Im 76, 5, 130# and after treading only 5 minutes or so, I start to salivate excessively and feel like heart burn rather anything to do with heart.  I have had a heart murmur for 4 years.  Do I push and tread more or stop.  I dont know if its my heart, Im not short of breath nor have any pain.
Hi, Welcome. This is Chat Doctor. The symptoms you are telling could be because of your heart condition. Gastritis or heart burn does not increase on exercise & it can occur on rest too. I would recommend against doing excessive treadmill now & would advise you for doing Tread Mill under ECG monitoring (Tread Mill Test) which can rule out cardiac condition if any. If that is negative, you can safely continue your treadmill. Come back if you need more help. Thanks