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The Hamstrings!

The hamstrings are one of the most misunderstood muscles in the body and the explanation of them shortening when we bend the knee or lengthening when we straighten the knee is a huge simplification. To also view them simply as a sagittal plane beast does a disservice to the power that they hold in other planes of movement.

The first question is why are there three and why do they attach in different places?  The attachment of the biceps femoris on the lateral fibula straight away gives us control in the transverse plane. As the lower leg goes into internal rotation the hamstring is able to eccentrically control this motion.  This is similar to the gluteal attachment on the femur that allows it to control hip internal rotation. If we look at the universal function of gait and how much of the gait cycle is spent in internal rotation, due to ground reaction and gravity, it becomes easy to understand why.

The semimembranosus and semitendinosus are on the medial side of the femur attaching into the pes anserinus and onto the medial tibia. From this position they will have much more control of external rotation of the lower limb, either femur on tibia or tibia on femur. If we look at the pathomechanics of ACL injuries for example, the ability to control real femoral internal rotation, thus creating relative external rotation at the knee, is hugely important. Add to this the eccentric control that these muscles will exert on valgusing of the knee, especially with its close proximity to the MCL, we can see the multi plane importance of having these two distinct portions of the hamstrings. In fact should we even lump them together as a single entity??

The might Gary Gray described them as the like the reins of a horse which is a pretty accurate description.  This multi dimensional ability though is rarely noted.

The fibre arrangement remains fairly longitudinal in the sagittal plane. This gives the unique ability to control the range of movement through the other planes. Reduced ability for the fibres to move and lengthen in directions away from the fibre arrangement gives it an inherent stiffness to control motion.  A function related example of this would be how the hamstrings can help control foot pronation through slowing down tibial motion in the frontal and transverse planes at the proximal end.

The fact that the pelvis and the tibia/fibula are both connected to the hamstrings mean that the hamstrings can lengthen when the knee is bent and shorten when the knee is straight. This is all dependent on which section is rotating faster, something that is key to a bi-articular muscle. This means that if the tibia is rotating forward faster than the pelvis then the hamstrings will lengthen. We see this in the front foot phase of gait. The tibia’s distal end is rotating posterior while the superior portion of the pelvis rotates anterior. The tibia closest to the ground has to deal with more force so is rotating quicker creating knee flexion but lengthening of the hamstrings. If the pelvis rotated faster we would spend a lot of time looking at the floor!!! Add into this the anterior translation  of the femur due to gravity and connection to the tibia and we also get a lengthening force on the hamstrings at both the distal and proximal ends.

Equally during the up phase of a squat if the pelvis is rotating posterior faster than the anterior rotation of the distal section of the tibia then we will get shortening of the hamstrings, even though the knee is extending!

The two attachments of the hamstring can be important for understanding hamstring injury.  Many times we see hamstring injuries as lower limb dominant. However a top down drive e.g. pelvis driven, can make a huge impact. If the hamstrings are already under a large amount of tension as we may see during swing phase (large hip flexion of swinging leg) of sprinting. Then any additional tension caused from movement of the head affecting the pelvis may be too much for the hamstrings to handle.  This could be more sagittal plane tension or rotational tension from looking side to side.

In the video clip below we see Fernando Torres as he is sprinting for the ball.

[youtube=http://www.youtube.com/watch?v=d6rhDpELsSg]

He is looking behind him.  This would create some posterior rotation at the pelvis. As we drive the leg (femur) up into hip flexion this posterior rotation would reduce force created through additional eccentric tension on the hamstring that is generated from the anterior rotation of the tibia of the swinging leg. The problem comes when the ball drops and his head comes forward creating more anterior rotation of the pelvis. Now the hamstrings are being lengthened in opposite directions from both attachments. Under extreme force such as sprinting this can cause the hamstring to close down to resist this extreme force. The tissue confused from a proprioceptive standpoint and unable to lengthen will be at far greater risk of being damaged.

So why is it important to know all this about the hamstring?? Well it helps us create an authentic strategy with which to treat and train the hamstring. If the hip or ankle lacks internal rotation and therefore does not allow the hamstrings to lengthen in the transverse plane, then by understanding this need for multi-plane flexibility, created in different ways, we can factor this into our programs or techniques we use.

 

 

 

 

 

 

 

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Knee pain-Patellofemoral. A functional approach.

Knee pain is very, very common. Although there are many types of knee pain affecting the various bursars, tendons and ligaments in that area, one of the most common is patellofemoral pain.

Rather than delve too deep into the minutia in this blog post it maybe much better to have a conceptual understanding of what is needed for successful patella femoral mechanics.

The patella is attached to the femur and tibia via the patella tendon.  In fact it sits in the groove or Condyles that are both medial and lateral on both bones. This means that for successful movement of the patella, these grooves need to stay pretty close. A great way of describing it would be “in sequence”.  Otherwise the patella can smash into the groove causing pain.

We have two pretty important bits of the body attached to these two bones.  Namely the hip which attaches to the femur and the foot attaching to the tibia. That means the sequencing of the grooves can be affected by excessive movement or limitations in movement at either end, the hip or foot.

A common approach is to try to limit the movement at the hip and foot by tracking the knee in the sagittal plane, in effect reducing the variability of motion. The wondrous nature of a ball and socket joint is the huge freedom and variety of movement it gives us.  In fact this freedom and variety could be described as tri plane. An attempted reduction of motion into the sagittal plane will reduce the load to the hip musculature that displays a distinct tri plane nature. Look at the glute and its oblique fibre orientation. Without frontal and transverse plane motion of the femur it will not work effectively. In fact the glute will control the femurs motion into adduction and internal rotation.  Deviations away from the sagittal plane, that occur frequently in functional weight bearing movement, of knee valgus (femur adduction) and femoral internal rotation will need to be slowed by eccentric activation of the glute and hip musculature. This maintains the optimum sequencing between femur and tibia for healthy patellofemoral mechanics

Equally the operation of the foot will affect the sequencing of the tibia. This will also disrupt the patella in the groove. Using gait as an example (and universal function) a rearfoot or forefoot varus will have an acceleratory effect of the tibia following the foot into pronation, creating increased tibial internal rotation and abduction. The sequencing of pronation will also affect the sequencing of the patella femoral mechanics. Late rearfoot pronation will decrease the external rotation of the tibia that along with femoral external rotation keeps the grooves closely sequenced. In fact we may get opposite rotation of femur and tibia. The patella attached to both, as my friend Gary Gray says, “gets caught in the middle with no place to go’.

A lack of motion in sagittal plane such as ankle dorsi flexion may also increase pronation affecting the knee.  This is why people may complain of feeling their knee more when using the stairs. Increased dorsi flexion is required when ascending or descending the stairs. If this dorsi flexion is not available at the talo-crural joint the body may use increased pronation at the Sub-talar and mid-tarsal joints to create more flexion. This increases the frontal and transverse plane forces on the tibia and therefore patella. So increasing the sagittal plane demand as traditional exercise aimed at dealing with patellofemoral mechanics does, may actually cause an increase in the motions that cause pain! An understanding of why dorsi flexion maybe limited could be a more successful approach rather than just try to force more sagittal plane knee motion!

Functional tri plane assessment of both of the hip and ankle are required to understand what maybe causing knee pain rather than generic one size fits all exercise. So many structural foot dysfunctions are present in the general population that without understanding functional biomechanics and structure we cannot effectively treat these problems. A knowledge of how the knee acts when weight bearing rather than just on a plinth is vital as tri plane motion occurs mainly when weight bearing.

Something that always confuses me is the dissociation between foot pronation and knee motion. We classify pronation as movement into dorsi flexion, abduction and eversion and is well documented. This will create tibial internal rotation following the talus. This tibial motion connected to the femur will create internal rotation of the knee. How then can the knee work as a simple hinge joint when weight bearing moving exclusively in the sagittal plane??? Equally the abduction of the tibia at the distal end will result in the proximal end falling in towards the midline of the body creating a valgus at the knee. Again how can we see the knee simply as a hinge???

It is vital that close association of both the femur and tibia occurs in all 3 planes for functional success. This means assessing the foot and ankle in weight bearing and dynamic positions! At Cor-kinetic we always use this thought process when dealing with these types of problems!

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Hypermobility!

Being flexible has always been seen as a great thing. The more stretchy the better!! The ability to assume any number of crazy yoga poses at will.

Hypermobility however can present its own set of problems.

As we start to understand the body as an integrated unit that relies on the chain reaction of movement for its success, the more we realize that a certain level of tension is a good thing.

The body relies on the eccentric lengthening of muscles to create concentric shortening. All of this has to happen within optimal range and sequence. With a hypermobile person the pretension to create the transformation from one contraction type to another will now not occur in the optimal parameters.

An example of this chain reaction in gait would be of internal rotation of the hip and supination of the foot. As the stepping leg passes over the standing leg it creates relative internal rotation at the hip-joint. This internal rotation will create information and energy for the explode of external rotation of the leg. This also occurs because as the internal rotation runs out at the hip, the pelvis also drives the femur round with it. All this helps the foot to go through supination.

With the hypermobile person, the level of pretension is not there. This means that to get tension for proprioceptive information, energy and to drive the leg from above the pelvis will have to travel a hell of a lot further. If we look down at the foot, by the time it has taken for all the reactions to occur above the correct time for supination has passed. This may mean that the foots effect on the hip in terms of extension may also have passed. This leads to an ineffective gait cycle.

The increased elastic elongation of the muscle has swallowed any tension that may have been generated by the movement.

As we learn to walk as babies we can see the lack of pretension or stiffness regulation in their movement. As we become more effective our joint ranges become more controlled and our internal level of tension improves. This enables the effective transfer of energy and information and hence chain reaction biomechanics to occur.

Hypermobility has implications for energy consumption and speed of movement.  Simply put the larger the joint and muscle range the more energy we dissipate as heat through the splitting of ATP. The larger the joint range the more time it takes to control.

If we see stability as control of movement, rather than the rigidity than the current ‘core stability” trend promotes, then hypermobility may not succeed. In fact rigidity maybe what the body uses for stability in lieu of controlled movement. This would be dysfunctional. Hypermobile joints will interfere with the correct sequence of motion that leads to pain-free movement. It may also force rigidity into other areas of the body to control overall range. This will also interfere with sequencing.

The lessons I have learned from my experiences of working with hypermobile people have always been to find the inevitable areas of rigidity that seem to appear. Also working within ranges that can generate tension in the system, many times this is best done weight-bearing and moving, as this will generates its own tension demands on the system.

Tension too much or too little will also have an effect on the pain receptors and their threshold. Certainly the more tension a rigid area is under the lower the activation threshold of the pain nerve endings becomes.  Although I am not sure of the research into laxity and pain thresholds I would believe a step away from optimal might have some impact.

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Dynamic stretching!

Its been a while since I last wrote so I thought I better had! Today's blog is about dynamic stretching.

To stretch or not to stretch, dynamic or static, these are all questions posed in the fitness industry. Another question is does stretching reduce injury?? This is not a question that I want to get into but instead look at stretching as improving our exercise experience and performance. For me, if we want to increase movement we do this by, increasing movement.

First of all I think we see stretching as a mechanical experience that increase tissue length. To some degree this is true. However I also see dynamic stretching as a neurological experience that increases information flow around the body. So many of the bodies receptors that live in the skin, fascia, joint capsules and muscles respond to change. This would be change in angle, length, tension, pressure and vibration to name a few. Dynamic movement creates constant change, a static change of position only creates one change!

By increasing the movement sphere and therefore information sphere we increase the potential for more movement. As movement increases, so does the ability to increase the range or sphere. A good friend of mine coined the phrase "movement begets movement" I think this is pretty good way of summing this up! So by remaining static we will not increase this sphere or give the body the potential to increase the sphere.

If we look at the information mechanisms in the body and were to look solely at muscles for this information the muscle spindles would be a great place to start. The spindles have two types of Efferent (info towards the brain). One is based on tissue length and one is based on the rate of change of this length. These intrafusal fibres are vital for the feedback loop, through the gamma and alpha motor neurons, that then regulates the stiffness (resistance to lengthening) of the extrafusal muscle fibres and hence successful movement.

By statically lengthening the muscles we are only giving half of the picture. Movement requires both length and rate of change of length information to be successful. Imagine having the GPS system of your car only relay half the information, and the bit omitted was the speed you were traveling at. I think you would be missing a lot of turns!!!

We also tend to only stretch along the fibre direction or longitudinal axis of the muscle. If we look at the mechanical nature of the spindles then this would lengthen and put the spindles under tension but also imagine that when under longitudinal tension adding in perpendicular and rotational tension. This would affect the information flow also. This demonstrates from a muscular perspective why three dimensionality and movement are pretty vital to the stretching or movement enhancing process. Especially as functional movement uses all three planes!

Also we must see stretching as an integrated procedure. In an integrated system such as the body the range of one joint maybe inhibited by the range available to another. If we stretch the joints separate of their function specific chain we may get a different ranges to if they are integrated. In fact a smaller individual range but a larger integrated movement may be the best desired outcome for some joints to avoid tissue stress.

Many factors may also affect the flexibility of the body. These could be stress, diet, disease and eyesight to name a few. If we can understand the feed forward  mechanism of the gamma motor neuron upregulating the stiffness of the spindles and therefore the alpha motor neuron changing the stiffness of muscle fibres, it is easier to see why the above stressors of the system can have such a huge impact on flexibility and therefore the biomechanics of the body!!

I have never understood how remaining still will help us move!!!

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Golf: Hip Overpronation!

If you have ever looked at the biomechanics of the backswing in golf it becomes obvious that being ‘on plane’ is a perfect functional combination of the three planes of movement available to the body, sagittal, transverse and frontal. My recent foray into the world of video analysis with golf has inspired my post!!

This also kind of ties in with my friend Dave Westerman’s recent video explanation of biomechanics involved during the golf backswing.

When we may start to see problems is when the body does not have the capacity to move in the plane required. A strategy we may see is the body obtaining more movement in the plane it can get to compensate for movement in the plane that it can’t get.

The required motions in the backswing at the hip are extension (in a flexed position), ADDuction and internal rotation. The aim in the backswing is to not shift the Centre of mass to far to the right for a right handed golfer. The larger shift in mass and translation of the pelvis comes during ball striking and follow through. This acceleration of mass creates the force required to propel the ball.

A common swing fault can occur when instead of using the transverse plane to create relative internal rotation at the hip, we instead utilize frontal plane translation. This pushes our centre of mass over to the right for a right handed golfer.

What we now see is an inability to sequence correct motions in the swing. The shift in weight cannot be reversed in time so that the hips can create a proximal acceleration to provide additional load to the core, chest and shoulder. By the time the hands have started the down swing the hips are still lagging behind, unable to cover the range in the timeframe available. This frontal plane translation could also compensate for the ability to get opposite side lateral flexion. The shift in mass through hip motion creating more or the illusion of more lateral flexion.

This change in sequence can lead to inefficient and ineffective swing mechanics and also to injury to the tissue that relies on this correct sequencing. The lack of mass in the F=MA equation will also severely reduce power.

This is very similar to what happens during overpronation at the foot. The large motion and increased range into pronation means that the body is unable to reverse this motion into supination by the time the swing phase of gait is initiated. This leads to a back foot pronation and reduced movement in the rest of the kinetic chain.

As with all sport golf, relies on the sequencing of movements to accelerate our mass at the correct time.  Our ability to understand our client’s function and our clients ability to perform their function is vital to our success.

Check out Cor-Kinetic facebook.com/corkinetic for loads more functional info and course dates.

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Using your mass!!!

This post is on moving our COM (centre of mass) during training and assessment.

During sport and many functional activities such as walking we are constantly moving our COM. Walking is about controlling the change in position of our COM that comes about from the bodies momentum carrying it forward once it gets moving! Try and throw a ball without shifting you COM from the back to the front. The same is true of throwing a punch or hitting a tennis shot. By transferring our COM we are putting the M (mass) in F=MA, Newtons second law of motion that deals with acceleration and ultimately force production. The more mass we can accelerate the more force we can produce. If we threw with just our arm that mass would be small. By moving our entire COM that mass becomes much larger and so does the force we can generate.

The question is do we use transfer of COM in our training and assessment??? A step beyond that is do we displace our mass in the horizontal e.g forward and back, rather than just in the vertical e.g up and down.

How many traditional gym exercises move COM. Well quite a few. Deadlifts and squats both do in the vertical (up and down). How many in the horizontal (forward and back) erm....not so many!! How many of the movements discussed above use forward and back COM transfer for power...all!!! So when we are training for sport really we should be looking to train COM movement away from just the vertical. Does that mean the clean and press is not going to help us punch harder or throw better??, I think that's exactly what it means! We have to examine the functional crossover of our exercises rather than just apply gym based exercises to any sport or function feeling they will have crossover to generic 'strength'

What is described as timing in sport such as when we hit a great shot in cricket or tennis is being able to move our COM at the perfect time in the right direction to impart the most force on the ball!!

Many times during assessment our clients will be able to translate their COM forward effectively on one side but use rotation on the opposite side as they are unable to decelerate the COM transfer in the hip or ankle joint. It is much easier to rotate in the sagittal plane into flexion using gravity and keep the COM central rather than moving the COM forward through translation. A simple test is to see whether a client can lunge forward effectively in the horizontal vector without sinking downwards towards the floor. This would show effective transfer of COM. If we do not look to move COM in assessment we cannot tell if the joints and muscles in question can decelerate our mass and resultant momentum vital to functional success.This deceleration will lead to effective acceleration as we eccentrically load the muscle for concentric force production.

In fact effective horizontal translation in the sagittal plane will increase motion in the transverse plane at the hips and therefore the feet and spine too!

Using 3 dimensional space will force our bodies to shift COM, decelerate and harness momentum for force production. Most traditional exercises keep us rooted to the floor!!

Think outside the box for functional success!!!

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Optimal range. More may not be better!

This blog comes courtesy of a conversation I had with my good friend Mike. Its all about optimum range of a muscle. It kind of followed on from this piece of info…

The eccentrically-loaded muscle will start its contraction weak and then get stronger; the concentrically-loaded muscle will initiate strong, but get weaker as the contraction continues.

 I had never given this much thought before but this makes a lot of sense when we think of length tension relationships. A muscle will struggle to produce force when both too long and too short.  Being weak in both positions. Cross bridge attachment has an optimal range.  This will be true of both force production and conservation of energy. Too much cross bridge detachment will also cause a more thermodynamically expensive scenario as we split ATP and dissipate energy as heat.

Elastic energy will also I believe have an optimal range. Studies have shown that spring stiffness (ability to return energy) comes from optimal joint angles or ranges. Going beyond this range means that we dampen or absorb energy, again dissipating as heat through visceoelasticity of tissue. Different tissues have varying levels of stiffness and compliance, different ranges will bring into play these different characteristics as will our neurological intention (land or jump again) to move control stiffness through efferent spindle stiffness regulation.

If we look at the way we jump when we want to jump again, we can see that we use a shorter joint range than when we land for the final time.  When we finish we have a large bend of the knee to absorb ground reaction forces rather than reuse them. This has implications for our understanding of height, range and repetition programming for our training me thinks!!

Ecconcentric (both eccentric and concentric muscle contractions occurring in different planes) muscle action may also play a role in optimal cross bridge attachment. If a muscle was to lengthen in all three planes this may cause a scenario where we are going beyond the optimal range for the muscle in terms of force production and elastic energy recoil. By mitigating elongation of the tissue in a plane of motion through concentric shortening we may also keep an optimal range. It maybe this would happen in a more sub maximal scenario where energy return and energy conservation are more important than maximal force production. I feel that gait is a great example of this. Although maximal force production may also be mitigated by creating too much loading through joint range that is hard to transform.

This then got me thinking about how we train. Many times we are looking for maximal ranges in our training. Maybe we should be looking more at optimal ranges. This may have more implications for sports where we can control the range through skill however. Running is a great example. Controlling stride length will keep us within optimal joint ranges. We must also remember that optimal will be governed by the individual. This will be affected by tissue ability, limb length, speed ability and event. I expect it will be that different events within running e.g. 400 metres will need different joint ranges from a marathon as we balance need for all out power, power-endurance and endurance. Going beyond optimal means our ability to start the next phase of movement, either eccentric to concentric or vice versa, will be compromised. I think that deceleration and acceleration are part of running (unlike the pose method ideology!) However we can mitigate excessive amounts of both having to occur, increasing energy conservation.

If we look at a game of tennis it is much easier to hit a powerful shot when we can manoeuvre our bodies into position. When we are out of position our range of movement may have to be extended to reach the ball. The transformation from eccentric to concentric is sub optimal and affects the power of the shot. The tennis player many times at end range will hit a defensive shot back, aiming to get it in the court rather than a winner! Increases in amortisation from eccentric to concentric reduces cross bridge attachment also decreasing energy return. The closer we get to and stay at end range stretching for the ball the longer we have the amortisation phase reducing the energy gained in the loading motion.

This is a very theoretical piece and mainly my own thoughts (so blame me!!) but it may give us food for thought when we programme ranges/heights for our clients to move through when training.

More may not be better in all circumstances!!!

 

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