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Jigoro
November 11th, 2007, 06:33 AM
I have folowed a lifeguard course and we always had to swim with our head above water.
2 requirements for the exam were:
- From the side jumping into the water, one lap entirely under water, 2 25 meter laps on back with arms above water (to prove that the kick is efficient enough) within 100 seconds.
- 200 meters in 4 minutes and 15 seconds (which is even quite doable with the breaststroke), of course with head above water.

At the university swimming pool I noticed a list for the sportmasterstudents (they study sport at an academic level) with required times and laps.
This got me wondering. How much faster can you swim a lap when you swim with your head under water compared to when you swim with your had above water?
I suspect that the relative difference in speed will be larger for a sprint than for an long distance.

tomtopo
November 11th, 2007, 12:07 PM
Unless you're a fish, pulling and kicking with our appendages provide the lift and drag forces which are the most important propelling forces for humans as they swim. Swimming underwater is slower for many reasons, the recovery stroke underwater slows you down compared to above water. The inability to effectively use your hands is also a negative when comparing the two. The dolfin kick is extremely effective underwater but without the use of the arms, the dolfin kick cannot compete with the butterfly done above the water. I hope that answers your question.

There may be a few weird rebuttals but they'd only be weird. Good luck.

rtodd
November 11th, 2007, 01:10 PM
I would say about 50-75% faster regardless of distance.

But I suppose as a lifeguard it is kind of improtant to locate the exact spot a person goes under as you are swimming out to them.

Jigoro
November 11th, 2007, 03:46 PM
Unless you're a fish, pulling and kicking with our appendages provide the lift and drag forces which are the most important propelling forces for humans as they swim. Swimming underwater is slower for many reasons, the recovery stroke underwater slows you down compared to above water. The inability to effectively use your hands is also a negative when comparing the two. The dolfin kick is extremely effective underwater but without the use of the arms, the dolfin kick cannot compete with the butterfly done above the water. I hope that answers your question.

There may be a few weird rebuttals but they'd only be weird. Good luck.
Tomtopo, I'm not sure that we're talking about the same thing. I'm not asking about swimming with your entire body under the watersurface, I'm asking about swimming with only the head under water. For the breaststroke this would be during the gliding phase (as you swim it normally), for the crawl this would be during the entire stroke with the exception of the moments that you breath. The difference between normal swimmers and lifeguards/waterpoloplayers is that the last group of people needs to constantly observ the environment.

When you need to constantly keep your head above water it greatly compromises the hydrodynamics since your body is much less straight.

With regard to swimming with your entire body under the watersurface, my experience is that I'm obviously slower. I do not master the dolfinkick yet (I am experimenting with it though).


But I suppose as a lifeguard it is kind of improtant to locate the exact spot a person goes under as you are swimming out to them.
That is what we had been taught.


I would say about 50-75% faster regardless of distance.
Thanks for your insight. Are you talking about the breastcrawl or both the breastcrawl and breaststroke?
I schould experiment with it but then I would have to bother someone with taking the time and I could only experiment with the breaststroke since my crawl is technically not good enough yet (I'm getting some lessons, dutch schoolswimming as always been oriented on the breaststroke since they considered it to be easier than the crawl). Besides, it might differ depending on the individual his technique and physique.

geochuck
November 11th, 2007, 03:48 PM
Head up front crawl I have done lots when playing waterpolo. But we swim faster with the face in the water and the body in a streamlined position.

The higher the head the legs drop lower. We then are swimming up hill and that is hard to do.

I take it that you are talking face down in the water, not the head completely submerged.

I know it can be confusing as I have seen a person talking about the head being submerged when he swims but when I watched a video of his swimming in a race it was not completely submerged. It was low but not much lower than mine. I saw other videos of instruction that he produced and the head was submerged in fact it was very exaggerated. Head too deep will not make you faster.

Jigoro
November 12th, 2007, 08:10 PM
I take it that you are talking face down in the water, not the head completely submerged.

Yes. I understand that it's not about the head being under water but that it's about having a straighter posture so you decrease the resistance.