I have never made a secret of the fact that I despise those casual warm-ups many coaches give. You don’t have to look far to find one: 400 choice swim, 200 to 400 kick, 200 freestyle. That warm-up simply wastes precious training time in the water and it is an absolute disservice to a beginning swimmer.
If you’re intent on continuing with a foo-foo casual warm-up, at least limit it to just a couple hundred yards so you waste as little time as possible.
Might I suggest as an alternative, warming up with 4 x 100 freestyle @ 20 RI, 4 x 50 freestyle build @ 20 RI, 1 x 100 kick, 1 x 100 freestyle at STP, with 30 seconds between sets.
The first 100 you swim at an easy pace and simply feel the water. Feel your hands go through the water, feel your feet as you kick. Get in touch with the feel of the water as you swim. The second 100, increase pace just a bit, become aware of your technique. Is your entry correct? Is your catch and pull effective? Are you releasing at full extension? Bi-lateral breathe the third 100. Is your technique still correct as you breathe bi-laterally? Increase the pace just a bit more for the fourth 100. Is your technique still good?
The 4 x 100 is to get you to THINK. Think about what you are doing and why you are doing it. Focus on your technique. Think about pacing. Can you predict your time per 100?
The 4 x 50 set is to get you ready for harder efforts during the workout. Build from a relatively easy effort on the first 50 to slightly less than race pace on the final 50. Continue to focus on technique!
100 kick with or without a kick-board. Focus on kicking from the hip, pointing your toes and keeping your feet “in-contact” to create as little drag as possible.
Finally, close out your warm-up with a 100 at STP. Focus on pace, can you swim a 100 at your exact STP time? Are you able to maintain technique at STP?
I believe this warm-up will get you warmed up faster and ready for the workout to come. You will have turned casual warm-up time into productive work-out time.