For a while now, I’ve used a Garmin Forerunner 245 to track my running. Overall, I’ve loved it – except for the occasional cadence lock. I couldn’t get reliable heart rate data until I started using a Garmin heart rate monitor with a chest strap.
I originally received a Garmin HRM Dual Heart Rate Monitor as a Christmas gift, and I’ve used it for over a year. It has eliminated the problem of cadence lock, and I’ve generally noticed smoother and more accurate heart rate data.
If you want to track your heart rate while running, I’d definitely recommend you pick up an HRM Dual. It’s relatively cheap and it’s effective.
But first let me explain what the problem – cadence lock – is and how a chest strap heart rate monitor helps eliminate it.
The Problem with Optical Heart Rate Sensors – Cadence Lock
Overall, I love my Forerunner 245. It has a decent optical heart rate sensor. For much of the summer and fall I didn’t notice any major problems.
There is a bit of a lag in the measurement, and it won’t register the increase in heart rate from a hill or interval at first. But over steady state runs, it seemed to do a good job.
But once it got cold outside, I started to have some problems. On several runs my heart rate would be in the moderate range – 140 to 150 – and then all of a sudden it would shoot to 180 or 190. I knew there was no way my heart rate had actually spiked that much. I quickly realized that this was the phenomenon often called “cadence lock” by runners.
One thing that can exacerbate cadence lock is cold weather, so I’m guessing that’s partially responsible. If I notice it, I can sometimes fix it. Tips I’ve read are to a) tighten the watch, b) move the watch higher on your arm, and c) cover your wrist and keep it warm. Slowing down or simply removing the watch can also help it get back to normal. These fixes sometimes work, but there’s no guarantee.
Another thing that can spark cadence lock is when you run up or down hills. I’ve noticed this on some trail runs. In some cases, I think this is because the incline causes an increase in heart rate – and eventually makes it lock on to the cadence. In others, I think the acceleration and force of the downhill steps is the cause.
If you’re interested in the science behind wrist based heart rate monitors and cadence lock, take a look at this blog post. The author understands the underlying science better than I do.
Why Does Cadence Lock Matter?
While it’s not the end of the world, it’s very annoying.
It disrupts the advanced metrics on my watch, like performance condition and training effect. If I go out for an easy run, but half of it is measured at a heart rate near my maximum, my watch is going to think that I went out for a very hard effort. This is going to increase the reported recovery time, and when compared with the actual pace it may lead to a decline in estimated fitness / VO2 Max.
It also muddies the waters if I look at a run in Garmin Connect, and it makes it difficult to gauge what my heart rate really is throughout runs. Part of how I use heart rate data is to compare runs of similar effort across time – and see if my pace is getting faster. If I can’t accurately determine the heart rate during a run or interval, it’s hard to objectively quantify the effort level.
I also occasionally use heart rate during a run to get feedback. This is usually the case for an easy run without a planned workout. I try to keep my heart rate in a low range – approximately 130 to 140 – to make sure I’m not pushing the pace too much.
The graph above is a good example of the problem in practice. I took this chart form my long run last week – an easy 11 mile run.
After about a half hour, my heart rate varied quite a bit and the reading spiked to 160 several times. It’s possible I went over some hills, but unlikely that those readings are accurate. But clearly, after the 50 minute mark, the heart rate reading spikes to 180. It fluctuates a bit and briefly recovers, but for the majority of the rest of the run it’s clearly way too high.
Just for reference, my maximum heart rate is around 175.
If you plan on incorporating heart rate training into your workout routine – whether to get feedback during a run or to analyze data after the fact – this just won’t do.
Thankfully, there’s a solution – a chest strap heart rate monitor like Garmin’s HRM Dual.
Example of Heart Rate Data from a Chest Strap Heart Rate Monitor
Let’s compare that graph above to an example from a different run – using a Garmin HRM Dual to track my heart rate.
There are still a few fluctuations in the data, but this isn’t surprising given the fact that my pace varied a bit throughout the run. I also ran up several hills, and this definitely caused the spikes around the hour mark. Some of the quick recoveries were probably caused by the fact that I had to stop a couple times to tie my shoelaces or wait for a traffic light.
But there’s clearly no cadence lock going on, and I’m confident that the data in the graph is more or less accurate. When I used the heart rate strap yesterday on a steady state tempo run, it gave me a very smooth heart rate graph.
Overall, my experience so far has been that the heart rate strap is a much more reliable measure than the optical heart rate sensor on the watch.
Other Impressions of Garmin’s HRM Dual Heart Rate Monitor
Here are some of my first impressions after first getting my HRM Dual.
It fits well.
The straps are a little hard to adjust, but once you get them to the right length they’re great. On my first run, it seemed a little loose, so I tightened it up after getting home. On the next run, I did 12 miles and it felt great.
It’s not too tight, and it feels comfortable while running. There’s a vague sense of pressure as I breath in and my chest expands, but nothing that is constrictive. After a couple of miles, I hardly even noticed I was wearing it. Now that I’ve been using it for over a year, I don’t notice it at all.
Once you have the straps adjusted, it’s easy to put on. It clips together under the right armpit and holds snug.
You have to put it on for it to turn on and start sending a signal.
This can make it a bit finnicky to connect at first. When I first put it on, my heart was at rest, and I don’t think it was beating hard enough for the sensor to register something and turn on. I couldn’t actually connect the heart rate strap to my watch until I went outside and got a bit warmed up. And again, the next morning, it didn’t pair at first until I moved around and got my heart rate up a little.
In retrospect, it’s also possible that these issues were caused because I didn’t wet the chest strap. Now that I’ve started doing that, the heart rate monitor connects just as quickly as my GPS resolves.
The heart rate monitor snaps onto the strap, and you can easily take it off to wash the strap. The instructions say to put it in the washer but not the dryer. I typically throw it in with my running clothes, and then take it out before they go in the dryer. Depending on how often you use it and how much you sweat, you may want to wash it up to once a week.
The heart rate monitor uses a watch battery for power, and it’s supposed to last over three years. I’ve had mine for about a year and half, and it’s still ticking. If and when the battery does die, you can easily and cheaply replace the battery. You can get a 4-pack of CR2032 watch batteries on Amazon for about $5.
Issues to Be Aware Of With an HRM Dual
Over time, I’ve also noticed a couple of issues that you may want to be aware of. They’re easily addressed if you know what to expect.
First, the strap can sometimes get stretched out over time and become more loose. You may have to readjust the length to get it to fit right. Over a year and half, I think I’ve only had to tighten it two or three times.
But one time in particular, it had gotten loose and it fell down to my waist during a run. I had worn it in the car while I drove to the track, and when sitting upright my chest expanded more than it normally does while standing. I could feel that it felt tighter than usual. When I got out of the car and started running, it had stretched out and needed to be tightened.
Second, you can ensure that it connects properly by wetting the contacts. I simply lick my thumb and rub it along the four sensors on the back of the strap, and then I do the same the skin on my chest where those contacts touch. If I don’t do this, it sometimes takes a little time for the heart rate monitor to connect.
Third, and on a related note, the HRM Dual will sometimes report inaccurate data during the first ten minutes or so of a run. I noticed this more early on, but it doesn’t happen anymore. I would start running, and my heart rate would rapidly increase over the first ten minutes to well above my actual heart rate, and it would then settle into the correct reading. If this occurs during a run, I go into the options to turn off the heart rate monitor and then I turn it back on once I’m ten minutes in. However, I think wetting the contacts on the chest strap has largely eliminated this issue.
Final Thoughts on the Garmin Heart Rate Monitor – HRM Dual
In the time that I’ve had it, I have really grown to like my HRM Dual Heart Rate Monitor. I was beginning to get frustrated with cadence lock on my Garmin Forerunner 245, and this new chest strap seems to have fixed the problem.
Have you tried out the HRM Dual or another Garmin heart rate monitor? I’d love to hear your comments below.
And if you’re looking for a heart rate monitor to pair with your watch, head over to Amazon and pick up a Garmin HRM Dual. You won’t be disappointed.