<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR><font face="Verdana, Arial" size="2">Originally posted by JerryKarin:
To strengthen your heart, you should do aerobic exercise intensely enough to reach your target heart rate. This is 60-80 percent of your maximum heart rate - which is 220 minus your age. (Example: if you're 50 years old, your maximum heart rate is 170; your target heart rate is 102-136.)</font><HR></BLOCKQUOTE>
I was a high school and college track/cross-country coach for ten years (most of that at the college level) and can tell you those formulas can be taken with a grain of salt. There's another one out there that is somewhat more accurate, but there's just too much variation in people's physiology.
As an example, I used heart rate monitors pretty regularly on my athletes and had them record their resting heart rates on a daily basis. For the most part, I couldn't do lab tests to find an athlete's actual heart rate at their anaerobic threshold, VO2max, etc., (small college) so I had to rely on formulas and guesswork.
One athlete, who ended up being an All-American in cross-country and the long distances in track, by the formulas should have had an anaerobic threshold heart rate somewhere around 175 (this was about ten years ago, so my memory is a little hazy). When I would have him attempt to do a workout at that (10-15 minutes running, I believe), he would complain that it was really taxing on him and he couldn't do it. It shouldn't have been that hard. So, I did a max heart rate test on him and, sure enough, the highest we could get his heart rate up to was in the mid 170s. His max according to the the tables should've been just under 200.
As far as the main topic, I personally would encourage moderate aerobic exercise in addition to TJQ. It, too, has health benefits that I think compliment the benefits one gets from TJQ.