Heart Rate zones on the Navigator

There is a new feature on the Navigator for everyone on the BETA programme: you can now see your current training zones. The tab structure has been changed slightly so that when you’re not logged in the tab bar now looks like this:


Notice in particular the MORE option on the right. When you choose this you get the log-in screen that takes your BETA programme password screen. When you log in, the tab bar changes to this:


You can see that the HR Zones and Regularity tabs have appeared and I’ve selected the HR Zones tab. This shows my current training zones as calculated from the Crickles estimate of my current Lactate Threshold Heart Rate (LTHR). It also shows the date at which the zones were last changed – such changes are triggered from time to time in response to athlete activity data.

If you don’t yet have a BETA log in and would like one, please read this post and then, if you’re happy to proceed, send me an email requesting a password along with your date of birth.

Separately from the BETA programme, the standard Seasonal tab has also changed: Zone 5 was previously spilt into Z5a, Z5b and Z5c. These have now been consolidated for easier zone-to-zone and quarter-to-quarter comparisons:


Improved Relative profile report

The Relative CSS report – which is at the time of writing is the landing page on the Navigator – shows how the chosen athlete’s totalled Cardiac Stress accrued over the period defined by the Date range compares with others. This total CSS is a product of three factors:

  1. The number of activities
  2. The duration of each activity
  3. The cardiac intensity of each activity.

The first of these is straightforward. Information on items 2 and 3 is available on the Relative profile report. Here’s how it now looks:


In this case “Athlete” is me. The chart on the left shows how the duration of my activities over the chosen period (the last six weeks) compares with that of others, with the y-axis being scaled in hours. I’m in green. The widest part comes at about half an hour, indicating that more of my activities have been of this duration than any other. By contrast, other athletes – the blue shape – are doing a far greater proportion of their activities over a period of 1-2 hours. Unlike others, I have no activities – zero width – around the two hour mark over this period.

It’s important to note that the number of activities (item 1 on the list of three factors above) is not reflected here at all – from this chart alone it’s impossible to know whether I’m doing three times as many or half as many total hours as others. This only shows the proportion of activities at each duration.

The chart on the right shows the distribution of cardiac intensity. Again, the chosen athlete (me again) is in green and others are in blue. From this I can see that for me the widest part – the intensity at which I most frequently exercised – is at about 87% whereas for others it lies at about 82%. On the other hand, some other athletes have exercised at over 100% intensity in this period and I haven’t. (100% is not a magic value – you can think of it, approximately, as exercising at or above your established Lactate Threshold Heart Rate.)

Like most of the reports on the Navigator, it responds to your choices for Athlete, Date range and GroupGroup defines who is counted as “Others”.

This form of chart is likely to be unfamiliar to most people. However, compared to the old visualisation, it more clearly shows the relative distributions and has less risk of misleading at the extremes. Once you get used to it, it’s an intuitive plot that conveys its information nicely.

New on the Navigator

Following some early feedback from the Beta, a couple of new features have been added to the Navigator.

First, to make the Navigator quicker and easier to find, there’s a new big green button on the home page of this website:


(Depending upon your browser, you can probably see the picture of the buttons above as well as the actual buttons.) Old School access is still, of course, available using the web address navigator.crickles.org.

Second, when you’re using the Navigator there is now a small block of help text pertaining to each report. As in this example, this appears in the side panel and changes according to the tab that you’re looking at (in this case Fit-Fat):


General help on the use of the Navigator, such as how to reset the Date range quickly, is still available here.

Crickles BETA features

You may have noticed recently that there is a new report on the Navigator that requires a password, and that a few of the posts on this website are now password protected. This reflects some significant changes to Crickles that are being released initially in a BETA programme. If you’d like to participate and check out the new features please read on…

To access the BETA functionality

Send an email requesting access to ian@crickles.org.

I will need your Date of Birth – this will enable us to factor in age into the new analysis.

This aside, you are only asked to agree to:

  1. Accepting the confidentiality terms;
  2. Giving me feedback;
  3. Acknowledging the limitations of the beta.

This is all described further in the Mechanics of the beta section below.

Please do try it out!

Here’s what’s in the beta:

More analysis of heart rate data

One of the main features of the BETA is a new Regularity report. This gives a new type of analysis on your heart rate data. It also gives some analysis on the “strap crap” that is filtered out by the Crickles data cleaning routines.

For those on the programme, a full description is available here.

Just your data

To date, all of the analysis on the Navigator has been available to everyone on an “all see all” basis. The new report is potentially more confidential in character and so each athlete can see only his or her own data. This is why we now require a password to access that report. In future, we may password-protect more information, such as FTP curves – subject to what people would prefer. However, peer comparisons are super-useful and we’ll keep these as a prominent feature.

Strava Friends

To date, you can compare yourself to others using the Group dropdown. However, apart from the gender sub-selection that this offers, this isn’t useful for most of the Crickles population. On the beta, once you’re logged in you can now choose Strava Friends from the Group dropdown. This then enables you to compare yourself specifically against your Strava friends on the relevant reports (Relative CSS, Relative Profile, All-in and This week). This is much more meaningful – and you can still compare yourself to the overall Crickles cohort and your gender group.

Mechanics of the beta

  1. Please email me as above to request a password. All passwords are encrypted in use and cannot be hacked in plain from a web server. However your password is not encrypted “in flight” when I send it to you. If you are concerned about security I can text you your password instead of emailing it, and if you’re very worried I can give it you by phone.
  2. At this stage I haven’t built a mechanism for you to choose or re-set your own password. Also, the password setting process is still manual and it may take me a while to get round to sending out yours if a lot of people ask for them.
  3. As far as I’m aware, this new analysis, and indeed some of the existing analysis, is unique and unavailable anywhere else. While I’m continuing to develop it, please treat it as commercially sensitive – for example, don’t email Strava describing it and asking for them to copy it!
  4. To log in, choose the Regularity report, which will throw the log-in screen (unless you’re already logged in). The User ID you need is simply your Strava ID (e.g. mine is 301194). You can see this on the Athlete dropdown in brackets. Once you’ve logged in you’ll be returned to the main page (Relative CSS) and will need to choose Regularity again to see it.
  5. While this functionality is still in beta, you can always escape back to the current way that the Navigator works by refreshing the page. This will log you out. On Safari at least, the browser caches your ID and password so you don’t need to re-enter them. The iPhone doesn’t do this – when we move beyond beta I intend to build this into Crickles so that you will rarely need to re-enter your credentials.
  6. You will also get a general-purpose password for accessing the protected posts on crickles.org.

If you sign up to try out the beta, please could you give me feedback on the new features. It would also be super-helpful to know:

  • what you use Crickles for;
  • what you never use;
  • roughly how often you look at the Navigator;
  • whether you ever use Crickles Activity Charts;
  • what further improvements would make Crickles most helpful.

Cycling is harder than you think

A couple of weeks ago Cardio Mark ran the Dublin marathon in a very creditable time of under four hours. I’m impressed. When I used to run regularly, I once or twice managed half marathon distance and I never finished wishing I’d done twice as much. Completing a marathon requires months of training and resolute determination.

A couple of days before Mark’s marathon I went for a bike ride. I had the day to myself so cycled over to Dunkery Beacon – the highest point in South West England and the region’s signature bike climb. It’s not the longest climb and not the absolute steepest but its combination of length and severity is nonetheless testing. The rest of my ride was not without interest, extending to 93 miles with 7.5k feet of ascent and taking me around 6:40 with a couple of stops. It was equivalent in difficulty to a reasonably stiff domestic sportive. Fit cyclists do not need to train for such sportives – they’re easy enough that you can just rock up and do them.

Out of curiosity, I compared Mark’s marathon with my bike ride using Crickles Activity Charts. Charting a histogram of our heart rates gives this, with Mark’s histogram in pink lying over mine in blue:


On the morning of my ride my resting heart rate was 46 bpm, which is marginally above Mark’s (44 bpm). Crickles shows our prevailing Lactate Threshold Heart Rates to be similar too (mine was 162 bpm and Mark’s was 157 bpm). The chart thus shows that not only did Mark record far fewer beats during his marathon than I did during my ride, he also managed his effort much more prudently with the entirety of his cardiac activity well under his LTHR in contrast to my ride in which I was well over my LTHR for a significant portion of the time. It is graphically evident that my ride placed a much greater load on my heart  than Mark’s marathon placed on his. This is reflected in our respective Cardiac Stress Scores – 570 for me and 300 for Mark. (Reflecting on this, I realised that the Crickles CSS methodology does not fully capture the restorative effect of my two coffee stops. I calculated the effect of these and it decreases my CSS by 17 points – just under 3%, so not a significant amount.)

By contrast, the differences in our Suffer Scores on Strava was much narrower – Mark’s Suffer Score was 255 compared to my 299. This confirms my previous finding that the Strava Suffer Score is not a good measure of cardiac stress.

There is an important point here for cyclists. Mark’s marathon felt hard and was hard because of the intense amount of corporeal stress that running for four hours places on the body. Skeletal muscle and the bones, ligaments and tendons to which it is attached, can feel the pain. There is also that intangible of “the wall” as it is harder to refuel adequately when running. Cycling inflicts far less strain on skeletal muscle and doesn’t pound our body in the same way. Unlike our peripheral muscles, our exercising heart does not feel pain and we thus have no direct real-time index of the stress to which we subject it. So long as we ride within our strength limits and eat and drink well, the wall of bodily pain that marathon runners have to run through has no analogy in cycling and there is nothing to indicate how much cardiac stress we’re accruing. The only direct evidence that our sportive was equivalent in cardiac stress to two marathons might be a histogram or a CSS number. An appreciation of this might spur us to think more seriously about the amount of recovery we need to build into our exercise schedule.

New Summary tab for the Navigator

The Crickles Navigator has a new Summary tab giving headline figures for the athlete and a comparison of each with peers. Currently, there are six figures shown in the Value column:

Period CSS shows the total Cardiac Stress Score for the period defined by the Date range. This period defaults to the last six weeks but can easily be changed in the side panel.

Period XSS extends this measure to cover also activities on Strava for which there is no heart rate data. The estimate of cardiac stress is less good than CSS, which  requires a heart rate monitor, but better than assuming that it’s zero. If you always wear a heart rate monitor CSS and XSS will be equal (though not for the peer group). If you never wear a heart rate monitor, CSS will always be zero but XSS will usually be positive.

Current LTHR is the latest Crickles estimate of your Lactate Threshold Heart Rate. (Occasionally this estimate may lag one activity behind your last effort.) This only appears if you use a heart rate monitor.

Current Fitness, Fatigue and Form are as described here. Since they are current estimate, neither these values nor Current LTHR change as you change the Date Range.

The numbers alongside these in the Crickles Percentile column show how you compare to the Group chosen in the side panel (by default, the entire Crickles population). If the Crickles Percentile is 100 you have the highest value. If the Crickles Percentile is 50 you’re on the median.

By design, this tab works particularly well on the iPhone.


Over time, we may add more information to this tab.

NB: There is a known bug that the Summary tab will be totally blank (i.e. no data) if you have included the character “(” in your Strava name. If this affects you and you’re interested in seeing your Summary data before I otherwise get round to fixing it, please let me know!


Improved layout for the Timeline

The Timeline (previously called CSS (Cardiac Stress Score) Map) on the Crickles Navigator has been overhauled to display data differently. Now, the x-axis is the timeline, which still reflects the Date Range on the side panel, and the y-axis shows the CSS for each activity. This makes it easy to pick out which activities have the highest CSS (those that lie highest on the chart) and when you did them (more recent to the right, least recent to the left). The composition of CSS into its elements is now encoded through size, which represents moving time – larger dots are longer activities – and colour – the least intense activities are green and the most intense are red.

Here’s an illustration – note that CSS Map now appears as Timeline as the tab name:


In this example, the activity with the highest CSS occurs half way along the chart at the top. The size (large) and colour (medium orange) indicates that the activity was long in duration but only moderately intense.

You will also see that there are some grey dots. This is because the Timeline now also includes activities for which there is no heart rate data and so Cardiac Stress has to be estimated from moving time alone.

Changes to the Navigator

There are a few improvements to the Crickles Navigator:
Athlete selection
It now remembers who you are (i.e. which athlete you selected) between sessions. This is achieved using a cookie (it simply stores the athlete ID); the first time you load the Navigator following this change there is a notification that pops up alerting you to the use of cookies. The cookie will periodically expire but in the main you’ll now no longer have to find your own name in the Athlete list.
The same has been done on Crickles Charts too.
Group selection
Group selection is now under Athlete selection so that you only have to select from the groups to which you belong. For the majority of athletes, this reduces to a choice between “All” athletes (the default) and Male or Female.
Lactate Threshold Heart Rate (LTHR) and Functional Threshold Power (FTP) are now charted on separate tabs. This makes changes in LTHR in particular easier to discern. Obviously if you don’t cycle with a power meter you won’t get an FTP chart.
Last loaded date/time
The notice of when Navigator data was last updated was previously given in the arcane UTC timezone beloved of computers. This is now changed to London time.
Please let us know if you have issues with any of the above.

“All-in” analysis on the Navigator

CSS is a great measure of Cardiac Stress and, quite naturally, it relies on the athlete wearing a heart rate monitor (HRM) during exercise. However, sometimes we exercise without a HRM and sometimes we want this to “count” towards our overall accrued CSS. This is recognised in the Fit-Fat tab, which makes an estimate of CSS even for activities in which a HRM is not used.

This same estimation methodology has been extended to give an estimate of CSS its components; this is shown on a new All-in tab. Here, you can see four charts:

First, an estimate of CSS that takes into account all activities recorded on Strava, even those where an HRM was not used:


Here, the purple mass (technically, a density plot) shows the distribution of estimates amongst all Crickles athletes over the chosen period. We can see in this example that the most common value is at about 2,500, there are quite a few athletes (around 1/5th of the number at 2,500) at 5,000 and even a blip indicating one athlete over 20,000.

The vertical black line picks out the value for the chosen athlete (me in this example), and you can see that in this case the athlete (me) is bang on the most common value.

If an athlete wears an HRM all the time the estimate of CSS will be as good as we can get. Conversely, to the extent that an HRM is not used the quality of the estimate will decline. The second chart shows this quality for the given athlete over the chosen period:


Again, the purple mass is a density plot showing where Crickles athletes overall lie on the quality chart. Happily, the most common value is at over 90%. About 1/6th of the number at this high value are at zero, indicating that they didn’t use an HRM at all over this period. Again, the vertical black line represents the chosen athlete and again it’s me. I’m at about 87.5% usage. To verify consistency, you can multiply this percentage (87.5%) by the CSS estimate (2,500) we just saw and that will show the CSS that you see on the Relative CSS tab (about 2,188).

Very thoughtful readers may correctly spot that when you’re on a bike with a power meter Crickles is able to give a high quality estimate of CSS even in the absence of a HRM. This is indeed true but this is not reflected on this quality chart.

The third and fourth charts show the components of the full CSS estimate. These are Intensity:


and average weekly exercise hours:


The Intensity estimate is subject to the same estimate quality as the full CSS estimate (more HRM usage -> a better estimate) whereas the weekly exercise hours are a simple sum of “moving times” and are unaffected by HRM (non-)usage.

These charts work the same way as the others: for example, the most common weekly exercise time amongst Crickles users over this period is shown by the last chart to be five hours (the peak of the purple mass) and I did fractionally more than that (the vertical black line).