thanks guys jerry I am not winded at 15 min, but my caves start cramping. just need to get use to it. Dave I did check bpm 2 min after it drop 7 beats is that enough, or will it in prove as I get in better shape . thanks both of you for your time.
The HR sounds reasonable to me, you haven't given us many metrics or related facts. My guess is the HR of 115 is a good starting point, you may be able to work you way up to longer/brisker walks (maybe up hill/grade) and get you HR up to 140 or so. But, not until you have a time to get in condition... are you now short of breath when at 115?
Your resting HR may come down if you exercise regularly and lose 50 pounds (estimate) I have weighted 250 myself, but I am near 6' 6" or was before old age brought my height down about one inch.
I assume atenolol is a beta blocker, and yes it affects your HR, but I don't think it should be considered when you set you exercise rate target. That said you resting HR of ab out 80 is a little high, not over the acceptable range, but without a beta blocker you resting HR may be closer to 100.
I than a BB and a calcium channel blocker to lower my HR and with atrial fibrillation my resting HR is around 80 even with these drugs.
I hope your BP is controlled, it is an important "Number". When you lose weight you may find you BP comes down too, maybe enough to get off the atenolol, one can hope.
Now, what is really important is not how long it takes the HR to come back down to your resting rate, but rather how much it comes down in the first 1-2 minutes after exercise. I would encourage you to take it 1 min after walking and if you notice an initial drop that is healthy. The harder you exercise and the longer you exercise the longer it will take to return to normal. As a runner, at the end of a 45-60 min run I might be sitting at, say 180, but 1 min later I am 140, and then it takes 10-15 minutes to come back down to 60 or so. This is totally normal and healthy.