Factors Limiting Aerobic Capacity

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Muscle Endurance/Volume

While these terms above are not new to the field of fitness and sports, much has been discussed on their importance in improving aerobic performance. My aim for this post is to highlight aerobic capacity and show how some factors, like the ones listed above, may have an effect on our ability to improve upon it.

Aerobic capacity is the “highest amount of oxygen consumed during exercise or activity” -Oxford. While there is strength, sprinting, and quick workouts in CF, most require a decent aerobic capacity. Many associate aerobic with simply long running. However, in CrossFit, believe it or not, we are constantly required to be “aerobic” in a multitude of exercise modes and time domains, whether it’s light running, using barbells or dumbbells, bodyweight movements like burpees or box jumps, and gymnastic movements. Because it entails more than just running, when dealing with aerobic capacity, you must specify what areas you want to be aerobic in and train it. There are some training factors that can limit our ability to being aerobically trained in CrossFit and I’ve highlighted some below:

Intensity. For significant improvements on aerobic performance, you must do more sustained, moderate, and sometimes low intensity work for longer periods of time than you would at higher/sprint intensity. Most research says that it’s actually harder to make as much improvements on anaerobic capacity, as much is genetic, than it is to improve aerobically. Check out this guy showing the differences. Also, while training at high intensity has some benefit to longer events, really, in order sustain work longer, you must work moderately. If you simply do sprints, or you make everything a sprint, you’re body will only get used to metabolizing the high intensity stuff (carbs/creatine/lactate). You must learn to train below your anaerobic threshold for this effect.

Muscle endurance/Volume
Often times, we each lack specific muscle endurance on movements which don’t allow us to make a workout “aerobic” or sustained. A personal example of this is mashing the early part of Open 17.4 up until the 55 HSPU only to get stuck midway through them. Because I am poorly trained…and weak 😉 for HSPU, I was not able to be aerobic within that workout. In order for me to improve my capacity in those workouts with those movements, I need to up my muscle endurance. Training with more volume (more reps at a time and more sets) helps with this.

This might be confusing, but try to hear me out. If you lack a TON of strength and a workout or event requires a moderately heavy load, you will not be able to be aerobic. Obvious of course. Single rep strength is often times a limitation (think 17.3 with heavy snatches). If the goal is to simply get better at working at heavy weight in the metcon, there is benefit to going heavier. However, just note that ALWAYS going heavier can make your aerobic capacity suffer for moderate/lighter weights. If there is a workout where ADV or Beefy weight is too heavy, you will loose your ability to train aerobically within that workout. This is why, when aerobic capacity is your goal, it is good to scale the weight in order to keep moving. While 1RM strength is important, it does not guarantee a quicker metcon time with light clean and jerks.

You hear Nabil and I talk about this all the time. When all capacity and skills are equal, the more efficient mover wins the race. Doing things with solid technique might be slower in cycle time, but, if your goal is to sustain work in longer workouts, moving more efficient saves energy. The more efficient mover will work more aerobically than the one who isn’t. Even at light weight, poor techniques adds up in those high volume/rep workouts. Try to maintain efficiency throughout the entire workout so you have a little kick at the end.

Many times, people don’t improve aerobically simply because they do not practice pacing. If you REDLINE on the first set of a 15-20 minute workout, you already set yourself up at a metabolic deficit (as Nicole Carol says). In other words, rather than start more aerobically, you tap your carbs and create lactic acid earlier than you need to. I see this a lot when folks try to pace off of others rather than knowing or being conscious of when they are going beyond that anaerobic threshold. Another example of this is getting tricked into thinking that just because the weight is light, means you should go fast. Again, if the goal is to sustain a pace throughout the workout, there’s no point in going out so fast only to stop in your tracks in the middle of the workout.

So how can I start improving upon these areas? First, you should identify the areas limiting your aerobic performance and as highlighted in this post, be conscious of the opportunities to work on them in each WOD. For myself, muscle endurance is a big one. I know that, in order to sustain intensity with things like handstand pushups and light barbell cycling, I need to practice doing bigger sets and trying to do more unbroken but relaxed sets. While I don’t need to do every workout like this, when workouts come up with them in it, I will can approach them with this mindset rather than just trying to WIN! I can also do extra reps after or before the workouts. For others, it might be adding a couple extra days where you work around 70% exertion to really know what it’s like to sustain effort for long periods. Get more comfy with not being so trashed on the floor after exercise. Endurance Rx workouts are good for this. Lastly, at the end of the day, it falls on programming. While us coaches at the Shop are very proud of what we have accomplished with our programming over the years, we always look for areas we can improve upon. We really believe we’ve come a long way with areas of strength and gymnastic skills since the inception of Sweat Shop and adding a little extra focus on aerobic capacity is only going to make us even more fit. I hope having this knowledge of aerobic capacity helps you a bit more in your approach to not just new workouts, but even in past workouts that you can re-test! As always, feel free to chat with a coach to help you identify areas you can work on!


7 replies
  1. Art Hoover
    Art Hoover says:

    If I would have known this before the open I definitely done better! What I am getting out of this is less snatches more metcons!

  2. Gomes
    Gomes says:

    My aerobic gainz are so lacking!! It’s no secret that running isn’t my favorite thing, but this week I started running at my school! I’m going to make it a strength.. maybe.. lol. Thanks for taking the time to write this blog, James, it was super helpful and good to read!!

  3. Tara Swarts
    Tara Swarts says:

    One of your very best and most informative articles James! I am learning a lot about this in rehab. Thanks so much for a great article!


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