Workout of the Day:
Front Squat
and then,
Three rounds for time of:
10 Front Squats (60-70% of today’s 1-RM)
20 Burpees
30 Sit-Ups

Yay Burpees!
Yay Burpees!

The Myth of the Fat-Burning Zone
Written by Mark Riebel

An old article from the CrossFit Journal has this same title, and I’d like to give a quick synopsis here if you’re not a subscriber (which you should be).

How many times have you heard that in order to really burn fat, you’ve got to work in heart rate range of 50-70% of your maximum for at least 30 minutes? There’s even convenient charts posted on nearly every piece of cardio equipment in all the traditional gyms you go to (if you’re cheating on us here at Invictus), so it must be true. Fortunately for us, it’s not.

Yes, it is true that fat makes up the bulk of your body’s fuel for most of your daily activities and in low-intensity aerobic exercise where you’re either working for long periods of time or not breathing exceptionally hard. This fact is where the idea comes from that you must be in a certain sub-maximal heart rate range to maximally burn fat. The problem is that this is a misunderstood point.

If I work at a slow and steady pace for my prescribed 30 minutes on the stairmaster while I watch TV, I might burn, say, 100 calories, approximately 50% of which are from fat. Now, if I do that same 30 minutes at a much higher heart rate (and therefore intensity level), I could burn about 300 calories, of which maybe only 30% are fat, with glucose and glycogen making up the bulk of the rest (a small amount of protein gets burned as well). “See, you burn more fat at an easier pace!” the exercise magazines will tell you. But anyone with some basic math skills can see that more total fat was burned in the high-intensity workout (90 calories vs. 50) than the lower one, and the first workout merely had a greater percentage of calories burned from fat.

Most of you will be thinking at this point, “But our workouts aren’t that long, so there’s no way we can burn this many calories!” This is a forthcoming post in itself where I’ll tell you a bit more about geeky science things like exercise post oxygen consumption and why you get much more bang for your buck with the style of workouts we do instead of watching television on the stairmaster for 30 minutes. For now, though, trust in the programming and try to hold back your snickers when someone tells you about weight loss and the fat burning zone.

  • christine

    Thanks for the post Mark. Had to laugh because by the time I read the last paragraph, you addressed my exact thoughts. Wouldn’t longer WODS at the same high level intensity be much more productive? I look forward to the forthcoming post.

  • M

    Crazy C, is that you?

  • Cynthia

    But I like Snickers….

  • christine

    Hi Michele! Did the “longer WOD” part give me away?

  • Mark Riebel

    There’s a typo in the last paragraph. It should read “excess post-exercise oxygen consumption.”

    Christine, as far as the longer workouts go, you have to find the right balance between duration and power output. Most of what we do focuses on the shorter end because you’re able to put out much harder for brief periods as opposed to long ones. As time goes on in the workout, eventually you’re forced to slow your pace because your body simply can’t keep up with the effort level. An example would be something like Grace. If you’re tasked with 30 clean and jerks, many athletes can complete this in a relatively short amount of time, and we could calculate how much work they did in that time to give an average power level. Now I task you with 100 c & j at the same weight. Obviously, this would take you far longer and you’d have to rest for much longer periods of time during the workout. If you were to calculate your power output for this it would be far lower than the first workout. While power output is the end-all be-all for every workout, it is a very powerful indicator of the effectiveness of a workout, and it’s what we like to maximize. Does all of that make sense?

  • Mark Riebel

    Kind of forgot to wrap that up…

    This doesn’t mean that endurance work has no purpose. Particularly for long-distance athletes such as yourself Christine, longer time domain workouts are something that need to be trained. We visit these occasionally to get some aerobic work as well as developing the mental fortitude it takes to just keep going. But from what we’ve seen, nearly everybody will see larger improvements in fitness by training in relatively short, high intense workouts.

  • richard


    Also, doesn’t all the short, intense training we go through also help us sustain maximal aerobic effort, say like running a 3-5 miles? I haven’t run months, actually, haven’t run since the last Navy PRT back in April and the other day i ran a 5k in 25 minutes and wondered how much crossfit actually played a role in that run for me. I never felt stronger during a run than i did that day and it the last half of the run i felt the strongest. So don’t all the brief, intense workouts we do also help us sustain those aerobic efforts, or should also periodically train those longer time domain workouts?

  • Mark Riebel


    You’re right that there is some increase in aerobic capacity when you train mostly anaerobically, though the reverse is not true. Again, that’s why we prioritize for the anaerobic side of things. Aerobic training will improve your efficiency is oxygen uptake and fat burning (this means you burn less fat for the same amount of work–usually not something you want when considering fat), as well as a host of other adaptations. We primarily see long aerobic training as a benefit from the mental fortitude side of things, so it’s definitely something to visit from time to time.

  • POS

    Perfect segue today. Today marks the start of the Fall Rowing Challenge by Concept 2. Crossfit Invictus has an online rowing team. Adam T set it up and you can sign up and contribute. If we have 10 people row a total of 100,000 meters in 30 days we will earn a chance at wining a new C2 rower. This is such an obtainable goal, just think if you ge to the gym a bit early and want to warm up, sit on the rower and pull 1 or 2K and at the end cool down with another few K. You can log all of your meters online. Either I or Adam will post something about this in the next day or so. Start rowing everybody.

    Did you do your 100K yet you sick man?

  • Lizzle

    You guys are so smart . . . makes me want to sniff you.

  • tony m

    wonderful begining here.
    when someone has a heart-ache about the short duration for our WOD’s and the “fatburning zone”, is it taken into account the amount of the time we spend warming up, dynamic stretching,the Oly lift time,etc?
    i know i spend about an hour in the gym when i come in, and i will bet that if i had a heart rate monitor on the whole time, most of that hour would be spent in or well above my 50-70% zone.
    or are the exercise “gurus” just taking into account the time doing the actual WOD?

  • Mark Riebel


    My guess is that the only time considered by critics of shorter, more intense workouts would be the time spent directly on the WOD. You are right about the structure of our classes keeping your heart elevated for most of the time. We try to keep the traditionalists happy too 😉

  • Carla Mac

    I will contribute to the rowing team. I may be out of San Diego by the 25th of this month if my house sells…but I’m good for some major miles on the Concept 2. I have one at home…does this count or do we need to rack up miles on the gym rowers so it will be recorded?

    Today’s workout was a butt kicker…I thought. Going from FS to Burpees gave my legs a challenge.

    PR on FS today at 82K

    WOD: 13:54 with 50K on the bar.

  • Nice post Mark – keep up the good work.

  • AT

    POS – I have been out of commission ever since the games with a shoulder thing…I am going to start easing into things again…starting today.

    I haven’t done my 100K challenge yet…that is on my “bucket list”…right now I just kicked off marathon training for the Carlsbad Marathon.

    I will try to chip in 5K on the rower today. Everyone should row at least 500m before or after the workout. 500m takes the slowest person 3 minutes and is a great way to warm up.

    The contest officially starts tomorrow. Here is a link with the details.

    Go to this page and wander your way through to sign up as a member of CrossFit Invictus and start rowing.


    If we have 50 members row 500 meters a day for 30 days it is 750K meters…thats a lot for a little effort.

    Start pulling!! POS and I will share responsibility for keeping everyone updated on how we are doing as a team!!

  • Carla Mac

    OK…I have signed up on the Concept Rower site and joined the team. I will row 2,500 meters per day for the next two weeks at a minimum to add some miles.

  • POS

    Thanks for the post AT, posting something about the challenge was on my bucket list. Be smart with that shoulder.

    Carla Mac, welcome aboard! As Adam said you can row anywhere as long as you log your meters. I row at home before breakfast and then pre-wod and also post wod. I agree that FS to Burpees was a nice burn by rep 15. Time 8:03 with 150# on the bar. Did a Oly WOD prior to the Met-Con today.

    You can row on your off/rest days everyone. A great way to watch others workout while you row merrily down the stream.

  • ShaneF

    I’m trying to register for the C2 Challenge but Crossfit Invictus isn’t listed on their drop down menu of teams available to row for. Should I just type it in or is something amiss?

  • Mark Riebel


    Where’s our team on the site? I looked on the pulldown menu and it wasn’t on there. Shane said he was having the same problem. Anyway, I started off with a 2K this morning…only 98K more to go.

  • shanef

    10K today!

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