Data-driven triathlon training

Using technology to track data is incredibly easy in today’s day and age. Most triathletes use GPS-watches, heart rate monitors, mobile apps, and other gadgets to track and monitor all sorts of data on their training, racing, and general health.

But tracking and monitoring data is one thing. Using the data to drive your decisions about how to train and race is a different story. Knowing how to filter and decipher all the information that you have can be difficult and confusing. Focus on the wrong metrics and numbers, and your training is likely to stagnate, or worse, you might get yourself injured or overtrained.

Those triathletes and coaches that do learn how to effectively use data stand to gain massive advantages. The opportunities are almost endless, and will only become greater in the future. You can learn exactly when you need to push or back off your training, how to plan your training to peak perfectly in time for a race, when to move on from one training phase to the next, and so on.

In short, triathlon is at a crossroads where those not embracing and mastering data-driven training will inevitably get left behind their data-savvy competitors.

In this article you’ll learn about 13 high return on investment ways to use data to improve your training and racing performance. I’ll show you specific examples of how I use data-driven training in my own training and for athletes I coach. Feel free to copy my methods exactly, or adapt them to suit your needs.

I’m a big advocate of using the Training Peaks software platform for planning and analyzing your training so many (but not all) of these tips are specific to Training Peaks. Training Peaks offers both free and premium accounts that are worth every penny. I suggest you sign up for a free account and try it out for a while, and if you like it and want to get the full benefits of data-driven training, then you should definitely upgrade to a premium account. Enjoy the article!

1. Regular fitness assessments - the prerequisite for data-driven training

A prerequisite for data-driven training is knowing your current fitness level in all three disciplines.

To improve fitness, you must have an appropriate progression of your training workload be part of your training program. In other words, you have to induce the right dose of training load or training stress on your body, and this dosage should be progressive.

You can measure training stress and use this knowledge to manage your training load progression (see point 2). However, measuring training stress accurately requires you to know what your fitness level is in each discipline.

Although there are some variations in terminology, essentially you’ll always assess your fitness level in terms of functional threshold pace in swimming, functional threshold power (FTP) or functional threshold heart rate in cycling, and functional threshold pace or functional threshold heart rate in running.

Knowing your functional thresholds allows you to set training zones (pace, power and heart rate), and that in turn will help make your training that much more effective.

There are a few different test protocols you can use to test your fitness. As long as you stay consistent and test the same way each time, it doesn’t matter that much whether you pick one over another, but the tests I like to use are:

A 400 m and 200 m swim time trial to calculate your Critical Swim Speed (functional threshold pace) in swimming. See the exact protocol and plug your times into the calculator here.

A 20 minute bike time trial (ideally on the indoor trainer), where 95% of the average power you can hold is your functional threshold power

A 30 minute time trial run, where your average pace is your functional threshold pace and your average heart rate over the last 20 minutes is your functional threshold heart rate.

It’s critical that you reassess your fitness regularly. I recommend doing it at the very least every 8 weeks, but during times of the season when you progress a lot (such as during the base and build phases) every 6 weeks or even every 4 weeks is preferable.

If you don’t reassess regularly, not only will you be potentially doing a lot of your training at incorrect intensities. But all the rest of your data-driven training efforts and analyses will be wasted, since everything we measure in data-driven training is based on your functional thresholds.

2. Plan, assess and periodize your training using Training Stress Score

Traditionally when mapping out a periodization plan for a season, athletes and coaches have been combining quantitative data like weekly training hours or weekly distance (in running and cycling) with qualitative “thoughts and ideas” about what kind of training to do in which period.

This is a good approach, but it has some flaws.

Primarily the fact that it’s very difficult to know whether any given planned progression of training duration will work in practice when training intensity changes as you move through training periods.

These days you can get around that problem by using Training Stress Score (TSS), which takes into account both duration and intensity of training to periodize your season.

So if you periodize by TSS, you can go into every new training week knowing that the week before that you managed a similar workload. You don’t have to worry about doing too much or too little training as your distribution of volume and intensity shifts. It’s all accounted for in the TSS.

You can get an estimate of the TSS of every workout in your training plan, as long as you know it’s duration and have an estimate of its intensity as a percentage of your functional threshold. This is all pretty easy to learn, it just takes a little time and effort up front.

The image below shows and annual training plan based on TSS. You can see that the weekly TSS increases gradually until three weeks before as the athlete’s goal race (with the exception of recovery weeks every third week). Knowing the target TSS for each week allows us to tailor the athlete’s workouts to meet the target TSS each week.

It’s all well and good planning and and periodizing by TSS, but you should also assess your actual completed training, and see whether you’re hitting your target TSS.

The image below shows how this athlete has done that very well so far in her periodization. As a result, her fitness is progressing very well, but not too fast (this would lead to a high risk of injury, illness and overtraining).

3. Use the Performance Management Chart to monitor fitness, fatigue, and form

Understanding the Performance Management Chart in Training Peaks is key to understanding how your training is progressing.

First, let’s cover some important terminology:

Fitness = CTL = Chronic Training Load

This is your average Training Stress Score over the last 6 weeks. Obviously, the higher this average, the fitter you are.

Keep in mind that it’s still all relative to where you started. Having a higher CTL than another athlete doesn’t mean that you are faster than the other athlete. But if your CTL is steadily increasing (as in the image below) then you are getting fitter.

This is your average Training Stress Score over the last 6 weeks. Obviously, the higher this average, the fitter you are. Keep in mind that it’s still all relative to where you started. Having a higher CTL than another athlete doesn’t mean that you are faster than the other athlete. But if your CTL is steadily increasing (as in the image below) then you are getting fitter. Fatigue = ATL = Acute Training Load

Same as fitness, but this is the average TSS for the last 7 days only. So if you made a big increase in training stress over the last week, you will see a big increase in fatigue, whereas a slow and steady increase in training stress will keep your fatigue more level.

Same as fitness, but this is the average TSS for the last 7 days only. So if you made a big increase in training stress over the last week, you will see a big increase in fatigue, whereas a slow and steady increase in training stress will keep your fatigue more level. Form = TSB = Training Stress Balance

TSB is simply the difference between fitness and fatigue. During periods of heavy training, TSB will be negative (sometimes quite a lot), because even though you might be very fit, the amount of recent training stress greatly reduces your freshness.

However, once you reduce your training load, fitness might decrease only slightly, but fatigue will decrease a lot (since it’s a one-week average instead of six-week average like fitness), which means your form will quickly increase.

There’s a lot that goes into the PMC, but the bottom line is:

During your training and up until your taper, you want to see a general trend of increasing fitness.

In this period, your form can and should be low, and your fatigue can be high. Not constantly, though. Take rest days and easy weeks to counteract that.

Once you start peaking for a race, you want to decrease your training load so that your fitness decreases just a little bit, but your form increases a lot. This means your ready to race.

Don’t worry if your fitness is not constantly increasing. It’s absolutely necessary to accept periods where it decreases slightly. These periods, an easy week every fourth week for example, are what rejuvenates you so that your body can the adapt to the stress you put on it once you get back to progressing your training load.

What the PMC does in this case is help you determine how much rest and how easy training is just enough, so you don’t do too much and end up carry too much fatigue, but don’t do too little and end up losing too much fitness either.

4. Know your ramp rates

If you plan your training using TSS and pay attention to your PMC, you should see a steady increase in fitness (CTL), Just how rapidly your CTL increases is known as your ramp rate.

Obviously, it’s nice getting fitter faster, but if you do too much too soon you’ll be flirting with injury, illness and overtraining.

That’s why keeping an eye on your ramp rates is crucial. In the image below, you can see that this particular athlete has a ramp rate of 3.4 CTL over the last 7 days, and a CTL of 71. This can be considered a conservative, low-risk ramp rate.

What a sustainable ramp rate for you is will depend on a lot of different individual factors, but coach Jim Vance offers some guidelines in his book Triathlon 2.0:

Low risk ramp rate is 4 or less if your CTL is 45 or less, and 6 or less if your CTL is 70 or more.

is 4 or less if your CTL is 45 or less, and 6 or less if your CTL is 70 or more. Moderate risk ramp rate is between 4 and 6 if your CTL is 45 or less, and between 6 and 8 if your CTL is 70 or more.

is between 4 and 6 if your CTL is 45 or less, and between 6 and 8 if your CTL is 70 or more. High risk ramp rate is 8 or more if your CTL is 45 or less, and 10 or more if your CTL is 70 or more.

But remember, these are just guidelines, and at the end of the day, it is you or your coach that needs to find the sweet spot that works for you.

5. Assess your aerobic endurance

Your aerobic endurance is essentially your “base fitness”. Your ability to keep going for a long time at a relatively low intensity (around 80% of your functional threshold heart rate).

Since all triathlon distances, even the fast and furious sprint distance, are primarily aerobic in nature it’s critical for triathletes to have a well developed aerobic system, or a “good aerobic base”.

Once your aerobic base is good enough, you can maintain it with a relatively small amount of low to moderate intensity training, and turn your attention to developing other aspects of fitness, like muscular endurance.

How do you know whether your base is good enough or if you need to keep working on it?

By measuring your decoupling and efficiency factor.

Decoupling refers to a drift in heart rate compared to pace (in running) or power (in cycling). It’s measured as a percentage, where a high percentage indicates that your heart rate increases a lot even if your pace or power stays constant, and a low percentage indicates that if your pace or power stays constant, then so does your heart rate.

Look at the chart below:

Here you can see that heart rate (red line) follows pace (green line) very well. There’s only a very small increase in heart rate towards the end of this workout even though the pace stays the same.

The decoupling here is 3.01% (decoupling is “Pa:Hr” in the right sidebar). In the Triathlete’s Training Bible, author Joe Friel states that aerobically fit athletes have a decoupling of 5% or less. When you see this low a decoupling in your longer workouts, you can be confident that your aerobic endurance is where it should be.

Contrast the above decoupling with the decoupling of 7.18% seen below:

While heart rate doesn’t necessarily increase, it stays quite constant while the pace seems to drop towards the end of the workout. This results in the greater decoupling, and is a sign that aerobic endurance should still be a focus for this athlete.

A second way to measure your aerobic endurance is by using the efficiency factor (EF).

EF is simply the distance you can cover per heartbeat, so a higher value is better. In Training Peaks, EF takes terrain into account, since it uses a calculated normalized graded pace as input for the EF calculations, and not just regular pace.

Note that EF is not comparable between different athletes, since different athletes can have very different heart rates for the exact same effort.

The way you can use EF to assess aerobic endurance is by comparing similar workouts you’ve done over time, and check your EF trend. The workouts should be done at a steady pace and at a low to moderate intensity. Ideally, select a route that you can repeat in the exact same way every couple of weeks at a similar effort, and monitor your EF for this workouts.

As long as EF keeps increasing, your efficiency at aerobic intensity levels is increasing, and you still have gains to be made.

But once your EF starts plateauing and no significant improvements have happened over the course of several similar test workouts, it’s a clear sign that you’re close to maxing out on the gains you can make from this kind of training, and it’s time to move on to the next training phase.

The efficiency factor is highlighted in the two images you already looked at for decoupling, with the first one showing an EF of 1.68, and the second one an EF of 1.48.

6. Monitor your muscular endurance

Muscular endurance is in simple terms your ability to push moderately high (tempo or zone 3 efforts) to high intensities (up to threshold efforts) for extended time periods. Your muscular endurance plays a huge part in determining how fast a triathlete you are.

Since it’s such an important ability for all triathletes, you should be monitoring it closely.

During the periods of the season when your goal is to increase muscular endurance you should be seeing a steady increase in certain key metrics that indicate increased muscular endurance.

If you don’t, you have to take some time to analyze whether you need to change something up in your training.

The key metrics I recommend you track are P20 and P60. These metrics show the best average power you have held in training (or racing for that matter) for 20 and 60 minutes on the bike, and the best average pace you’ve held for 20 and 60 minutes on the run.

Take a look at the images below. I’ve marked the P20 and P60 columns for an athlete’s power progression (first image) and pace progression.

For power, you can see a clear trend of increasing P20 and P60, indicative of increased muscular endurance. For example, the last 3 complete weeks show a progression of 192, 202, and 220 watts for P60.

For running the picture is less clear, and P60 is completely lacking from 3 weeks ago and for the month of October. For P20, data is available, but not clearly increasing. This is a sign that we need to keep an eye on the run training and start seeing a progressions soon, or otherwise we may need to change things up a bit.

A word of caution:

Things like fitness assessments (FTP tests and the likes) and races can skew these data. If that happens, you may want to filter out dates when you raced or did your assessments to get a more realistic overview of your muscular endurance.

7. Optimize your taper

My favorite part of the Performance Management Chart is how it allows you to take much of the guesswork out of tapering and peaking for goal races.

In order to peak perfectly, your job is to optimize for two things:

Minimize fitness loss (decreased CTL)

Get your form (TSB) into your sweet spot range

Let’s make one thing clear. You WILL lose fitness when tapering, and that’s perfectly fine. Your freshness (form) on race day will more than make up for it.

Generally speaking, the longer your goal race the more CTL you can and should probably lose. To give you some rough guidelines, up to at most a 10% loss of CTL might be ok for an Ironman goal race, but for an Olympic distance goal race up to 5% would be more appropriate.

Form (TSB) on the other hand should increase, but not excessively. You can only raise your TSB so much before the decrease in fitness will be too much and the balance is off.

The reference values for TSB is between 0 and 20 on race day.

But, as with anything in triathlon, this is highly individual. Try to find a narrower range that seems to work really well for you, and then try to get TSB to that personal sweet spot in future races, while minimizing your CTL loss.

Let me illustrate with an example PMC, where I’ve marked where peak fitness occurs relative to race day, and what happens to CTL and TSB in between these two time points.

This athlete was preparing for an extreme Skyrunning race. It was 32 km long, but with 2500 m of elevation gain and with it being very technical, this was an almost five hour long event, so comparable to a 70.3.

The athlete’s CTL peak happened 8 days out from the race. CTL was 72.6 at this point, and TSB was a negative -5.8. Taper had already started, but it obviously takes a few days before the trends start turning.

On race day, CTL had dropped to 65.6, so a 9.6% decrease in CTL. TSB on the other hand, had increased to 11.1, right in the middle of that 0 to 20 reference range.

This athlete ended up having an excellent race, so for future races, we now know with more certainty what to shoot for when we plan the taper period for goal races.

8. Reverse engineer your key workouts

This is another trick I learned from Jim Vance’s Triathlon 2.0. It applies specifically to 70.3 and Ironman racing, as for those distances your “big days” of training (long ride, potentially followed by brick run) start to play a big role.

To reverse engineer your key workouts you need to know your

FTP

Target race intensity (as a power number or percentage of FTP)

Goal time for the bike leg of your race

Note that you need to have a fairly realistic estimate of what power output is required to achieve your goal time. For example, let’s say your FTP is 250 W and you want to ride the Ironman bike leg at 70% of FTP. That’s 175 W (0.7 times 250 W). Then you can have a look at roughly what average speeds you’ve been holding for training rides at that power, and extrapolate that to the Ironman distance.

Of course, this assumes that the terrain is fairly similar, that there aren’t extreme wind conditions to account for, and that you ride with about the same overall weight (rider + bike + nutrition) and aerodynamics.

For example: let’s say you’ve been training with the right setup on similar terrain as the race course, and you tend to average 31 km/h in speed at 175W. Then you just divide 180.25 km with 31 km/h and get a time estimate of 5.81 hours, or 5 hours 49 minutes.

TOP TIP: You can use this handy calculator to get a second opinion on whether your time estimate is realistic.Here are some reference values to give you an idea of what percentage of FTP might be realistic to hold for the Ironman bike leg:

If your goal is to finish: 60-65%

If you’re a mid-packer: 65-75%

If you’re very competitive in your age group: 75-80%

For the 70.3 distance, you can add about 5% to these reference values.

If it makes more sense to you to work off target watts rather than target intensity as a percentage of FTP, you can do that just as well. Let’s say you think that 170W is what you can hold for the bike leg. Then your target intensity is simply 170W divided by 250 W (the example FTP), in this case 68%.

All right, so now we are at the final calculation: getting your estimated TSS for your goal race bike leg.

Plug your target intensity and estimated time (in hours) into the following equation to get TSS:

TSS = Time x Intensity2 x 100

= 5.81 x 0.72 x 100

= 284

This is a high TSS value. Jim Vance recommends those who just want to finish shoot for a bike TSS of 220-260, midpackers for 240-270, and very competitive age-groupers for 270-290. But let’s roll with it.

How do you use this in training?

Build your long ride up towards the goal bike TSS, and include longer and longer segments of riding at race intensity to see if you can handle it.

If not, perhaps you need to re-evaluate your goals.

And finally, you should try to run off the bike at target run intensity to make sure that you’re not burning all your matches on the bike.

Reference values for run intensity (again from “Triathlon 2.0”) for the Ironman are 70% to 80% for midpackers and 75% to 85% for competitive age-groupers. Add 5% if you’re targeting a 70.3.

Even if you don’t do extremely long brick runs in training (for most athletes long brick runs are way more risk for it to be worth any potential reward), you’ll probably be able to tell even based on a 30 minute run off the bike at target intensity whether it’s a realistic target or not.

If it isn’t, was your bike too hard, is your run intensity target too high, or do you just need to keep training your ability to sustain that pace?

These are the questions that reverse engineered race-specific workouts help you answer before the race, so you can make any necessary corrections to your race plan or to your training in time.

TOP TIP: The power (Watt) values used in these calculations are all normalized power (except for FTP). Normalized power takes variations in power output into account. If you ride perfectly evenly your normalized power equals your average power for a ride, but given that there’s always some degree of variation present, you can expect normalized power to be around 2% to 5% higher than average power. The difference may be even bigger for challenging courses with a lot of climbs, descents and turns.

9. In-season and season-to-season comparison of key performance indicators

Comparing your key performance indicators over time allows you to objectively assess how your current season is progressing, and how you’re doing this season compared to previous seasons.

We already talked about this to some extent in sections 5 and 6 for aerobic endurance and muscular endurance specifically. In those cases, we monitored how decoupling, efficiency factor, P20 and P60 developed over time within a season.

After a completed season, it’s very useful to compare these metrics, and other key metrics (see the next section for my most recommended metrics to focus on) not only in-season, but also from season to season.

Was your decoupling significantly better this year than last year, and could you notice that in your race performances?

Was your CTL (fitness) clearly higher for your goal races this season than last, and how did that translate to results?

What about TSB (form). How did it develop in-season? Did you get sick or injured at some point when it dropped too low? Did you find a TSB sweet spot that seemed to give you the best performances on race day?

These are some examples of questions you can ask yourself around your data. A thorough analysis at the end of the season where you chart out these comparisons and write down your conclusions can help a lot in planning even more effective training for next year.

In the images below you can see a couple of visual examples of what kind of analyses you can do.

10. What data and which metrics should you focus on?

Since we’ve passed the 4000-word mark I’ll keep this section short and sweet. I’ve just added my list of top-recommended metrics to focus on in your data-driven training, and a brief description of what to do with each metric.

Remember, there’s no point just collecting data and looking at data for the sake of it. You need to actually use data to help you make smart training decisions, and focusing on too many metrics won’t help you do that. It’s more likely to just overwhelm you.

CTL

Monitor CTL (aka Chronic Training Load aka Fitness) in your performance management chart (PMC). You want to see a generally increasing trend (see image), although small drops are allowed and expected during easy weeks, taper periods, and a large decrease will inevitably happen in off-season.

It’s useful to monitor CTL for swim, bike and run combined, as well as separately for the bike and the run.

TSB

As with CTL, you monitor TSB in the PMC. There are two things to look for with TSB.

Make sure it doesn’t get to below your individual threshold for high risk of injury, illness and overtraining. It’s impossible to say exactly what this threshold is, you need to find it out based on experience.

Get it in the 0 to 20 range on race day for your A-races. And with experience, you might be able to narrow that range down even further.

Ramp rates

As discussed in section 4, you can’t ramp up your CTL too fast. I recommend staying in the low to moderate risk ramp rate ranges as per these guidelines:

Low risk ramp rate is 4 or less if your CTL is 45 or less, and 6 or less if your CTL is 70 or more.

is 4 or less if your CTL is 45 or less, and 6 or less if your CTL is 70 or more. Moderate risk ramp rate is between 4 and 6 if your CTL is 45 or less, and between 6 and 8 if your CTL is 70 or more.

is between 4 and 6 if your CTL is 45 or less, and between 6 and 8 if your CTL is 70 or more. High risk ramp rate is 8 or more if your CTL is 45 or less, and 10 or more if your CTL is 70 or more.

TSS and IF

Keep an eye on your weekly TSS and IF (intensity factor - your average training intensity as a percentage of your functional threshold). Depending on where you are in your season, you may want to increase one or even both of them, but you need to make it a controlled increase.

Plotting your weekly TSS and IF as in the image below and comparing with the average from a period of a couple of months or so is a good way to make sure you are seeing the desired increase in TSS and/or IF, but that the increase is kept at a sensible level

Decoupling and EF

We talked about decoupling (your heart rate drift compared to power or pace output) and efficiency factor (EF, your distance covered per heartbeat) in detail in section 5, so refer back to that section for more explanations.

The takeaway message is that until your decoupling is 5% or less for your long, steady, workouts you still have a lot to gain from improving aerobic endurance through relatively easy or moderately easy training in relatively high volumes.

When you get below that 5% mark, though, it’s probably time to start focusing on some more intense training to improve things like muscular endurance and VO2max.

Another sign that you’ve maxed out on long slow distance training is that your EF has stagnated and isn’t improving any more in your steady workouts at low to moderate intensity.

P20 and P60

Lastly, as discussed in section 6, you should track P20 and P60 (the best average power/pace you’ve held for 20 and 60 minutes) to see where you are in terms of muscular endurance.

This is especially important in the build period of your training program, when you’ve started to incorporate muscular endurance workouts. If you’re P20 and P60 are not improving in this phase, then something’s up and you need to figure out a way to get back on track.

11. How to set up your dashboard in Training Peaks

Training Peaks is an amazing platform to easily collect, analyse and use training data in all the ways we’ve discussed in this article.

One of my favorite features in Training Peaks is the ability to completely customize your dashboard to get a quick overview of all the data that’s important to you and your training.

Here’s a screenshot of the dashboard I like to set up for triathletes:

Conclusion

If you’re completely new to data-driven training, I realize that this can be a bit too much information to digest all in one go.

But I hope that you realise how massive potential benefits data-driven training can have on your triathlon performances.

If you do, and you need some more help and clarifications on these topics, don’t hesitate to send me an email and I’ll be glad to help you get started.