It’s not at all what you think; there’s a tightness in mine lately that’s been causing me some distress, frightening me of being yet another unexpected young victim of a heart attack (like a girl I knew in high school); last night, however, I got on the treadmill and pushed my rate to 197+ remarkably without need for EMS. And because I noticed it first while driving I considered the culprit was the air and changed in-cabin microfilter finally after 60K only to have it occur anytime while seated. Could it be poor posture, or atrophy of my upper body? Maybe I need to do more pushups.