Luckily for me, that chest tightness has gone away completely every time I've swum, biked or ran this week. But I've noticed that my workouts are harder than usual this week. I'm swimming slower (and the bar is pretty low to begin with!), I can't push as hard on the bike, and every time my running pace dropped to an 8:something today, my heart and breathing were like WTF STOP!!!
(Disclaimer: I have seen a doctor for this in the past. It's anxiety. It only happens when I get really stressed. My ticker is fine. =) )
Of course, every doctor will tell you that exercise REDUCES stress with the endorphins and everything else. But here's a thing I found that confirmed my suspicions that stress reduces your ability to have a good workout. Like, in this article, number 5, Stress Hampers Your Fitness Gains. I knew it wasn't a coincidence.
Next week should be a lot easier and it's the weekend now, so things are better already. Hopefully my workouts will pick up, too.