Not getting to target heart rate

[plclemo]

I am 51 years old.  My THR is about 140.  Yesterday while using the treadmill, I could not get it over 121.  THe machine practically had me walking straight up a wall (steep incline) and my pulse just got to 121.  My legs were killing me.  I was not out of breath.  But the treadmill was relentless in its pursuit of a good THR.  What causes this? Should I be concerned?

[Jerry_NJ]

If your legs are "killing" you (I think I know what you mean), and you're not out of breath or showing a target HR (have you ever hit a HR of 140?  Doing what, the same thing?  How did your legs feel back then?) it may be good to get your circulation to your legs checked.  I've had that done both as part of a general physical and under orders from my cardiologist.  It may also be you legs are the "weak link"... you heart "thinks" all is fine, no need to increase the oxygen supply.

When I was a runner it was always my HR that limited my speed, that and general exhaustion.   I don't remember any specific leg complaints.  Now things are different, older, no longer run, and am in permanent atrial fibrillation.  My legs get "tired" real easy, long before I become breathless.  Given I've had my circulation checked out I assume it is just poor condition on leg muscles.  My mind remembers the legs I had as a runner, my legs have completely forgotten about running :(

[curmudgen]

are you on any medication?  how did you determine your pulse?  machine or palpation?