I watched the video on Schoeman's start swimswam.com/.../ and it raised a question I have had for a long time;why jump straight out from the start? Schoeman noted another swimmer who dove slightly up at the start and "stalled out"..In a previous thread Rich Abrahams said a coach told him the same thing about stalling out.The physics of this statement make no sense to me.Horizontal velocity is going to remain fairly constant,vertical velocity will decrease as one goes up and then increase again past the apex. I emailed Brent Rushall and he said to jump straight out or slightly down,but the article he referenced said
" Enter the water steeper rather than flatter (this should reduce the amount of splash (irrelevant water movement)).
Practice diving out as far as possible (maximal horizontal velocity produced primarily by leg drive off the block) before entering the water.
Dive deep so that resistance is reduced and more effective double-leg kicks are executed before surfacing."
To maximize distance(diving as far out as possible) one should angle up about 35-40 degrees(if the top of the block was even with surface of the water it would be 45 degrees(Rob Copeland said 32 degrees in another thread but: en.wikipedia.org/.../Ballistic_trajectory )
No one still does that,but some really good starters used to 1984 Olympic Men's 100m Breaststroke final - Steve Lundquist - YouTube .
When I ask coaches why the start should be straight out instead of angled up I never get an answer other than it has been found to be faster.In researching "found to be faster" I have found very little real confirmation.The best study I found(which I can no longer find the reference for) stated that the most important variable in speed to 15M was clean entry and that the greatest correlation with clean entry was experience.This also means that studies that just compare speed to 15M of different starts need to take experience with the start into account.
When I try the straight out start I have variable success with my entry(as would be expected with a new start.)I am willing to practice to get more consistent if I can get an explanation of why it is faster that makes "physics sense". I have seen too many trends in swimming change to think something is right just because everyone does it.(The first lesson I learned about starting was "ït is not a good start if it doesn't give you a red chest". I have been variously taught to swim freestyle without rolling and to kick out on BR kick so I know common wisdom isn't always wise.)
All those free body diagrams in college and they finally pay off 20 years later!
I'm contemplating a cheap way of setting things up for empirical analysis. I've got an underwater camera. I just need a way of marking distance for video in the pool. Might take a couple weeks but I'm curious enough to try this out.
Was thinking about those free body diagrams this morning driving into work and your really cool analysis. Not sure i can do that anymore, but clearly you and qbrain can.
you might be able pull this off on the deck with two timers, a tape, and maybe a third person timing and marking off the positions. Wondering about the angle/height of the swimmer, although i think you and others have pretty proven diving as straight out as possilbeis is the best approach. There are scanners that can collect position data very accuratley, but im not sure if they would work on a subject moving through the air.
When I get the time(after the next meet) I was hoping to get time to entry,distance to entry and time to 15M for flat,slightly up,and about 30 degrees for grab and track starts.This won't be a totally fair comparison given my familiarity with my current(grab) start but it will give some(hopefully interesting) data.
The other thing this may help me with is how much if any distance is lost from track start(without fin) compared to grab start.
I'll post what I get when I get it.Please post the results of any experiments Yáll conduct.
Actually I was thinking the same thing myself.I have a taper meet this weekend so it will need to wait til after that.
I think I can be with Fort to 15Min BR(if SDK is involved she'll kill me.)
Then you should use van der Burgh as your benchmark to be fair.
I'm contemplating a cheap way of setting things up for empirical analysis. I've got an underwater camera. I just need a way of marking distance for video in the pool. Might take a couple weeks but I'm curious enough to try this out.
High speed HD video camera, fixed position. The video editing software does all the work. If you are just comparing starts, you need to mark two points. The point that you set the camera on and the point that you aim the camera at and you can duplicate the setup so that you can compare starts across different days (assuming the same pool).
Underwater analysis is much more difficult mainly because lighting has to be really good for a fixed camera point to be able to "see" well enough across 15m for analysis.
I predict that your biggest bang will come from just practicing starts. If you compared two techniques with max effort, trained starts for a month, then compared them again, the starts at the beginning would not be nearly as fast as the starts at the end.
Agreed. Allen needs to go try different start techniques at stop pestering us with mathematical justifications for one side or the other. When he gets to the 15M mark faster than Fort, he should stick with that approach.
Actually I was thinking the same thing myself.I have a taper meet this weekend so it will need to wait til after that.
I think I can be with Fort to 15Min BR(if SDK is involved she'll kill me.)
I'll see if there is an easy way to estimate this but I'd guess that and empirical approach would be much easier.
Yeah, I don't think there is. There are just too many variables. If you start by assuming the human body is going to behave like a streamlined, rigid object you could certainly do it, but to me that's not a good assumption at all. We all know that exactly how your body enters the water on a dive is very important just from observation.
Empirical is the way to go. Videotape and time lots of starts to the 15 meter mark. Vary things like takeoff angle and entry angle and see how these seem to affect time to distance. It would really be cool to be able to overlay multiple starts and see the differences.
Why is there a starting distance in your calculations? Is it an approximation of how much the block moves under Fort's earthquake like 6.0 start?
My understanding from Peter's analysis - the swimmer is 2m long and so when the feet leave the block at end of force application, when swimmer then becomes projectile-like in a horizontal position, his CG is already 1m from the starting wall. If you look at his caclulation of the 30 deg start, you'll notice that swimmer's CG is only .87m from the wall because of the vertical takeoff (cos angle). Peter damn near thought of eveything!
Its interesting that James's and Fort's reaction times of around .6 sec are greater than the time from block to the water (calculated by Peter ~.4 to .6 sec). It would interesting to time Fort, or James or both from when feet leave the block to the point where they hit the water. Then time from the point where they hit the water to the 15m mark (pullout).
This would allow caclulation of the component horizontal velocities and we'd have actual velocities in the air and actual sdk velocities underwater 'til pull out. Peter is using 4.55m/s (= 25 m in 5.5 sec) in the air and assumed 25% less for underwater sdk or underwater Vx ~3.4m/s (= 25m in 7.35 sec). Possibly a little high for underwater, even for Fort and James? Having the three components: reaction time; air time and distance; and underwater time and distance; it would be easy to evaluate where the actual relative potential time savings are in a start.
Kicking speed vs swimming speed would (or should) strongly influence start strategy. I don't know how many max effort starts (to the 15M) you could string together and still have timing be meaningful.
Maybe measure times and calc velocities (as above) at a meet that has the capability to measure reaction times and where they are swimming 3 or 4 events with some rest between starts.
Actually I was thinking the same thing myself.I have a taper meet this weekend so it will need to wait til after that.
I think I can be with Fort to 15Min BR(if SDK is involved she'll kill me.)
Allen swimming Br too would provide another dimesnion. That would be three swimmers for this experiment.:banana:
