Frans Bosch and Soccer Performance Training

“thinking of strength training as coordination training with appropriate resistance is a giant step forward. If nothing else it will make us more efficient in utilization of time, along with a greater chance of transfer. We need to challenge ourselves in the area of strength training, to break away from conventional wisdom and seek out new possibilities for improvement. This approach has challenged me.”



1.  Dynamic Systems Theory > Reductionist Approach

Human movement is the result of a highly intricate network of co-dependent sub-systems. "If you look at running, for example, performance is tied to diverse elements such as muscle fibers, neural control, elastic properties, distribution of loads over many joints, the respiratory system, and more." - Bosch.   A reductionist approach to science seeks to understand a whole by analyzing its parts. Reductionism is a tremendously successful way to explain the behavior of things like physics, chemistry, and engineering. But it has significant weaknesses when applied to the human being. In a complex system like a human being, the whole is in some sense far greater than the sum of the parts.  

When asking ourselves what will lead to great performance or why did we have a poor performance,  we must take everything possible into consideration. The touch of the ball was off today...ok, why? Did you eat a food that caused inflammation and slowed your reaction time or mental acuity? Did you sleep like shit? Did you over-train and cause staleness mentally and/or physically? Maybe you have not practiced enough with the ball causing you to be poor in specific technical situations.

Thinking more holistically about things is a dynamic systems approach to problem solving and setting up training plans. 

2. Don't Ignore Phase Transitions 

Phase transitions are the sudden shifts in recruitment of body parts that occur when velocity and force are added to movement. The sudden changes that occur in sport  call upon completely different muscle actions than movements done at lower speeds or forces. This is especially important in returning from or preventing injuries. For example, while the trunk musculature will organize a certain way when performing a plank (ie. transversus abdominus) with slow speed and low forces, the total trunk musculature will work in an entirely different way when performing a side volley or jumping header. Faster speeds call upon muscles to use cocontractions of agonists and antagonist (opposing muscle groups) to protect the joints. Another example is going from a basic stabilization exercise like a single leg balance for the ankle to a high speed plant in a game to change directions. When cutting sharply muscles around the ankle joint must cocontract and have different firing patterns than simply finding center of gravity at stance.  In rotation, muscles must produce power while simultaneously protect against injury and this is a specific type of coordination.  




 Choose your motor control programming wisely and don't think that after a back injury because your "core is strong" in planks you're ready to  compete. Expose yourself to higher forces and velocities in specific movements gradually.  If you haven't played soccer in awhile, ease into it both in terms of volume (how much time you play) and intensity (the speed in which you run, cut, and the power you strike the ball with). All of those things need to progress.  If a movement of yours is slow or awkward, perhaps there is an element in your training that is missing related to phase shifts.    

3.  Optimize Transfer of Training

The whole point of doing any exercise or drill is for it to transfer to the game and improve our performance. Bosch talks about how every time we choose an exercise we must take into consideration negative transfer as well as positive transfer. He says overload in the form of more resistance comes at a cost of specificity.

  • Frans’ Rules of Specificity as the main requirement for transfer
  1. Types of muscle action must be similar to those used in competition (Inter/Intra muscular)
  2. Structure of the movement must resemble that used in competition (motion of limbs)
  3. Sensory information must resemble that present in competition
  4. Dominant energy systems used in competition must be called on
  5. Result of the movement must be the same as competition   


Bosch goes on to say that a power measurements can therefore only predict competition performance if movements are decelerated in the same way. Ie. single leg versus double leg movements are different based on the pelvis and trunk's ability to rotate in single leg movements and not in double leg or arm. In a punch we can get trunk rotation, but not the case in a bench press or push up when both hands are fixed. Soccer is played predominantly on one leg at a time and has different demands placed upon it- our training should reflect this and include single leg strength, power, lateral exercises, balance, etc. through similar ranges of motion, velocities, and forces. That is taking transfer between exercises into account.


 4.  Reduce Muscle Slack 

Imagine a rope that is loose versus a rope that is tight before you want to walk across it. The time it takes for the rope to tense to have enough force for you to put weight on it is time lost in athletics.  The degree to which a muscle's operative tension must be increased in order to become taut is known as muscle slack.  Bosch says the speed at which muscles can build up their tension and overcome muscle slack is usually more important to performance than the amount of force they can eventually produce. This is why technique and timing is so important in athletics.

This concept of muscle slack is also why in a vertical jump a countermovement, or the quick dip and drive is so effective in adding inches - it pretensions the muscles. Even if the squat jump without the countermovement has more total force production, the jump wont be as high as the countermovement jump because force is generated too slowly.  

In sports, Bosch argues that the best athletes make smaller countermovements and allow storage of elastic energy to work.  He then argues that training based on large countermovements will lead to longer muscle slack and poorer performance. Athletes who require the use of large counter movements when performing running or jumping activities are trying to take the slack out of their system.  An athlete with a lot of muscle slack is not springy and takes a too much time to generate force.  Plyometric exercises that involve a rebound like a depth jump, absorption exercises to teach the muscles to cocontract and develop tension quickly like depth drops, and isometric exercises like the video below help eliminate muscle slack in the athlete. Bosch doesn't even use counter movements in his lifting for this reason. 



5.  Train the Elastic Properties of Sport Actions 


Related to muscle slack is making the most of our elastic muscle properties in movements. Elasticity refers to the ability to return to normal resting length following a stretch.  Our muscles have contractile elements and SEC (series elastic components) aka elastic elements such as our tendons and the intrinsic elasticity of the myofilaments. The SEC or muscle's elastic components,  have a major impact on force production. The SEC's also function as as shock absorbents in unfamiliar, changing environments.

Depending on how the contractile elements of muscle are forced to behave, series elastic components will or will not be stretched. This will depend on the external force that is trying to stretch the muscle. If the force exceeds the maximal isometric force in the CE such as dropping from a really high height, the CE will lengthen at the expense of the SEC being utilized.  In other words if opposing forces are not too high for the involved muscle action then the contractile elements are tensed to the maximum while the SEC are stretched and loaded with a great deal of potential energy. Once the external force ceases to be applied, the energy in the SEC parts is unloaded and the muscle shortens vigorously. Developing more ability to absorb force and not have the knee or ankle buckle upon impact has a relationship with the discharge of elastic energy. 

Elasticity and isometry belong together. Speed skating involves no rebound actions and mostly explosive pushing into the ice, so virtually no elastic muscle properties.  Something like a high jump is highly dependent on the ability of the muscles of the leg to contract isometrically (think minimal knee flexion in the plant leg) so that the SEC produce elastic power like a kangaroo.  

Playing soccer will give us some elasticity, but we need to train our body to absorb higher and higher forces without deforming at the joints so we become more elastic. Lifting weights is not the way to develop this elastic strength although maximal strength is related to a certain extent to reactive strength, especially in beginners. Many plyometric exercises such as depth drops, depth jumps, bounds, hurdle hops, lateral hopping,  are great for developing elastic qualities and I will cover some of my favorites soon in more detail. 

6.  Understand Differences in Explosive Power Development

 During the vast majority of soccer movements there is not enough time to produce maximal force. Your foot only contacts the ground for a short amount of time and there is no way to use all the force generated in something like a heavy back squat.  Therefore it is not the strongest athletes, but those that can produce the greatest force in the shortest time that have an advantage. Training to increase the rate of force development allows reaching a higher level of muscle force in the early phase of muscle contraction. See below how jump training versus barbell strength training differ in the ability to generate force quickly: 


The total amount of power an athlete produces depends very much on how fast force can be built up in the muscles. With very fast speeds, little amounts of force will be able to be developed. Once the bodies' inertia is overcome in a movement, performance becomes  less and less  dependent on maximal strength. It is like pushing a the beginning it takes a lot of strength to get the car moving, but once momentum kicks in it becomes less about strength and more dependent on other factors such as developing power.  The car will eventually be going really fast and it is the ability to continue to generate power at those very high velocities that separate the faster sprinters from slower sprinters (some of those qualities are genetic).

All of this is not to say maximal or heavier strength training is out.  Bosch acknowledges in his book “In beginners, strength training does have a positive impact on some aspects of rate of force development.” In most studies that don't involve the elite, adding strength improves (or is correlated to) acceleration in the first few steps, jump height, and the ability to change directions.  
"Increases in maximal force include an increased neural drive and enhanced intermuscular coordination (McBride et al., 2002Cormie et al., 2010), rate of motor unit recruitment (size principle), and the activation of type II muscle fibers and subsequent improvement in maximal strength capabilities (Cormie et al., 2011). These changes may also be associated with effective changes in synchronization of action potentials and antagonist co-activations leading to an improvement in dynamic force and power production (Folland and Williams, 2007)."

The take away here is that strength training is contextual, meaning it is both vector specific and velocity specific. Training with overload but without specificity usually has very little positive impact on athletic movement, especially in higher level athletes. 

(Additional note: A new study by French researcher JB Morin on Force/Velocity profiles and maximal power output show that training should be specific to the Force/Velocity profile of the athlete. If you are already strong but produce force slowly, then abandoning strength exercises and working on increasing velocity, even if you lose strength will increase your jump height. In contrast, if you are fast but have no force behind it, focusing on strength will improve your jump height. A better relationship or balance between force and velocity was more important than total power output in terms of jump height.)

7. Find a Balance Between KR (Knowledge of Results) versus KP (Knowledge of Performance) Feedback 

  • Frans detailed a study that split discus throwers in to 2 groups that received feedback from:
    • An elite coach – giving them Knowledge of Performance (KP – how well or poorly they executed the throw)
    • A measuring tape i.e. they were only told how far each throw went – giving Knowledge of Results (KR)
  • Those in the Knowledge of Results group attained results as good as those receiving feedback from a coach in the short term and performed better in the long term
  • KP results in an internal focus for athletes where they are thinking about where to position their limbs, sequence of movement which can result in overload (otherwise called reinvestment) and poor performance
  • KR leads to an external focus whereby the athlete is only thinking of achieving the goal

What this means is that by giving too much feedback to the athlete or obsessing over small details about where your foot is pointing and the angle of your hip can delay and hamper improvement. Of course there are times for technical tips and feedback, especially in beginners, but letting the body do the thinking by trial and error with a goal in mind (ie."keep the shot on goal" or "pass to your teammates right foot") work superior to constant internal feedback.   This is because movements are primarily organized according to their intention, as opposed to the required combinations of joint movements and muscle activation. If anything is to be taken away from this, don't over coach technique and let the athletes or your body figure things out through repetition. 

8. Finding Attractors

An attractor is a universally valid, underlying principles of the movement and leaves room for variants that develop from self-organization and are related to the individual properties.  Another way of putting it is "a state of organization to which a complex system will tend to gravitate".   

An example of this in soccer is when soccer player goes to strike the ball -  some things need to remain stable while some things need to be flexible in order to adjust to the speed and location of the ball. The opposite arm of the kicking leg movement acts as a primary attractor or stabilizer, while the bend of the trunk, the rotation of the pelvis, and base knee flexion act as fluctuations to adjust. The better the attractors the easier it will be to adjust to perturbations, unpredictability, or "noise" as Bosch calls it that inevitably show up in soccer.  


9.  Variability Is The Road To Success 


Variability is basically changing things up in the training every now and then. Ideally this is done in an intelligent way. Mixing things up is a great way to continually get results, avoid burnout, and challenge the athlete to learn faster and better. An example of this is player exposed to playing futsal, 11v11, 1 on 1, and beach soccer with a variety of teammates and even ages compared to a soccer player who always trains with the same team and plays 11v11 against kids his or her own age. I cant help but to think of my experience in Brazil when I was 21 and all of the different  types of soccer they have there and that I was exposed to from beach to society 8v8 to 11v11 on all sorts of fields to futsal to futevolley to street.

The player exposed to a variety of surfaces, perceptual demands, ball sizes, physical bodies, etc. will become a more physically robust, complete player than the one who always plays the same style of the game.   

Wrap Up

I am still in the middle of Bosc's thought-provoking work. It has definitely changed my views on the role of strength training in athletic preparation and now it is time to start giving some of these principles a try.