ACL injury prevention

Here is a link to the website for the FIFA 11 plus program for ACL injury protection. It is meant for kids age 14 and above. The program concept is simple. Why wait until after a knee injury to strengthen the joint? The warmup section can be used independently as a pre-match warmup so you don't have to teach multiple warmup routines. Notice also that it has progressive exercises.

http://f-marc.com/11plus/

 

Scary. I thought it was more a concern with teenage girls. I was really lucky coaching U-Littles. No injuries beyound simple bruises and strains. With my adult team we sometimes go 2-3 years without a serious injury. This year has been really bad. Four serious injuries in six months, two were ambulance runs. Very sad for adults. I can't imagine how you felt with the injured 11 year old.

 

Clint Mathis got his second ACL trying to stop himself to keep from hurting another player. That was the one that ended his first step speed so after that he could not create his own chances off his dribble any more. After that he needed someone to get him the ball for him to get a chance to finish. He could not get his own off his dribble.
----------------------------------------------------------

Maybe too much information. But I doubt if you read any of the first stuff before unless it was from me. So at least check out the first posts.
I have a lot of exceptional stuff on ACL prevention and a test to see on who is susecptable to having the problem.

It is going to be a the long side, but you guys might find it interesting.

These are other peoples posts.

This first post was made by a pretty famous Belgium national team player. He sent it in the early 1990's.
-----------------
Post #1
With regard to hereditary factors, they do seem to exist, even if they might more properly fall into the "physical make-up as a result of heredity" category.

The key seems to be the ability to hyper-extend joints. This would also explain why girls are more prone than guys, as they are more often able to hyper-extend joints.

The knee test is simple: sit on the floor with your leg straight, and pull up on your foot. If you can lift your foot off the floor with the back of your knee still touching the ground, you've reached hyper-extension.

This is good if you're a swimmer, but not good if you want to play soccer and avoid knee surgery.

People who can hyper-extend their joints (I can get my foot a good three inches off the floor in this exercise) must pay special attention to quad-hamstring strengthening exercises, as well as abductor-adductor exercises for lateral stability.

Get 'em in the weight room, keeping weights low and repetitions high if they're younger need an experienced physical trainer to help with that to get the right weight and reps depending on the age.

Also, don't neglect training like jogging and step-climbing: some research has shown that low-level impact training can strengthen connective tissues like tendons and ligaments.

Coaches should also emphasize the importance of trying to maintain a slight bent-knee position through most pivots and twists, as well as during contact. It's almost impossible to tear an ACL while your knee is bent, even if it's ever so slightly.

A straight leg (or worse, hyper-extended) is the surest way to an ACL tear
-------------------------------------------

Post #2 from other poster

ACL injury prevention program
in cooperation with a local PT here in the Seattle area. The program
was developed by the Santa Monica ACL Prevention Project and is called
the PEP (Prevent injury, Enhance Performance) Program.

The PEP Program is a highly specific 15-minute training session that
replaces the traditional warm-up. It was developed by a team of
physicians, physical therapists, athletic trainers and coaches, and has
funding support from the Amateur Athletic Foundation of Los Angeles
(AAF). The program's main focus is educating players on strategies to
avoid injury and includes specific exercises targeting problems as
identified in previous research studies.

The goals of the program are to:
1) Avoid vulnerable positions
2) Increase flexibility
3) Increase strength
4) Include plyometric exercises into the training program
5) Increase proprioception though agilities

The entire program can be found at
<http://www.aclprevent.com/aclprevention.htm> and only requires that you
document any need injuries that occur on your team. The will send you a
video tape which is essential to show the proper way to do the
exercises. I would also strongly recommend you contact a local PT to
come out and demonstrate the exercises using the proper technique.
Optimally the program should be performed at least 2-3 times per week
during the season.

Some of the exercises and drills we already did in our warmup, but PEP
does require we do them in with far better form and attention to detail
than we previously did. Whether it will actually work for us is still
unknown but it is based on documented studies and at the very least has
given our team an appreciation of proper technique and strengthening of
the leg muscles.

The exercises are on their webpage but here is an example of one that I
like. However, this is only one of many exercises out of many, so you
need to look at the entire program.

Bridging with Hip extension Purpose: Increase hip and trunk strength and
improve balance Instruction: Lying on your back with knees bent, place
both feet on top of soccer ball. Lift hips off the ground so that your
shoulders, hips, and knees are in a straight line. Slowly lift one foot
off the ball and straighten the knee without dipping the hip down.
Return foot back to the ball and repeat on the opposite leg. Repeat 30
times and rest.
B. Ball toss with abdominal toss (buddy) Purpose: Increase
abdominal/trunk strength Instruction: Lie on your back with hips and
knees bent. Have your partner toss a soccer ball to you. Catch the ball
and bring your arms overhead. Now, catapult yourself by bringing arms
back toward your center as your perform an abdominal crunch and toss the
ball to your partner. Wait for your partner to toss the ball again and
repeat exercise 30 times.


If for some reason the web link does not work or you just would rather
have a fellow coach send you a copy of the program, contact me at
<orlay@attbi.com> and I will send it to you. Needless to say, I have no
monetary link to this program and I am sure there are other equally good
programs out there (maybe better?), but this is the one we are using.
-----------------------------------------
Post 3 by the same poster as #2

One other area to look at is endurance conditioning and/or player fatigue.

That the girl in question was at the 2nd day of practice (fatigue
from the first day?) and no one near her brought my incident to mind.

I tore my ACL a few years ago skiing. It was the start of the 4th
day of skiing and I was exhausted before I began (and admittedly not
warmed up, just the ride up the first lift of the day). An observer
might have wondered why I fell on such a gentle slop while skiing
slowly at the top of the run. In soccer terms, no one was near me.
Exhaustion was the key, I turned at the top of the hill without
unweighting my skis my left foot did not turn and the ACL was torn.
(52 year-olds should not try to keep up with 17 year-olds).

Fatigue will reduce the athletes ability to effectively achieve the
programs goals. Item 1 was clearly violated because I was tired.
Item 2 was an issue because it was the start of the day. Item 3
fatigue does effectively reduce strength. Item 5 coordination
(proprioception) was comprimised by the fatigue.

I can clearly remember just before the turn not having the energy to
bend my knees to begin the process of unweighting my skis, had I been
either fresh or properly warmed-up, i would probably not be making
this post.

>Coaches,

<snip>
>
>
>The goals of the program are to:
>1) Avoid vulnerable positions
>2) Increase flexibility
>3) Increase strength
>4) Include plyometric exercises into the training program
>5) Increase proprioception though agilities
>
>The entire program can be found at
><http://www.aclprevent.com/aclprevention.htm> and only requires that you
>document any need injuries that occur on your team.

http://www.aclprevent.com/aclprevention.htm
---------------------------------
Another post
I have a couple of articles on ACL injuries...from a great source. Dr. Bert
Mandelbaum is the Dr. for the USMT, and has been since before 1994. When
the Euro based US players have injuries, they fly to see him. The second
article is written by a Physical Therapist on his staff. He has also done
surgery on both me, and my husband (not ACL's). He is like like our primary
care physician. We have more sports injuries than anything else in the
family. At the end of the 2nd article lists their website for more
information on the project.


Epidemic: Torn ACLs
8/12/2002 4:03:00 PM
Theories abound on why women have a higher incidence of torn ACLs than men
do. A recent study pegs the way women jump and land as the primary factor.
Mentoring in the WUSA isn't just about what happens on the field. Players
increasingly are feeding on colleagues' experiences with knee injuries.
Sources for information seem at every turn.
A rash of torn anterior cruciate ligaments - eight since the WUSA kicked
off, five this season - and scores of lesser knee injuries has plagued the
world's top women's league. Nearly two dozen players - including U.S.
national team veterans Mia Hamm, Carla Overbeck, Kate Sobrero, Christie
Pearce, Sara Whalen, Danielle Slaton and Tracy Ducar - have been sidelined
in 2002 by one knee ailment or another.
Whalen, a defender and midfielder for New York, was the fourth high-profile
player knocked out for the season by an ACL tear this year. Philadelphia
lost forward Rakel Karvelsson during preseason preparations and star
midfielder Kelly Smith at the start of June. Midfielder Lindsay Stoecker,
Washington's leader, went down on June 15. Whalen was injured 11 days later.
The experts are not surprised.
''Not at all,'' says Dr. William DeLong of the University of Pennsylvania
Health System, who works with the Philadelphia Charge and handled Smith's
and Karvelsson's ACL repairs. ''I expected to see it last year. ... Everyone
that does ACL [surgery] knows we're seeing more women than men now. There's
lots of theories about what's going on, but we don't know the science behind
it. We don't know what is the true incidence of ACL injuries in women and
men.''
DeLong is planning a study of MLS and WUSA players to learn more, and
there's plenty of places to look, everywhere from the angle of knees to the
size of femoral notches to the effects of hormones in the menstrual cycle.
One of the most popular notions is that women's generally larger ''Q
angles'' - the angles at which the femur and tibia meet at the knee,
determined by the width of the pelvis - leaves their knees susceptible to
inward torque when jumping, landing, turning and planting.
''Look at a player like Mia Hamm,'' says Randy Rocha, the Washington
Freedom's trainer. ''She's bow-legged, and she's never had this type of
ligament injury. She has something different [articular lesion], from wear
and tear on the knee. The mechanism isn't the same as with ACL tears.
''Now look at Lindsay Stoecker. She's knock-kneed, and her legs hyperextend,
which is another mechanism of an ACL tear. It's another characteristic in
females.''
The strength of various muscles surrounding and supporting the knee also are
much weaker in women than in men.
''There's some sense,'' DeLong says, ''that maybe the hamstring muscles get
overpowered by the quadriceps muscle in women.'' The ratio of strength
between the hamstring and quadriceps should be even or close to it. In
addition, the ''VMO,'' another supporting muscle, located above the knee on
the inner part of the lower thigh, is poorly developed, generally, in women.
''Female skeletons are built differently,'' notes Carolina Courage trainer
Cody Malley. ''The significance is that, mechanically, the ACL injury is
usually a rotator injury - one bone rotates on the other. ... Because of the
increased 'Q angle,' more weight comes down on the legs, the knee caves in,
the femur will twist on the tibia, and it causes a rupture.''
GENDER DIFFERENCE. Anatomic differences cause women to adopt different
posture than men do. ''A new study,'' Malley reports. ''Female athletes
carry themselves a little higher. They don't have as low a center of gravity
when they're playing - they don't have their knees bent. When knees are in a
more-bent position, more a half-squat or quarter-squat, the muscles
mechanically stabilize the knee. When legs are straight, the ligaments are
much more susceptible to stress.''
Dr. Bert Mandelbaum, who runs the Santa Monica (Calif.) Orthopedic Sports
Medicine Research and Education Foundation when he's not seeing to the U.S.
men's national team's needs, says the ''real question is twofold, really:
Why is it happening? And can we do something about it? And if we can't do
anything, what are the long-term ramifications.''
Mandelbaum took part in a study that examined all the possible factors and
theories - looking at anatomical, hormonal, environmental and biomechanical
factors - before determining that the greatest influence was how women leap.
''Biomechanics and neuromuscular [elements were identified] as the major
risk factor,'' Mandelbaum said. ''We reviewed numerous videotapes, and what
we found was, occurring in comparison to boys, girls jump and land
flat-footed, with their knees in straight or extended positions, their hips
in the same positions, and that puts the ACL at very significant risk.''
Everything else, he says, from ''Q angles'' to ovulation to turf and shoe
concerns, ''is not a major factor.''
PREVENTION. U.S. women's national team coach April Heinrichs isn't surprised
by such findings. Her theory, she says, is that the best and most agile
female athletes avoid such injuries. The agile Whalen was hurt, unlike in
most ACL tears, after contact rather than in a plant-and-twist situation.
''I think we can all scientifically reduce or anecdotally reduce it to the
way women jump and land,'' she says. ''You can't talk about agility without
talking about jumping and landing. That's what agility is.''
Mandelbaum says studies in Italy, Kansas and Cincinnati suggested that
athletes can be trained ''to be stronger, more agile, to jump and land a
different way'' and that incidence of ACL tears could be severely curtailed
with proper education and training. The group in which Mandelbaum
participated studied the elite Coast Soccer League in Southern California
for two years, developing a five-step program (PEP, for ''prevent injuries,
enhance performance'') to teach avoidance tactics, increase strength and
agility, improve jumping and landing technique and educate players on how
injuries occur.
''We developed basically a 20-minute warmup at the front of all club soccer
practices,'' Mandelbaum reports. ''In 2000 we found an 88 percent reduction
[in ACL injuries]. In 2001, it was 75 percent.''
The next step is a study involving 75 universities in collaboration with the
NCAA, FIFA, the Centers for Disease Control and Prevention, and national
orthopedics associations.
Texas A&M University's women's program participated in a PEP pilot program
last year. ''When it came across the airwaves,'' Aggies coach G. Guerreri
said, ''I had to be first in line. We're the poster program for ACL
injuries.''
Nine A&M players suffered torn ACLs in an 11-month period, culminating with
six losses during the 2000 fall season. After implementing PEP procedures,
there were no such injuries in 2001.
''We've taken it far enough that we're actually teaching the motor movements
in our camps,'' Guerreri says. ''We have 1,700 kids coming through camp this
summer, and they're all being exposed to these ideas, especially the
girls.''
EVOLUTION. Why women jump and land and carry themselves differently than men
- and differences in their muscle structures - is most likely product of
evolution.
''If you go back 100,000 years ago,'' Mandelbaum says, ''you'll find women
were usually carrying the babies on their side or back. Men, basically, were
hunting and stalking, with knees bent, running over long distances. ... Man
has evolved to the able to run and jump and cut and pivot and land and stop
at high velocity, and women haven't done that.''
It's led to an ACL epidemic among women in all jumping sports, Mandelbaum
says. He sees basketball and volleyball players, ''and in other countries,
it's happening in netball and team handball. It's the same problem, and also
the same statistics.''
It's more common to women's soccer than many believe. Nearly one-quarter of
the players in the WUSA have torn ACLs at some point in their playing
career; San Jose's Brandi Chastain and Boston's Maren Meinert, two of the
league's most capable players, have torn both. So has Santa Clara
University's Aly Wagner, who might be the first selection in next winter's
draft. And University of North Carolina defender Leslie Gaston, another pro
prospect, has undergone five ACL surgeries. She's playing without an ACL in
her left knee.
''I'm not having any instability,'' Gaston says. ''I really don't see any
reason to get it fixed.''
''I was not aware it was so common,'' says Karvelsson. ''You never think
much about it until it happens to you.''
Finding someone to turn to isn't difficult. Karvelsson was there to support
and advise Smith when she went down. Whalen, who expects to undergo surgery
in late July, has been leaning on Power teammate Christie Pearce, who
suffered her ACL tear last August, just before the WUSA playoffs.
''She's someone I look to,'' Whalen says, ''to see if my feelings are normal
at this stage, if my outbursts are normal. It's good: She's been through it
and come out strong, and it's encouraging to see that. To have her advice
makes me feel I'm doing things right.''
Stoecker says cards ''are pouring in from friends who have had knee
injuries. It's nice to see someone that you know has torn their ACL and you
can't tell at all.''
Similar tales are told throughout the women's game. It's almost as if there
were a club, albeit one ''I never wanted to be part of,'' Whalen says.
''It's not like there's a Web site where we all chat all the time, but that
might be something we need to start.''
by Soccer America Senior Editor Scott French


----- Original Message -----
From: U.S. Soccer Communications
Sent: Thursday, April 08, 2004 4:26 PM
Subject: RESOURCE CENTER: Training Techniques Effect Frequency of ACL
Injuries

As part of our continuing effort to service and educate our membership, each
Thursday U.S. Soccer will provide an informative article from one of its
departments. Once a week, we will bring you an article/paper/essay that will
hopefully enhance your enjoyment and knowledge of the game of soccer - on
and off the field.

This month, we will look into the world of sports medicine and revisit ACL
injuries in soccer players. Some of the research in this article was
presented by Dr. William E. Garrett, Jr., who has worked with the U.S.
National Teams.
Training Techniques, And Their Effect on Frequency of ACL Injuries in Female
Soccer Players?

By Holly J. Silvers, MPT
Director of Research / Physical Therapist
Santa Monica Orthopaedic & Sports Medicine Research Foundation

Anterior Cruciate Ligament injuries are among the most common of all
sports-related knee injuries, affect the lives of more than 250,000 people
in the United States each year.

Studies conducted during the past three decades have indicated that female
athletes sustain non-contact injuries to the ACL of the knee more frequently
than their male counterparts. In a study conducted at Duke University, Drs.
Bing Yu and William E. Garrett, Jr. found that female recreational athletes
incur non-contact ACL injuries 7.3 times more often than that of male
recreational athletes.

ACL injuries are often season-ending and require reconstructive surgery and
four to six months of rehabilitation. Players who opt to delay an ACL
surgery often suffer secondary injuries such as meniscal tears, articular
cartilage injury, or medial and lateral collateral ligament injury.

Possible prevention strategies for ACL injuries were discussed at a panel
briefing during the American Academy of Orthopaedic Surgeons Annual Meeting
in San Francisco, Calif. earlier this year.

According to research presented, four risk factors have been studied in
order to understand the causes of ACL injury: anatomy, hormones,
environmental factors and biomechanics. The studies, including the one
conducted at Duke University, indicate that by intervening just within
biomechanics, there can be a decrease in the number of significant
injuries in the female athletic population.

The Santa Monica Orthopaedic and Sports Medicine Research Foundation has
collaborated with U.S. Soccer, FIFA, University of Southern California and
the Centers for Disease Control to better understand the mechanism of injury
of non-contact ACL injuries and has worked diligently to develop an
effective prevention program.

These researchers completed a randomized controlled trial with sixty-one
Division I NCAA women's soccer teams in the 2002 season. Each team was
randomized to one of two groups: those performing the program (intervention
group) and those who continued to do what they were doing in previous
seasons (control group).

The study was conducted for 14 weeks over the course of the fall season. The
athletes in the intervention group performed a twenty-minute alternative
warm-up called the PEP Program (Prevent Injury and Enhance Performance).
This intervention group demonstrated a 100-percent decrease in non-contact
ACL injuries during practice and an overall 45-percent decrease in
non-contact ACL injury (game and practice) compared to the control group.

Additionally, the rate for ACL injury was reduced even further - a
72-percent reduction, when analyzing the last six weeks of the season. This
is because muscle adaptation and neuromuscular training takes approximately
four to six weeks to make an effective change in an athlete.

This research indicates that a program that addresses landing technique,
core stability, balance and proprioception (joint awareness) can effectively
decrease the incidence of ACL injuries in the soccer athlete.

Dr. Timothy E. Hewett of the Cincinnati Children's Hospital and the
University of Cincinnati College of Medicine, noted at the conference that
sports programs commonly use training programs for athletes in order to
reduce significant injuries.

Hewett and his colleagues initiated a study to examine the effects of a
comprehensive training program in order to analyze injury rates, performance
and biomechanics in female athletes. The athletes trained three days a week
for 90 minutes followed by 15 minutes of stretching exercises. The results
demonstrated that females increased speed during timed sprints after
training.

The study also demonstrated significant desirable biomechanical changes
during a landing maneuver following the training. In contrast, the control
group demonstrated no significant increase in any of the above measured
parameters.

Overall, these studies and the research that was presented show that by
focusing on a player's movement patterns, individual performance deficits
can be determined. By giving all players a comprehensive intervention or a
warm-up program, such as the PEP Program, these deficits can be addressed.
As the research shows, with the use of a program, that the players are more
likely to continue performing at a high level without incurring season
ending injuries.

For information on the research presented in this article and the PEP
Program including a downloadable .pdf describing its components, visit the
Web site at www.aclprevent.com or e-mail the author of this article, Holly
Silvers, at HollySilversPT@aol.com.

For more information from U.S. Soccer's Sports Medicine Department, please
contact Hughie O'Malley, U.S. Soccer's Manager of Sports Medicine
Administration, at homalley@ussoccer.org or 312.528.1225.
- www.ussoccer.com -

Gwen Keck

-----Original Message-----
From: nas-bounces@americakicks.com [mailto:nas-bounces@americakicks.com] On
Behalf Of Peter Kurilecz
Sent: Friday, March 02, 2007 5:06 PM
To: NAS-list
Subject: [nas] ACL injury study

Q&A with the scientist studying women's ACL injuries
Mercury News

The alarming number of knee-ligament injuries seen in women's
athletics has confounded the medical community for years.

While theories abound, no one has a definitive answer as to why ACL,
or anterior cruciate ligament, injuries occur two to eight times more
in women than men.

<<http://www.mercurynews.com/mld/mercurynews/sports/16819183.htm

 

Thanks, Nick....

 

Just some history for the different comments. PEP, by a clinic in the US, and the original FIFA 11, were developed about the same time. The PEP people were also one of three organizations that developed FIFA 11 so it is not surprising that they are similar. In 2006 the FIFA program was improved and it is now called FIFA plus. The FIFA program is designed for recreational and amatuer players.
(Professional players are going to have individualized training plans created for them by their clubs.)

The original objective was to reduce the higher incidence of ACL injuries in women. Testing has indicated that the program does reduce injuries, but has not shown a statisically significant reduction in ACL injuries, the targeted injury. So now in the literature you will see it described as an injury prevention program.

The current thinking is that imbalances between the hamstrings and quads increases the risk of ACL injuries. Imbalances are more common in women than men. Which is one reason experienced coaches are needed for weight training. Clubs (and national teams at camps) assess professional players for muscle pair imbalances (among other things) and design individual training programs to correct any.

One caveat: I am no expert. I am just going by my impression of what I have read over the last 10 years about ACL injury prevention.

 

Over the past year I have been using the FIFA 11+ program with my JV girls soccer team as well as my youth U12 and U11 teams. We have been trying to have them really focus on good neutral knee positioning on running, planting and jumping. With the older girls I also use the strength portion during training. I really like the structure of the program, I feel like it provides a good thorough warmup and gives me a chance to help them focus on proper mechanics.

I do agree, however that their form and mechanics are very poor at the start, but I feel like they are improving.

 

I heard this a while back. I just remembered it check it out to see if I am right. Field hockey players get very few or no acl problem. It is about there body position the field. Those that also play soccer also get less acl. Check it out. I have no clue when field hockey starts in HS. But if the girls can play both it might be a good thing for them to do.

 

In the northeast field hockey is during the same season as scholastic soccer (fall)

 

Someone just told me field hockey players have back problems

 

One of the reasons I've heard given for the preponderance of ACL injuries to girls is that they tend to run upright more than boys. In field hockey, since the sticks are ridiculously short, the girls have to play lower to the ground. Also, they can't run as fast, bent low to the ground, as in soccer.

I've always felt field hockey was the outdoor equivalent of Iowa girls basketball. Maybe I was right, not just snarky. Though my version of snark differs from chief Elessar's....

 

This is an interesting topic. I have a question, and a comment.

First, the question. At what age group do we, as coaches, need to start paying attention to this? I read Elessar's comment about an 11-year old tearing her ACL, and I was quite surprised. That seems extremely young to suffer that kind of injury. Is that unusual? Here's my dilemma. I am coaching U10's and 11's this upcoming soccer year. I, quite frankly, don't want to waste my limited practice time on stuff that doesn't involve a ball and/or isn't helping to develop technical or tactical abilities if I don't have to. In the various coaching courses I've taken--I have a National Y, plus its prerequisites--I seem to recall the general idea that you don't need to do fitness/ conditioning/stretching as separate component of your practice until the kids are maybe U13 (I'll have to review the materials and notes from the courses, but I seem to recall that being the case), and I don't. The necessary conditioning comes from a well-constructed practice, and the literature suggests that at younger ages stretching is actually counterproductive.

Second, regarding field hockey, I think the comparisons betwee the two are not particularly useful. In field hockey, the legs are used to run, period. There is very little body-to-body-contact permitted, and there is no jumping or leaping (the ball stays on the floor). In soccer, the legs are used to run, but they are also used to tackle, to kick, to dribble, to jump, to dive in, etc. I'm no expert, but it seems to me the opportunities for something bad to happen to the leg are far greater in soccer.

 

This is not a simple issue. The first area of focus in athletic development for any youth sport is fundamental athletic skills, like running, jumping, turning, stopping, accelerating, decelerating. This is speed and agility training. For youth you focus on proper technique. You don't train them like a high school team.

For pre-teens we don't use periodization. That means we don't have strength training sessions or endurance sessions. That is theory behind the statement that we should focus on technical and tactical training at our practices. The players are getting fitness training, but it is through the technical and tactical drills and games. The players are also getting mental training, but likewise it is through the technical and tactical drills and games.

Next the focus is on sport specific skills. At your age range the focus is on sport specific skills, but the players should already have developed basic athletic skills. If they haven't, then they need remedial training to make up for it. You can include a ball in the training to a large extent (dribbling and marking for instance). IMO dribbling is 50% athletic ability and 50% ball skills. If your players lack basic athletic skills it is going to hold back their dribbling.

 

Probably somewhat unusual. Basic rule of thumb should be when the body begins maturing. Girls, basically in 6th grade (u-12) boys in 7th (U-14), between the growth and muscle development they will become more prone to injuries.
Generally, earlier than that, stretching, etc. doesn't do a whole lot, other than getting focused on training/game at hand.

 

You are oversimplifying the issues.

Stretching is not used earlier IN WARMUPS because young kids are naturally loose.

We don't do periodization, i.e., we don't do separate fitness training, because at that age its a waste of valuable training time that could be spent on technical and tactical training. The goal here is to develop good senior players. Fitness training them at age 10 realistically doesn't help in the long run. Development of basic athletic skills and sport specific skills does help in the long run. Not to mention kids don't have the fitness requirements of a senior player (120 minute match fitness).

Coaches should always be concerned about developing basic athletic skills, which is in essence movement skills and the earliest form of "body weight" strength training. Focus is on techique and age appropriate "games." Kids should have basic athletic skills by age 10. In reality too-early specialization has lead to some professional athletes lacking basic athletic skills. You guessed it. They start remedial training on basic athletic skills.

Coaches should also consider improvement of player fitness when planning technical and tactical practice sessions and managing the work/rest ratio while running the sessions.