High elbow vs straight arm catch

It’s the direction of force - back. With the elbow bent it happens earlier and produces less arm drag I think

Some sprinters do well with nearly straight army driving hard down on the catch with a rapid turnover. The efficiency is all in favor of the high elbow. With the straight arm the initial forces are down, not back and the ending forces are up and not back. High elbow with EVF gives the longest time for the large surface of fingertips to elbow to be pushing backwards.(Actually. Done right it is not so much pulling your arm back as it it pulling your body foward.)

You might also be able to exert more force on the water with the bent elbow. For instance, if you are using a tricep press machine, you will be able to press much more weight if your elbows are bent than using a straight arm in front of you (or better explained - imagine getting out of shallow water in the pool by pressing your body out with straight arms in front of you to the deck vs bent elbows). Jeff

We've done drills before with a straight arm catch and I found that it placed a lot more load on my shoulders than a high elbow catch, or so it seemed. YMMV

If you are thinking about physics then you have to think about the physics of the human body and the muscles involved. The bent elbow catch uses your lat muscles and the straight arm catch uses your pectorals. The lat muscles are a lot bigger and stronger than the pectorals and much better for preventing injuries in adults. There are you tube videos showing swimmers trying both strokes on a swim bench with a computer that measures the force of each pull. The bent elbow always wins. You tube is amazing because that equipment is too expensive for the average person to try. After working the bent arm for at least a few weeks, try a time trial of both for yourself. 25 of each with a pull bouy. Every person really is different and you should do what works for you.