is heart rate the key to excercise as long as I keep my heart rate up this is what counts because I was told that I should cross train but if I only walk or run if I keep my heart rate up is that what counts. or is it something with the muscle and that I need to cross train

another question is I walk/jog 30 minutes a day then do 5 minutes of adominal excercise can I just drop the 5 minutes of adominal and just do 5 more minutes of walk/jog I basicly keep my heart rate up to where I can just bare it

thanks

First of all, what is your goal with cardio?
Cardio is specific, so if you want to get better at for example rowing, then you should row and not run so much. Just an example.

Everything that keeps your HR up qualifies as cardio.
what do you mean by cross train?

I hope I can help answer your question nester9. I am a Certified Personal Trainer, so I get asked this question alot. First things first, heart rate is important during exercise, but it's not the only important thing. If you are looking to lose weight, then you need to keep in mind the number of calories you burn vs. the number of calories you need to take in per day. The reason why you have heard that crosstraining is important is it builds muscle. Even the slightest addition in muscle on your frame is going to boost your metabolism. Put simply, the more muscle you have on your body, the more calories your body will burn at rest (and exercise).

To answer your second question, abdominal exercises are not only good to help give a good looking core, it's also quite important for your overall health as strengthening the abdominals can help control blood pressure, protects your inner organs, promotes a healthy back/spine, helps blood flow, etc. so I would probably recommend you stick to doing the abdominal workouts if you can.