When I run any moderate distance, (1/2 mile+) I get a pain in my chest that seems to be somewhere between my heart and my lungs. Also, after about 50 burpees, I decided to rest on my back for awhile. I noticed that not only could I feel my heart beat throughout my body, but I could partially see it. Now keep in mind that I'm pretty skinny, but I was wondering if this was normal or do I have something to worry about.

Also, is there any excercise I can do to specifically work the triceps?

Thanks.

Don't worry, it goes away when you get a little stronger. It could be a few things: your heart is a muscle and can get tired (although usually your body stops first), it could also be your diaphragm, which is the muscle that controls the inflating of your lungs.

If you're still worried, get a watch and make sure your heart isn't going much over about 200 beats per minute when you exercise, which could be too much stress. But once again, actually getting your heart rate that high takes a long time and you'd have to be in olympic shape to be able to get it that high...

If the pain comes "everytime" you run and it comes even quicker if you run up hill, I'd get it checked out with an EKG stress test.
That's the classic symptom of angina, or insufficient blood flow to the heart upon exertion.

It could simply be what is known as a runner's stitch, or stitch in the side..
It usually appears in beginning runners and becomes less common after a month of training.
I'm not certain if the exact cause of a stitch has ever been determined.
It could be your diaphragm as Stuuuuuuu pointed out.
This link shows multiple possible sources for the pain:
http://www.runnersweb.com/running/rw...JT_Stitch.html

To clarify some other points.
The more fit you are, the more blood is pumped with each beat (the stroke volume), and it takes more time to fill the chambers (ventricular filling time) before ejection out into the circulatory system (systole).
So a very fit person, like an Olympian, commonly has a lower max heart rate than an unfit person.
That's also why their resting heart rates are typically low, in the 30s or 40s etc.
Max Heart Rate is reached when working even harder doesn't cause the heart to beat any faster.
An unfit person will reach max heart rate much quicker than someone who is fit.

The heart, while being a muscle, typically doesn't get tired. The Tour de France bicyclists race for over 5 hours daily, near max heart rate, and probably could go 10.
Fatigure isn't fully understood, but generally, the periphery (legs , arms, back, etc) fatigue long before the heart shows any signs of slowing down.

But if there's blockages in the heart's arteries, or the arteries start to cramp (cocaine can cause that), then the heart does begin to falter and that's commonly when pain (or at least an odd feeling often termed as "pressure" (angina) results.

As parts of the heart not receiving proper blood flow begin to cramp, the heart's electicity detours around the cramped area and that shows up as EKG changes.

That's the test I mentioned above.

Incredibly helpful, both of you. I'll look into that. Appreciate it.

Yeah, that's right, stuuuu blew it there.

To work your triceps with your own bodyweight without any equipment you could do pushups but with your hands nearer to each other than normal, just separated by like5 or 6". At the beginning it's really hard to do them, so begin by a longer distance between your hands and reduce it as you get more fit.

Thanks, Ralili.

the same happens with me...but i have a chronic respiratory problem...you might want to get that checked if the pain is severe...if its not then like already mentioned it might be that you need a little getting used to it and youll b fine