My Normal Resting Heart Rate Is 60-65. I'm 55 And

My normal resting heart rate is 60-65. I'm 55 and active. When I'm on the treadmill at the gym I do interval walk 1-2 minutes and run 2 minutes. After the run, my heart rate is 182. I thought maybe it was the machine, but my husband also uses the treadmill there and his only registers in the 140's. I get a little light headed, but other than that I feel fine. I'm not sure what to do.