A little Off-Topic physics question

[BlueIcarus]

Just out of curiosity...
Does anyone know the wattage required to swim underwater (w/fins & w/o fins) at a 25 seconds/25 meter pace? The missing data here is the 'rolling resistance' used in cycling, but applied to hidrodynamics (I suppose hehe) ... the resistance
of the water in contact with the body. I suppose (again) that it dependes in such a huge number of factors (skin surface, hidrodynamic profile, and so on) that one can only make a rough guess

Sorry for the OT. Less noise even if I don't explain the whole story besides this . Let's say I can win a couple of beers in a bet :duh

 

[efattah]

A way to approximate it would be to go to the gym, go on a cardio machine which measures watts, take your breathe-up and find the wattage which allows you to bike/run/work for a similar duration as you can in the pool in dynamic. Without immersion reflex effects, it would only be approximate.

Even without going to the gym, if you know the average wattage of walking, that is already an approximation, since people can apnea walk for similar times as they can swim.

I'm sure the calories-per-hour of walking is posted on the net somewhere, and there must be some conversion to watts.

 

[BlueIcarus]

yep, that was the way I was going to try: I have a tacx flow bike trainer
at home (although its watt-measuring capabilities is a little crappy.. +- 10%, but
sure at the gym it's not more accurate). So breath-up as usual and find the wattage
that make my first contraction come at the same time or cycle for the same amount of time.
Walking @ 5kmh burns 320 calories/hour, so 408 METABOLIC Watts. With a typical
cycling efficiency of 25 % (4 metabolic watts ---> 1 watt transfered to the bike), it's
about 110 watts on the bike.
This was to prove that freediving at the pool isn't harder (on an energy level) than
walking... but I guess there's no direct way to demonstrate this
Anyway... a new alternative to apnea walking for dry training discovered!!

Thanks,

Oscar

 

[land shark]

a human is capable of aprox 1/3 hp
this translates to 746 watts per hpX.3333=249 watts going flat out till u drop for one hour.

or so ive been told

jim

 

[Bill]

Jim
That figure sounds a little low. Of course, the output depends on how you produce the power. A few decades ago there was some literature on tests of 'super' athletes and both cyclists and rowers were capable of over 5/8 horsepower. I think that was for thirty minutes, but max human power is very flat from 15 minutes to 1 1/2 hours.
Aloha
Bill

 

[Decca]

To work out the power consumed swimming a certain distance underwater you need to know the resistance force created by the water.

Power (W) = Force (N) x Velocity (m/s)

Finding the velocity wouldn't be too hard.

Several factors contribute to the resistance force of the water.

The first is drag due to the projected area of the human body. The second is the skin resistance as you swim through the water. A knowledge of boundary layer theory would be useful for this calculation.

These calculations are relatively easy for a steel cylinder passsing through the water. Doing the calculations for the human body is a bit more tricky.

If you jumped into a channel of water flowing at the same speed at which you swim and hold onto a piece of string attached to a mass scale you could get an estimate of the resistance force. Alternatively you could hold onto the string in water and get a buddy to drag you along at the required speed while checking the reading on the mass scale.

mass (kg) x 9.81 (m/s2) gives you the resistance force in Newtons.

Your body movements while finning are different to being dragged along, and you would expect this to vary the resistance forces, but it would give an approximation.

 

[BlueIcarus]

Hi,
The NASA curve for 'healthy' men (Bicycling Science, Wilson & Papadopoulos, 3rd ed, MIT Press, page 44) provides:
400 Watts for 1 minute
300 Watts 5 minutes
250 Watts 30 minutes
125 Watts 3 hours, which I think should aproximate power put in walking, which
should be near dynamic power requirements.
For 'first-class athletes:
600 Watts / 1 minute
425 / 5 minutes
380 / 30 minutes
No Data extrapolated for 1h+

Now I know I'm a litle more than a 'healthy man'

Yesterday I tried apnea cycling @ 120 Watts and the times endured seemed to be very
close to the ones I have doing dynamics, but the contractions went stronger and uglier than at the water (diving reflex??). Contractions came after 45 seconds cycling, very close to the situation @ water, too. My HR was around 80 bpm at the middle of the interval (!!!). While breathing I have around 110-120 bpm, so very close @ 120 Watts to fast walking too

Decca method seems the way to go, but don't have a dynamometer!! .
Are you refering to the same mass scale where you put food to know how much it weights?? This should be easy to do! Going to find a mass scale!!

Thanks all

 

[Bill]

To work out the power consumed swimming a certain distance underwater you need to know the resistance force created by the water.

Power (W) = Force (N) x Velocity (m/s)

Don't know if it makes any difference in this discussion, but I think that's supposed to be the square of the velocity?????

Aloha
Bill

 

[Decca]

I had in mind the type of scale you use to measure the weight of a fish. You actually measure mass (grams or kilograms are units of mass) not weight, which is a force. In everyday language the terminology is a bit loose.

The resistance force due to drag is proportional to the square of the velocity.

 

[land shark]

just read my swimming book

For what its worth. It makes reference to work done by Doc Jim Counsilman.
One study showed that at a kicking speed of 60 sec /for 50 yds. Termed a moderate speed for a competitive swimmer. Used 4 times as much oxygen as being pulled at that same speed. Perhaps this may help some.


btw
">>>>The NASA curve for 'healthy' men (Bicycling Science, Wilson & Papadopoulos, 3rd ed, MIT Press, page 44) provides:
400 Watts for 1 minute
300 Watts 5 minutes
___________250 Watts 30 minutes
125 Watts 3 hours, which I think should aproximate power put in walking, which
should be near dynamic power requirements.""

not a bad guess for an electrician hey Bill

jim

 

[Bill]

0.4% error. You almost got it right. How many joules is that, Jim?

Aloha
Bill

 

[land shark]

450,000 watt seconds??
or joules??

any ways it was just a lucky guess

jim

 

[subaquaticus]

To work out the power consumed swimming a certain distance underwater you need to know the resistance force created by the water.

Power (W) = Force (N) x Velocity (m/s)

Don't know if it makes any difference in this discussion, but I think that's supposed to be the square of the velocity?????

Aloha
Bill

excellent remark !! 10 X

in fact it is very complex.... F = (1/2)*rho*S*V**2.....

in no fins it would be extremely complex...

rho is well known since it is the volumic mass of the water ; S is the "obstructing" surface...

in DNF, all the parts of your body do not have the same velocity...