The Cyclocross Workout Of The Day for Tuesday, 9.13.16. “Marshalling our intervalic forces”

Howdy folks,

It’s Tuesday, and guess what? We’re doing the same thing we did last Tuesday!


Well, frankly, because it takes a couple/few reps to really get the hang of doing these damn things. And because this workout is good for ya, in a “What doesn’t kill you” kinda’ way.

What workout is this that we’re talking about?

It’s the…

The MB15 – 

Warm up well. (Seriously. Warm up for this one, it’ll help.)

The basic idea here is to do a series of very short efforts with very little rest between them, for a pretty long period of time.

Sound confusing?

Here’s how it breaks down…

Warm up.

Get set…


15 seconds on

15 seconds off

15 seconds on

15 seconds off

…and so on and so on for the duration of the interval.

How long are you going to do this for?

– Ten minutes

How many sets?

– Three -four sets, 5 minutes between sets. Ideally, you aspire to pile enough ten-minute segments on top of one another to equal the duration of your races.

How hard do you go during the “on” segments?

– Pretty darn hard.

You’re familiar with the level of effort you put out in your 2×20’s by now, right?

You need to go harder than that.

More than a little bit harder.

Ideally, you’ll hit these on periods at right about 150% of your FTP, if that’s a number that means anything to you. If it doesn’t, it’s harder than what you’re dong your 2×20 effort at. A lot harder. For most folks it’s going to be about 50% harder.

Like I said, “ouch.”

How easy do you go during the “off” segments?

– A lot easier, but you aren’t soft pedaling.

Right about 50% of your FTP, or in the neighborhood of half as hard as your 2×20 level.

This is going to seem way too easy when you’re starting out, but by the end – if you’re doing these right – it’s probably going to be really damn hard to keep the “off” that high.


It gets worse.

Ultimately, you want to be able to do however many of these it takes to equal the duration of your typical CX race.

Seriously, Ouch.

Do what you can.

That’s the basics of this workout, but let’s talk about how folks tend to screw this up, shall we?

First of all, you really can’t do this workout correctly with a power meter that’s set to anything other than instantaneous power display. Even a 3-second display rate can screw things up; that’s 20% of the interval duration!

So, go check your PM settings and adjust accordingly.

Next big screw up? These aren’t sprints.

You’re looking to nail these output levels for the duration of the intervals, not way overshoot them and then coast back down to them.

If you’re doing a 300 watt “on” segment, that means 300 watts for 15 seconds, not 400 watts for 5 seconds and then 250 watts for 10 seconds.

That’s fine and all, but it’a different exercise.

A corollary to this is, on the “off” segment, you aren’t coasting. Ever. You’re doing 50% of your ftp. It’s not uncommon at all for people to experience the “off” portion as just as hard – or harder! – as the “on” section as the overall duration of the interval set reaches the duration of your race day.

In graphic form, your workout should look more like a square wave –


Than like this…

niki microb

(yup, snipped from a real-life attempt at this workout)

Make sense? Have at it!

Oh, almost forgot!

Last week, after doing this same workout reader Bart De Wever asked…

Hello, Just did the MB15 today (which is indeed pretty hard to do it exactly like you describe it). Great training, love it ! I was just wondering where the name comes from ? Did a google search and all I could come up with was a classic Marshall amp😆 !





Definitely not the amp, Bart!

The naming convention for this is actually pretty simple. This type of interval workout is called a MicroBurst interval, and we’re doing them for 15 seconds, so MB-15. You may also see some MB-30’s later on in the season, so stay tuned!

Thanks for asking, and for reading!






What’s that you say? You’d kinda’ like to have a cycling coach help figure this stuff out for you? Check out…


~ by crosssports on September 13, 2016.

4 Responses to “The Cyclocross Workout Of The Day for Tuesday, 9.13.16. “Marshalling our intervalic forces””

  1. Well my second guess, after the Marshall amp was…..Micro Bursts…pretty obvious but nevertheless it took me a while to figure it out…..maybe because I was ‘cooked’ after the training ;-).

  2. Is this exercise done on the road or on the soft tracks?

    • Hi Peter,
      Either/or. Wherever one can manage to pull it off. Personally, I almost always do these on the trainer due to the difficulty of easy local access to suitable terrain.

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