It's always recommended to consult your physician before starting an excercise regiment. If your having conserns it's still not to late to talk to your Doctor. It's a better safe than sorry type of sitiuation. Talking to a trainer isn't a bad idea either.
Here is some info from webMD on your exercise heart rate.
How to know if you are getting a good workout
To know if you are exercising hard enough and also at a safe level, you will need to figure out your target heart rate
. Your target heart rate can depend on the type of exercise you are doing.
Moderate exercise includes activities like fast walking, swimming, dancing, or water aerobics
Vigorous exercise includes activities like jogging, aerobics, basketball, fast swimming, or fast dancing. This level of exercise is more intense.
To figure out your target heart rate:
Stop exercising briefly to take your heart rate (pulse). Take it within 5 seconds of when you stop exercising. We recommend taking your pulse at the wrist (as shown in the picture). You can feel your pulse on your wrist in line with the thumb. Place the tips of the index and middle fingers over the artery
and press lightly. Do not use the thumb since it has a pulse of its own. Take a full 60-second count of the heartbeats, or take it for 30 seconds and multiply by 2. Start the count on a beat, which is counted as "zero."
Later, when you're back on your computer, using the calculator below, figure out your target heart rate. The calculator will give your maximum and minimum heart rate. This is called your target zone. See if the number you remembered as your pulse falls within this zone. Try to exercise in this zone.
You can also try using the talk/sing test to make sure you are working out at the right level.
- If you can talk while you are doing a physical activity, you are probably moving at a pace that is good for you.
- If you are too breathless to talk, you should slow down.
- If you can sing while you are doing a physical activity, you may not be working hard enough; so, you should pick up the pace!
You may be looking to measure your exercise success in pounds, or by how much weight you lose. If so, it is important to know that muscle weighs more than fat, so weighing yourself won’t tell you if you are fit. Being able to exercise in your target heart rate zone is a better sign of your fitness level. It is still important to be at a healthy weight for your age, which can be measured by your Body Mass Index
Interactive target heart rate tool : http://www.webmd.com/heart-disease/tc/interactive-tool-what-is-your-target-heart-rate-what-does-this-tool-measure
They also have a BMI indicator that you can fill out.