Robin,

Be patient with your body and celebrate the progress you have already made! One thing that you may find helpful in increasing your endurance is to reduce the speed at which you are jogging. If you slow it down a bit, you may find that you can last longer. However, it sounds that the pace you are doing now is getting you into that High Intensity interval zone that you want for HIT cardio. Another way to increase your indurance is by increasing the time spent exercising, although I would not suggest you try this until after your BFL challenge because I've found the more you tweak the program, the less likely you will to stick with it. If and when you try this, try adding an extra five minutes to each workout or every other workout until you reach 30 to 45 minutes and continue with your run/walk routine. In order to increase indurance, you have to continually challenge your body to go longer, even if you have walk breaks (which some of the leading endurance running experts highly recommend taking anyway). Good luck and congrats for sticking with it for 7 weeks! The best changes are yet to come!

Thanks marathonmama. I've never been a runner, so I guess my body is trying to figure out what the heck I'm doing to it. I was jogging at a 4.0 pace but that proved to be too slow, so I found myself walking more than jogging. Now the 4.2 seems slow as well, but I can't keep the endurance. So I'll just be patient, as you said, and see what happens.

Prettybrains,

I could not properly run on the treadmill my first year of BFL.  So I didn't.  The elliptical was my bread and butter.  But between shedding the fat, and strengthening my LB, I was able to do treadmill after that first year.  I'm at 2.5 years now, and ran a 5K in 27:45 over Labor Day.  The point I'm trying to make here is the transformation keeps happening over a longer duration that the first 12 weeks, so if you want it, keep at it.  In my opinion, it has become the easiest, most natural lifestyle I could ever have.

Jacium

the only way to really increase endurance is build your base. Let's say all you do ever is 2 miles and you've never ran over that. The only way to build endurance is to run farther than 2 miles. You should increase the mileage in increments of about 10% every other week and like MM said, take it slow on the longer runs. So if you're pace is about a 9:30...then your pace for the long runs should about 2-3 min slower. The long runs are not intended to act like HIIT, you're goal isn't to exhaust yourself and get your heart rate up there, your goal is to go beyond the mileage that you're used to.

I am a marathoner and now I am training for another one 6 months postpartum, so I am pretty much starting from scratch again.....and a lot heavier too. Every other week, I would increase my mileage so that I can get my endurance back. It's not easy, and honestly,  it was a lot easier running when I was pregnant than it is now.  

Also, look into doing the Galloway method which is a run/walk method. I am doing this now for my next race and have my Garmin all programmed for it. I would run for 5 min and then do a brisk walk for 1 minute.

I found this nice quote "Long distance runners never quit or give up, we just run one mile at a time."  So basically, just take it one step at a time.

Thanks Jacium and CaliRunner13. Jacium, I agree that though I've never liked running before, I am really starting to like it now, and will continue to run post the 12 week challenge, even if it's just for more HIIT. CaliRunner13, I am not at the point of doing 5Ks or marathons yet (actually, I don't know that I'll ever want to do them). I just wanna get through the 20 minute HIIT without having to walk. LOL. But I will definitely take your advice into consideration if I ever get to that point. Thanks again ladies!

Prettybrains - Am I correct that you are doing this:

Minutes 1 - 2 4.2 mph

Minutes 3 - 10 4.5 mph

Minutes 11 - 20 30 sec 5.0 mph, 30 sec 5.5, 30 sec 4.2

That's not a BFL HIIT workout. You might try this instead:

Minutes 1 - 2 warmup, level 5 (say 4.2 mph)

Minutes 3/7/11/15 level 6 (4.5 mph)

Minutes 4/8/12/16 level 7 (4.8 mph)

Minutes 5/9/13/17 level 8 (5.2 mph)

Minutes 6/10/14/18 level 9 (5.5 mph)

Minute 19 level 10 (6.0 mph)

Minute 20 cooldown (4.2 mph)

Changing between the levels is what burns the most fat. Think of it like your car - do you burn more gas in stop and go traffic or on the highway? As far as building endurance, DebMO, who got me started with BFL, ran her first 5K with no training other than the BFL HIIT pattern. Also you can work on increasing the speeds of each level as you continue. Crank up minute 19 to the fastest you can possibly sustain for 60 seconds. I am constantly having to give myself pep talks about being able to do this only for one minute (kinda like the little engine, instead of "I think I can," it's "I know I can (just for a minute)."

Best wishes.