Friday, July 30, 2010

HRM (Heart Rate Monitors)

As soon as you start getting serious with any cardiovascular activity (be it running, elliptical, cycling etc.), the first thing you need to do is stop and take a stock of your activity level.

Are you doing the cardio too slow?  A cardio activity that does not push your heart rate will not yield any positive results.

Are you doing it too fast? You will burn out and run the risk of injury and other complications.

In order to ensure that you are getting the benefit of your cardio exercise, you must make sure you are doing it in the target heart rate zone.

That begs the question. What is my target heart rate zone? The target heart rate zone for each person is dependent on age and fitness level. Use this calculator to determine the target heart rate zone for you. When I plugged in my age and my fitness level, I got my target heart rate results. When I am doing any cardio activity, my heart rate should be between 105bpm and 140bpm. That's my target heart rate zone. (Note: bpm=beats per minute).

The next question is how do I monitor my heart rate?. Most modern treadmills and other cardio-equipment comes with built in heart rate monitors. You place your palms on the HRM sensors and the machine takes a reading of your heart rate. I find 2 problems with this approach:
1. The sensors do not give a very accurate reading because your heart rate is measured using the readings from your palms. And as we all know, palms are a long distance away from our heart.
2. You need wrap your palms around the sensors at regular intervals to get updated readings. This is not very practical - especially if you are running vigorously.

The best way of determining your heart rate is to use a heart rate monitor. These devices come with a strap (containing the sensor) and a watch that receives the signal and displays the results. Advanced models can keep track of your history, calories burned, and even have a GPS chip (such as the Polar RS800CX) to keep accurate history of your exercise data.

Personally, I use the entry-level Polar RS100. But don't let the low price fool you. It is actually quiet a nifty device. Before using the device you need to setup the following data.
1. Weight
2. Height
3. Birth-date (Notice that you don't input the age. Inputting the birth-date allows the computer to compute your age accurately).
4. Max Heart rate (The default is the standard based on the simple formula of 220 minus your age. In my case, that's 175)
5. Resting Heart rate (You need to calculate this immediately after waking up. Use this guide to compute your resting heart rate).

The computer calculates your ideal heart rate ranges, but also allows you to override these values, if you so choose.

Once everything is setup, you wet the strap (to get good conductivity) and strap it around your chest with the sensor right on top of your heart. You then click on the start button on your watch and start your activity. When you reach your target heart rate zone, a small heart will start blinking telling you that your heart is ticking along nicely. If you increase your intensity and go beyond your limits, a beep will go off alerting you to slow down. The beeping will continue as long as you stay above the limits.

Another advantage of the Polar brand of heart rate monitors is that most professional cardio equipment that you find in the gym are compatible with the Polar heart rate straps. That means that these machines can detect the strap and show the heart rate readings directly on the big display. That can be very useful when you are concentrating on your exercise and don't have the time to look at the watch.

Somehow, this article reminded me of Celine Dion's "My heart will go on". If you are feeling nostalgic, click this link to relive the Titanic theme song on YouTube.

After writing the above article, I had a perfect opportunity to give my Polar RS100 a workout. I have not used it for quiet some time since I know the zone in which I normally run hence I don't use it on a daily basis.

The event was my weekly Saturday morning half-marathon run. I went to the gym with the goal of completing the half-marathon in under 2 hours as I had missed this goal by just 2 minutes last week.

I strapped on the HR monitor and started my run. At the end of the run, the data from the RS100 is as follows:
Duration of Activity: 1 hour 56 minutes and 16 seconds
Average heart rate: 144bpm (82% of max)
Limits: 114 - 149
In Zone: 1 hour 35 minutes and 15 seconds
Above Zone: 19 minutes 56 seconds
Below Zone: 1 minute 5 seconds
Calories burned: 1462 (Fat % 35)

Based on the actual data, It took me just 1 minute to enter the HR zone and since the average is 144, I was essentially in the upper end of the zone the entire duration of nearly 2 hours. I was checking the HR on the watch and it was switching between the range of 140 bpm to 145 bpm. A strange thing that I noticed is that every time I took a sip of Gatorade, the HR would drop to 140 and then steadily climb to 145. Guess it has something to do with the shock of cold drink hitting the body. During the last 30 minutes, I pushed myself and essentially was above my desired zone (known as the Red Zone). That is okay for me as I am experienced in running and used to pushing myself. Beginners should not do this, of course.

I also had my Nike+ sensor tracking my run and the details from the Nike+ sensor shows the actual run in graphical form.

The interesting thing to note here is the calories burned as computed by the Nike+ sensor. 1565 calories. There is a difference of about 100 calories compared to the calculations by the HR monitor. In this case, I would give more preference to the values from the HR monitor as they are based on the actual heart beat rate while the Nike+ sensor computes based on the distance run.

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