Interval training for cycling is a crucial type of workout that should be in all triathletes', duathletes', and cyclists' training plans, from beginners to advanced athletes. Interval training is also known as HIIT (high-intensity interval training), SHIIT (super high-intensity interval training), or VO2 max intervals.
It is a powerful tool for increasing cycling speed and performance because it helps build aerobic and anaerobic capacity. Aerobic capacity refers to the ability of the body to produce energy using oxygen, while anaerobic capacity refers to the ability of the body to produce energy without oxygen. Both types of capacity are crucial for performance on the bike.
While endurance athletes should spend 70-80% of their total training hours at a low intensity, to make progress, they need to spend 20-30% of their time training at a high intensity. Triathletes and cyclists can make significant progress in their performance by doing these sessions as part of a well-designed training plan.
In this article, you will learn:
- Is interval training good for cycling speed
- What is the best type of interval training
- How long should bike intervals be to get faster
- What is the best ratio for interval training on the bike
- What’s the difference between cycling intervals and HIIT
- How fast to go during cycling intervals
- How to prepare for an interval bike workout
- What are some great interval cycling workouts you can do
- Are 30 second intervals effective
6 Key Benefits of Interval Training for Cycling Speed
Interval training is a highly effective way to improve your cycling speed and overall fitness. Here are just a few of the many benefits of incorporating interval sessions into your training plan:
- Better cardiovascular health: Intervals are a great way to improve heart and lung health by pushing these organs to their limits and making them stronger in the process. Studies have shown that cardiovascular health is a very important predictor of life expectancy.
- Improved endurance: Interval training might seem counterintuitive for building endurance, but the short bursts of intensity actually help your body produce energy more efficiently, leading to better endurance.
- Neuromuscular power: Short intervals of 15-60 seconds are highly effective for increasing your top-end anaerobic power, allowing you to sustain better speed for longer periods.
- Faster overall: Interval sessions are key to becoming a faster athlete. They improve your V02 max, lactate threshold, and pain tolerance, making it easier to perform fast efforts.
- Improved exercise economy: Doing intervals reduces the amount of energy required to perform at the same effort level, improving your exercise economy.
- Increased fat burning: Super high-intensity intervals are highly effective for burning calories, even after the workout is over, due to post-exercise oxygen consumption. These may be short, but they have lasting benefits for your health and fitness.
The Science of Intervals for Cyclists
The goal of interval training is to push yourself beyond your comfort zone to trigger a Hormetic response that leads to improvement. By pushing your limits, your body will adapt by getting better, stronger, and faster so it can perform better the next time you train.
Polarized training plans, where the majority of your time is spent at a low intensity, while a small amount of time is spent at a very high intensity, work so well because low-intensity training builds mitochondrial density, while high-intensity intervals teach those mitochondria how to work more efficiently.
Interval bike workouts, particularly intervals of 2-8 minutes, have been shown to significantly increase an athlete's VO2 max, the maximum amount of oxygen they can process each minute. A number is strongly correlated with improved race performance and increased energy production.
Interval training can also improve an athlete's ability to buffer lactate in the body. This means that during high-intensity efforts, less lactic acid will build up, allowing you to perform at a higher level for longer periods of time.
Three Different Types of Interval Workouts for Cycling
Super High-Intensity Intervals
Super High-Intensity Intervals, also known as sprint intervals or even SHIIT training, are 15-60 seconds intervals performed at your maximum possible effort, with large amounts of rest between the intervals, such as a 1:4 work-to-rest ratio, to allow for proper recovery.
Coaches and athletes often overlook these intervals, but they can have significant benefits, including raising VO2 max, increasing FTP (functional threshold power), and boosting neuromuscular power. They're particularly important for older athletes who might have lost some raw speed from their younger days.
Sprint intervals are typically only performed during the base-building season as they are too short and don't reflect the demands of most endurance races.
An example of a SHIIT workout from a baseline training plan can be found in our training app.
High-intensity intervals (or VO2 Max intervals) are longer, typically 2-8 minutes, which has been identified as the optimal time for building VO2 max (the maximum amount of oxygen you can process in a minute.) Developing this is critical as it has been found to be a key factor in determining success in triathlons.
These intervals tend to be at a lower intensity than sprint intervals as they are done for longer and have shorter rest periods, usually around a 1:1 or 4:1 work-to-rest ratio.
High-intensity intervals should be performed during the main race season when training specifically for a race. These intervals should gradually get longer, with the rest period becoming shorter as you progress further into the race season.
You can see the two workouts below from a half-IRONMAN plan in our app, where the first includes shorter intervals with longer rest at the beginning of the plan, while the second is closer to the race and features longer intervals with short rest
Not all intervals are actually HIIT workouts, and tempo intervals are a prime example. Tempo intervals are 10-60 minute intervals done at a moderately fast effort level. They don't build top-end speed or VO2 max the way sprint intervals or HIIT intervals do, but they're critical for race performance as they build the ability to hold speed for a long period of time.
Tempo intervals should become a focus closer to a race; they are typically done to build the ability to maintain a moderate pace. They bridge the gap between speed and endurance and are not typically considered either HIIT or cycling intervals.
An example of a long tempo-focused bike session from our half-IRONMAN training can be found in the final few weeks before the race.
Incorporating Interval Training into a Cycling or Triathlon Training Plan
In low intensity training, we recommend athletes use heart rate to determine their training effort. However, for interval training, athletes should use the rate of perceived exertion or power on the bike instead of heart rate. This is because heart rate takes 1-2 minutes to reflect the actual effort level, making it unsuitable for these intervals.
Power is a more accurate measure, but it requires a smart bike trainer paired with Zwift or a power meter on the bike. Whether you have a meter or not, we'll give you guidelines to incorporate a bike interval session into your plan.
Step 1: Calculate Your FTP (for power meter users)
Calculating your bike training zones is the first step in incorporating bike intervals into your training. To do this, you need to perform an FTP (functional threshold power) test. FTP is the approximate maximum power in watts that an athlete can hold for 60 minutes.
There are several ways to calculate FTP:
- 60 minute test: Ride for 60 minutes at an all-out effort, finishing feeling completely spent. Your average power over 60 minutes is your FTP. This is a brutal test that requires a lot of experience and preparation to execute.
- 20 minute test: Ride for 20 minutes at an all-out effort where you finish feeling completely spent. 5% lower than your average power over the 20 minutes is your FTP. This is also a brutal test that requires a lot of experience and preparation to execute.
- Ramp test: In a ramp test, like the Zwift ramp test, you will start cycling at a low intensity and increase the wattage slightly every minute until you can no longer continue. The FTP number is 75% of your best 1-minute average.
We prefer the Zwift ramp test because it is accurate, easy for developing athletes to perform correctly, doesn't require much pacing, and can be performed every two months without rearranging your training schedule to keep your cycling power zones up to date.
Once you have your number, you can insert it into the calculator below to get your bike zones.
How Long Should Cycling Intervals Be?
If you're in the northern hemisphere, your races typically occur between April and October. November and December will be considered your off-season, and January to March will be your base building season. The length of intervals builds from short to long as the season progresses:
- Off-season: Intervals are very infrequent, with a focus on sprint intervals of 15 seconds to 2 minutes to keep top-end speed, Functional Threshold Power, and VO2 max activated.
- Base building season: Athletes should focus on sprint intervals to bring up their top-end speed and gradually make the intervals longer, building to low-end Vo2 max with 2-3 minute intervals.
- Race season: Athletes should focus primarily on Vo2 max building intervals of 2-8 minutes, with a sprint interval workout once every 6-8 weeks to keep top-end power activated. In the final eight weeks before a race, intervals should become longer, transitioning into tempo intervals of 10-60 minutes.
What Rest Should You Take Between Cycling Intervals?
There is no set best rest interval, but the general rule of thumb is that the rest should be greater the longer and more intense the interval is.
- Sprint intervals typically require a work-to-rest ratio of 1:8 to 1:2
- HIIT intervals, the ratio can range from 1:1 to 4:1
- Tempo intervals, the ratio is typically 4:1 to 10:1
How Fast Should You Go During Cycling Intervals?
Speed should not be used as a metric for your intervals while on the bike. Variables such as road incline or decline, wind, road surface, and body position can greatly affect your speed, making it an unreliable measure for training purposes.
A power meter is a useful tool for measuring your cycling performance. Still, it can be confusing for beginner cyclists and triathletes, so we don't mandate that new athletes train with one.
Rate of perceived exertion (RPE) is a simpler and more accessible method for guiding your intervals. You should go as hard as you can within the following three requirements:
- You don’t fade by the end of any interval, and they have to be the same effort from start to finish.
- You don’t fade as you’re doing the final interval, and they all have to be at the same effort.
- You end the workout feeling like you could have completed one more interval, this makes sure you didn’t go too hard overall, and you’ll be able to train well the next day.
If you have a power meter, the following guidelines can help guide you based on your cycling power training zones:
- Sprint intervals: Aim to reach 50-100% higher than your FTP
- HIIT intervals: Zone 5 for short intervals of 30 seconds to 2 minutes, and Zone 4 for longer intervals of 2-8 minutes
- Tempo intervals: Top of Zone 3 and the bottom of Zone 4
Where Should Cycling Intervals be Scheduled in Your Training Plan?
It's important to know when to plan your interval bike workouts because it's not enough to simply do these workouts. You have to know when to do them so you can execute well and adapt properly. Here are some guidelines on when to schedule your HIIT bike workouts:
- On a day when you’re feeling well-rested and prepared to perform at your best.
- Due to their shorter length (30-75 minutes), we recommend doing these during the week when time might be tighter for those who work from Monday to Friday.
- If you have two workouts in a day, make the interval session is the first one, so you’re not starting already tired.
- If your job is physically or mentally demanding, consider doing these before work so you can give them your all.
In the training plans in our app, we like to make Tuesday-Thursday fairly intense, allowing Monday and Friday to be easier days for recovery and rest.
Here's an example of a weekly training schedule for an intermediate IRONMAN triathlete, where you can see where the interval cycling workout is placed following these guidelines.
How to Prepare for an Interval Bike Workout?
It's important to make sure you're primed and your body has everything it needs to perform to the best of its ability.
In the 30 minutes before an intense workout, you should eat 20-40 grams of carbohydrates to ensure high blood glucose levels and quick access to energy.
Finally, have music or motivational videos ready to get pumped up and ready to tackle the challenging workout.
Wrap-Up on Cycling Interval Sessions
Hopefully, you have a good grasp on including this type of workout into your triathlon or cycling training plan.
If you want a training plan that is done for you and completely personalized to your capabilities, race schedule, and goals, check out our training app that has triathlon training plans from Sprint triathlons up to IRONMAN races, and cycling plans for Gran Fondos, road races, and ultra endurance bike races.