Source: swimswam.com Mike Lewis
Back in April this year (2014) I wrote about how it was possible to get HR underwater using ANT+ and a MIO Link optical HR Wrist strap. Things have moved on a bit since then with more optical HR options and new sports watches from Garmin (920XT), Suunto (Ambit3) and Polar (V800).
As I write this towards the end of October 2014 there is still no easy way to properly and ubiquitously get analysable underwater HR data. But there are several workarounds and near-solutions.
I’m writing this as I personally want to get reasonably accurate HR data for my swim sessions. And then to share it with anyone else who might also benefit.
Just to be clear for some: For a Garmin It **is** possible to get HR Data Underwater AND merge it with a Garmin Pool swim activity AND look at HR by length.
NOTE: This document is not yet complete and fully checked. It’s probably in a final draft version now. I need to clarify some of the details as it all get a bit complex at times! and add some bits that I know are currently missing need adding. However it’s good as a general guide for you now.
We need to first look at sensing and transmitting the HR Data.
1. Legacy Polar
Even the ancient Polar watches were able to record HR underwater. They used a signal that went MUCH further through water that ANT+ or Bluetooth.
I’m not sure exactly why Polar moved away from this, probably: to use more standard protocols; to use protocols that can uniquely pair devices; and to use more energy efficient methods.
The problem with Polar (October 2014) is that they do not have proper pool metrics that go around the underwater HR that they CAN already record. These metrics are scheduled for imminent NOV2014 release. Cool.
2. Chest Straps vs Optical HR Wrist Monitors
Chest straps are probably the best and most accurate way of sensing electrical impulses and then broadcasting the beats to whatever is listening. However, if the strap broadcasts using either Bluetooth or ANT+, then the signal will only travel a very few centimeters ie NEVER to the watch on your wrist.
But !! now we have devices like the MIO Link which record data optically and then transmit via ANT+, Bluetooth or both/either. If that wrist monitor is sufficiently close to your watch (on the same wrist) then your sports watch IS able to receive a HR signal.
MIO make their own technology which they sell to other companies, like TomTom, and there are also other companies like Epson who also make their own wrist technologies – so the accuracy WILL vary from manufacturer-to-manufacturer.
Newer optical HR sensors on the wrist are great. Especially devices like the TomTom MultiSport Cardio where everything is on your wrist in one unit. They might want to enable HR recording from swimming…
However. Optical sensors shine a light onto your skin and measure it bouncing back. If water gets between your skin and wrist strap then the readings can be way out. Having said that, I’ve also had fairly good success with this method.
The Scosche RHYTHM+ is a similar product but is reported to be better suited as upper forearm-worn…this is too far away from the wrist for a Bluetooth or ANT signal to travel.
So. Wrist-based Optical HR is a reasonable way forwards but maybe not perfect.
In comes Suunto and Wahoo.
The Suunto Smart Strap (Bluetooth for the non-ANT+-supporting Ambit3, using Movescount) and the Wahoo TICKR-X (for generic ANT+ and Bluetooth devices, using WAHOO FITNESS) both use a conventional chest strap BUT their HR pods have a memory that is able to store HR data. In the case of the TICKR-X a whopping 14 hours…more than enough for any of my water-based sessions.
At the end of your session, or during pauses in your session (Suunto) the strap synchronises with a smartphone app. This could be at the end of your lane, the car park at the edge of a lake or at home. Sorted.
Surely then this ‘caching’ really is the way forwards?
Well, maybe. The catches are that, firstly, a HR strap doesn’t look great when you are in a pool. OK you might have it under a swimsuit or wetsuit. But many guys will not want to wear one in the pool. There are further problems as, secondly, even a half-strong push off from the end of your lane can dislodge even the tightest of chest straps. Still women are OK and everyone is fine in the sea or in a lake with their wetsuit on.
I also found problems with the TICKR-X having drop outs or too-low readings.
Thirdly you still have to get the darned data back to your sports data analysis tool of choice – be it Garmin Connect, Training Peaks or SportTracks AND be able to analyse it against your other swim metrics.
3. Getting the data where you want it.
This section talks about getting the data into the right app. The next section talks about combining it into 1 session.
Well I want it in SportTracks. You might well want it in Training Peaks. Newbie triathlete Jo Doe may well be happy to keep it in the Wahoo fitness app. Many Garmin devotees will go for the ever-improving Garmin Connect. The issue is that there are tens of thousands of us who want our data in different places compounded by manufacturers who want to ring-fence and monopolise their particular product set.
Well if you are a Suunto user then you are already sorted. You have the data in the Movescount environment. You’ve nothing more to do.
Similarly with the Polar V800, it records HR underwater. However the analytics are not yet there (due Nov-2014)…
Let’s say you want the data in TrainingPeaks. Well if you have the pro edition then you could quite readily use Tapiriik.com to synchronise with dropbox, SportTracks and Garmin Connect.
Oh hang on a minute!! none of those include WAHOO Fitness or Movescount (which is where your HR data would come from).
so there would need to be an extra step. If you put it in Strava then you should be good to go. You can connect Strava to Movescount and then Tapiriik will sync Strava with all the above. (I’ve not tested that)
And therefore if you are a Garmin Connect or SportTracks user then this method is also fine. ie using strava as a staging post. (eesh)
If you are a Garmin WATCH user then the situation is a bit more complex thatn I’ve alluded to so far.
For starters, in openwater swim mode, the 920XT records HR data from a wrist based Opticla ANT+ strap. Sorted.
But if you have a 910XT or indeed any other Garmin model you are NOT sorted. Neither are you sorted in pool mode on the 920XT, although it is possible this might be enabled in future firmware releases.
Garmin Forerunner 920XT
With the 910XT, or indeed any other Garmin, you can only record HR data underwater if you set it to, say, run mode where it will record HR but then you will not get any of the swim metrics supported by your watch. Dilema.
So the solution here for the Garmin watches seems to be to use one of the chest straps that store data and upload the information in a second/parallel exercise file. And here is where the Suunto comes in.
These are the ‘workflows’ of data from the chest straps:
- Suunto strap-to-SuuntoMovesount-to-Strava-to-Tapiriik-to-GarminConnect OR SportTracks OR TrainingPeaks)
- Wahoo TICKRX strap-to-WAHOO FITNESS-to-Garmin Connect-to-Tapiriik/SportTracks-to-TrainingPeaks (iOS only)
However you are still left with two separate activities: a heart rate track and a swim track without HR.
I believe you cannot merge them in any of: SportTracks MOBI, TrainingPeaks or Garmin Connect.
However there is a 3rd way. and this is the only way I’ve found. Tell meplease if there are more.
4. Combining The Data How You Want It
As I said previously, with the Suunto Ambit3 and Smart Belt and with the Garmin 920XT+optical wrist HR (eg the MIO Link) you are either OK now or probably will be soon in the case of the 920XT (if Garmin turns on HR during a pool session). Similarly with the Polar v800 you might be OK in November 2014.
My suggestion for the 910XT and 310XT (and currently for the 920XT in pool swim mode) is to use the WAHOO TICKR-X or Suunto Smart Belt alongside using the watch – you would use the watch how you normally would (but obviously without the HR).
When you have finished your swim set; the WAHOO FITNESS app can trim the data to get rid of unwanted bits at the start and end of your session (this is important if you want the HR to match the lengths later). You can then export to, for example, a TCX file. If you manually import that TCX file into SportTracks (having first already imported your regular pool activity) then SportTracks will allow you to add/merge the HR track to that activity AND to synchronise the start times.
This definitely works (see the image below)
However. It’s a bit longwinded (understatement) as now you can automatically sync your PC SportTracks with SportTracks Mobi (requires a paid for account), tapiriik (requires an annual contribution for automation) and the paid for version of Training Peaks and the free Garmin Connect.
and, no, I haven’t tested every possible combinations of software and linking them !!
In the PC version of SportTracks with the POOL plugin (excellent) the developer, mechgt, has recently shown HR by length. So you can see how it varies for the different components of your pool session.
This clickable image clearly shows this (HR to the right) and this is the final solution that you want and need (well if you use sporttracks, it is, if you use another software package you will have to export the recently combined session from sporttracks!!):
Pool Plugin With HR Combined Files
Think, why do you actually want HR data from swimming?
I use it to measure/validate the swim component of my overall training load. That’s all. So I only have to do it properly once every few months to make sure my estimate of TRIMPs per length/per 100m is up to date. I then apply that to my swim sessions..takes about 5 seconds. (Unlike the method above!).
If you want to look at HR data while you are physically swimming (you are mad, concentrate on your stroke).
If you want to look at average HR for your last set. That’s reasonable. You could just get out of the pool and check your HR or use one of the belts that cache your HR.
Would I go through that synchronisation malarkey 3 or 4 times a week. Err…no! But at least now you know how it can be done.