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Strength

So I have not blogged for a while. It feels like I have been here, there and everywhere teaching in November. From New York to the Manz fitness conference in Portugal and more locally in the UK.

In this blog I want to look at a more functional approach to the concept of strength or maybe more importantly force production during function. One way of defining strength, as always there will be different definitions, would be the ability to move an external resistance or generate force to overcome a load (and its inertia if we are being consistent with Newton) . Generally in the gym this would be a weight.

Now with a weight it is very easy to quantify the fact we are moving a larger external resistance or mass. In fact it usually says it on the side in a numerical form. The question we have to ask is does this make us better at force production within our function (if that is what we want of course)??

Lets go back to our good friend Newton. His second law of acceleration defines force production or F=MA. This is force = Mass and Acceleration. This equation tells us that force can be produced in two distinct ways, M over A or A over M. As we tend not to walk around with Newton meters to measure force it is much easier to just quantify the mass element of this equation. So we look at M (mass) over A (acceleration) as a simple way of measuring our ability to produce force. The question is are most sports high external resistance and therefore M over A or lower external resistance and more A over M. This is a harder question to determine but if we look at a couple of sports this might give us an answer. Sports such as tennis and football (soccer) would have a lower external resistance and rely much more on changes in velocity to generate force or A over M. This would also be true of throwing a punch or ball. In these circumstances would ability to move large masses help us??

If we look at the Hill curve (1953), which is the hyperbolic force-velocity curve, this implies that velocity of muscular contraction is inversely proportionate to load. We can see that large muscular force cannot be exerted in rapid movements, as we would see in weight lifting, that would be associated with changes in velocity or A over M to generate force .

So do we need to be strong to be good at our sport?? One perspective is that the greater someones strength (M over A) or hypertrophy and physique the better. Although I think this is often not the case in the sporting arena as we see amazing performances by people on a regular basis who do not fit this bill. It maybe that within a more functional context a sub classification of speed strength maybe more applicable. We would define this as the ability to execute a movement against a small resistance with a high velocity.

Speed and intensity of movement will recruit the fast twitch muscle fibres associated with maximal effort. These fibres are recruited as per force needed. As previously highlighted this force can increase A over M as much as M over A! So do we need to be specific in the way we recruit these FT fibres if we can recruit them also M over A? Moffroid & Whipple (1970) found that there was little transfer effect from low velocity training to high velocity training, couple this with the Hill curve data that force decreases with the velocity of contraction, it would appear that specificity plays a role in increasing applicable force.

So we need to specific in the way we produce force. So then what about the position this force is produced from in terms of movement or motor pattern? By using set classic gym based strength exercises for strength in a wide variety of sports, this would indicate strength is perceived as generic in terms of position rather than specific. However research does not support this assumption. Verkhoshansky (1968) sees the kinesiological pattern as important in special strength training and the patterns of force production depending on a specific neuromuscular process. Sale and MacDougall (1981) also see "Increased performance is primarily a result of neuromuscular skill". They also comment "increased strength is apparent only when measured against the same types of movements used in training". This all seems to point to the fact that specific function related movement patterns and their mastery is important in increasing our force production and performance. Bompa (2000) says “Strength adaptations are angle specific and thus all possible angles must be utilized". Lifters have known this for a long time as they often change angles through inclines and declines, however they rarely use planes other than the sagittal. Different angles, as well as interactions with different planes of movement, occur in different functions and sports. This means that function related angles, planes and movement patterns could be important in increasing force production and strength in a classic sense if required.

We also cannot replicate maximal forces produced in a single plane of movement during non function related fixed positions when in dynamic upright function.  Force would have to balanced across all 3 planes of motion (as function is three dimensional) and also relate to three dimensional external forces acting on the body. This would also diminish applicability of non specific strength training to functional performance.

The body has found a unique way of controlling and harnessing external force for force production and energy and information efficiency. This would be the load to explode of eccentric before concentric muscular actions involved in the stretch shorten cycle. The vast majority of functions use this process from hitting or throwing a ball to standing up from a chair (we flex forward before extending). This action of creating tensile force on the muscle elicits the myotatic reflex for neurological muscular activation vital in functional force production and also storage and recoil of kinetic energy from the more passive myofascial structures such as tendons. We know that energy conservation is vital to prolonged force production involved in sporting endurance. As energy decreases so does skill and likely hood of injury.

As always this is purely my personal opinion on the concept of strength. It is a different view from the traditional paradigm and may not be shared by strength purists. However differing opinions are vital to understanding the complexities of the human body we all love and cherish!

Ben Cormack

 

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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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