today, the pendulum has swung in the opposite direction with most people rejecting the idea thanks to the rise of CrossFit, hybrid training, hyrox, and everything similar.

Moreover, the research has also swung the opposite direction, with the most recent review papers suggesting that the presence of endurance training does not alter the results gained from strength training. [1]

With all that said, I'll still be one to tell you that the interference effect isn't a total myth; it just doesn't work the way most people think it does.

First things first

Lifting can interfere with your endurance gains and cardio can interfere with your strength gains if the program your following is rubbish.

The ins and outs of programming is obviously impossible to cover in a single sub-section of a single newsletter.

But: I just thought it was worth adding that this is a pre-requisite consideration before you write off the results you've achieved to the interference effect.

How I view the interference effect

As I mentioned before: the best evidence indicates that the presence of one form of training does not inherently subtract from the other.

Meaning:

If you are lifting 2-4 days per week, performing cardiovascular training on the other days is unlikely to take away from your strength gains (and vice versa).

However: what if you only had 4 days in the week to dedicate toward structured exercise?

In this instance, you have three options:

• You can max out the gains from strength training by only strength training

• You can max out the gains from endurance training by only endurance training

• You can get most of the gains from each by splitting your time up 50/50

Both forms of training are volume dependent. Meaning: The more you do, the more results you get.

This is much more true of endurance training, but is still somewhat true of lifting.

Any time you spend toward one goal means time not spent toward the other.

So, I don't think the interference effect is a total myth. It's just more a matter of opportunity cost than some sort of physiological subtraction.

Goal setting

Most of the articles & videos I've produced on training start with the notion of getting crystal clear with what you want to achieve out of your training.

This is in part because you don't have unlimited time in the week to devote to this stuff.

Let's go back to the example of having 4 days in the week available for structured training.

You can maximize strength or endurance by only doing one or the other.

Or, you can get ~80% of the results of each by doing 2 days of strength and 2 days of endurance.

This is a key point: doing double the training doesn't give you double the results. There are diminishing returns the more you do.

The question then becomes: how valuable is that last 20% to you?

There's no right or wrong answer to this, but it is a question you're forced to answer (whether you know it or not).

Because any training time spent training one fitness quality means not training another; it's worthwhile to have your pursuits clearly articulated so that you truly get the most out of your efforts.