Generally for freestyle you want to follow these rules to avoid shoulder injury:
1.) Don't cross the center line of your body with your arm. If you were climbing a ladder you wouldn't ever do that. Freestyle is kind of like climbing a ladder horizontally.
2.) Keep a good rotation around your center line in the upper body. This helps to use your back muscles/lats to do the big work. You want to be sore at the end of the workout in your lats, core and maybe chest. Not your shoulders.
3.) Don't over-extend your arm in reach. Many people end up pushing down on the water they initiate their stroke, this is wasted work and also shoulder strain. You want to as quickly as possible have your hand pulling parallel to your body, which usually means a high, wide elbow in the catch.
This is a course I've been meaning to try but haven't. It purports to reduce shoulder injuries:
> Don't cross the center line of your body with your arm. If you were climbing a ladder you wouldn't ever do that
Hmm, that doesn't sound quite right to me. I claim no knowledge especially in swimming technique so this is just for curious discussion and you can put me right - as a weightlifter, the most natural and least impinged arm motion for me is a diagonal across the body whereas perpendicular swinging motions are crunchy and impinged.
If I climb a ladder, I'm propelling myself with my legs and only holding on with my arms by pulling my chest to the ladder so that seems like a bad analogy. Incidentally, if you ever want to feel like your forearms might split out of their skin, try climbing a wind turbine ladder! I think I ended up having to finish it by hugging the ladder in my elbow creases having lost all grip strength due to forearm pump.
It’s true ladders are mostly leg. It’s not the best analogy perhaps a better one is pulling yourself up onto a box. You wouldn’t put your hands close to the center of the body, you’d have them out wide as you push.
Not sure what you’re referring to in terms of lifting diagonally, but as another comment noted in swimming you’re rotating around the center line with each stroke. If you were doing right-arm cable pull downs, you likely aren’t going to have the most strength with your right hand level with your left shoulder. You may rotate, using your core an back to bring the arm down but in those cases I doubt you’re crossing the center line high up in that motion.
Because of the rotation in swimming you can end up with your arm that way which will impinge on the rotator cuff.
Essentially you want to stabilize your shoulder with your lats and scapular muscles so that it doesn’t fall forward in the socket. That is what causes swimming repetitive use injuries. I say this as someone with two surgically repaired shoulders. I’ve done a lot of stroke work to keep them fixed after years of bad form.
You are sort of making a diagonal movement anyway because of the rotation, that rotation is what's engaging the rest of your muscles to help you pull the water. If you cross the line, it's much harder to use your lats, your core or your chest to pull the water and instead you're using almost solely your shoulder and with increased resistance too.
That increased resistance is not helping you propell forward either, you're propelling diagonally with the stroke in that case which is a waste.
I read a blog of someone preparing for a 24-hour swim around one of the Swiss lakes and he was explaining about how it's important to get the reach and catch right. I understood this to mean getting your body rotation, shoulder and slightly-bent, extended arm into the most mechanically advantageous position. I imagine that this minimises "difficult" stresses on the shoulder joint. I'm trying to implement this without a trainer and it seems not to be irritating my (unrelated) shoulder injury.
Can you share any resources or personal thoughts for maintaining form that avoids injury?