The CEXI Workout: Let's Make Intervals Sexy!
Updated: 5 days ago
Let's talk about cyclocross executed intervals (C-EX-I), otherwise known as the "sexy" workout.
It's that time of year when the racing season is winding down, the days are getting shorter, and the motivation to stare at power numbers on an indoor trainer is fading fast. Welcome to the transition season!
This is the time to loosen up the structure, recharge mentally, and have some fun on the bike. But that doesn't mean we should completely abandon intensity, especially for masters athletes who benefit from keeping the high-intensity engine warm.
Enter the CEXI workout.
This is my cyclocross-centric take on the classic 30/15 microburst interval workout, with a twist. Instead of grinding out intervals on a perfectly smooth road or indoor trainer, we're heading to a grassy field, setting up a miniature cyclocross course, and putting down some serious watts.
We're going to add some corners, a little rough terrain, and maybe even a few sexy curves.
The result? A challenging, full-body cycling workout that develops power, sharpens bike-handling skills, engages your senses, and reminds you why riding bikes is fun.
Why CEXI?
The CEXI workout has three primary goals.
Keep the intensity engine warm. During the transition period, we want less structured training, but we don't want to lose touch with higher-intensity efforts. This is particularly important for masters athletes. An occasional dose of high-intensity work helps maintain familiarity with the demands of racing without committing to a full training block.
Learn to put down big power when things get rough. Producing 125–135% of FTP on a smooth road or trainer is one thing; producing that same power while bouncing across uneven grass, controlling traction, and preparing for the next corner is another. This is a skill that transfers directly to fast, rough sections of gravel, mountain bike, and cyclocross courses.
Get out of your comfort zone. Training shouldn't always be about chasing physiological adaptations in a perfectly controlled environment. Sometimes we need a challenge that engages the whole body, demands concentration, and stimulates the senses.
What You'll Need
The equipment list is pretty simple:
A gravel, mountain, or cyclocross bike
A large, relatively flat grassy area, approximately two soccer fields in length
At least four corner markers (cones, flags, water bottles, colorful jerseys, etc.)
A backpack to carry your markers
Course Setup 1: The Basic Track Loop
We'll start with a simple rectangular course using four markers. The idea is to create a loop with two long power sections and two shorter recovery sections. Think 30 seconds ON, 15 seconds OFF, repeated continuously.
Step 1: Warm up.
Ride easily for 10–15 minutes. Save your final two big warm-up efforts for the course setup; we'll use those efforts to help establish the length of the straights.
Step 2: Set your first corner.
Place your first marker in the grass. This will be your starting reference point.
Step 3: Establish the length.
From a rolling start, ride past your first marker and accelerate into Zone 6, targeting approximately 125–135% FTP.
Hold that power for about 30 seconds.
Come to a controlled stop and place your second corner marker.
Congratulations! You've just completed one of your final warmup efforts and established the length of your course.
Step 4: Establish the width.
Repeat the effort along your established straightaway.
As you approach the second marker, begin braking, coasting, and turning 90 degrees across the width of your rectangle.
Start your lap timer, or simply count in your head.
When 15 seconds have elapsed, place your third marker.
Step 5: Complete the rectangle.
Place your fourth marker so it lines up with markers one and three, completing your rectangular loop.
You now have a basic course designed around approximately 30-second power efforts and 15-second recovery sections. Simple, effective, and ready to ride.
Course Setup 2: The CEXI Loop
Let's make it sexy and add some curves! For those looking for a little more adventure, we're going to add some fast, flowing S-turns. The goal is to make the recovery sections more engaging and fun without introducing unnecessary risk.
You'll need approximately ten markers, depending on your layout.
Step 1: Establish your straightaway.
Follow the first three steps of the basic setup above, establishing a straightaway that takes approximately 30 seconds at Zone 6 power.
Step 2: Shorten the width.
After your 30-second effort, begin coasting and turning 90 degrees.
Count off approximately 10 seconds while soft-pedaling across the width of the rectangle.
Place your next outside corner marker. We're leaving a little extra time for the curves.
Step 3: Build your S turn.
Starting from the outside corner:
Measure approximately 4 bike lengths across the width.
Turn 90 degrees into the rectangle and measure 2 bike lengths. Place a marker.
Turn 90 degrees again, parallel to the width, and measure 3 bike lengths.
Turn another 90 degrees and measure 2 bike lengths back toward the outside edge.
Use these reference points to create a flowing S turn that you can negotiate quickly and smoothly.
Step 4: Repeat at the opposite end.
Mirror the layout at the other end of the course, adjusting the markers to create flowing entries and exits onto each power straightaway.
The objective is to produce approximately 15 seconds of recovery and cornering between your 30-second efforts.
Don't get too hung up on exact measurements, and adjust the curves to match your handling ability.
Watch the video below to see a demonstration of how to set up the loops.
Workout Execution: Time to Get Sexy!
Now that the course is built, it's time to put down some watts.
The execution is straightforward.
30 seconds ON: Accelerate hard out of the corner. Your power will spike into Zone 6. Settle into a target of approximately 125–135% FTP and keep driving all the way down the straightaway.
15 seconds OFF: Begin braking approximately 5 meters before the corner, adjusting for speed and traction. Coast, steer, and soft pedal through the turns in Zone 1–2.
As you exit the final corner, accelerate hard again.
Repeat continuously around the course, don’t forget to ride it in both directions!
Workout Prescription
Component | Prescription |
Work interval | ~30 seconds at 125–135% FTP |
Recovery interval | ~15 seconds at Z1–Z2 |
Set duration | 6-12 minutes |
Recovery between sets | 3-6 minutes |
Number of sets | 2-4 |
Frequency | Once every 1-2 weeks |
Start conservatively, especially if you're new to microbursts or riding hard on grass. Six-minute sets with generous recovery are plenty challenging.
The goal is repeatable, high-quality efforts, not simply surviving the longest possible workout.
Power targets are a guide. As fatigue accumulates, focus on maintaining good execution and consistent efforts. However, if you drop below Z6 for more than 5 seconds, stop the set and recover.
Tips for Getting the Most Out of CEXI
Wear a racy kit!
Seriously. There's something about putting on your favorite race kit that makes you want to ride f
fast.
Don't let off the gas!
This is probably the most important execution tip. Power will easily spike above 125% FTP during the initial acceleration, especially in the first 10 seconds, but here's the catch: it's the remaining 20 seconds that really matter.
When you're bouncing across uneven terrain, your body will subconsciously ease off the pedals. It still feels hard because you're working to stabilize the bike, absorb bumps, and maintain control. But your watts can drop quickly. This is what Coach Tim calls "spike and fade." Don't let that happen. Upshift as your speed builds and keep driving the pedals.
The objective is to maintain strong power throughout the entire effort, not just produce an impressive acceleration. And remember to downshift as you approach the next corner. You'll want the right gear to start recovering immediately after the effort and be ready for the next acceleration.
Big numbers!
Set up your head unit with just two fields: 3-second power and lap time. Make them as big as possible.
When you're putting down a big effort, fatigue is building, the bike is bouncing around, and your ability to process tiny numbers isn't getting any better. If your head unit supports color-coded power zones, even better. A quick glance on a clear straightaway should tell you everything you need to know.
Adjust your course as needed.
After a few practice laps, adjust the markers so you're getting approximately 30 seconds of work and 15 seconds of recovery. If the straightaways are too short, lengthen them. If the S-turns are too tight, open them up. If you're carrying too much speed into the corners, adjust your braking points.
The goal is a course that lets you maintain the rhythm of a traditional 30/15 workout while adding the demands of off-road riding.
And don't be afraid to get creative. You could use 20/10 intervals, make the corners more technical, or introduce different terrain features.
Don't hit your lap button for every ON/OFF interval.
It’s not sexy. You have enough to focus on, live in the lap, and focus on execution. That's the whole point.
Good, Better, Best: Where Does CEXI Fit?
I like to use a Good, Better, Best philosophy when evaluating training options, and from a purely physiological perspective, CEXI falls into the Good category.
If your primary objective is to maximize the physiological adaptations of a classic 30/15 microburst session, a controlled road or indoor trainer workout will generally provide a more consistent stimulus. You can hit your targets more precisely, control the recovery periods, and minimize the interruptions associated with cornering and uneven terrain. That would be the Better or Best option for a focused interval session.
But that's not really the point of CEXI. During the transition season, we're not necessarily trying to squeeze every possible adaptation out of every workout. We're trying to maintain some intensity, sharpen our skills, and keep training mentally stimulating.
CEXI introduces something that traditional structured intervals often lack: the challenge of producing high power while actually riding your bike. You're accelerating, shifting, braking, cornering, managing traction, and absorbing terrain. You're training your ability to execute power under real-world conditions. And perhaps most importantly, you're having fun.
The Takeaway
Not every workout needs to be perfectly structured or physiologically optimized. Sometimes a good workout is one that gets you outside, challenges your body, engages your mind, and leaves you smiling. That's what CEXI is all about.
Grab your bike, find a grassy field, set up some cones, and give it a try before winter sets in. Who knows, you might even get a little "cross curious" and decide to get between the tape.
Enjoy!
At BaseCamp, we believe that every cyclist has the potential to achieve greatness, no matter where they start. Our mission is to create a community-driven training environment where cyclists and triathletes of all levels can train together, support each other, and grow stronger, faster, and more confident in their abilities. Our cycling training programs are expert driven and tailored to your needs. Whether you're a seasoned pro or just getting started, BaseCamp is where you belong. Click here to learn more about Coach Doug.
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