Please Don’t Break My Heart

Phew…glad to get through Fri 13^th unscathed. Now I can safely look forward to 14^th of Fe…oh wait, you gotta be kidding me? COME ON?!

I’m as single as you can get, so I’m ignoring EVERYTHING today! But subconscious had other ideas and served up some short but intense dreaming this morning. About finding my father being still alive (he’s not) and being able to have a conversation with my ex (which I can’t).

Then the bell goes off. I wake up and the reality of my existence kicks in. Head. Is. Messed!

So, okay, I’m gonna open up and talk about my heart.

It can beat at over 200 times a minute when I’m giving it my all. It can fall to below 50 beats per minute when I’m relaxing in bed. And rather than talking about extinct friend zones, I’m gonna talk about heart rate zones instead. Here’s a really nice, simple diagram to start off with:

http://g-ecx.images-amazon.com/images/G/02/uk-sports/aplus/Training_Zone_Diagram.JPG

Before I try to start putting my own heart rates against these percentage values, it’s important to know a bit more about the zones. So based on a plethora of information in books and on the inter web, I’ve summarised what I’ve found. It may not be totally accurate, especially for the percentage burning values for carbs, fats and proteins. But the sources are fairly consistent.

Rather than basing the zones on actual HR, first consider some of the various indicators. Zone 5, you should be gasping, doing a full on sprint which you can maintain for only short periods. Zone 4 is when you can’t talk and it’s a bit uncomfortable. Zone 3 you can hold a conversation, but only in a few short sentences before you need to catch your breath. Then a few more words etc. Zone 2 is an easy jog and can hold a full on conversation without breaking a sweat. Zone 1 is a brisk walk, and you should be able to sing as merrily as you can. These are key indicators of EFFORT.

I will probably leave the benefits of each zone for another blog entry to do with pacing and training with HR zones. For now, let’s look at how to work out what heart rates we should be looking at for each zone.

First thing I need to know is my max heart rate. There are age related formula, but I have a good idea of mine from using a HR monitor for so long. It’s been up to 209 a year ago on a hill sprint, but that must be an erroneous reading, as I think I’d be dead. 205, 204 and 203 all come from over a year ago. 202 come from the Aztec 5k PB only last month. And this is probably a good gauge, because stress tests usually increase in intensity for 20minutes, and this was a 19:35 effort with a hill sprint at the end. There are also two more 202 peaks from this year and some 201s. There’s meant to be a drop off of 1bpm per year. And although the consistent story is 202 recently, I think if needed to do it, my heart could do 205 as a max.

Right, so according to the original Zones devised by Sally Edwards, that percentage relates to Max Heart Rate only. Which perhaps works for beginners or general fitness. But it doesn’t take into account the fact that your resting HR drops, and your Lactose Threshold HR increases the fitter you become over time. This is perhaps why GARMIN HR Zones are based on both Max and Resting HRs, based on the formula by Karvonen. Find the difference between your max and resting HR, and multiply by the percentage effort, but then adding on the resting HR.

So how do I calculate my resting HR? Advice is to wear the HR monitor when you first wake up, and take an average over three days. I wore it while I lay in bed for 20mins listening to some chilled out music. After a while it hovered around 50, but often dipped to 46, 47bpm. I’ve taken 46bpm.

But why do the Strava and Garmin HR Zones differ so much? Surely there must be some consistent logic. This is science after all. However, it’s sports science. As you do more research, you find there are even more ways to calculate HR zones. A very simplistic method is by Zoladz, which simply takes set bmp increments off your max.

A more “scientific” sounding method is based on Lactose Threshold (LTHR). The Lactose Threshold is meant to be the HR which you can sustain for 60minutes. It can be estimated from the last 20minutes of a 30min solo run or the last 3k of a recent 5k PB. Luckily, I have runs which can be used for either. So I exported the .tcx file from Garmin into Excel to look at the average heart rates during the last 20mins of my 32minute 8k at Weston and the last 3k of the Aztec West 5k where I got a time of 19:35. These give me 192.7bpm for Weston and 196.2bpm for Aztec. Given that this is a HR that should be sustained for an hour, I’m gonna say that the 193 is more accurate. Heart rate zones can then be based on the LTHR value, with 100% LTHR = 90% Effort = Z4/Z5 Interface.

So how do all these different ways of calculating heart rates for each zone differ? The key thing to remember, is that the zones relate to effort, not strictly heart rate.

My heart rate zones based on bpm using different models.

These are probably best presented and compared on a chart (I love charts and graphs):

Chart comparing different heart rate zone models.

So wow, quite a difference hey! Check out the difference is spread between the original Sally Edwards based on Max HR alone, and the Karvonen used by Garmin using both Max and Resting HRs. Let’s look at Zone 2. The effort should be that I can easily talk while keeping to an easy jog. Having a heart rate of 160bpm seems too high, so actually I think Karvonen/Garmin zones are too short and too high. However, consider Zone 5. This should be for sprints for very short periods. A heart rate of 185bpm seems too low. And I’m inclined to go with a value more similar to the LTHR method, since the 193bpm has some basis in my runs.

When I first compared Strava zones with Garmin, I was more convinced by Garmin as it used the Karvonen method which uses Max and Resting HR. However, researching the zone effort indicators, and comparing the zones, I can say that actually the Strava zones are closer to what I believe my zones are. Basing Z5 on 195bpm for now should keep that upper zone narrow and exclusive for all out painful efforts. And lowering and widening Z2 gives me a set of heart rates which seem more appropriate, particularly if I look at my long, slow runs where I’m able to have easy conversations below 160bpm. Above that and my sentences get a little shorter. So, these are what I believe my HR Zones actually are, and will be slightly tweeking Strava and more so on Garmin: