I am doing my own Hitt type program, basically at every third minute I increase speed for 45 seconds. I do somthing like this; 3=5.0,6=5.5,9=6.0,12=6.5,15=7,18=7.5,21=8.0,24=9.0 then 5 min. cool down =30 min.program. At the end I am at a heart rate of around 160, I have had no problems and have been doing this for almost 4 months. I have read on this forum that some people suggest not to go over 120 for your heart rate.
I am a 60 year old male in pretty good shape:tucool: 5'11", 184.4 lbs, 15-16% bf. What do you guys think?
I also get a doctors check up every three months and have NO medical concerns or problems EXCEPT for minor joint aches and pains, torn rotator cuff from baseball, torn ACL from basketball and football.

I'd say that after 4 months of doing the same thing it's time to change things up a little. If you're not seeing more results, then try sprinting for a minute instead of 45 seconds. You could also try sprinting hills instead of a flat surface. I would constantly try and better your sprints or increase the time...keep your body guessing. There are lots of things you can do. Have fun!

Kind of depends on what your main motivation is for your running;

-- Performance / Training for a timed event?
-- Cardiovascular health?
-- Fat loss?

If you're pushing yourself gradually as time goes on so your body can perform at a level a little higher than it could previously, then I'd say you're in good shape for all three categories. If you've been doing the exact same workout with the same speed/interval pattern for 4 months, then depending on your goals/results, it might be time to think about switching things up a bit.

Thanks Guys,
Since I started I've gotten' down to 15-16% BF (from over 20%)and my main focus is to get the body fat down to 12%, and I've changed it up just today i'm at 2 min intervals and the first three were for 1 min. sprint. What do you think my top heart raterange should be?

well i regularly touch 200 on my heart rate.

my resting heart rate is in the 40s, and i have double digit blood pressure again.

so, uh.. don't be scared of 150-160. just don't kill yourself on my account.