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.)
I'd argue this. You're not going to create lift with a negative angle of attack (i.e. your hands are lower than your legs). In fact any hydrodynamic forces created will be oriented toward the bottom of the pool. I'd also argue that you probably don't want to create lift. All that's going to do is cork you up toward the surface. If you're a good underwater kicker you might want to stay under longer.
I'm thinking the body at entry from a dive is similar to your arm entering fingers first with high elbow producing llift forces acting perpendicular to your arm (although I've never believed the lift forces acting on your arm are significant - the catch and newtonian reaction force being more significant). However, because your body is a much bigger wing, could the perpendicular lift force on the body be significant at entry from a dive? At entry, components of the force would be upward and forward until you level out underwater at which point they would be upward (along with bouyant forces). Once ascending to the surface the lift forces on the body would be acting perpendicular to your body and seemingly upward and backward, definitely not good.
The drag forces underwater are considerably more substantial than those acting on the airborne body leaving the block.
Regardless, in case 2 the swimmer travels further in the air but spends more time in the air. In case 3 (as Roland Schoeman describes) the swimmer is getting into the water faster at a shorter distance with more energy transfer down the pool underwater. Can the swimmer in case 3 reach the same point where the case 2 swimmmer entered water in less time? I think so.
I'd argue this. You're not going to create lift with a negative angle of attack (i.e. your hands are lower than your legs). In fact any hydrodynamic forces created will be oriented toward the bottom of the pool. I'd also argue that you probably don't want to create lift. All that's going to do is cork you up toward the surface. If you're a good underwater kicker you might want to stay under longer.
I'm thinking the body at entry from a dive is similar to your arm entering fingers first with high elbow producing llift forces acting perpendicular to your arm (although I've never believed the lift forces acting on your arm are significant - the catch and newtonian reaction force being more significant). However, because your body is a much bigger wing, could the perpendicular lift force on the body be significant at entry from a dive? At entry, components of the force would be upward and forward until you level out underwater at which point they would be upward (along with bouyant forces). Once ascending to the surface the lift forces on the body would be acting perpendicular to your body and seemingly upward and backward, definitely not good.
The drag forces underwater are considerably more substantial than those acting on the airborne body leaving the block.
Regardless, in case 2 the swimmer travels further in the air but spends more time in the air. In case 3 (as Roland Schoeman describes) the swimmer is getting into the water faster at a shorter distance with more energy transfer down the pool underwater. Can the swimmer in case 3 reach the same point where the case 2 swimmmer entered water in less time? I think so.
