Repeated Sprint Ability aka “Larger Sprinty Motor Units”

In Crits, Cyclocross, MTB XC and Short Track we need to be able to sprint out of corners and up and over obstacles repeatedly. How do we improve our repeated sprint abilities?

Is this simply that we need a larger FTP and/or better aerobic capabilities to recovery faster from these efforts or is there more to it?

Explosive efforts require the use of larger motor units, ones that we don’t typically tap into when training at/or below FTP.

How can we aerobically train our “Larger Sprinty Motor Units”?

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I think you have part of the picture; having a solid aerobic system is critical to being able to recover from hard repetitive efforts. The other part, IMO, is the ability to produce torque. One of my all-time favorite intervals is standing starts. Foot down or track stand is your choice, but do a max effort in a relatively hard gear and spin it out.

I could go either way as to whether it is better to do these on loose terrain / uphill or not, to exercise technique. Generally it’s not ideal to practice technique during a maximum effort, but once you have a good technical foundation and are close to your events, it isn’t a bad idea.

I have read articles by other coaches: Tim Cusick and Kolie Moore recommending the use of 15/15’s to target this ability. (Example 3 sets of 10 minutes 15/15’s, 5 min rest interval).

Studies have shown that XC skiers have well developed fat burning capabilities in their type 2 muscle fibers, due to the large force requirements of their sport.

It makes sense that the power we can push for the 15 second intervals would high enough to recruit these type 2 fibers with sufficient force.

@shawnfife, great topic! There is definitely the improvement of FTP and aerobic capabilities that will allow for improved recovery from those efforts. And I feel it’s a combination of factors. So a high threshold or VO2 max never hurt to have for endurance sports that require repeated sprints. I tend to think about it in terms of the type of athlete and what happens metabolically -

A very sprinty athlete (perhaps one with a high VLamax) could show a very high power output in the initial sprint, but then display a faster fatigue rate in subsequent sprints. A less sprinty athlete might not have a large initial peak power, but because of their lower fatiguability, may be able to repeat moderately high peak powers over and over again.

I would consider training these two athletes differently too. The sprinty athlete may have a larger inhibition of glycolysis with repeated sprints so would think about shortening recovery periods and extending the amount of sets completed, or time under tension to get that athlete to feel the stress of the aerobic contribution of repeated sprints with an aim to improve repeatability. The other athlete that may have a better VO2 max but lower peak power, so I would consider longer rest periods to allow the ATP/PC system to more completely restore and encourage higher peak powers with the aim to allow the strong aerobic system to help with recovery while we focus on peak power production.

@SteveHerman makes a good point about the terrain. Maybe early season/trainer season you can train the systems with structured intervals, and then in-season take that and apply “how” you produce that power on variable terrain to improve specificity. It’s a great question that came up in strength & conditioning circles back when I was in college - when unstable training was becoming a hot topic. Do you train maximal strength on, for example, a stability ball? I was in many debates with a girlfriend (also a strength coach) at the time and I always argued to train maximal strength under stability first, and then move to unstable surfaces (not only from a safety perspective, but in terms of generating maximal force to recruit those type IIb fibers and let them do their thing). BTW, that research still seems to be inconclusive if you’re wondering.


@ryan, this is where getting an Inscyd Test and knowing your Vlamax definitely can be important to guiding us as athletes!!! (All ya’ll hit up Ryan and Steve for a test!)

As a more “Sprinty” athlete, trying to become a less sprinty (lower Vlamax) athlete I have been using lower cadence work.
If we introduce torque and cadence into the equation. This also can be a part of event specificity. Off road has lower cadence efforts.

At what torque value do we think is adequate to get the fiber stimulation we desire?

Looking at a few recent rides I found this:
Endurance : 175 watts / 86 RPM / 20 Torque
Tempo: 240 watts / 56 rpm / 40 Torque
VO2: 395 watts / 60 rpm / 62 Torque
VO2/Ana: 420 watts / 50 rpm / 75 torque
Sprint : 800ish watts / 90-100 rpm / 80-90 torque

Do we need to be 2x, 3x, 4x our endurance torque???

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@shawnfife, thanks for sharing your data.

In terms of how much beyond endurance torque we need to be, that’s a good question. If we’re talking about lowering VLamax in your case, I would think about metabolically where are we starting to recruit more of the IIa fibers? That’s usually going to happen as we work into the tempo range and sub-LT. The closer to threshold we get, the more carbohydrate is oxidized. Above threshold of course, then we get more heavily into the IIb fibers, which can start to hamper reductions in VLamax.

I always think of Dr. San Millan’s “metabolic map” in this case. Having had the pleasure of working with him as he was putting this together, it made a nice, clear picture of how our metabolism and fiber recruitment change throughout exercise, and really does support the recommendations on bringing that lower cadence into your work.

In terms of torque, I was curious to see some previous training sessions and when I was doing lower cadence to work on torque below threshold, I was approximating 2x my endurance torque, which seems to be similar to your tempo range too. Comparing that to some maximal sprint intervals I’ve done where torque was 5-6x endurance torque, it seems like somewhere on the lower end would be safe. Particularly if we’re doing longer efforts, pushing high torque and high power can only last for so long, and if we’re going for fat oxidation improvements we would likely go to probably zone 2/low zone 3 based on our physiological profile.


I may be getting lost in the weeds here thinking about watts vs torque.

"The size principle states that as more force is needed, motor units are recruited in a precise order according to the magnitude of their force output, with small units being recruited first, thus exhibiting task-appropriate recruitment. "

Low cadence tempo/sweet spot does train some of our IIa fibers, but does it recruit the even larger motor units we need to jam 600-800 watts out of turns?
My gut says no, have to push harder.

Going back to the idea of 15/15 intervals.
700ish watts @ 100 rpm
400ish watts @ 50 rpm
Ok, event specificity, crits higher rpm, cyclocross likely lower rpms

If these two efforts produce the same torque values, are there benefits to one over the other (outside of event specificity)?

That’s what I would say too - low cadence tempo/sweet spot hits those IIa fibers, but it’s not enough to jam the bigger powers out of turns in races.

Outside of specificity, there’s the VLamax benefit from a physiological perspective, but also rate of force development on the neuromuscular side. With the size principle to guide us, I would expect that the 400w @ 50rpm would not achieve maximum force development, but it may get close (80-90%). The 700w @ 100rpm approach would seem to give a more likely maximal recruitment for a 15/15 workout. There is always the difference in fiber type as well, with greater rate of force development tending to be higher for athletes with greater type II fiber distribution.

What are your thoughts on benefits of each one? How do you use them now?

Potentially we could tolerate an increased training load/Increased time under tension with the low cadence work.

I race cross and have time to play around with some of these things before specific race prep.

I have recently built up to intervals 3 sets x 7 reps (1 min on : 2 min off) @ 400-420 watts @ 50-60 rpm. Building tolerance to 20 ish minutes of high torque load.

I am now trying VO2 intervals, 4 x 4 minutes @ 50-60 rpm @ about 400 watts.

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great conversation here.

@shawnfife have you looked at the torque requirements of the specific events you are discussing? If so what software did you use to do so?

@steveneal, I have been looking at torque using
Is torque a reasonable way to estimate motor unit activation? Or am I chasing my tail here.

I looked at a few cyclocross races from 2019. I consistently saw efforts of 5-7 seconds, at mid 50s to mid 70s for torque.

Maybe someone else can answer this as I couldn’t and be certain.

What I can say is that looking at the race tells you WHAT YOU did in that event.

Now you have to decide, was WHAT YOU did the right way to race?

By this I mean, are you getting speed with the torque you are generating?

Let’s think of this in a different way.

In an event with lots of corners, does your competition pull away from you out of the turns and you are always playing catch up?

Are you exiting the corner in the correct gear? or too big? or too small?

Are you losing ground getting to the turn (braking too early) then requiring a harder acceleration?

I believe looking at the torque demands is a great idea, but also let’s look at the bigger picture and strengths and weaknesses as well.

One thing I have my athletes do is: Ride a section with a number of turns, have a start and finish line, and roll past this at the same speed every time. Now, use a gear that is too easy for sure, time the section. Next time one bigger gear, and so on. Figure out if you only had one gear for that section what is fastest. Then you start to play in between the start and finish to see if shifting can actually give you a better time.

I am pretty sure you have a good practice course so you could try this on that course you know well, then let’s look at the torque versus speed (fast vs slow times)


I don’t want to speak out of turn here as there are biomechanics experts within our community that can dive much deeper on this with greater understanding, but what I’ve read seems to point to the power-EMG relationship allowing us to get a sense for the volume of motor units involved in force production (but not the actual force), and this appears to be fairly linear in that there is greater EMG activity at higher torque and cadence values.

I’ve been looking at torque in more detail with as well, and it has been interesting. Analyzing short track races has been fun because you can see how the changes in torque, cadence, and speed impact your performance. What @steveneal suggests in how we apply that torque is the important piece for performance, so looking forward to seeing what you come back with in terms of speed on a practice course!

I plan on getting some laps on course this weekend!

In an effort to squeak out some more gains on this subject, what are your opinions on active versus passive recovery between intervals?

In my experience passive recovery during short on/off efforts (like 15/15’s), allow for great power output for “ON” efforts.

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Yes, so I’m all for active recovery. If we look at the INSCYD data that has the very nice lack of pyruvate graph (basically showing how well you can recover after hard efforts), we can see that there is a power range that allows us to combust the most lactate, so in terms of that, active recovery at a specific range would be helpful.

For short on/off efforts, I’m still a big fan of active recovery only because those rest periods are so short that I like to keep the legs moving between intervals and by the time the legs spin down and get some rest, it’s time to spin them back up again. The typical scenario when we seem to see a lot of support for passive rest is in track workouts where there are massive efforts with long recovery periods of riders lying on the ground after their sprint(s).

Borrowing from rock climbing, there’s some good support in the literature (and in my personal experience) in using active recovery between climbs. So rather than letting the arms hang loosely once they get a pump, there seems to be good support for shaking them out, moving them around, etc. to help that muscle pump move the blood around to enhance recovery.

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@shawnfife were you able to get some laps in?

@steveneal I went to my CX course only to find a group of pesky MTB-ers doing a skills camp. Hopefully my awesomeness will have converted a few :crazy_face:
I made a small/tight course with a variety of turns that required me to accelerate out of them.
I did laps (lasting about 90-120 seconds) for each gear working my way down the cassette.
I did this 3 times.
The first 2 sets to dial in the lines, and dropping/dialing tire pressure. 3rd set pushed harder just under race pace, to get good info.

40x36/32/28 - way under geared, spinning up to 120-130rpm on course to build momentum.
40x25- 97 seconds, This felt better, torque values between 75-90 for accelerations.
40x22 - 94 seconds, Winner, better balance of pushing to accelerate, but not having to spinout cadence, torque values between 80-110 for accelerations.
40x19- 97 seconds, cadence was bogged down a bit, accelerations weren’t as sharp,

Here is the 40/22 Lap
I also did a longer course, at a tempo effort. This muted the spikes, torque peaks 70-80’s



Thanks for doing that.

Did you find it helpful to do a real-world test do really feel the difference in the legs?

Darn, pesky mtbers…

I think it was very helpful. As soon as I went 1 gear too large, I could definitely feel cadence getting dragged down, lost a bit of snap in the pedal stroke. Not as smooth between turns.

As far as “leg feel”… I’m not sure what to say here. In only 90 seconds it wasn’t enough to determine fatigue difference. I think I need to do some longer timed efforts, and also compare those to laps when I shift (like you suggested previously).

All in all, I’m super happy with how my legs felt with repeated punches out of these turns (especially with the tempo laps feeling super controlled). I feel like the work I have been doing has been helpful.


@shawnfife great feedback. Yes I believe you will learn even more from longer sessions, the right gearing on the difference courses and terrain will really help near the end of the race.

I think this will help fine tune the knowledge of your body and pacing.

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