A related discussion,
Sinus Tachycardia--Heart Ablation was started.
100 tachycardia is by definition a heart rate greater than 100.
so that means that the higher pulse rates ,over 100 not at rest is not tachyardia
It seems to me you are just a little bit out of shape. My pulse can shoot up to over 100 just by bringing in a couple of bags of groceries. I am sue you know your pulse goes up to give your body more oxygen, as you are burning more moving around then sleeping or lying still. It does seem a little bit high, but like what my doctor told me, if I don't have any smptoms and it goes down with rest it usually means you are okay.
Have you had a stress test?
It sounds pretty normal. Perhaps your heart rate increases faster than you are used to when you change from rest to activity, but a resting heart rate in the 70-80 range is normal. Everybody has a different set point for how quickly their heart rates increase with activities of daily living. A beta blocker like atenolol should decrease your heart rate. Increasing aerobic exercise should also help bring down your resting heart rate. When you are doing everything you can do to keep it low like exercise, it does not sound like something you should worry about. If I saw you in clinic and you were worried about it, I would order a 24 hour holter monitor. It the monitor is normal, I would suggest that this is normal for you.
I hope this helps.