I can't believe you kids are telling a 260lb. 54 year old man to do wind sprints. Are you trying to kill him?
First of all you are to big. Unless you are 6'6". You rarely see a 260lb 70 year old alive. Second you could have a serious blockage of one or more of your arteries. Get a walking stress ekg. Maybe a 64 slice artery scan of your arteries.
If the doctor gives you the ok start walking fast on a treadmill. See if you can walk at 3.8 mph. If that's to fast, work out the speed for yourself. First quarter mile lap do 3.8 on a level elevation. Second lap at 1% elevation. Third at 2%. The goal is to see how far up the elevation ladder you can get.
Say you get to your third quarter mile lap a 2% and your getting close to exhaustion. Make your final lap on level elevation for your final lap. Your goal eventually is to make it up to elevation 12% by going up 1% for every quarter mile. Do the work out a minimum of 4 times a week.
I ran track in high school and college. I severly hurt my arm a while back and I couldn't run because the jarring hurt my arm. I did the above workout to level 12% almost every day. When the arm was out of the sling I went for a run. I ran like a deer being chased by a mountain lion. Walking can kick your ass if done right.
At your age don't be concerned so much with strength that you neglect conditioning.
