The interference effect of aerobic exercise on strength and hypertrophy is well known. Also, a recently published RCT by Jones et al. found that in recreationally trained males (with an average max starting Bench of 154 lbs) high-intensity interval training did not result in any less interference than moderate intensity aerobic work, in fact it looks like it may even be worse for lower body hypertrophy.

“The main findings of this study were that, compared with resistance training performed alone, concurrent training incorporating either HIT or work-matched MICT cycling similarly attenuated maximal lower-body strength development and improvements in peak counter-movement jump force and power, while increases in lower-body lean mass were attenuated with concurrent training incorporating HIT, but not MICT.”

-Jones et al. 2016

I would hypothesize that as you get further along the continuum of strength and power this interference effect will become more and more pronounced, potentially mitigating all gains. To know this we really need more data in highly highly trained subjects, because a beginner can get bigger, stronger, and more powerful from endurance work alone, and regardless of weight, I would label a male with a 154 pound bench presser an extreme novice.

You think the Mountain is increasing his deadlift with an uphill bike ride? No.

Thus, if your goal is simply to get as strong and as jacked as genetically possible for you then it seems prudent to lower any moderate or high intensity endurance work to as little as possible. YET, to my knowledge we have nothing in the literature on the potential interference of low and very low level movement. There is some literature that shows short low-end aerobic cooldowns may accelerate recovery. I hypothesize that there is a baseline level of activity that we need for to promote blood flow and appetite regulation (seems to be around 7-8,000 steps), but even this is contextual because if someone really doesn’t want to regulate their appetite, they could feasibly sit on their couch decked out in compression gear, Marc Pro muscle stimulator pads, and/or NormaTec leggings.

Now, here is where things get even more complicated, inside of the interference studies there are responders and non-responders.

Let’s bring this where most people want us to…if you are involved and silly successful in CrossFit you are probably one of those subjects who shows less of an interference effect. You are also part of the largest interference study ever assembled because your sport by its very nature involves driving constantly competing goals. Therefore, I would work with a coach who has experience testing and isolating which systems are your limiters and then knows how to improve those systems while not letting other critical aspects of your physiology decline. Train Adapt Evolve, Opex, and Training Think Tank are the heavy hitters that come to mind, however, I am sure there are many more that are analyzing these intricate, interesting, and novel exercise phys problems.

For example, I was a decent CrossFitter, a fairly good mover, a solid breather, with a substantial aerobic base, but I had one very big problem, genetically I am an extremely high occluder, this means that when you put me in endurance events (especially with an external load) I cannot get blood into and out of the system locally. Basically, I will turn a longer wall ball metcon into a blood flow restriction nightmare, likely not such a bad thing from a hypertrophy standpoint, but maybe not so ideal if I am racing other humans for pink slips. I am sure Coach Davis could train this out of me, but in the process would he also drastically limit my ability to push higher percentages than I am supposed to?

Let’s ask him.

“It’s all contextual, but I have the advantage of knowing Dr. House as an athlete. House does increase strength well after a period of specific unloading while simultaneously microdosing both maximal and speed-strength type lifting.

Does this mean the Ben or anyone else can’t improve 1RM strength by training for CrossFit?

Not at all.

It’s all a function of time. If I need House strong in 8-12 weeks or if he needs to prepare for a Weightlifting/Powerlifting meet then the above holds true.

Now If I have a year or so to improve occlusion trends along with maximal strength in the realm of CF then both can be prioritized.

Improving the occlusion trend takes more overall work but the emphasis will be to build resiliency in the big three – cardiac, respiratory, and the peripheral muscles.

The heart is automatically relieved of work once the respiratory muscles improve. So it’s a no brainer for consistent respiratory training via SpiroTiger. For cardiac stimulation we need to find the proper internal reaction that is conducive for cardiac improvement. This is done best when the occlusion trend is limited and the cardiac system is teased to increase delivery. Once this sweet spot is found the underlying goal is to improve extension and intensity over time.

Increasing the force of both oxidative and glycolytic fibers will show a marked improvement in peripheral muscles. So periods of strength endurance and maximal strength will be weaved in and out of the program. Again we will test to find when occlusion occurs. This will be represented as a percent of the 1RM. An example would be to take the squat and start at body weight and increase external loading over sets while monitoring Smo2 and tHb. A quick note – the speed of movement needs to be factored in, but the goal is to pinpoint when occlusion occurs (% of 1RM). This will give us workable parameters to construct strength endurance protocols.

As for getting jacked AF – CrossFit type training can definitely still accomplish this goal. In fact, it might be one of the reasons why so many people gain an exorbitant amount of muscle on programs like MASS. If you are weak or super strong chances are you occlude. This is liken to blood flow restriction creating metabolic stress which signals adaptation – Gains will be made.”

Thank You Sir. You are scholar and a gentleman!

Remember the law specificity reigns AKA if you want to get good at lifting heavy weight – lift heavy weight, but in general the contrasting groups in these studies still produce adaptations, albeit less adaptation, but adaptation nonetheless.

Thus, if your goals are to get big and strong and you don’t like cardio – don’t do cardio, but likely still find a way to move throughout the day. A shot in the dark is at least 8,000 steps. On the flip side, if you get bored out of your mind progressing sets in prototypical strength and hypertrophy ranges, but love metcons and lifting weights for time, you can very likely still produce quality adaptations – it is just a lot of other factors likely need to be measured and monitored AKA everything Coach Davis highlighted above as well as total volume and recovery metrics (which should also be monitored and manipulated/progressed in the first scenario as well).