Why You’re Wasting Your Time Doing Only Long, Slow Aerobic Workouts

Affiliate Disclosure

Articles, Fitness

In many of the programs that I write out for my clients who are pursuing fat loss, I include a weekly or bi-weekly “long slow fat burning session”. This is chance for an individual to train their body how to oxidize and utilize fat efficiently during exercise, and is a good opportunity to still burn calories and burn fat, without breaking down the body in the same way as a hard session would.

After all, if you go hard all the time, every day, you're just going to get hurt or burn yourself out.

But some people, and especially longer distance endurance athletes such as triathletes, get stuck in a rut, performing a long slow fat burning session for nearly every workout – completely avoiding intensity or just not doing intense workouts or intervals because it takes them outside their comfort zone.

There are even trainers, athletes and coaches who would argue that long slow distance training is the ultimate way to get fit, since it turns the body into an aerobic machine and allows for superior development of the “slow-twitch” muscle fibers, which take a longer time to fatigue and primarily utilize fat as a fuel.

But this really isn't true. As a matter of fact, you're wasting your time and getting subpar results if all you're doing are long, slow aerobic workouts.

It's a myth that LSD is the best way to train. And this holds true for everyone from the 50 year old woman trying to shed a few pounds of fat to the triathlete attempting to qualify for the Ironman World Championships in Kona.

Data from animals provides some insight into this issue. In a study published in the Journal of Applied Physiology in 1982, researches Dudley, Abraham and Terjung observed that peak oxidative capacity of muscle fibers occurred when training sessions were performed at 94% of VO2 max intensity, which is far more difficult than the “long slow fat burning” zone.

To really get you fit FOR ENDURANCE OR FOR FAT BURNING, try the following workout, which was suggested by Stephen McGregor at the 2010 USAT Art & Science of Triathlon Coaching Symposium and is based on a 1998 study in the Journal of Applied Physiology, which noted that 30 second efforts led to incredibly significant increases in power output, peak power and VO2 (VO2 is your maximum oxygen consumption during exercise, and the “gold standard” measurement of performance potential in something like triathlon).

You'd probably expect the increases in power and VO2 mentioned above, but the interesting part is that the study also found significant increases in the oxidative process of mitochondrial enzymes, which basically means that the body's cells became more highly equipped for efficiency during aerobic activity – the type of activity you need during a triathlon, or for burning fat.

30 second all out “sprints”
• Start @ 4 x 30 sec all out w/2-4 min rest (3 x week)
• Increase to 10 x 30 sec all out w/2.5 min (3 x week)
• Do for 7 weeks (6.5-15 min/week)

Some people will also argue that hard exercise doesn't increase capillary density in the same was as long slow distance workouts, which means that the body wouldn't actually be able to feed sugar and oxygen to muscles quite as well if somebody were doing “interval” style training instead of low intensity, steady-state aerobic training.

But data suggests this isn't true either. A study in the Journal of Physiology in 1977 showed that high intensity training, around 80% VO2 max, increases capillary density to a greater extent than low intensity training. In this study, participants did the hard efforts 40 minutes per day, 4x/week for 8 weeks.

Another study in the Journal of Physiology in 2004 found that high intensity training increased capillary density by 20%! Both studies suggest that high intensity exercise is significantly effective at increasing both capillary density and capillary growth factor release (growth factor being another highly important fitness training response).

Obviously, some of these studies are old and some of them were done on animals, but the take away message is this:

Don't let anyone convince you that long, slow aerobic training is the best way to get fit, even for something like a triathlon. Sure, it should certainly be ONE component, but high intensity interval training will get you more bang for your buck, especially if you're pressed for time.

I'd love to hear your comments. Do you agree? Disagree?  I'm especially interested if any of you are going to begin incorporating the “7 weeks of 30 second intervals” workout suggested above. If so, keep me posted below on your progress!

Ask Ben a Podcast Question

33 thoughts on “Why You’re Wasting Your Time Doing Only Long, Slow Aerobic Workouts

  1. I have read so many articles about the blogger lovers but this article is really a
    good post, keep it up.

  2. Jon Miller says:

    High ben how about something like 4×8 minute intervals could these completely replace steady state cardio

    1. That’s pretty good but you also need to do some shorter intervals, and here’s why: https://bengreenfieldfitness.com/article/anti-agi…

  3. Han-Lin says:

    If we haven’t exercised for a long time, how long after starting an exercise program should we do an all out effort?

    1. I'd wait a good 2-3 weeks so that neuromuscular adaptations set in first.

  4. Andrew Turner says:

    Why exactly does the fastest old marathon runnerin the world do 3 hours slow running daily when preparing for a marathon?

    1. You should read the section in BeyondTrainingBook.com on "Polarized" training in which I describe various ways to stimulate mitochondrial pathway and assuming the long runs are purely aerobic (and time permits!) this is one of them.

  5. Kevin Smith says:

    Love 'em, but not early in the season. Too fast too soon brings = injured. Build a base first.

    1. “Too fast too soon brings = injured” – prove it. ;)

  6. friendhy.wall.fm says:

    Hey there! I simply wish to give you a huge thumbs up for your excellent info you’ve got here on this post. I will be coming back to your site for more soon.

  7. Janusz says:

    Maffetone used as a base-building program is great, but after some time I think it's good to inncoorporate intervals and hill sprints. In my case, after almost 3 months of doing only maffetone, I improved my time per mile by 1.5 minute (within the low maf HR), but my LT HR droped down from 188-185 to 170.

  8. tom says:

    I am really curious about the maffetone's method where Dr. Phil encourages 99% aerobic running at optimal HR and virtual no workouts above that limit. This seems in direct contrast with what you have talked about. Any advice for a marathon runner?

    1. You should listen to my interview with maffetone here. That's not really what he recommends. But that style of training would theoretically work if you a LOT of time to train, like 30 hours per week…

  9. steven says:

    Hmmm….I'm sorry I must be dense. I don't get the Interval work-out described. Some questions:
    1) do each step 3X per week or do each step for 3 weeks
    2) Each week I currently have 1 speed day, 1 hills day, 4 long days. Are you suggesting changing it to 3 speed days?
    3) for the start, if I select 2.5min rest. It means 3min cycle X 4 for 12min total. Is that all for the day? Or doing a slow 10K in the morning and then these 12min Intervals in the evening is ok.
    4) 10 cycles in Part 2 means a 30min Interval workout. I don't understand the 6.5min-15min per week comment

    1. 1) 3x/week
      2) depends on you and your goals. I'd be happy to help you with consulting at http://www.pacificfit.net/bengreenfield.html
      3) Again, depends on you and your goals.
      4) that's 6.5-15 minutes of total time spent at high intensity, per week.

  10. Alan says:

    Interesting article and viewpoint on HIT. I am 50 yrs old and ran my 1st marathon in 2008 at 48 shedding 36 lbs in the process over 6 months training.

    I have now plateaued 2 years on as I train for Ironman UK 70.3 triathlon and whilst I have only being doing HIT for 6 weeks both my pace in running and fat loss has started to kick in again. I am following the Dominator program.

  11. Scott says:

    I prefer intervals for the variety they offer during the exercise session vs. the stagnation that a slow paced workout offers. I enjoy experimenting with different time intervals (a concept I learned from Ben’s Shape 21 book) to determine my maximal efforts for 2min, 3min, 5min, etc. If I’m pushing my HR up to my max, I definitely feel like I’ve done some work. I believe they offer more bang for your buck for those who don’t have tons of time to work out during the week. It’s a nice jump start to begin your day with a short, intense workout, though proper stretching and warming up/cooling down is vital.

  12. ira says:

    Two Questions:

    1) Is the ‘rest’ active rest or complete rest ?
    2) Why are these better than tabatas ?


    1. The rest is “active rest”. The difference between these and Tabatas is that Tabatas almost require you to have a “gun to your head” to do. 3x a week would be pretty tough, mentally and physically. This is more do-able.

  13. jill says:

    great post. When I started incorporating intervals into my marathon training program I took my pace per mile down by almost 20 seconds.

    Its much easier to go out for a long, slow run, but I wasn’t getting any better without the intervals, so i’m definitely a believer.

  14. Christine says:

    I’m not an endurance athlete, so although this post doesn’t apply to me, I just wanted you to know that when I’ve incorporated “sprints” into my routine, whether they be tabata or fartlek type, I’ve always noticed an improvement in all areas of fitness. I see improvements in functional fitness as well as in strength & cardio. They always seem to get me out of a rut or past a plateau & are a really efficient use of time.

  15. brian says:

    ben, thanks for the info. i will try it out as i have trouble pushing myself for tempo type workouts but can do the short hard repeats.

    How would you or would you suggest doing both a bike and run workout in the same week?

    1. Brian,

      I personally do 3 bike workouts and 3 run workouts in a week but only ONE of those (one bike and one run) is a hard interval routine.

  16. Eric Petersen says:

    Great read Ben! I am / was in the same boat as Jeanine…just could not ‘max’ the HR out on my trainer. However, I think if I were outside, I could have as it seems I can manage to get the HR up more quickly when riding outside…. Also, on a side note…I ‘was” a LSD long training type a few years back when I was running marathons regularly…the Dominator HIT style training has ABSOLUTELY increased my mile pace over long distances…I am a believer!

  17. Dru says:

    Is HIT more beneficial for certain body types? I am predominately built for sprinting – lots of fast twitch fibers. I love HIT, and find it makes me faster for shorter events, but I still run out of gas on on longer distances, unless I go very slow. Can it really help me go longer? I guess I’ll have to try the experiment. My husband, on the other hand, is a classic marathoner: 5’11”, 150lbs of slow-twitch fibers. HIT really helps him go faster during long-distance events, but he already is hard-wired for going long.

    1. HIT is actually supposed to be BETTER for fast twitch types. Bur remember, if you’re running out of steam, there could be way more at play than just training…right?

  18. Jeanine says:

    This was a timely article, because I just did the first high-intensiy bike session in your Triathlon Dominator program. After the warm-up, it was a 6 -8 reps of one- minute max efforts, requiring max HR after just 30 seconds. I managed to reach near my max HR for the first two reps, but my legs weren’t able to push hard enough to drive my HR up so high for the next four reps. Is going as hard as possible, but not reaching max HR still give me the same benefit? I know I pushed as bard as I could because I felt sick after each one, but my HR was 10 beats lower than the first two reps. Thanks in advance!

    1. Sounds like your muscles need to catch up with your cardiovascular system, Jeanine. You experienced either glycogen depletion or neuromuscular fatigue before your heart and lungs were maxed out. As you gain fitness, you’ll be able to achieve the same heart rate for all the intervals.

  19. Rob Eachon says:


    Good article and clarification on the debate that currently seems to be pervasive throughout the triathlon community.

    1. XCHScoach81 says:

      Ben, great article.

      However, I think you make a few assumptions. Most of what you criticize seems based on your feelings rather than sound science. I would agree that just doing LSD workouts is outdated. However, referring to long slow aerobic workouts as a waste of time is absurd. Regardless of goals, becoming fit should utilize a varied approach that would include a lot of aerobic training. Your article incorrectly dismisses the importance of aerobic training.

      For example, I would train an 800m runner very differently than someone running a marathon, or loosing weight. However, the philosophy of training and how to train would stay the same. The body utilizes 3 systems of energy at any give moment for physical activity. The amount of each system used determines the intensity and duration of the workout and or activity required to enhance or increase that system. To be truly fit, one should train all three systems at varying degrees based upon their workout goals. You never really determine what your training for in the article. You sorta leave us to conclude that aerobic training is a waste regardless of activity. This is incorrect.

      In closing, I feel your intentions were good. However, you might have incorrectly and unfairly attacked aerobic training as "non beneficial" and or "a waste of time". Keep in mind aerobic training (especially from longer and slower duration runs) can give the following adaptations and benefits listed below, Also, you will see the energy requirements for two events on opposite ends of duration. The best true "bang for buck" training is a varied approach which certainly utilizing a healthy usage of aerobic workouts. Just my two cents.

      1. Cardiovascular System (increased heart size, decreased resting heart rate, increased stroke volume, increased cardiac output, increased blood flow, and increased blood volume and composition.)
      2. Muscular System ( slow twitch muscle fiber increased and enhanced, oxidative fast twitch muscle fiber increased and enhanced, increased capillarization, increased mitochondria, and increased oxygen extraction)
      3. Metabolic System ( increase in levels of myoglobin, increase in fatty acids, storage and use as substrate, increase in Aerobic Enzymes, Volume and Activity. (Taken from USATF Level 2 Endurance Training)

      Aerobic and Anaerobic contribution for events (two examples)

      1. 800 m 40% aerobic, 55% anaerobic glycolytic, 5% anaerobic alactic
      2. Marathon 98% aerobic, 2% anaerobic glycolytic, 0% alactic

Leave a Reply

Your email address will not be published. Required fields are marked *