Understanding Strava: how to use Suffer Score, Fitness and Freshness, Weighted Average Power, Intensity, Training Load and Power Curve
Are you using Strava to its maximum potential?
by James Spragg
Many of us love to use Strava, whether it's as a training diary, to plot routes, chase KOMs or have a sneaky look at what training your friends, club mates and rivals have been up to.
However, Strava can bring a lot more to the table than just a way to log your rides. With the rise in the use of power meters among club and sportive riders alongside racers, as well as accessibility of training with a heart rate monitor, Strava can also be used as a valuable tool to interpret your training rides, identify your personal strengths and weaknesses, learn how to peak for an event and avoid over training.
Besides fighting for position on segment leaderboards, Strava has a number of metrics and analysis tools available that, if you know how to use them (and that's the key), will help you improve as a rider.
Unfortunately, most of the most detailed ride analysis tools are only available to users who unlock Strava's premium features, but if you take the plunge then there's a wealth of information at your fingertips.
Here's our guide to understanding six key Strava metrics: Suffer Score, Fitness and Freshness, Weighted Average Power, Intensity, Training Load and Power Curve. What are they and how can you use them to guide your training?
What is Suffer Score?
Suffer Score is one of Strava's premium features and there's something satisfying about putting your feet up at the end of a tough day in the saddle and seeing an 'extreme' score. But what exactly is a Suffer Score and how is it calculated?
In a nutshell, Strava's Suffer Score tells you how hard your ride was. Of course, that bit may be obvious, but what isn’t obvious is why you might go out with a friend on the same ride and come home with different Suffer Scores. Surely you've both done exactly the same ride?
The explanation lies in how the Suffer Score is calculated - it's personal to you as a rider and is based on your heart rate during a ride. Needless to say, you need to be wearing a heart rate monitor.
The first thing Strava will do is find your maximum recorded heart rate. From this it will calculate your individual training zones. You can find these under the My Performance tab in the Settings menu, where you can also set your custom training zones - the most accurate way to calculate your Suffer Score.
Strava then associates a value (or co-efficient) to each zone - the higher the zone, the higher the value, and this value represents how many Suffer Score points you will score for one minute in that zone. For example, one minute in zone one may accumulate half a Suffer Score point, whereas one minute in zone five may accumulate ten points. At the end of a ride Strava adds up the total amount of time in each zone and multiplies it by that zone’s co-efficient. Add all these scores together and you have your personal Suffer Score.
This explains why two riders doing the same ride may come home with very different Suffer Scores. If one rider is a lot fitter than the other then the fitter of the two riders will likely be riding in a lower heart rate zone, and so will be accumulating less Suffer Score points through the ride.
However, Suffer Score does have its limitations. For example, if you were to do a short time trial, say five miles, you might be riding for anywhere between ten and 15 minutes. Because the duration of the ride is short, there isn’t a lot of time to accumulate Suffer Score points even though you're working in high heart rate zones. Therefore, if you did a very gentle two-hour ride you might actually accumulate as many Suffer Score points as you did in the time trial. Suffer Score, therefore, isn’t always a fair reflection of how had you went or how tired you will feel the next day, and is best used in conjunction with other Strava features.
That said, Suffer Score can still be a useful way to track your training. For example, if you do the same ride every week then as you get fitter you should see the Suffer Score start to come down. As you get fitter your heart rate is lower for a given intensity, so if your score in December for the club run was 200 but by March it's down to 180 then you know you've had a good winter, though it's worth bearing in mind there are various other factors that can affect your score.
Similarly, if your Suffer Score for a ride seems unusually high then that could be a sign that your heart rate is abnormally elevated. This could be the warning sign of an oncoming cold and, therefore, it might be a good idea to back things off for a few days.
For an even greater insight into your training the scores you generate on each ride can be tracked over time using Strava's Fitness/Freshness graph.
What is Fitness and Freshness?
The Fitness and Freshness graph is a tool that anyone looking to peak for an event should be using.
The graph tracks three variables over time:
- Fitness - how much training you have done
- Freshness - how much fatigue is in your system
- Form - a product of both fitness and fatigue
Form is what we're all aiming for come the day of an event and represents how good you will - or, rather, how good you can be - on the bike during that sportive or race.
Roughly speaking, form is determined by how much training you have done minus how much fatigue you are carrying; your fitness score minus your fatigue score.
If, for example, you have been training very hard your fitness will be high but if you are so fatigued that you can barely get out of bed then your form on the day will be low. The opposite is also true. You might be as fresh as a daisy because you haven’t ridden for weeks but your fitness will be very low and, therefore, your form on the day will also be low.
But how does Strava calculate fitness and fatigue in order to plot your form?
The graph, found under the Training tab for premium users, plots the Suffer Score and/or Training Load of each ride you do, depending on whether you use a heart rate monitor or power meter - you need to use one of the two, or both for maximum accuracy.
To calculate your fitness all of the rides you have done in the last 42 days are used, it's therefore vital that you log all of your rides, and use either a heart rate monitor or power meter to capture the relevant data.
Taking a rider who uses a heart rate monitor as an example, Strava creates a weighted average of these Suffer Scores over the 42-day period. What this means is the formula gives more recent rides a greater weight as they have a bigger impact on your current form than rides you did six weeks ago. Your fatigue is calculated in a very similar way although this time the average is taken only over the last seven days.
The 42 and seven day averages used for fitness and fatigue come from research into how long the effects of a training session can be felt and also how long it can take to recover from a hard training session.
Both your fitness and freshness are then given scores and, as we've already covered, form is calculated as fitness minus fatigue.
So, if you have trained harder in the last seven days than you have on average across the last 42 days then chances are you will be tired and your form will be low. Conversely, if you have had an easier week then you will be fresh.
Every rider has a form range that works best for them. Some perform better when a little fatigued, others perform better when very fresh. I would recommend that if you have a day where you feel brilliant on the bike then, having already been using the Fitness/Freshness graph to track your progress, you record your form score on that day. Then, when preparing for your next event, you tweak your training to try and get as close to that form score as possible.
"Every rider has a form range that works best for them. Some perform better when a little fatigued, others perform better when very fresh"
One downside of the Fitness/Freshness chart is that it needs at least 42 days of data before it will give accurate results. As a result, if you want to track your progress over time it will need a concerted effort to ensure every training session goes online for a minimum of six weeks. Once you have this data is place you can begin to track it to see how your form varies according to different levels of training and result. The result will mean you can accurately chart your form and use cold, hard numbers to hit peak form.
While Suffer Score and Fitness/Fitness can be calculated using heart rate only, for those of you who use a power meter, there are a number of other additional metrics on Strava that you can use.
What is Weighted Average Power?
Weighted Average Power is a key figure that you'll see at the end of each ride if you use a power meter and is very similar to what people often refer to as normalized power - the metric used in Training Peaks' software. The idea behind Weighted Average Power is that average power alone doesn’t tell the whole story of a ride.
For example, if you do a three-hour ride at a constant 150 watts, this (depending on how powerful you are, of course) may be a gentle ride and not leave you too tired. Now, imagine on the next ride you put out a constant 100 watts for the first hour and 100 watts for the last hour of the ride but in the middle you ride for one hour at 250 watts. The hour effort in the middle may leave you feeling pretty tired and you then have to ride on for another hour, so it's clear the second ride would be much more fatiguing than the first ride but this wouldn’t be expressed in the average power - 150 watts for both rides.
This is where the Weighted Average Power comes in. As your power goes up, the amount of effort it takes to sustain that power goes up by an even greater amount. For example 300 watts feels more than twice as hard as 150 watts and so Weighted Average Power gives more authority to higher power outputs than lower, while it also looks at the variation in power on your ride and calculates an average power which is a more accurate indicator of your effort and, therefore, represents much better how hard the session was physically.
For the first ride in our example, the weighted average would be 150 watts, whereas for the second ride the weighted average would be 192 watts. As a result, Weighted Average Power provides a much better estimate as to how hard a ride was than average power alone.
What is Intensity?
If you use a power meter then, along with Weighted Average Power, you'll also see two other figures when you upload your ride to Strava: Intensity and Training Load.
Training Load we'll come on to but first Intensity. This metric compares the Weighted Average Power of your ride to your Functional Threshold Power, which you can put into Strava on the My Performance page under Settings.
FTP is the maximum average power you are able to sustain for one hour (here's how to calculate your FTP). Therefore, if you go out and do a 25-mile time trial in one hour then you would expect your intensity to be 100 per cent if you pace your ride correctly and empty the tank. If, then, the next day you decide to treat yourself to a nice easy ride to the local café you would expect your Intensity score to be around 50 per cent.
Intensity can be used to see if you are riding easily enough on your easy days and hard enough on the hard days. As a rule of thumb:
- A score less than 50 per cent would be an easy day
- 50-65 per cent would be an endurance ride
- 65-80 per cent would be a good tempo ride
- 80-95 per cent would be a where you want to aim for in a long event or sportive
- 95-105 per cent would be your aim for a time trial
- 105 per cent or above would be expected for a very short time trial or criterium
What is Training Load?
Training Load is very similar to Suffer Score, however, instead of being calculated based on heart rate, it is based on power.
Training Load takes into account the Weighted Average Power, your personal FTP and the Intensity score of a ride to give you a number that represents how hard a ride has been.
To give you an idea on figures, a score of 100 means that you have gone as hard as you can for one hour. You can, of course, score more than 100 but the maximum score you can achieve per hour is 100.
Although the formula to calculate Training Load is actually quite complicated, the easiest way to imagine a Training Load score is if you mark your ride on effort between one and ten and then multiple that by how many hours your rode. So, a score of five on the effort scale for three hours would give you a Training Load score of 150.
Training Load is also used in the Fitness and Freshness chart. Therefore, if you are using a power meter then the Fitness and Freshness graph will be using Training Load scores rather than Suffer Scores.
One useful application of Training Load is that it will tell you roughly how long it will take for you to recover from a ride. So, if you score...
- 0-125 - you should have fully recovered in 24 hours
- 125-250 - you will probably feel the effects for 48 hours
- 250-400 - you will need three days to recover
- 400 and above - it might take up to five days to fully recover
What is Power Curve?
Power Curve is a graph that plots your best ever power outputs for given time periods and you'll find it under the Training tab on Strava. For example, it might say that you can sustain 200 watts for two hours and 400 watts for two minutes.
This graph serves two purposes. First of all, you can track your progress over time and you can change the time period that is displayed in the graph, using the last six weeks, a whole year or a custom date range. Therefore, you can compare your best ever power outputs in 2016 to those in 2017 or the last six weeks compared with the last 12 weeks. This allows you to see if your power outputs are improving - or if things are heading in the wrong direction.
Using the Power Curve graph in conjunction with the Fitness/Freshness chart gives you valuable information about how much training you have been doing and how good your current power outputs are. For example, you might see that last season you were actually training more than this season, however your power is better this season, and this tells you that you were probably overdoing it last year and that you have now found a better balance between training and recovery.
The second way you can use the Power Curve is to help with pacing. If you know your maximum power for any given period then you can make a very good guess at what sort of wattage you should be aiming for when out training, racing, time trialing, or riding a sportive.
As an example, if you know you can hold 250 watts for 60 minutes, then if you are climbing the Col du Tourmalet you know setting off at 300 watts isn’t a good idea.
You can take this a step further. If you're hunting a KOM or a good placing on a Strava segment, look up the segment you are aiming for and then select your weight category in the left hand menu. You can then go through the power and time figures to get a pretty good estimate for what sort of time you should be aiming for on that climb. Again, let's use the Tourmalet example for a rider of 80kg who can hold 250 watts for 60 minutes. Looking through the times, the first rider to climb the Tourmalet at less than 250 watts in the 75-84kg category did the climb in 1h 10m 27s. Therefore, a realistic goal for the climb would be 1h 10m.
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