I have been running for about 2 years now. I usually run or do some cardio at least 3-4 times a week. For some reason, my heart rate is not improving. It I were to stay within the suggested heart rate for cardio exercise, I would have to just walk. Is there anything I can do to improve this?
Thanks

how are you measuring your improvement ( or lack thereof )?
what is your resting pulse? how are you measuring it? when do you take it while doing cardio? I'll give some examples: my resting is around 40s if I'm relaxed, if I'm driving or working (at desk on PC) it's in the low-mid 50s usually. At night (as I've posted) during sleep it can go down to 32. When I start a run- I try to get it up to the 80s or 90s by walking before running. During the 1/2 mile it may only get to the 140s but I am not pushing for speed at that point. After a mile I'm warmed up better and go a little faster. It'll be around 160-165 then. Then I may push a bit harder to get into the 170s. Then if I start doing about 95% it'll start pushing 180. I think your rate should stay fairly consistently high when pushing your body - to get oxygen where it needs to be. Where you should start seeing a lower rate is during walking or just resting. The 'average' men's pulse is around 72. I have to walk fairly quickly to get up to that.
Let me know what your circumstances are and maybe I (& others) can lend more insight.