My Target Heart Rate Zone
Saturday February 24th 2007, 12:43 pm

In addition to giving up sweets for Lent, I also started exercising on my treadmill yesterday. I started with two 10 minute sessions in the afternoon and evening, and will increase it to two 15 minute sessions within the next week. Apparently multiple shorter exercise sessions of at least 10 minutes each, are as good as a single longer session. I prefer two or more shorter sessions, at least for now. Some people prefer to exercise in the morning, but my favourite time is after lunch, when it helps regulate my blood sugar better. I also like to exercise in the evening about 8:30, before I start watching television. These times seem to suit me now, but I may vary the times depending on my plans for the day.

I only started yesterday and I started feeling better immediately, because I didn’t over exert myself. I was a little concerned about heart rates while exercising, because I’m middle aged and not in very good shape, so I did some research on the internet this morning. I found more than one formula for determining my target heart rate zone while exercising. The Karvonen Formula advises that it’s safe to exercise at 50% to 85% of your maximum heart rate, and uses my resting pulse to determine my zone. You must never exercise above 85% of your maximum heart rate, which can cause both cardiovascular and orthopaedic risks, without any extra benefit.

The Karvonen formula is as follows:
- Subtract my age (58) from 220 (max. heart rate per minute) = 162 BPM (beats per minute)
- Take your resting pulse rate for one minute = 73
- Subtract 73 from 162 = 89 (low end heart rate)
- 50% of 89 = 44.5 (low end heart rate)
- 85% of 89 = 75.7 (high end heart rate)
- Add 44.5 (50%) to 73 (resting heart rate) = 117.5 BPM
- Add 75.7 (85%) to 73 = 148.7 BPM
My target heart rate zone is 117.5 to 148.7 BPM using this formula.

The most accurate way to determine my maximum heart rate is to have a cardiac stress test, but I decided to use the predicted maximum heart rate for my age. This is determined by subtracting my age, which will be 58 soon, from 220. The predicted maximum heart rate for a 58 year old is 162 beats per minute.

An easier formula than the Karvonen formula is to take 60% of 162, which is 97, and 85% of 162, which is 137, to get the range. If you don’t want to do any calculation, you can use age range figures, which states that the target heart rate during exercise for people between 55 and 59 years old is 116 to 140 BPM, and the danger zone is over 145.

All of these formulas have given me different figures for my heart rate during exercise. To be on the safe side, I will start with the most conservative rate of 60% of 162 which is 97, and try to keep my heart rate in this range for the first week. I will gradually increase the heart rate, but not go above 80% of 162, which is 130 BPM, until I am in much better shape. Determining which percentage to use within your heart rate range is based on how long you have been exercising, and your physical condition. It is recommended to stay in the 50 - 60% of your maximum heart rate when beginning to exercise.

With this information, I feel better about exercising, although I couldn’t do much damage by doing only 15 minutes of walking on a treadmill, regardless of how fast I walked. I think the key to my continuing to use the treadmill is to set small attainable goals. In the past when I walked on the treadmill, I had no goal and stayed on it until I became tired. This made exercising an unpleasant chore, so I found excuses for not doing it.

My long term goal is to be able to walk on the treadmill as long as and at the same pace as my husband. During the winter when he doesn’t walk outside often, he uses the treadmill for 30 minutes a day, five days a week. When the weather improves, he walks outside at a brisk pace, for an hour a day, five days a week. It will take some time on the treadmill before I will be able to keep up with him on an hour walk, but that will be my goal for this spring. I also realize that resistance training is as important, but I want to take one step at a time.

My treadmill is calling me, so have a nice Saturday,