Reducing ACL Injury Risk

In my first summary of a pair of excellent review studies addressing non-contact ACL injuries, I listed the modifiable factors. Review that article here. This article summarizes how and why training can reduce the risk of injury.

You can also access the full review studies here and here. (References in parentheses refer to these articles)

KEY POINT

"The implementation of interventions that incorporate core stability training, including proprioceptive exercise, perturbation, and correction of body sway, has the potential to reduce knee, ligament, and non-contact ACL injury risk in both female and male athletes [79]." By contrast, "continued performance in the presence of faulty technique increases the likelihood of the athlete’s sustaining a training induced knee injury." [56]

It seems that non-contact ACL injuries can be brought down to posture at landing or during movements. Most of the athletes (if not all) who would fall into the the at-risk category are not aware of it. A good start for reducing risk would be education- teach them what it is that is putting them at risk so that they are aware. Consequently, athletes will work with trainers and coaches in their efforts towards "technique modification, proprioception training, and plyometric training [as this] is essential to evoke changes in kinematics and kinetics of joints during sports tasks."

The conundrum of training is that some of the components that will be mentioned here as measures of training effectively, and thereby reducing the risk of injury, are age specific. Young players learn to kick, throw and jump as is appropriate for their level. As they mature physically, training/coaching generally only "matures" in that the intensity is increased- kick further, jump higher, run faster. This is not surprising at all as there is a natural shift from the fun in learning the fundamentals to more results driven competition. Feedback in practice is concerned with tactics, rather than technique; positional play, when it is incumbent upon coaches and trainers to realize that there are fundamentals at every level. But, thus driven, the window at which training technique would be most effective both for performance and injury risk reduction may be passed by. A recent article was published suggesting that "ACL injury risk can be reduced by 72% in players who begin an injury prevention program during their early and mid-teenage years."

STRENGTH TRAINING FOR MUSCLE WEAKNESS

The injury prevention/performance enhancing benefits of strength training do not lie in the strength of the muscle. Instead, they lie in the muscle's ability to activate and react in time and in sequence with the other muscles involved in a movement. Consider the hamstrings.

Hamstrings have an important role in protecting the ACL by preventing or decreasing the anterior, varus-valgus, and rotatory displacement of the tibia on the femur. Hamstring recruitment reduces the load imposed on the ACL from the more powerful quadriceps [155, 185], and by resisting anterior and lateral tibial translation and transverse tibial rotations, may help to provide dynamic knee stability [104].

Strength training is the obvious solution to cases of muscle weakness. Overall, training aimed to improve hamstring-to-quadriceps, hip, and trunk muscular strength is considered adequate to reduce the risk of non-contact ACL injuries. Eccentric loading of the hamstrings was shown, in various studies, to be more effective in increasing hamstring-to-quadriceps strength ratios than traditional concentric exercises in professional and semi-professional male soccer players.

STRENGTH TRAINING FOR ALIGNMENT AND JOINT STABILITY

Dynamic joint stability is provided by muscles as well as the elastic components of the musculotendinous unit, the sensorial and neural system. Single-component preventive programs have limited impact on biomechanical risk factors, as they may be too focused on the muscle component thereby minimizing potential improvements in other important components of the dynamic joint stability function.

Because muscle actions must be coordinated and co-activated in order to protect the knee joint [185], antagonist–agonist relationships are crucial for joint stability. Hence, preseason and continued in-season conditioning focused on hamstring strengthening is indicated. Research also shows that "coactivation of gluteus maximus and medius and hip joint position are essential elements to provide a safe biomechanical profile." Further, "relative weakness of the abductors, extensors, and external rotators, compared to the flexors and adductors, coupled with increased hip flexion , may severely limit the ability of the gluteal muscles to stabilize the hip and maintain a neutral alignment of the hip and knee [69]."

Both joint stability and muscle co-activation were adequately addressed following plyometric training. "The plyometric component of preventive programs trains the muscles, connective tissue, and nervous system to effectively carry out the stretch-shortening cycle and focuses on proper technique and body mechanics [29]. Following training, a significant increase in firing of adductor muscles during the preparatory phase was noted. A significant increase in preparatory adductor-to-abductor muscle co-activation was identified, as well as a trend toward reactive quadriceps-to-hamstring muscle co-activation."

LANDING

Landing presents a load of several time the athlete's body weight on the knee. Typically its the "extended hip and knee joint posture upon landing" that poses a risk. Coaches need to teach their athletes to land softly, "with initial contact at the forefoot with hip and knee flexion with knees over the toes." Also, it was shown that increased trunk flexion during landing avoided excessive anterior translation. This is a more desirable landing technique in order to reduce the risk of non-contact ACL injuries [32, 65]- land on the balls of their feet and sink into the ground, bending knees and hip, as in a squat.

EXPECT THE UNEXPECTED

Cutting maneuvers performed in response to changes in the direction of play, or a dribble constitute a particularly high risk position in soccer. This is mainly because players have so little time to respond if they want to keep up. The results are unplanned movements, unaccompanied by the small steps and other changes in posture which ordinarily decrease the external varus/valgus and internal/ external rotation moments applied to the knee. Warned, players can prepare better and it is therefore advisable to add components of visual cue interpretation to increase the time available for pre-planned movement.

In support, Nyland et al. support programs that focused on coordinated lower extremity closed kinetic chain tasks-

• mini-squats, 
• single-leg vertical and horizontal hopping,
• lateral shuffles in a mini-squat position,
• back pedaling, and 
• quick multidirectional movement responses to cues [56]. They recommended that these tasks should be performed progressively and with an emphasis on movement quality.

Besier et al. further recommended that training should involve drills that familiarize players with making unanticipated directional changes. Applying all reason and precautions for safety, practice should mimic as much as possible the game situation, particularly in speed and tempo. Drills are often slow so that even if players are familiar with certain movements, it is the added speed and perturbations that predispose them to injury during matches.

Applying these will go a long way in decreasing the risk of injury and improving performance as well.

The Wisdom of Coaching II

The Charlie Francis Training System is one of the most powerful books I have ever read. I highly recommend it to anybody who is interested in learning how to train (or become!) a successful athlete. In a previous post, I shared some of the quotes from it. Here I share a few more (all unless otherwise referenced), as well as quotes from other sources:

"The basic principle underlying all training is to bring only a fully regenerated (rested/recovered from a previous performance) athlete to each training element. The element is then performed with the highest quality possible."

"The great majority of athletes are [still] training and performing with hard-spasmed muscle (both organ and skeletal muscle) with the result that a full complement of tissue is not being presented to the training stimulus, let alone involved in performance. This fact becomes doubly significant when one considers that the body must use protective inhibition in the presence of such spasmed tissue in order to survive training and performance without injury."- Paul Patterson

"If you try to communicate with an athlete when he or she is upset, very little of what you say will penetrate."

"I never write programs on paper for an athlete because....this [manner] will prevent the athlete from ever taking responsibility for their own training. Athletes must interpret training programs through their bodies; programs written on paper redirect the athlete's focus and encourage athletes to interpret training programs through their heads."

"Some coaches dump too much information on the their athletes which is either an attempt to prove to the athletes that they are smart or it is a reflection of the coaches' poor communication skills."

"Whenever you are in a really pushy type of program and are always trying to get athletes to do stuff, you can't be listening to them because they are not listening to themselves; they are simply busy trying to do what you asked them to do."

"You must keep the lines of communication with your athletes open, otherwise you are both in real trouble."

"Plan your work, work your plan."

Some thoughts from other authors:

Direction-Specific Leg Power: The traditional test for power has been the vertical jump test, highly relevant considering that we jump quite often for headers- depending on the position, of course. However, to suggest heading is the only place power is utilized in the game is to grossly underestimate its demands. Kicking, running, cutting maneuvers all require power but they are not vertical in direction. As such Jennifer K. Hewit, PhD, CSCS discusses Direction-Specific Leg Power. This seems obvious but we rare quantify power in these 'other-direction' movements, giving them their proper value in the testing process. To quote, "... testing athletes's power capabilities in only one direction limits the amount of information gained from testing that is used to develop and implement appropriate training programs.." "...therefore, assessing athletes' unilateral leg power capabilities across multiple directions is recommended when compiling a complete athlete profile for programming, performance and progression purposes." More info here.

Mechanisms of non-contact ACL injuries

In a review of data spanning over a decade, a number of risk factors were identified as far as non-contact ACL injuries are concerned. Female athletes, it appears are at 6 times greater risk than their male counterparts in the same sport and when matched by age, level of play, etc. The review studies are very technical, with the authors having used biomechanical terms for large sections of it. It would negate their work to try to present their work any differently so I have highlighted the key things in an attempt to make it more "user friendly." For those with the prowess for biomechanics, anatomy and physiology, I have posted links to the actual studies at the bottom of the page.

Risk Factor Summary

• The "Position of No Return"
• Weak hamstrings (I discuss risk factors for hamstring injury here, and here.)
• Inefficient gluteal muscles
• Poor or lack of Pelvic Stability
• Poor or lack of Knee Stability
• Core Stability
• Decreased Muscle Stiffness
• Decreased Proprioception
• Fatigue

The greater majority are related to valgus collapse- the knees coming together when you drop down into a squat. This is not a risk factor in itself, but it increased the potential for an ACL injury in the presence of load. However, there is a position the authors dubbed "the position of no return" - hip low forward flexion, hip adduction, hip internal rotation, knee valgus, knee extension, and knee external rotation may place the ACL to a high risk of rupture.

Boden et al. reported a lower extremity alignment associated with non- contact ACL injury in which the tibia was externally rotated, the knee was close to full extension, the foot was planted during deceleration with valgus collapse at the knee [17]. Teitz reported very similar deceleration positions and indicated that most often the center of mass of the body was behind and away from the base of support (area of foot to ground contact) [177].

Anterior pelvic tilt places the hip into an internally rotated, anteverted, and flexed position, which lengthens and WEAKENS THE HAMSTRINGS and changes moment arms of the GLUTEAL MUSCLES [37]. Hamstring muscles are important to prevent static and dynamic genu recurvatum and to prevent anterior tibial displacement. Gluteal muscles are important to assist hip flexion (gluteus maximus) and to prevent a dynamic valgus collapse (gluteus medius). Anterior pelvic tilt also increases knee valgus and subtalar pronation. It is debated whether the risk is caused by the altered pelvic position itself, or by the functional malalignment it creates [167]. What is important in any case, is that PELVIC STABILITY IS KEY.

Femoral torsion is defined as the angle between the axis of the femoral neck and a transverse line through the posterior aspect of femoral condyles [122]. Femoral anteversion, an increase in the mentioned angle, may cause GLUTEUS MEDIUS INEFFICIENCY. A WEAK GLUTEUS MEDIUS may influence dynamic valgus collapse because of the muscles’ inability to keep the hip abducted, especially during weight-bearing activities such as landing, cutting, or changing direction.

Landing, cutting, and pivoting maneuvers in some females have been shown to differ from males [51, 52, 115]. Essentially, female soccer players perform playing actions with increased adduction and internal rotation of the femur, reduced hip and knee flexion angles, increased dynamic knee valgus, increased quadriceps activity (with a concomitant decrease in hamstring activity), and DECREASED MUSCLE STIFFNESS around the knee joint [69].

Studies show that ISOLATED QUADRICEPS CONTRACTION near extension strained the ACL more than exercises with co-contraction of both quadriceps and hamstrings [48]. Chappell et al. [28] found that female soccer, basketball, and volleyball players prepared for landing with increased quadriceps activation and decreased hamstring activation, which may result in increased ACL loading during the landing of the stop-jump task and the risk for non-contact ACL injury.

In contrast, WEAK HAMSTRINGS contribute to a greater ground reaction forces that place the ACL at a higher risk of rupture [71]. On the other hand, peak landing flexion (reflecting net quadriceps muscle activity) and extension moments (reflecting net hamstrings muscle activity) at the knee did not change after training and were not significant predictors of peak landing force.Hamstring muscles are important to decrease anterior shear forces and greatly reduce load on the primary restraint to anterior tibial motion, the ACL [7, 126]. Through knee joint compression, hamstrings limit anterior tibial translation by allowing the concave medial tibial plateau to limit anterior drawer [82] and by allowing more of the valgus load to be carried by articular contact forces, protecting the ligaments [71]. Moreover, hamstring compression could protect against torsional loading, which has been found to be greater for females compared to males [104, 189]. Women demonstrate decreased hamstrings-to-quadriceps peak torque ratios and increased knee abduction (valgus) moments compared to males [71]. Hamstring muscles are activated by ACL receptors when the ligament is placed under stress, which evinces the hamstrings' support to the ACL as an antagonist. This ACL receptor- dependent muscle activation suggests that DECREASED PROPRIOCEPTION could have an impact on KNEE STABILITY.

Muscles crossing a joint provide stability to that joint. In other words, muscle stiffness, or the resistance to dynamic stretch may protect ligaments from rupture when a load is applied. The quadriceps and hamstring muscles provide anterior–posterior joint stiffness. Others suggest that sagittal plane knee joint stiffness is also relevant for ACL injury prevention. Studies demonstrate that female athletes show less muscular stiffness than their male counterparts [58, 59, 67, 79, 88, 161, 186, 189]. Males activate their lower extremity muscles significantly earlier [67], and have longer activation duration in muscles that initiated and maintained knee (gastrocnemius) and lower extremity stiffness (gluteus) than women [88]. DECREASED MUSCULAR FITNESS in females was shown for both anterior tibial translation [58, 59, 81, 88, 186] and rotational forces [58, 59, 161, 189].

Since muscles contribute to joint stability, muscular fatigue might be a risk factor for ligament injuries. FATIGUED MUSCLES are able to absorb less energy before reaching the degree of stretch that causes injuries [108]. Gastrocnemius muscles act as a synergistic and compensatory dynamic knee stabilizer in a closed kinetic chain situations as the quadriceps femoris muscles fatigue [140]. McLean et al. concluded that fatigue-induced modifications in lower- limb control, such as this, may increase the risk of non-contact ACL injury during landings.

Comparative studies have demonstrated that female subjects prepared for landing with a decreased hip and knee flexion angle which may result in increased ACL loading during the landing of the stop-jump task and the risk for non- contact ACL injury [28]. It was postulated that a decreased hip and knee flexion angles at landing places the ACL at a greater risk of injury, because a GREATER PEAK LANDING FORCE is transmitted to the knee [74]. Burkhart et al. [25] reported in a prospective research study that an athlete who landed with an increased heel to flat-foot loading mechanism was more likely to sustain to a non-contact ACL injury during competitive play.

Trunk displacement in any plane was greater in athletes with knee, ligament, and ACL injuries than in uninjured athletes. Lateral displacement was the strongest predictor of ligament injury. Trunk displacements, proprioception, and history of low back pain predicted knee ligament injury with 91% sensitivity and 68% specificity. This model predicted knee, ligament, and ACL injury risk in female athletes with 84, 89, and 91% accuracy, but only history of low back pain was a significant predictor of knee ligament injury risk in male athletes [199]. Therefore, CORE STABILITY may be an important component of ACL injury prevention programs.

Here is the link to Part 1 of the original review article.

In this article, I discuss ways of reducing the risk of injury, now that we know what the risk factors are.

What Makes You Think You Can Coach- Part 2

There is often the question of whether a great player will necessarily (and automatically) be a good coach. Maradonna has provided evidence that that is not a given. Sir Alex Ferguson, Jose Mourinho and Arsene Wenger have and continue to argue that a great career as a player is not a prerequisite for a great coaching career. However, we cannot ignore the runaway successes of Pep Guardiola, Frank Rikjaard, Jurgen Klinsman and many others. At the end of the day, what matters is results.

But, concerned with youth sport as I am, the result-oriented approach is misguided, inappropriate and even dangerous. Many a poor coach have destroyed the dreams of young players whether it is by inappropriate practices which have led to injuries or simply discouragement that has turned players away from the game. For my part, the opportunity to compete in an environment in which I could have proven my worth and gone on to greater things was frustrated. Others have not been as lucky- unlucky?

CASE STUDY

Not long ago, I met an athlete 17 years of age. She's been playing basketball for a few years. Her love for the game is not left to question- she is officially in the off-season and is playing community basketball to stay in shape. Her regular season had ended poorly as it had the year before. They had played for 2 hours a day, five times a week, six if you counted the game on the weekend. Not seeing the results he wanted, the coach had requisitioned an additional before class session 2-3 times a week, for the players to put extra work towards their weak areas.

• Where was periodization? Is it possible that the ridiculous volume of work could be part of the problem?

What are your strategies/techniques for recovery? In typical teenage speak, she said, "I don't know. I just sleep or watch TV when I'm not going to school, or if I'm not working."

What are you eating before and after the game? "Does it matter that much? Like in the mornings, I don't eat anything because I'll be late for the session. Then I'll have a bagel or something like that. Generally, I eat whatever I feel like from the stuff we have at home."

What are your athletes eating?

She came in to see me because she wanted to lose a few pounds- she thought she was a little too slow. Also on her list of goals: increase endurance ad upper body strength. Other than a few ankle sprains here and there, and occasional aches in her hips, she had no major injuries to talk about. I proceeded with a basic movement screen to establish a baseline. Her scores were poor and I wasn't surprised. After doing the deep squat, she added as one of her goals she wanted to jump higher. Her knees collapsed as soon as she started her descent, but I thought explaining valgus to her would not be very productive. Instead, if I could ask her to jump, point it out, do some correctives, and then have her jump again, she could see and feel the difference.

(Image from fitnessgoop.com)

"I don't know how to jump. I've always been told I don't know how to jump but nobody has ever shown me how."

If a basketball coach is meeting his athletes 5 times a week, sometimes twice per day, and his forward can't jump, what is he coaching? Was this athlete lucky to have gone through several coaches, all of whom told her she can't jump but didn't show her how to? After all, she is still playing the game she loves. Or was she unlucky, for the same reason? After all, she is still playing the game she loves, whereas I walked away.

As a youth coach and personal trainer, my job, I believe is set the foundation so that my athletes can go on to collegiate and/or professional careers if they wish. Regressing to teach an athlete how to jump, or cutting down the number of sessions so that they rest adequately- these will give my athletes durability. This should not be sacrificed for a good win-loss record at the end of the season.

Ever had a bad coach? Tell me your story in the comments section below.

What Makes You Think You Can Coach?

As I reflect on my own experiences and those of others, I have to say I am disappointed. There is even a hint of anger, but I have a better hold of my emotions than that. I just can't help wondering though, what is it that makes some people think they can coach?

I remember trying out for the university soccer team. I even bought new cleats. We were allotted two hours to practice. With a good practice plan, clear objectives, tests and/assessments of some sort, by the end of the first session, the coach would know who's who and start to develop his roster. Mentally, I was prepared. On course to earn my bachelor's in Human Movement, I knew the science. Having completed a national level coaching course, I knew how to win the game from the side line, the dug-out and the locker room. More than just the weekend warrior when it came to actually playing, I was ready to go. After a brief intro, the man in charge blew his whistle start us off on a warm-up jog around the field.

                               

Perhaps I approached it with too much head knowledge, or maybe, that knowledge spared me from a season that would have been very frustrating. Seventy-five minutes after that first whistle, we were still running around the field. We had had more touches of the ball when we were messing around before practice had officially started. I couldn't find the coach anywhere. Until he came back, we were to keep running. The rest is an ugly blur in my mind, except for the questions that ravaged my mind then (and now).




Why were we running? Why is perhaps the most powerful question and the answer has the capacity to make or break the spirit. When personal training, I don't enter into any agreements with clients who do not have a definite why. Why do you want to lose weight? Why 15 pounds? Why? Why? Why? Why will energize you when you lose the drive to carry on? "When you are about to give up, remember why you started in the first place."
                     

Question. It's a good question. It also rarely gets asked. soshable.com (This caption was so good, I felt I should leave it as is.)

For my part, there was no justification for running around the field, seventy-five minutes later no less. My why would receive no satisfactory answer. You will never see anyone running around the field at a soccer match. What we were doing would have been more appropriate back in primary school when I ran cross country. It doesn't take a genius to figure out that soccer is an intermittent sport- stop and start. Sprint, jog, walk, sprint. Running at the same pace for over an hour does nothing for the aspiring soccer player. You can't even justify it with the old soccer players need a good heart or aerobic conditioning. Research shows that interval training has benefits for both aerobic and anaerobic capacities. I have already discussed these in this article here and this one as well. The evidence suggests different positions have different requirements for maximal performance. Surely you train them differently, holding them to different standards?

                     

Bottom line, this guy did not know what he was doing. I walked away sensing conflict between he and I. Of course, as the man in charge, in any confrontation I would always be on the losing end. His coaching style was nothing more than what his coach had made him do. That philosophy probably came from his coach's coach, and his before him. Coaching is an art- a mix of science, practice and some simple common sense. Common sense was not on the field that day- if you could somehow convince me why it was necessary for the outfield players to run like that, what would be the rationale for the goalkeeper running around the field for over an hour?

The Wisdom of Coaching

Every now and then, you come across someone who blows your mind. Someone who has put into eloquent words things you have only had musings about. Someone who has perfected what you have stumbled upon. Someone who draws a 'wow' from you, and has you looking into everything he/she said or did. One such a man for me is Charlie Francis. Charlie represented Canada at the 1972 Olympics in Munich before coaching sprinters, as well as professional football, hockey and soccer players. Of the many things he said and taught, I thought I'd share these.

FOR COACHING YOUNG ATHLETES

"Correct technique is the necessary prerequisite for an athlete...for optimal development to occur. The neural motor patterns of correct technique must be wired in place [as young as possible]." This quote from Siff, out of the book Supertraining, explains adequately Charlie's thoughts. "It is not only the exercise which modifies the body, or more specifically, the neuromuscular system, but the way in which the exercise is performed. In this regard, it is vital to remember that all exercise involves information processing in the nervous and neuromuscular systems, so that all training should be regarded as the way in which the body's extremely complex computing systems are programmed and applied in the solution of all motor tasks."- Siff (I have used this concept of programming in another article: Specificity of training).

"Always reinforce correct technique for the purpose of developing positive self esteem. Give athletes praise for their efforts- never criticize or ridicule."- Over the years, as I have coached different sports and different age groups, I have learnt the difference between developmental and biological age. There is a continuum when it comes to maturation on the physical, emotional and mental facets of every person, athlete or not, youth or adult. With this realization, I like to invoke loco parentis as soon as my time starts. This means taking charge over the content and even the tone used to address my players, even from their parents. I have seen careless sarcasm hinder and eventually turn away youth from participating from a sport they would have otherwise enjoyed and become very good at. Bottom line, coaching is building. Does your style enhance the self-esteem of the players in your charge?

"Coach one element at a time...Don't move away from one training element until it is correct. Teach increasing levels of skill- according to the individual's needs when the athlete's body and performance of training elements indicate a readiness to handle them."- I am a big fan of testing. My experience as a personal trainer has contributed to my thoughts on this point. Too many coaches and trainers do not bother with assessment with a couple of consequences. First, athletes are exposed to increased risk for injury as we, to quote Gray Cook, "add strength to dysfunction." Plyometrics are high impact and I have seen them imposed on weak ankles and knees that constantly display valgus collapse.

Secondly, the appropriate periodized program is important and can pretty much guarantee results. However, amongst those that use it, some hold rigidly to their micro and macrocycles. The attention that athletes and clients deserve is sacrificed leading to frustrating results. In most cases, the reaction from the coach is to blame the athlete for lack of effort, and push the even harder. Take the case of this seventeen year old girl.

Charlie's words are gold dust. Let the athlete's response determine progression.

"Youth training must not have too much low intensity. There must be enough high intensity so as to:

1: maintain and improve specific skill

2: Prevent loss of and maintain correct volume of fast twitch fibre

3: Promote differentiation of transitional fibre to fast twitch rather than slow twitch fibre."

Although this is specific to sprinting, I think it applies to other areas too. I have previously posted an article citing the ACSM's position on resistance training for juniors. It basically says that under qualified and careful instruction, strength training in safer than football, basketball and many other sports. The majority of athletes go through the prime years for instruction in elements that would lay the ground work for elite performance without that instruction because the coaches just don't know about it. The differentiation and specific instruction Charlie addresses here is foreign to many a program.

To be successful coaches, we must read more, and read our charges even more.

Specificity of Training

Tiger Woods hits about 1000 golf balls a day- he is back at the zenith of the PGA tour, and its only a matter of time before he wins another major. Michael Phelps reportedly swims for six hours a day, six days a week, without fail. He is now the most decorated Olympian- ever. These, and many others, are pros already, so why persist? Because they are programmers.

"It is not only the exercise which modifies the body, or more specifically, the neuromuscular system, but the way in which the exercise is performed. In this regard, it is vital to remember that all exercise involves information processing in the nervous and neuromuscular systems, so that all training should be regarded as the way in which the body's extremely complex computing systems are programmed and applied in the solution of all motor tasks."- Siff

THE SCIENCE OF A FREE KICK

An approximate 10 000 hours of practice is required before a skill can be mastered, before it can become second nature, automatic, and you can be called an expert. This automated response, in neurophysiological terms, however simplistic, is the formation of an exact pathway. Take for example, a David Beckham free-kick. As he prepares, he stands with his right leg slightly forward, his body at an angle. Were he standing upright, legs together, his hip flexion / extension would be at neutral, or 0°. Fast forward his run-up and single out the right foot he is going to strike the ball with. According to Levanon and Dapena, (1998), during the backswing phase, the kicking leg moves backwards, with the hip slowly adducted, externally rotated and extending up to 29° and moving somewhere between 171.9-286.5 deg·s-1 (also Nunome et al., 2002). At the same time, the knee, with some internal rotation, flexes at an angular velocity of 745-860 deg·s-1 (Nunome et al., 2002). Again, in that pre-run up position, feet on the ground, his ankles would be at 0°. While the hip extends and the knee flexes, the ankle is plantarflexed (10°), abducted (20°) and slightly pronated (Levanon and Dapena, 1998) reaching maximum plantarflexion velocities of 860 deg·s-1 (Nunome et al., 2002). On muscular level EMG activity suggests high activation of the iliopsoas during the start of the kick which was followed by a high activation of the rectus femoris during backswing. The biceps femoris and gluteus maximus demonstrated their peaks just prior to ball impact. (Dorge et al., 1999) All this, and he hasn't touched the ball yet.

THE SAME SCIENCE UNDER DIFFERENT CONDITIONS

A complete analysis of the kick is far beyond the scope of this article. What is within it scope is that the environment changes. It may be a shorter, left footed Leo Messi standing over the ball, or an older, medium height but no less competent Zidane. It may be right in front of the goal or some degrees either side of the posts, or even a corner. It may be a direct, or indirect free-kick, a lob during open play or an audacious attempt from the halfway line as Beckham did so many years ago. There could be a wall. Or maybe its the first ten minutes of the game, or the last minute- get this in and win the Champion's league; qualify for Euro, qualify for the World cup. And then there is the variable weather, and the crowd...

In each case, the technique is the same, but the variables must be taken into account if the kick is to be effective. If not- if the hip doesn't swing back far enough, if the knee does not flex that fast or the ankle is not at the optimum angle- I'm sure you know that if you are leaning back, even slightly when you make contact, the ball will rise and Tommy Smyth's 'auld onion bag' wont bulge. That's why they persist.

That's why you must persist. Make your first attempt. Analyze it- what went wrong? How can I change it? Pay attention to that, and try again, factoring in those changes. Got it? Good, now do it again. Whether you got it right or not, whatever you key in to the program will be recorded and that's what the system will produce when its required to. As Siff said, motor skills are a complex business and proper programming is essential. How does the program perform when its really hot outside? What about when its raining? Don't shrink from high pressure situations. Hone your skill during those circumstances just as much as in low pressure ones. Remember skill under demanding conditions is significantly different from skill under less onerous conditions. Program the neuromuscular system to perform optimally- FORM, FORM, FORM.

                                     

We must understand that it is not tireless hours of just kicking the ball that build the skill. Gross repetition of poor quality will never result in the sort of quality that improves play, result, wins trophies, etc. The difference then, between the best and the rest is the feedback they are able to collect during practice and the adjustments that they make as they strive for improvement. To quote Gray Cook (as he reflects on Geoff Colvin's Talent is Overrated), "The specific way practice is executed is what defines the deliberate practice common to those deemed talented." Only perfect practice makes perfect, so practice- perfectly.

References:

Kellis, E and Katis, A (2007). Biomechanical characteristics and determinants of instep soccer kick. Journal of Sports Science and Medicine 6, 154-165 

Levanon, J. and Dapena, J. (1998) Comparison of the kinematics of the full-instep and pass kicks in soccer. In Kellis, E and Katis, A (2007). Biomechanical characteristics and determinants of instep soccer kick. Journal of Sports Science and Medicine 6, 154-165 

Nunome, H., Asai, T., Ikegami, Y. and Sakurai, S. (2002) Three- dimensional kinetic analysis of side-foot and instep soccer kicks. In Kellis, E and Katis, A (2007). Biomechanical characteristics and determinants of instep soccer kick. Journal of Sports Science and Medicine 6, 154-165 

Siff, M. C and Verkhoshansky, Y. V (1999). Supertraining. Fourth Edition.