Here is a question a received recently (and I receive ones like it often): "Hi Lynda. I attended a workshop you gave in February, and I have a question that I bet you can answer. I joined a gym this week! My target heart rate is 112 and it doesn't go much above that when I use the treadmill. I tried the elliptical trainer today and my heart rate got all the way up to 130. Is this bad? I did have a stress test about 6 months ago and the doctor found no problems. The elliptical seems like a much better workout, but I worry about my heart rate. Should I?"
Here is my answer, plus a bit more info:
I am not at all concerned about your heart rate at 130, especially given that your doctor found no problems on your stress test. Target heart rates are a confusing issue since there are several formulas determining them and so much individual variation. But a target heart rate given as a single number instead of a range represents a number somewhere on the low to middle end of what your heart is theoretically capable of doing based on your age, gender, and depending on the formula used, sometimes your fitness level and resting heart rate. Many times, it is recommended that people stay within their "fat burning zone", which is a number about 60-65% of their maximum heart rate and sounds like your 112 number. The reality is that while you burn more of a percentage of calories from fat in this range, at higher heart rates you burn more calories, and thus more fat, overall. Studies are also suggesting that exercising at a higher heart rate will actually cause the body to burn more calories even after you finish exercising. As far as your general health is concerned, your heart is more than capable of sustaining a higher heart rate than 65% of your maximum, and exercising at a range between 65 and 85% of your maximum will definitely increase your cardiovascular health if you have no other health issues that would contraindicate this (this would include high blood pressure and coronary artery disease, so if you are concerned that you may have these issues be conservative about your exercise intensity and ask your doctor specifically about heart rate recommendations!).
About.com has a short article here explaining more about this principle.
Your number of 130 is well within a normal range and again, I am not concerned. Always pay attention to how you are feeling, though. If you are exercising comfortably at that heart rate, you're fine. If you start to feel weak, dizzy or otherwise off, you may need to slow down (although often this just means you just didn't have a snack before you worked out and your blood sugar is low).
Personally, I love elliptical machines because you can work harder without the strain on your joints from pounding as you step, which is why it tends to feel so much easier on your body. So keep it up, enjoy, and good luck!