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marc feldman


I was very happy to see part 5. So now to close the loop on a question raised earlier and you alluded to in this part:

What role, if any, do muscular endurance and anerobic endurance intervals have in the build/peak (last 12 weeks) before an Ironman.

Specifically, should I be doing Zone 4 or 5 intervals on the bike and run? And if so, how often and with what WIV per session/week.





My Power curve drops off pretty quickly around the 18-20sec mark thus I struggle in longer sprints (say 200-300m).

Interval workout suggestions to improve my sprint endurance & reduce my fade during a sprint & keeping closer to the sprinters?

- Longer Sprint Power intervals & work towards increasing intensity?
- Lots of Sprint Power intervals?
- Other?


Joe Friel

Bill--There are 3 variables here to consider: intensity, duration and tactics. I really don't know enough about these to make a decent suggestion. Even if I was your coach it could take a long time to figure out the primary limiter.

Joe Friel

Marc F--Anaerobic endurance not at all. ME only if you are are swimming fast (<1h), biking fast (<5h) or running fast (<3h). Otherwise stick to aerobic endurance as the primary limiter.


Hi Joe, thanks for posting part 5 I've been waiting to read it.

You mentioned decoupling was a good way to measure performance when doing AE workouts, ie the athlete isn’t ready to progress to advanced ability workouts until AE is excellent. So once they are excellent you are ready to progress to the advanced workouts such as ME workouts.

So I assume you do AE workouts until decoupling is excellent then start doing ME workouts for example. Do you just keep doing those or do the gains stop after a while, such as 12 weeks is the max you could do to get any gains before you plateu, or is there another way to measure this?

Also, i assuming once build period is complete you progress to a race, but when the race season is over do you go back to AE workouts? Your fitness should be high at this stage so why go back to AE workouts?



Hi Joe,

Very interesting reading part 1-5 and the MTB bible as well.

But I have some difficulty separating the anaerobic threshold, lactate threshold or functional threshold.
I have been testet to know my AT heart rate and watt output, but I can't get a hold of AT compaired to LT and FT?


doral real estate

I was your coach it could take a long time to figure out the primary limiter..good blog...d I be doing Zone 4 or 5 intervals on the bike and run? And if so, how often and with what WIV per session/week...

Christopher Psarakis

what do you think about longer ME intervals for cyclists? Do you use 3x15', 2x20', 3x20' sessions? Does the WI duration, depends on the race duration?


Barton Tofany

Excellent article on higher intensity training.
I have been trying for several weeks now to run with a more mifoot strike that will reduce braking at foot fall. I have been doing many of the Evolution Running drills yet I still seem to land with my foot ahead of my center of mass, basically digging my toe into the ground. Any suggestions on how to help plant my feet under my center of mass and reduce this braking action?

Adam M

I've read some studies lately - I'm sure you've seen them - talking about the correlation between long-time endurance athletes and scarring of the heart due to many longer duration workout sessions. It seems clear in your books that a solid aerobic base is important, such that you recommend erring on the side of 'too much' base, and to return to base after the end of each 'season'. But, if I am worried about the above issue due to a family history of heart disease, and a personal history of higher than normal BP, would it be advantageous for me long term to avoid extended base periods and instead focus my workouts on shorter duration interval work, with maybe only 1 AE run/bike per week (ie the long run)? You, I assume, may not be able to speak to the medical side of this, but would this type of training still help me maintain an upward performance arc while not hurting longer distance races (My training is a bit hybrid, bike/swim is geared toward sprint/int from YBT, run training is a combo of faster tempo work and marathon training - 50ish miles a week) Thanks!

marc f.

Thanks, Joe. That would be would be different from what I have previously done, as I always felt compelled to do some Zone 4 work to keep my "top end" sharp. But I guess there is no need to be running even a few 6:30 miles when the goal IM pace is more like 9:00.

It sounds like the Zone 3 aerobic endurance intervals desribed in Part 4 are the way to go.

But I'm a bit confused becasue in your books you refer to Zone 2 as aerobic endurance and Zone 3 as extensive endurance. Yet, the aerobic endurance intervals are actually in Zone 3. Is that right?

Joe Friel

marc f--I've found z3 to be more affective for building AE for advanced athletes.

Joe Friel

Adam--I can't say. Not enough is known about this.

Joe Friel

Barton T--run some strides on clean grass each week with your shoes off. Shoes encourage heel striking. note that I'm _not_ saying do all of your runs barefoot or even a lot of running that way. A few minutes a week at the start of a run will help you learn.

Joe Friel

Christopher Psarakis - I know some who do that. If it works that's ok then.

Joe Friel

doral--Sorry, I don't understand the question.

Joe Friel

Tom--Wow, lots of questions. You can search most of these on my blog home page. As for AE measurement, note that I mentioned power-HR ratio as another way of determining when AE is well established. Until then keep doing the workout.

Chris Livingstone

Joe, where does zone 5a fit in?

Joe Friel

Chris L--z5a is an extension of z4.

Michael H.

Nice post. It adds some detail to the info from "Your Best Triathlon", which I've been using this year.

Any thought to writing a post about brick workouts? I ran a site search and didn't see any in-depth coverage of the topic. Some people like to do longer brick workouts while others do shorter transition runs. Some don't do many bricks at all. I noticed that there was more variety with brick workouts in the Triathlete's Training Bible, while Your Best Triathlon switches the emphasis to shorter (15 min.) transition-type bricks.

I'd be interested to read whether there is specific research favoring one approach or the other. Or whether this is just one of those training topics that varies a lot according to the individual athlete. Thanks.


Perhaps a year ago at this time you wrote on the subject of VO2max intervals for older cyclists who want to retard age-related decrease in performance. Are there any conceptual differences in the design of such interval workouts - where the goal is not a specific race at a specific time? For instance, changing the work:recovery ratio or changing the duration of the work piece?

Joe Friel

Madeleine - The key, I believe, is to stimulate testosterone release. High intensity does that regardless of RI I suspect. All of this, of course, is pure conjecture on my part.


Hi Joe,

I'm trying to understand and apply some of your earlier comments on event-specificity and how training benefits of a given activity carry over to another.

What I'm missing is which of the "abilities" are specific to the muscle groups emphasized in that activity and which provide non-specific physiologic benefits.

In some cases it's clear. For example, clearly maximal force drills for cycling are of little benefit for swimming. On the other hand, aerobic training on the bike resulting in greater heart stroke volume clearly benefit all events, regardless of how you get them.

In other cases it isn't so clear. For example, when I do intervals on the bike that improve efficiency of lactic acid buffering, am I training just my legs or my entire body?

Joe Friel

mitch--That's a great question. Of the 6 abilities I listed (aerobic endurance, muscular force, speed skills, muscular endurance, anaerobic endurance and sprint power) the only one that I would say has significant carryover to other endurance sports (e.g., in triathlon) is aerobic endurance. There is certainly some transfer of cardiorespiratory fitness (heart, lungs, blood) to other sports. But it is not 100%. In other words, an hour of aerobic endurance training in the pool is not the same as an hour of bike/run aerobic endurance as far as sport-specific benefits. One reason is that much of what we call 'cardio' training actually occurs in the working muscles. (For ex, development of aerobic enzymes.) I have never seen any studies that tried to quantify this but there are some that show a bit of a crossover.

Dan M

Hi Joe,
first of all thanks for this great posts about intervals. I've also read your Training Bible and I have a question: what is the difference between the intervals for Muscular Force and Sprint interval?
They look similar to me.
Also when do you suggest to start the Muscular Force trainnig? At Base 2?
Thanks again

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