The Ultimate Guide to Interval Training: How to Build Massive Power and Smash Your PRs
If you want to get faster on a bike, you have to stop just "going for a ride." You need to start doing intervals.
Interval training is the single most effective way to improve your fitness. It’s how you take your current FTP (Functional Threshold Power) and move it from "pretty good" to "the person everyone struggles to follow."
In this guide, I’m going to walk you through exactly how to structure your intervals. We’ll cover everything from the "Goldilocks" Sweet Spot sessions to the lung-burning VO2 max efforts. By the end, you’ll know exactly what to do the next time you clip in.
What Exactly Are Intervals?
Think of interval training as a way to "cheat" your physiology. If I asked you to ride at your absolute limit for 40 minutes straight, you’d probably blow up after 15.
But if I break that 40 minutes into four 10-minute chunks with a little rest in between, you can handle it. You get the same amount of high-quality work done, but your body actually survives the session.
Intervals allow you to spend more time at a higher intensity than you ever could in one continuous block. That "time at intensity" is what forces your heart, lungs, and muscles to adapt and get stronger.
Why This Matters for YOUR Training
Without intervals, most riders fall into the "Moderate Trap." You ride a bit too hard on your easy days and not hard enough on your fast days.
This leads to a fitness plateau. Intervals break that plateau by giving your body a specific reason to change.
The Foundation: Understanding Your Zones
Before we dive into the workouts, we need to speak the same language. Everything in interval training is based on your FTP.
If you don't know your FTP, go do a ramp test. Once you have that number, your training is divided into zones. For the workouts below, we’ll focus on:
- Sweet Spot (88-94% of FTP): Hard, but sustainable.
- Threshold (95-105% of FTP): The "race pace" feeling.
- VO2 Max (110-120% of FTP): Full gas, short duration.
- Anaerobic (120%+ of FTP): Sprints and short, sharp attacks.
Sweet Spot: The "Secret Sauce" of Base Training
If you only have 6–8 hours a week to train, Sweet Spot is your best friend. It’s called the "Sweet Spot" because it offers the biggest physiological bang for your buck without leaving you so tired you can’t train the next day.
Why do Sweet Spot?
It builds your aerobic engine and increases your mitochondrial density (the "power plants" in your cells). It makes you more efficient at burning fat and sparing your sugar stores.
The Workouts
Try these progressions. Start with the first one and move down the list as you get stronger.
- The Foundation: 2 x 15 minutes at 90% FTP. Take 5 minutes of easy spinning between sets.
- The Classic: 2 x 20 minutes at 90% FTP. This is the gold standard for building a big engine.
- The Progressor: 3 x 15 minutes at 92% FTP. More total time, slightly higher intensity.
- The Boss: 1 x 60 minutes at 90% FTP. This is a mental and physical test.
Example: If your FTP is 250W, your Sweet Spot range is 220W to 235W.
Coach’s Tip: If you can’t finish the second interval, your FTP might be set too high, or you’re carrying too much fatigue (check your TSB!).
Threshold Intervals: Raising the Floor
Threshold work is about increasing the maximum power you can hold for an hour. This is the "bread and butter" for time trialists, triathletes, and climbers.
These workouts are harder than Sweet Spot. They require more mental focus and more recovery time.
Why do Threshold?
Threshold training teaches your body how to process lactate. When you ride at 100% of your FTP, your body is producing lactate at the same rate it's clearing it. By training here, you push that "tipping point" higher.
The Workouts
- 3 x 10 Minutes: 10 minutes at 100% FTP, 5 minutes rest. Great for your first threshold day of the season.
- 2 x 20 Minutes: 20 minutes at 100% FTP, 10 minutes rest. This is the ultimate FTP builder.
- Over/Unders: These are my favorite. Do 3 sets of 12 minutes. Inside each set, alternate between 2 minutes at 95% FTP (the "under") and 1 minute at 105% FTP (the "over").
Why Over/Unders matter: The "over" generates a bunch of lactate, and the "under" forces your body to clear it while still working hard. This mimics real-world racing perfectly.
VO2 Max: Raising the Ceiling
Imagine your fitness is a house. Threshold training raises the floor, but eventually, your head is going to hit the ceiling. VO2 Max training raises the roof so the floor has room to move up.
These are short, very intense, and—honestly—they hurt. But they are incredibly effective.
Why do VO2 Max?
You are training your heart’s "stroke volume"—essentially how much blood it can pump to your muscles with every beat. You’re also training your mind to handle the "burning" sensation of high-intensity efforts.
The Workouts
- 5 x 3 Minutes: 3 minutes at 115-120% FTP, 3 minutes rest.
- 4 x 4 Minutes: 4 minutes at 112-115% FTP, 4 minutes rest. This is a classic "Norwegian" style interval.
- The 30/30s (Micro-intervals): 2 sets of 10 minutes. Each set consists of 30 seconds at 130% FTP followed by 30 seconds of easy spinning.
Coach’s Tip: For VO2 Max, don't stare at your power meter too much. These should be "Full Gas" efforts. If your power drops by more than 10% from the first interval to the last, you’re done for the day.
Anaerobic and Sprint Intervals: The Finishing Kick
These are for the riders who want to win the sprint to the town sign or stay attached to the group when the road kicks up to 15%.
Why do Anaerobic work?
This isn't about your lungs; it’s about your muscles and your "anaerobic capacity"—your ability to work without enough oxygen. It’s a very small fuel tank, but it’s very powerful.
The Workouts
- Tabata Sprints: 20 seconds at 200% FTP (or max effort), 10 seconds rest. Repeat 8 times. It only takes 4 minutes, but it will ruin you.
- Hill Attacks: Find a short hill that takes 60 seconds to climb. Sprint up it at 150% FTP. Coast back down. Repeat 6 times.
- Winning the Sprint: 30 seconds at absolute maximum effort. Take 5 full minutes of rest between efforts. You need to be fully recovered to hit the high numbers again.
How to Plan Your Interval Week
You cannot do high-intensity intervals every day. If you try, you’ll end up in the "Red Zone" (TSB < -40) and your fitness will actually go backward.
Here is a sample "Build" week for a dedicated cyclist:
- Monday: Total Rest or 30 min very easy spin.
- Tuesday: VO2 Max Day (e.g., 5 x 3 mins). Do your hardest workout when you are freshest.
- Wednesday: Endurance Ride (Zone 2). Keep it easy!
- Thursday: Threshold Day (e.g., 2 x 20 mins or Over/Unders).
- Friday: Recovery Spin (30-60 mins).
- Saturday: Long Ride with Sweet Spot mixed in (e.g., 3 hours with 2 x 20 mins SS).
- Sunday: Long Endurance Ride (2-4 hours Zone 2).
The 3:1 Loading Rule
Always follow a 3:1 pattern.
- Weeks 1-3: Gradually increase the "Time at Intensity" (e.g., Week 1 is 2x15, Week 2 is 2x20, Week 3 is 3x15).
- Week 4: Recovery Week. Cut your volume by 50% and do no high-intensity intervals. This is when your body actually builds the muscle you’ve been asking for.
Common Mistakes (And How to Avoid Them)
Even the best athletes mess this up. Here’s what to watch out for:
1. Going too hard on easy days
If your "recovery" ride has a TSS of 60 and you’re hitting Zone 3 on the climbs, you aren't recovering. When you show up for your Tuesday intervals, you won't be able to hit your target power. Keep the easy days easy so the hard days can be hard.
2. Chasing TSS instead of Quality
Don't just try to get a high TSS score. 100 TSS from a 2-hour easy ride is NOT the same as 100 TSS from a brutal interval session. The interval session creates a much stronger stimulus for your body to get faster.
3. Ignoring the "Traffic Lights"
If your TSB is -45 (Deep Red) and you have a VO2 Max session planned, skip it. Your body is too tired to adapt to the stress. Swap it for a nap or an easy spin. You’ll be much faster for it on Saturday.
4. Testing FTP too often
You don't need to test every week. Test at the start of a block and at the end of a recovery week. Your FTP doesn't change daily, but your ability to hit it does.
Tools for the Job
To do intervals properly, you need a few things:
- A Power Meter: This is the gold standard. It tells you exactly how much work you are doing, regardless of wind, hills, or how much coffee you drank.
- A Heart Rate Monitor: Use this alongside power. If your power is 250W but your heart rate is 10 beats higher than usual, you might be getting sick or overtrained.
- Indoor Trainer: It is much easier to do a perfect 20-minute interval on a smart trainer than it is on a road with stoplights and traffic.
Summary: Your Path to Power
Interval training isn't complicated, but it is hard. Here is your cheat sheet:
- Find your FTP: Use a ramp test to set your baseline.
- Pick your goal: Want more endurance? Do Sweet Spot. Want to climb better? Do Threshold. Want to win races? Do VO2 Max.
- Watch your fatigue: Use the TSB (Form) metric. Stay in the "Green" or "Amber" zones for your hard workouts.
- Be Consistent: One perfect workout won't make you fast. Six months of "pretty good" workouts will.
- Recover: You don't get fast on the bike; you get fast while you sleep after the ride.
Now, stop reading and go look at your training calendar. Pick one of the workouts above and schedule it for tomorrow. Your future, faster self will thank you.
Ready to smash it? Let's get to work.