Before I started doing atkins I was doing really well with my jogging. Now I find it really hard to do my workouts and Ive cut back quite a bit. I usually jog 2 miles, which takes me around 20 min. Some days I only jog for 15, if Im feeling good I aim for 30 min on the treadmill. My legs feel super heavy, its frustrating to have to cut back so much. How long do I need to keep my heart rate up to achieve max fat burning and to speed up my metabolism? I feel that high intensity workouts work much better then lower intensity for a longer time. I keep my heart rate up pretty high when I workout, and I end up pretty sweaty, so is jogging two miles enough?

I am not an expert on this subject, but I have done a little research, and I do have some firsthand experience. There is conflicting research about aerobic versus anaerobic (or intense, or plyometric) in terms of fat burning benefits. The general consensus has been that fat burning begins after about 20 minutes of aerobic activiity at your target heart rate, but different studies and different trainers just do not agree on this issue. To solve this question, I do both types of exercise.

I personally believe, however, that the higher intensity anaerobic stuff is better. Even if I am doing an "aerobic" activity like a stationary bike, I do interval training, varying the intensity of the workout and pushing my muscles. I have found, however, that with LCing, the higher intensity stuff is tougher than lower intensity aerobic training. I started playing beach volleyball (anaerobic) a couple of months ago, and the first few times were brutal; the intense muscle demand of running and jumping in the sand killed me; since then, my muscles, and my body have started to adjust.

In both the aerobic and the anaerobic activities, sometimes I just feel like my muscles just aren't up to it. In general, however, my body has definitely adjusted to being able to do more and more exercise while LCing. Be diligent, be patient, and listen to your body.

How much time of aerobic activity do I need to do? I think that 20 min of jogging is better then 40 min of walking. I also play basketball and do other activities, you are right, varity is the best way to go.

Please see link at the bottom of this post for scientific explanation of fat burning.....

I used to be a total snob about walking; I believed that if you weren't sweating and out of breath, then it wasn't exercise. I do not believe that anymore (maybe because I am older?). I am not a fan of jogging or running, but I rollerblade about 4 days a week; somewhere in between walking and running in terms of intensity - I blade 15 miles which takes about about 1 hour and 20 minutes. I also use a stationary bike about twice a week, which is a more intense aerobic workout than blading, for about 1 hour to 1 hour and 20 min, depending upon how I feel.

With no particular basis other than my gut feeling and speaking to some fitness nuts and a couple of fit doctors, about an hour of good low intensity aerobics (walking, treadmill, bike, etc.) is a good amount of time for fat burning and cardio benefits.

I do not know whether 40 minutes of walking is "better" than 20 minutes of jogging; I am not sure anybody does. Again, with no scientific basis for this, if I had to choose, I would choose the higher intensity activity that makes me sweat and breath harder; but since I do not have to choose, I do both. I like the way the higher intensity makes me feel; I also believe I get more endorphins from the intense stuff.

As we both have said, variety is key. Find a few things you like, and do them. I get bored of things easily, so I need to have choices. Personally, I prefer the more anaerobic stuff like basketball or beach volleyball, tennis; but logistically, it is really hard to do these things frequently; so I do the stuff I can do alone and schedule more easily. Do the hour long walks and hikes, and also do the 20 minute jogs, and build to 30 minute jogs and more distance.

By the way, I have found that Potassium and Magnesium have helped me tremendously with my exercise and muscle function; I strongly recommend taking them, and possibly Calcium as well.

Here is a site that addresses your question. Good luck....

http://www.fatburn.com/article_show.asp?article_id=13

skibunnie, I feel the same way. I get up and run for about 15-20 minutes in the morning but I also do weight training every other day. I was always wondering if this was enough. Do you do any weight training?

IWillLose has a great point about lifting weights.

In general the consensus right now is that prolonged low intensity exercise is more for calorie burning while you are actually doing it. However, high intensity activity will stimulate calorie burning for hours after the exercise stops. This gets into issues of what type of nutrients are burned, but right now that's not as important as just making sure you keep going. You should definitely listen to your body and see if high intensity is for you. If it is not, then just keep at it with sustained moderate intensity exercise.

if you would like for me to go into detail about what types of calories are expended just let me know.