Swimming/Cardio Qu?

Sooo....I'm swimming the most I've ever swum in my life right now and enjoying it...I got good advice from the OG before, thanks for that!

What seems to be stopping my progress (I wanna get up to 2 1/2 miles...triathlon length) is more worry about shoulder injury than cardio...at the end of the session my shoulders ache...but my lungs could keep going!
I don't push it too much as I don't want to get a shoulder injury...I'm ok so far, just aches like after a good gym session.

Is that common?
Are my shoulders just fags?
Am I doin' it wrong? (is it my technique?)

Any advice much appreciated...this time last year I could hardly swim 10 lengths of the pool.

I could take this to a swimming forum...but meh, those guys don't even lift!!!

i used to swim on a private swim club as a teen and the high school team until i got sick of it then quit.

i recently started swimming again 2 years ago after knee surgery.

i'm lifting heavy again, so i swim once a week to stretch my body out. swimming is great for lengthening your muscles.

i've not experienced any shoulder problems swimming even though i played baseball up until i graduated high school. i recently injured my shoulder and kept on swimming. swimming is one of the most low impact forms of exercise you can do.

i would suspect it's your technique and/or a weak body part. there's plenty of videos online for technique.

some common freestyle stroke deficiencies i see:

swimming flat (not rotating your shoulders). you shouldn't be like a board on top of the water. pretend you are trying to squeeze through a small invisible hoop in front of you. to do so you have to turn your shoulders with each stroke. in order to reach out the maximum distance with your hands you have to rotate your shoulders. this helps you stay long in the water, which improves efficiency.

so, when you are at the apex of your stroke with your arm extended as far as it can reach in front of you, your shoulders should be bladed at least 45-degrees to the surface of the water. in other words if you are lying face down in the water flat, your shoulders are parallel with the water surface. when you swim they should be rolling at 45-degree (appoximate, work within a range that feels comfortable) angle side-to-side. never staying parallel to the water surface. this also makes it easier to breathe properly.

short stroking. removing your hand from the water before it travels to your lower thigh. standing on the deck note where your hand rests with your arms hanging by your sides. this is where your hand should exit the water after each stroke.

i would also recommend getting short-blade training fins (i use tyr burner ebp fins) and a pull buoy. these help tremendously in building power and provide isolation to concentrate on a specific area to improve technique.

Thank you Sir, that's a pile of good advice.

Off to look up training fins on AMAZON.