I can’t read the graph very well but I think I know what it says for the blue bars but what are the red bars?
Idk why it copied in so small, red is just births by month, blue is number of players in some UEFA league. Just from the wiki article for relative age effect.
In the us your birthday doesn’t matter when it comes to swimming (too much). Your age for any swimmeet is your age on the first day of competition. So every swimmer has to deal with being the young one and then later they get to be king of the hill.
So based on that, the kid whose birthday is literrally the day after the last meet of the season is the one who has the biggest advantage, beause they are older for longer through the next season?
In a triathlon context it is your age on Jan 1, so its best as a kid if your birthday is Jan 1 for triathlon but as an adult eventually every 5 years it is best if your birthday is Dec 31!
this has been proven in the book freakonomics if I recall
That’s actually where I first heard about it. There’s also a push in some countries (South Africa maybe?) to divide team sports not by age but by weight. IMO this really makes sense for a lot of sports, especially full contact sports like rugby and football.
I encouraged my sister to hold it in as long as she could so he had a jan birthday, she considerd my comments neither funny nor helpful. He has a late Dec bday.
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In any case, no matter how you do it (birthday on day of competition, age as of Dec 31, Age as start of that sport’s season, or end of that sports season), whoever is “oldest” has the season long advantage every year (or minimally every two years) and gets the positive reinforcement of “winning” or “being superior”. Positive reinforcement creates a virtuous cycle. The kids who have success stay in, their parents spend money and time to keep winning (parents are egotistical and love it when their kid wins, their interest wanes supporting kids who are not good at something)…and so the cycle goes.
Very rare that parents of kids who are not winning supporting a sporting path…being born in October and perpetually smaller in size, literally everyone around me lost interest in anything in sport, so I just stayed in because I liked the process since wins came almost never. Until I started longer distance running in young adult life and suddenly I was doing a sport that I was more designed for and 5 year age groups meant every 19 year old is competing with seniors in college anyway, so the Jan vs Dec advantage kind of goes away when there are athletes with 3 extra years of development.
In the US. Where short course is king. You’re going to make the argument that a March 1 birthday wouldn’t matter (too much)? Sure it doesnt matter when you’re already 15, tell that to the 10, 12, and 14 yo.
Dev, I’m sorry you seem like an amiable person, but i just cant read through this. The point of the catch up drill explanation was to show that you in fact can maintain direct backwards force. When your hips “clear” for lack of a better term, at the finish if the stroke, it enables your hand/arm to maintain the backwards force. Your example about rotation actually proves this out if you actually observe your rotating the hips out of the way (clearing) allowing the force to maintain backwards position. Im not sure what you think your see in the Ledecky picture, but except for the very initial portion of the catch and the exiting of the water to recover the best swimmers are in fact applying force directly backwards.
You like swimming. Thats awesome. But it does not equate to years and years of studying the actual dynamics. And i try to remain in constant learning mode myself. In freestyle, the forces are all backwards (in the top end) thats why the stroke is so fast.
Regarding another comment, i dont think yours, i dont believe I’d equate having fast 12yo to having “all the expertise” but it sure doesn’t hurt. We (it’s never just one coach) have had quite a few fast kids through from 10-college aged, quad-A times at all ages, D1 kids, you name it. We’ve observed a lot of very technically competent swimmers from which to provide input.
Im going to bow out of this conversation. I think I found the reason ive read this forum for 15 years and never signed up to contribute.
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When I started playing football in Canada, the Ontario Football Association had both an age limit and a weight limit. At around age 11, I was pretty close to the upper weight limit but they did allow you to go over during the season by maybe 5 pounds. This affected me at some point where my next season would have been against players 1 year older. I decided to play soccer instead which I ultimately preferred anyway.
I just checked for current regulations and it appears the weight limits for football in Ontario were removed at some point. OTOH, at Football Quebec there are weight limitations to match the physical stature of players. These weight limits apply at the Atom (110 lbs), Mosquito (135 lbs.), and Peewee (165 lbs.) levels.
Now it gets interesting: If the child exceeds the weight limit at contract registration time in August, he/she becomes eligible to play offensive line only. They make these kids wear a big X on their helmet which has created some controversy - like hey, let’s put a big X on the fat kids:
@Kid
@BfloTri thanks for writing this up. I THINK I know what happened here.
You said you have been reading for 15 years. So when you came on, you would have known the content and style of many posters. Meanwhile the rest of us, have zero idea who you are, what your background is, what expertise you have, what sports you may or may not be involved in.
If @garyhallsr or @SnappingT come on here and make any declaration about swimming, we’re all going to step back and ask questions to assist our understanding. If someone who has no background HERE makes a declaration in the vein of “its all this way, you are dead wrong” there will be questions and discussion. Any questions on the opposing point of view may have been perceived by you as an insult (because we don’t even know if you know anything about any topic in the first few posts). So perhaps if you have been coaching swimming for a while you felt that the questions or other point of view are out of line.
What I would suggest is post more so everyone can get to know you.
But moving on from there, we are somewhat saying the same thing. You are saying “backward” I am saying “backward net via a reciprocating motion of the entire body”.
OK you say you are coaching, I have coached other sports for 20+ years also, so spent a lot of time looking at human mechanics across all sports.
So let’s take a really simple example to examine how humas exert forces.
Go to a track and walk down the track with right foot landing slightly to the right of a line left foot slightly to the left.
What happened there? How is it possible to go forward when the force of the leg is moving center of gravity subtley from side to side through a longtudinal rotation of the spine. Now try walking down the line with feet landing on the line. You will see a bigger spinal rotation end up with 100% of the force pointing backward. Now go one step further and walk like a fashion model with right leg landing on left side of the line and vice versa. You will see a lot of force and spinal rotation going on, yet the NET force is 100% backwards because the sideways forces cancel out !!!
It’s a simple example of forces.
OK let’s go to the pool where we are kind of saying the same thing but its because we’re not defining frame of reference. In the Katie Ledecky image posted above in this thread, she is not pushing water backwards relative to her body, and she is not totally kicking water backwards relative to her body either. But towards the back of the pool, she’s maximizing her net backward forces that you and are are in agreement of.
I am pointing out that creating net backward forces on a fluid does not come from pushing the fluid backwards (maybe the only example I know of is the ramjet but that’s different fluide dynamics at supersonic speed requiring a combustion step). Pretty well all net backward forces in fluids are created by spinning up the fluid to a speed and propelling it backwards (be it in air or in liquid). You probably don’t understand that this is what is going on when you say, ‘all the forces are backward’. Yes the net force is backwards towards back of pool. At some points in the stroke its not backwards relative to the spine.
@SnappingT in the graphs you showed, you said that forces were measured relative to the back of the pool. Where were strain gauges placed to capture that data. I am mainly curious how the forces were measured given the swimmer is constantly rotating relative to the back of the pool. Strain gauges for example only measure in an axial direction, but wouldn’t that be relative to the orientation of the placement of those on a swimmer’s body? In which case the frame of reference is the swimmer’s body, not back of pool.Wouldn’t the graphs show forces being backwards relative to body not neccessarily back of pool ? Thus the advice to “pull backards” (relative to yourself) makes sense, because we have spatial awareness relative to our bodies not relative to the back of pool since we’re constantly rotating
It’s not a simple thing, I agree. The X isn’t just for fat kids, but kids who hit puberty first. (Aside, I’m not sure it’s entirely a bad thing to stigmatize childhood obesity, YMMV).
It’s a trade off as always. The age model is let’s kids who hit puberty first beat up in kids who didn’t. The weight model possibly stigmatizes kids who are bigger. (Personally, I have a hard time feeling bad for the poor poor overweight football players who would never use their outside stature to bully smaller high schoolers)
Ha. The only expertise I’ve gotten from having a fast12 yr old is realizing how little I know, not how much I know.!
There’s so much to learn from fast young kids ajt… some just “get it”. But i hear you, gambling on 12yo can make you broke in a hurry. However, whether it pans out for the athlete much can be gained from the study.
Thought I should chime in here, hoping to clear up some misunderstandings about how swimmers go fast.
Newtonian Mechanics (and Fluid Mechanics, which is derived from Newtonian Mechanics) substantially govern a swimmer’s speed. There are four factors which really matter: 1. Propulsion (generated mostly from the hands and feet (flatter surfaces)) 2. Coupling motions (in freestyle resulting principally from body rotation and arm recovery) 3. Frontal drag caused generally by the swimmers morphology, buoyancy and swimming technique and 4. Inertia, the ability to hold a more constant speed (mechanical efficiency).
The propulsion generated from the hands and feet are different. The water in front of the swimmer, where the hand enters, is still. Therefore, to generate propulsion from the hand (caused from the drag of the hand moving backwards) the hand must move backward relative to the water. Behind the swimmer, the flow dynamics are different that in front, caused by the swimmer’s slipstream. During the kick, the feet don’t move backward any significant amount. They move down, forward, up and forward. The feet can potentially generate propulsion in four different points in a single kick cycle: two by pushing back against the vortices caused by the feet and legs moving up or down and and two as the feet and legs pass through the slipstream on the way up or down.
Coupling motions are motions that we use to augment the resultant velocity from the given propulsion (they don’t increase propulsion…just the velocity derived from the propulsion).The effectiveness of coupling motions depends on the amount of kinetic energy in the coupling motions (length and angular velocity of the recovering arm coming down and angular velocity of the body rotation), the direction or vector of the coupling motion of the arm recovery (since the propulsion force from the pull is directed backward, a vertical arm recovery with the coupling motion from the arm directed forward is more effective than a more horizontal arm recovery), the timing of the peak energy of the coupling motions with respect to the peak propulsion from the pulling hand (ideally the two should coincide…but often don’t) and the amount of propulsion (strong coupling motions don’t work if there is not much force to couple with).
Frontal drag is the number one enemy of the swimmer (water is nearly 800 times denser than air). There are three different types of drag: pressure drag, wave drag and friction. All play a role in slowing the swimmer down (the relative contribution of each varies depending on the swimmer’s speed). There is not a huge long list of drag causing errors in technique, but most swimmers (and especially triathletes…sorry) manage to make most of them. That list includes bad head and body position, poor pulling motion, poor kicking motion, poor hand entry and poor streamlining (in the pool). When it comes to drag, the water has no mercy.
Regarding inertia, only two strokes (free and back) are relatively efficient (back is most efficient). Fly shows huge swings in velocity and breast is truly a stop-and-go stroke…like LA traffic on a Friday evening. Efficiency in freestyle can be improved by using a steadier, tighter, propulsive (6 beat) kick, higher stroke rate using a lower-drag, higher-elbow pulling motion and by having good head and body position.
At The Race Club, we are now combining two technologies (smart paddles and velocity meter) synchronized precisely to video to analyze swimmer’s technique. The smart paddles (developed in Finland) measure forces generated by the hand in 3 vectors using force plate sensors (not strain gauge). the VM measures acceleration, deceleration and velocity (every .02 seconds). Using the two technologies together combined with the video, we can now identify and measure virtually every error in swimming technique. Many of those, I cannot identify from the deck and, believe me, I look for them.
Hope this helps!
Gary Sr,
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Thanks @garyhallsr
I am having difficult understand on the kick what you mean by “forward”. Is that top of foot pointing to front of pool like the tail of a whale literally pointing forward relative to its direction of travel
The smart paddles, I assume they are measuring force on the paddle, in other worlds perpendicular to the palm. So from video you need to see where the paddle is to determine the force, but that force measured is not relative to back of the pool, it is just relative to palm.
The propulsion from the down kick is generated by the top of the foot moving downward (against or through the two vortices). The more plantar flexion and inversion of the ankle (which triathletes usually don’t have much of), the more surface area and propulsion from the foot can be generated. Propulsion from the up kick comes from the soles of the feet (pointed backward) and the back of the swimmer’s leg. If you follow a single point on the swimmer’s toe, the motion (relative to a fixed object) is not backward (remember that the swimmer is moving forward), but rather down, forward, up and forward.
Smart paddles are actually measuring the pressure (on both sides of the paddle on the hand). The difference in pressure from the front and back sides estimates the pressure on the hand moving backward. Pressure is converted to force by estimating the surface area of the hand. Since the SP also measures the direction of the hand motion (accelerometer, gyroscope and force plate sensors), the forces from the hand are measured in all three vectors: vertical (down and up), lateral (out and in) and backward (propulsion). You would be amazed (or perhaps not) at how many swimmers press in the wrong direction or let go with their hand force.
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From an ignoramus perspective (that’s me not you ftaod), Dev - have a reread of your phrase and take the opportunity of introspection.
Consider how the ‘you’ being addressed will feel (and I’ll give you a pointer: it’s probably not “gosh, Dev has got a point, I wish I understood better!”)
[quote=“devashish_paul, post:173, topic:1283457”]
I am pointing out that creating net backward forces on a fluid does not come from pushing the fluid backwards (maybe the only example I know of is the ramjet but that’s different fluide dynamics at supersonic speed requiring a combustion step). Pretty well all net backward forces in fluids are created by spinning up the fluid to a speed and propelling it backwards (be it in air or in liquid). You probably don’t understand that this is what is going on when you say, ‘all the forces are backward’. Yes the net force is backwards towards back of pool. At some points in the stroke its not backwards relative to the spine.
[/quote]
Fair enough, but it would be better to quote the entire context (it is easy for the words to be taken out of context. This is what I wrote
Maybe I could have said, “perhaps you can’t visualize that xyz is going on”
As is the case of anything the more we contribute, the more people will nit pick. On this sub text of the thead, I was trying to understand what is going on from a fluid dynamics perspective. @garyhallsr provided some very insightful information here. He ONLY won the silver in the 200 fly in the Olympics vs Mark Spitz and has been coaching for around 50 years at some of the highest levels