I'm really confused by the maximum heart rate. According to the formula, my maximum heart rate should be 174, and I shouldn't exceed 144 BPM's, but... when I use the elyptical at my gym, I am training at about 150 BPM's, and can't get it to slow down unless I stop. I can't train on a treadmill because of an ACL strain of my knee. I feel fine, and can carry on a conversation - huffing and puffing a little, though. I've got about 70 pounds to lose, so it's important to me to get a good workout. Can I injure my heart by training so hard? Any opinions or advice?

Dianne 

It is best to check with a physician to establish what exercise guidelines are best for you. Pay attention to how your body feels. Ideally, you should be able to work at 60-80 percent of your maximum heart rate. You should be able to carry on a conversation - even if you huff and puff a bit. Without a complete health history, we can't give any further advice or opinions. Keep your focus on your goals and consult with your doctor so you work out smart and stay safe.