Breaststroke Pull

Originally posted by Allen Stark Regarding lift,Bernoulles Principle is that as a fluid flows faster it's pressure decreases. An air plane wing is curved on top so the air has to travel further in the same time on top relative to underneath. Your first statement is correct, but your second is not. This quote from Wikipedia describes the flaw in this statement: Many readers new to this topic may be looking for the explanation that is commonly put forward in many mainstream books, and even scientific exhibitions, that touch on flight and aerodynamic principles; namely, that due to the greater curvature (and hence longer path) of the upper surface of an aerofoil, the air going over the top must go faster in order to "catch up" with the air flowing around the bottom (and hence due to its faster speed its pressure is lower, etc). Despite the fact that this "explanation" is probably the most common of all, it must be made clear that it is utterly false. There is no requirement that the air over the top must catch up to the air below, and in fact it does not do so. In addition, such an explanation would mean that an aircraft could not fly inverted, which is demonstrably not the case. It also fails to account for aerofoils which are fully symmetrical yet still develop significant lift. It is unclear why this explanation has gained such currency, except by repetition and perhaps the fact that it is easiest to grasp intuitively without mathematics. However, since it is wrong, the assumed intuition which serves it is also wrong, and the wise reader would do well to discount this approach. I also want to say that lift does NOT contribute to swimming propulsion. Since lift is defined as a component of force perpendicular to mean flow, it is impossible for lift to accelerate you in the water. If would be more proper to say that Bernoulli's principle is used by swimmers to create thrust--not lift. The same thing could be said about a boat or airplane propeller. OK, enough physics for today :)

Interesting. I am still a little confused. During your insweep, you catch water with your palm and sweep in fast. In that case, wouldn't the water under your hand (in your palm) be moving faster than the water above your hand? I guess that must be why I did not do so well in physics in HS. :)

Kirk,you are right. The curved air foil is a crude analogy. You are also right that lift isn't the best word to use in these discussions(and it's use contributes to many misconceptions) but it seems to be stuck in the swimming literature. Thanks for helping to set us straight. For a totally different(and at times nearly incomprehensible) theory of swimming propulsion see Cecil Colwin"s book"Swimming into the Twenty First Century"

Your question about recovery got me thinking about something I was doing more by feel than thought. What is hard to discribe is how the insweep becomes the recovery.It is one continuous movement with my forearms still providing thrust while my hands have come together,palms up and are shooting foreward. I have read that palms up is definitely better and I have read that palms down is definitely better,I feel it is a matter of what works best for you. What is not in dispute is that it is very bad to hesitate half way and it is important to REALLY shrug your shoulders foreward at the finish for maximum streamlining.

Newtons Third Law: For every action there is an equal and opposite reaction. While it is applicable,actually applying it in a moving fluid is much harder than you might imagine. In fact Bernoulli Principle applies directly only in a perfect(non viscous)fluid with laminar flow. Practically speaking this means that "feel for the water" is more useful than physics,at least at our current level of knowlege.

Originally posted by geochuck Bernoulles Principle is that as a fluid flows faster it's pressure decreases. I prefer Newtons third law over Bernoulles Principle. when it comes to swimming. Really they are one and the same. If anyone cares here's an article that describes this: www.grc.nasa.gov/.../bernnew.html

I have another question about breaststroke pull. Specifically, what is the end of the insweep? I am so focused on the idea of getting your hands out front as fast as possible that I sometimes catch myself rushing from insweep to recovery. Should your palms touch each other (or close to it) before you initiate the recovery? At the end of the insweep when your hands are under your chin, should you have your palms facing each other or palms up? Are there drills that make sure you finish your insweep?

Originally posted by knelson Your first statement is correct, but your second is not. This quote from Wikipedia describes the flaw in this statement: I also want to say that lift does NOT contribute to swimming propulsion. Since lift is defined as a component of force perpendicular to mean flow, it is impossible for lift to accelerate you in the water. If would be more proper to say that Bernoulli's principle is used by swimmers to create thrust--not lift. The same thing could be said about a boat or airplane propeller. OK, enough physics for today :) Just wondering how long has Wikipedia been a coach and do we believe everthing in Wikipedia is true???

Waynes website is a treasure trove of information and I highly reccomend it. I think Wayne would agree that the current trend is away from overlap stroke to now "ride the glide"i.e. stretch out the streamline position before starting the next stroke.That article isn't clear on when to breath,saying just on the insweep. As you recover your feet your knees will drop relative to your center of gravity(think of your body as a teeter-totter,do not raise your thighs at the hips.)This is simultaneous with the end of the insweep where the thrust forces are lifting your torso up. It requires little effort then to raise the torso further so you can breath without lifting your head.At least it seems this way to me. I am trying to put into words something that is easier to understand by observing great swimmers and feeling what seems right in the pool.

I think Wayne what calls the undulating style is the style Amanda Beard used to use with the exagerated bend of the back and raising the torso. Wayne are you there? I hate to speak for you.