Sinking hips during recovery in fly

Thanks a lot SolarEnergy, I like a lot your way of thinking of swimming through physics. I prefer it that way as well. All right. First, I have to slightly disagree with your statement of the facts. Your issue begins well before the arm recovery started. Your hips are already too low just a fraction of a second after hands entry (reference, minute 1:06 from slowmo clip). If you agree with this then we have to start analyzing your movements from this point on. Nicely spotted. I had a thought about it too and it could be that from the moment my head is low and the whole body is downhill, instead of pulling my head up with downward movement of the first phase of the pull, I try to lift my head by "body movement", from hips, basically pushing my hips down. That explains why I feel my hands have nothing to do in the beginning of the pull. The filling is like my hands are going through the air in that phase. It could be that since body "wave" is lifting the head, arms have nothing to do. I kind of had a mental picture of butterfly as "snake" movement, meaning chest follows head, hips follow chest (and go through the points where chest went through), knees follow hips :) Basically, I thought if we would take a picture of flier with a very long exposure (fixed camera), we would get a wavy line. Now, it looks like I was wrong about that. Now. Let us immediately drop all pre-formatted thoughts and stick to Newton's Third here for a moment. Which forces could account for this loss in buoyancy? What particular movements are taking place at this particular moment? I see two things: 1. You're raising your head to breathe, then 2. You're recovering the legs to prepare for the second kick Very interesting analysis of the second kick. If I try to analyze preparation for the first kick (the moment that worried me initially) what forces do we have? Downward forces: 1. gravity 2. upbeat of the second kick 3. hands leaving the water Upward forces: 1. buoyance. But since buoyance decreases at this moment since the arms go above the water, this force's overall contribution is more downward (it has negative change). 2. flow dynamics. The whole body is in "uphill" position after the pull and before the recovery and since the water flows towards the swimmer, water tends to lift the swimmer up. Since my second kick is finished too early, when my arms are somewhere half way through the pull, it could be that I loose lots of speed by the time pull is finished and then the only upward force (flow dynamics) becomes too small. Additionally, rotation of arms from shoulders (beginning of the recovery - upsweep), creates most probably counter force moment in the shoulder to the rest of the body which tends to rotate body counter-clockwise (when watched from the right side), which also brings hips down. Thanks for the no-arms drill. I actually used this drill (I posted this in one of my previous posts on my blog). Although I posted above the water video, probably more interesting would be underwater one. I'll make it and post it. Thanks again, I like long posts, if they are interesting :), and this one definitely was very interesting. Best regards. - Predrag.

Thanks a lot SolarEnergy, I like a lot your way of thinking of swimming through physics. I prefer it that way as well. All right. First, I have to slightly disagree with your statement of the facts. Your issue begins well before the arm recovery started. Your hips are already too low just a fraction of a second after hands entry (reference, minute 1:06 from slowmo clip). If you agree with this then we have to start analyzing your movements from this point on. Nicely spotted. I had a thought about it too and it could be that from the moment my head is low and the whole body is downhill, instead of pulling my head up with downward movement of the first phase of the pull, I try to lift my head by "body movement", from hips, basically pushing my hips down. That explains why I feel my hands have nothing to do in the beginning of the pull. The filling is like my hands are going through the air in that phase. It could be that since body "wave" is lifting the head, arms have nothing to do. I kind of had a mental picture of butterfly as "snake" movement, meaning chest follows head, hips follow chest (and go through the points where chest went through), knees follow hips :) Basically, I thought if we would take a picture of flier with a very long exposure (fixed camera), we would get a wavy line. Now, it looks like I was wrong about that. Now. Let us immediately drop all pre-formatted thoughts and stick to Newton's Third here for a moment. Which forces could account for this loss in buoyancy? What particular movements are taking place at this particular moment? I see two things: 1. You're raising your head to breathe, then 2. You're recovering the legs to prepare for the second kick Very interesting analysis of the second kick. If I try to analyze preparation for the first kick (the moment that worried me initially) what forces do we have? Downward forces: 1. gravity 2. upbeat of the second kick 3. hands leaving the water Upward forces: 1. buoyance. But since buoyance decreases at this moment since the arms go above the water, this force's overall contribution is more downward (it has negative change). 2. flow dynamics. The whole body is in "uphill" position after the pull and before the recovery and since the water flows towards the swimmer, water tends to lift the swimmer up. Since my second kick is finished too early, when my arms are somewhere half way through the pull, it could be that I loose lots of speed by the time pull is finished and then the only upward force (flow dynamics) becomes too small. Additionally, rotation of arms from shoulders (beginning of the recovery - upsweep), creates most probably counter force moment in the shoulder to the rest of the body which tends to rotate body counter-clockwise (when watched from the right side), which also brings hips down. Thanks for the no-arms drill. I actually used this drill (I posted this in one of my previous posts on my blog). Although I posted above the water video, probably more interesting would be underwater one. I'll make it and post it. Thanks again, I like long posts, if they are interesting :), and this one definitely was very interesting. Best regards. - Predrag.