I am a 76 year old male, excellent health, no meds. Runner from age 33-66. Last several years, walking 4-6 miles , three - four times a week Recently after about a mile, tightness in upper chest and pain in chest.... now I get tightness when walking a couple hundred yards. As a former college football player, always pushed through pain. Today, I tried to do that... walking 12-13 minutes on treadmill (twice). It didn't work... got tightness after a couple of minutes and significant discomfort.