The Rectus Abdominals

v  Origin – crest and symphysis of the pubis

v  Insertion – cartilage of 5,6 and 7 ribs and xiphod of the sternum. It adheres to the anterior layer of facia and linea alba

Traditional  Movements

v  Flexes the trunk if the pelvis is fixed

v  Lifts and posterior rotates the pelvis if the trunk is fixed

v  Bends the trunk to the ipsilateral side when stimulated unilaterally

Functional Movements

v  Assist in compression the abdomen

v  Assist in intra abdominal pressure

v  Decelerates trunk extension

v  Stabilise the contralateral side under dynamic conditions

v  Deceleration of pelvis motion during gait

v  Decelerates shoulder motion during gait

v  Creates elastic energy for locomotion

v  Stabiliser of the ribs during concentric motion of the shoulder girdle and scapular

v  Assist in inspiration and expiration (by attachments via the linea able, with the internal and external oblique)

v  Assist in forced expiration

v  Decelerates anterior rotation of the pelvis

v  Cross roads of the motion during rotation movements

The outer sling systems in action during gait

Part 1

The best way to see how the outer systems perform their true function is seeing it at its natural: that of gait. During gait there is a consistent activation of the inner unit, this activation though low it is strong enough to provide the correct amount of stiffness to joints which allows for more motion of the outer unit. The constant fluctuation of recruitment provided by the inner unit will differ as needed due to the principle laws of mechanics and the neurological reflex reactions created by the internal and external environment will provide the stimulus that is needed for amount of firing as needed to provide adequate joint stiffness and support. During the gait cycle, we swing one leg forward and the opposite arm back, termed counter- rotation. As we are about to strike a foot on the ground, the hamstring muscles become active this starts the process of turning on the deep longitudinal systems which uses the thoracic lumber facia, sacro-tuberous ligament and spinal muscles to transmit the kinetic energy provided by the ground and motion above the line of the pelvis to provide stabilisation of the sacro -iliac joint by tension created at the hamstring (bicep femors) and spinal muscle. This works to transmit energy up and down the kinetic chain, as the bicep femurs has a communication system with the peroneus trough the deep longitudinal system it allows for around 18% of the contraction forces created by the deep longitudinal system (bicep femurs) into the facia of the peroneus longus. Due to the attachment of the peroneal longus with the first metal tarsal and as the anterior tibialis also attach to the same place, this combination makes the motion of heal strike a co-contraction of peroneal longs and the anterior tibialis, via recruitment of the bicep femurs muscle vital in stabilisation of the lower leg and foot (deep longitudinal system). At this time the bicep femurs activates prior to heal strike which induces the foot to dosro flex and in turn activates a wind up of the thoracic lumber facia which performs a stabilisation act upon the lower extremities and the lumber, pelvis, hip complex and storing the kinetic force produced ready for the propulsive phase of gait.

Kicking for Success

The striking of an object with the foot is a uniquely specialised activity and needs specialised discussion, as the action it produces is the only common form of striking that does not directly involve motion from the arms. It is with this in mind that an understanding of the qualitative analysis, with a special interest of the open skill and a discrete motor sequence of kicking involved in the game of soccer. This discussion shall focus of such motion. In soccer the range shown to  the various techniques used to strike a football are numerous with a vast amount of angles in which to strike the ball from whether it be a side pass to a instep drive , they can range from a low velocity pass to a fellow player standing a small distance away using the side of the foot, a concentrated effort required when a stationary football needs precise accuracy and a high velocity when taking a penalty kick to the maximal effect needed and the Optimal angles involved when lifting a football from the ground and over participants’ heads away from your own goal; it is the latter statement that this topic is based upon using the skills involved with the instep. Throughout this discussion it is up to the reader to take a holistic approach to the skill of kicking and continue the research needed for a complete picture to the skill of kicking.

The highest speeds involved with striking a football have been quoted to be in excess of 30 m/s, and it is where the contact is needed to be with the instep of the foot for these speeds to be reached. It has also been seen that there is a 4 fold increase from the velocity produced by the three dimension motion created at the hip (5 m/s) to the velocity that the ball leaves the toes, with the knee and ankle increasing their velocity to the transfer of kinetic energy needed at 7 m/s and 15 m/s respectably. This interesting sequences of events has been shown in the sequential motion associated with the hip, knee and ankle motion or otherwise known as the proximal-to-distal sequence ( this describes the way energy within the muscles  is associated around  the hip, knee and ankle to the speed the ball leaves the toe). Looking within the figures above, the football leaves the foot within 0.22≈ seconds after initial contact and the timing of sequences involved in the destitution of force effecting the kick is shown as, hip 0.1≈, knee 0.15≈ with the ankle and toe showing a minimal difference at around 2≈. With the above information it is apparent that the striking of a football is a finite interaction of neuromuscular control and any timing, difficulties within this timing and control can then have an impact on the quality of motion need in produce an optimal kicking sequence. The instep kick in football has shown to have some major phases of motion, the following is a short description of the phases involved with a more in-depth discussion consisting the remaining of this topic.

The mature form of the kicking skill has been characterized by an approach to the ball of one or more strides with the final stride being that of a jump, step or lung. The placement of the supporting foot is at the side, and slightly behind the stationary ball. The kicking leg is first taken backwards and the leg flexes at the knee (called leg cocking). The motion of the swing leg initiates a action-reaction of the opposite arm (Newton’s third law of motion: If a body exerts a force on another, there is an equal and opposite force, called a reaction on the first body by the second) Forward motion is initiated by rotating the pelvis around the vertical axis (the supporting leg) and by bringing the thigh of the kicking leg forwards while the knee continues to extend. Once this initial action has taken place, the thigh begins to decelerate until it is essentially motionless at ball contact and the action-reaction causes the opposite arm to the kicking leg to reverse their rotations around its vertical axis. During this deceleration, the shank vigorously extends about the knee to almost full extension at ball contact the leg remains straight through ball contact and begins to extend during the long follow-through. The foot often reaches above the level of the hip during the follow-through.and a final jump or hop can be seen when conservation of momentum continues past its point of impact.

A characteristic of soccer kicking is the approach angle that the player takes to kick a stationary ball. Experiments have used various approach angles to established optimal alignment, these include angles where a participant was required to take a one-step run-up to kick a stationary ball using approach angles of 0, 15, 30, 45, 60 and 90° (the direction of the kick was 0°). As stated previously there is a 4 fold increases from the velocity of motion around the hip to the velocity produced by the toes at impact, this suggest that the motion of the shank (being involved with both the knee and ankle) in extension prior to impact influences the final speed in which the ball leaves the toe. The maximum velocity of the shank was achieved with an approach angle of 30° and the maximum ball speed with an approach angle of 45°.Therefore, an approach angle of 30 to 45° would appear an optimum angle for both velocity of the extension of the shank and maximal speed of the ball being reached at impacts. The explanation given for this is that an angled approach has three advantages, firstly the approach angle enables the leg to be tilted in the frontal plane towards the football with the standing leg being in slight flexion, without this lean the swing leg would not have enough clearance to make contact with the optimal angle of the ball as this swing leg needs to be in extension prior to impact for optimal alignment, without this lean the swing leg would make contact with the floor or a change in mechanics is needed for the swing leg to clear the ground resulting in instability of a stable base which is needed for the optimal kicking performance . The second advantage it provides is that the foot can if required, be placed further under the ball thus making a better contact and allowing for better control of the foot, the better control of the foot allows the foot to move across the ball, this gives a greater scope for the foot to apply spin to the football in any direction required. Finally during impact the swing leg will follow a path of a lateral to medial plane, this allows a transverse rotation of the pelvis (vertical axis) as well as the frontal devotion (ant-post axis) due to the lean into the ball, and the lean of the trunk (which will be explained later) enables the midsection (med-lat axis) to be loaded in a tri plane coupling (tri-plane axis, all axis and corresponding muscles are loaded-stretched  ready to be unloaded-contract) which enables a greater action-reaction of the upper trunk ( Newton’s third law) to counter-react against the motion created by the pelvis resulting in the opposite arm and leg meeting on impact and a greater force production impacted on the ball.

The placement of the supporting foot has received little attention in soccer. The optimal foot plant position for accurate direction is perpendicular to a line drawn through the centre of the ball for a straight kick. The ideal medial- lateral position of the plant foot as 5 to 10 centimetres to the left of the ball (assuming a right-footed kick), it is explained that if the plant foot is greater than 10 centimetres away from the ball, the direction of the kick and the kicker’s balance can both be compromised. The ideal anterior-posterior position of the plant foot is when kicking is adjacent to and in line with the ball. The anterior-posterior position of the plant foot is what determines the trajectory or flight path of the kicked ball. Novices tend to plant their foot behind the ball, which produces a higher ball flight path, whereas a forward plant foot position results in a low trajectory Foot placements in elite junior soccer players of 38 cm behind the ball centre, and 37 cm to the side of the ball centre. From other codes of football, it has been reported that the supporting foot should be placed 5 to 10 cm to the side of the ball, but the anterior-posterior positioning is equivocal, and suggesting say a placement of 5 to 28 cm behind the ball It is likely that the anterior-posterior positioning is a function of the type of kick performed and whether it is intended to keep the trajectory of the ball low or to make it go high.

During the last few years it has been noted that individuals who are involved in a kicking sport have taken advice from rugby. The crosses over from kicking a rugby ball to a football are very closely, if not identical in their motor patterns except for a few small changes. In football an instep kick from a stationary ball like those motions of a place kick by goalkeeper seem to produce a lateral to medial motion around the vertical axis, this has a biomechanical advantage for the tri plane loading of the kinetic chain, but a down side is seen in many who’s motor pattern has not matured enough to optimise this motion. An individual seen above may during the course of a kick and especially when induced by mental and physical fatigue as well biomechanical changes, could have a tendency to slice or hook the ball very much like those of a golfer, this will certainly reduce the accuracy and direction of the kick. In rugby, the kick is all dependent on the very finite accuracy and direction needed to covert a kick, where even if the accuracy of a goal kicker is poor as long as the ball arrives in the area of the team players this seems to be enough. There is information which has been taken from rugby in attempting to produce more accuracy through the biomechanical pattern of the kick, when the goalkeeper strikes a football we see that there is a angle of approach (this as discussed is vital for many reasons), and when there is impact it is shown that the leg performs the lateral- medial pattern around the vertical axis, if this path is traced it can be seen to be that of a C shape motion (from the initial run up to the impact implanted on the ball). Where rugby differs, and has been quoted to be more accurate in there kicking is, when the leg performs its lateral motion and preparing for the action back into the medial plane the angle is smaller, and where in football the swing leg appears to end past midline (the line between the standing leg and the swing leg on impact) in rugby the swing leg only goes through little medial rotation and never crosses the mid line, if this path is to be traced it will form a J shape pattern. This difference in the kicking styles allows the foot to lead the knee, shank and hip in pointing to the direction the ball is intended to go and enables the kicker to minimise a slice or hook. This seems to be an obvious statement but more research is needed to whether the C or J shape is better for accuracy and direction of a ball, as changing the kicking pattern can change the mechanics of the kick from the initial run up to the impact on ball strike (it also is interesting to see that the kicker in rugby has a smaller run up and a slightly increased approach angle then a football kicker).     

        

It is to be expected, up to a point, that a longer and faster approach would be a benefit in the generation of high ball speed, but due to the last stride being a jump, step or lung the speed on approach is influenced by the neuromuscular timing and sequencing of proximal-distal sequencing, the motor patens of repetition and the stride length, stride rate and cadence. Again there seems to be an understanding to the differences between a stationary and running approach when making a maximal instep kick. Maximum ball speeds of 23.5 m s- 1 when using a stationary approach and 30.8 m s- 1 when using a 5 to 8 Stride running approach. This approach suggest that the running approach has a greater influence not only on the momentum of conservation transferred through the kinetic chain but also in the maximal velocity required at impact through the toes to the ball, but a concern arises when excess speed compensates for a inadequate motor pattern. It is interesting to note how sprinters and long jumpers approach the acceleration phase of the sprint, as both of these sports will have to braking force applied to the ground either to stop or to apply force upon the ground and create an opposite reaction in directing them vertically and horizontal at take off.

During the start of a 100 meter event it’s recommended that the first stride is 50 cm in front of the front leg (by their rear leg), and is increased 10cm with each stride until full acceleration is achieved. This works out that there are 50 strides per 100 meters, 2 meters per stride, and leading up to 2.30 meters per stride which is the top stride rate. This stride rate occurs after 19 strides and approximately at 27 meters. it is after this 19 stride or 27 meter mark where the sprinters posture is vertical and in full stride, it has also been mentioned that these figures can increase to 15 cm after the first stride up to a maximum of 2.50 meters per stride, resulting in 14 strides in 22 meters, but these results seem to relay on the power, height of the individual and the length of the lower limbs. From these findings and using the equations stride length= height of individual  and stride rate=length of lower limb² (² being the square of either the height or length), an optimal running stride, stride rate and cadence can be equated for each individual. Due to the sequence of the last stride, being a jump, step or lung there is adapted compensation effect carried out due to the high impact produced through the kinetic chain, and with an increase in speed preferred over a motor paten this will require a deceleration and braking effect applied to the foot and up the kinetic chain reducing momentum in both vertical (ground reaction forces, centre of gravity) and horizontal (frictional forces) planes and force production in both theses directions decreases. An understanding of the optimal stride length and stride rate using the equations above along with an increase in stride length shown in the 100 meter sprinter and optimal performance for each individual can be implemented.

The long jump is an event that requires an athlete to jump as far as possible from a fast run up into a pit of sand. The distance jumped is largely determined by the flight distance and this is determined by the height, speed, and angle of projection of the centre of mass at takeoff. The speed and angle of projection are determined by the combination of horizontal and vertical velocity. The horizontal velocity is developed through the approach run, which is usually of sufficient length for the athlete to be close to maximum speed at

The takeoff board.

The vertical velocity is generated during contact with the board. If we assume that the athlete is able to generate maximum speed close to the board, the problem of long jumping becomes one of generating vertical velocity from the board. This vertical and horizontal velocity needed for distance in a jump has a close correlation with our kicker. As our kicker approaches the ball the amount of vertical and horizontal distance to the football is reliant on the amount of vertical and horizontal motion created by the proximal to distal segments and ultimately to the whole body as seen when the final position of the body is forward and upward of impact. But as previous stated a jump, step or lung when in the last stride is a fine coordination of the motor pattern whether in a open or closed loop control and comes across some mechanical advantages which if conditioned allows for the conservation of momentum to continue into impact and not lost in kinetic energy to the ground (some is lost which enables for ground reaction force to be used in vertical and horizontal motion). When the final stride is approached and a jump, step or lung is taken, there is pivot mechanism seen in the long jump which may enhance kicking. The pivot mechanism explains three of the main observations of the touch-down in the long jump, which are that successful jumpers have (a) a high approach speed, (b) a low centre of mass at touch-down and (c) a leg at touch-down which is extended in front of the body. The low centre-of-mass position enables the touch-down leg to be flatter to the ground when contact is made and is seen on contact phase of the last stride, thus creating the conditions for the pivot, while the high approach speed ensures the pivot is functional allowing the body to rise over the standing leg and continue the momentum up and forward. Furthermore, the pivot mechanism also explains why the high approach velocity is related to distance jumped. It is the combination of high horizontal velocity (generated through the approach run) and high vertical velocity (generated by the pivot) that enables a greater distance to be jumped, which can relate to the final body position seen after the football is struck. Due to the vertical and horizontal motion of the legs, arms and torso (in it’s every changing centre of gravity) the velocity of the proximal to distal segments as well as the velocity of the ball is at maximum. It is important not only to look at football for inspiration but to activities that closely resemble the motion in which you are studying.

Before we leave this section of approach angles and speed an interesting sequence of motion that is too often neglected is the action of posture in motor patterns. During the action of the kick there is a sequence of proximal to distal timing of the transfer of kinetic energy seen from the hips to the toes, with times as short as 0.15 (15 ms) to 0.2 (20 ms) seconds but what about the motions of the arms. We have seen that as motion occurs at the hips there is a counter reaction created within the mid section to produce an equal but opposite reaction of the arms so we have controlateral motion, but before the shoulder muscles allow for the pendulum motion of the arms to make this reaction, some 80ms before the shoulder starts to move there is activation within the lower back and legs muscles enabling the oscillation of motion to be small. Along with this timing of the back and legs in making their adjustments, it has been seen that some 10 to20 ms before the action of the hip allows for proximal to distal motion to the toes to occur, the muscles around the lower back switch on for the adjustment needed to counter balance the postural oscillation as shown. This short but precise input regarding of timing throughout the kinetic chain, and especially in motion associated with the arms a and legs, should make coaches question their core training when dealing with complex motor patterns such as  kicking.        

Transverse Abdominis (TVA) and its Function in Lower Back Stability

Lower Back Pain (LBP) as a generic term and is the main cause of work related absence and disability in industrialised societies (Frank, Kerr, Brooker, DeMaio, Maetzel, Shannon, Sullivan, Norman and Wells, 1996). It is suggested by Maniadakis and Gray (2000) that musculoskeletal disorder is the most commonly reported type of work related illness and back pain is the nation's leading cause of disability, with 1.1 million people disabled by it (Labour Force Survey, 1998). An estimated 80% of people will experience back pain at some time in their lives (O'Sullivan. 2005; Back Pain Association, 2006). Conditions experienced can be varied and include prolapsed discs, disc degeneration, osteoarthritis of the apophyseal joints, osteoporosis, and spondylolisthesis (Kelsey and White, 1980) and forty nine percent of the UK adult population report back pain lasting at least 24 hours (Back Pain Association, 2006.)

It is these musculoskeletal disorders that have been linked to trunk instability of the stabilizing muscles situated in proximity of the lower back (Marras and Mirka, 1996; Gorbet, Selkow, Hart and Saliba, 2009). But what is the classification of trunk stability?

Trunk stability is defined as the ability of the spinal column to survive an applied perturbation (Grenier and McGill, 2008) or a loss of spinal stiffness (Pope and Panjabi, 1985). Instability is often a term used to describe a mechanical lack of stability between two spinal segments and is considered to be present when there is "an excessive range of abnormal movement for which there is no protective muscular control" (Maitland, 1986) from stabilizing muscles, with the result being a loss of spinal stiffness (Pope and Panjabi, 1985) and a lack of survival application to applied perturbation (Grenier and McGill, 2008). Amongst the many muscles which may contribute to such stability, recent focus has turned its intention to the performance of the abdominal muscularity and in particular one abdominal muscle, known as the transverses abdominals (TVA) (Robinson, 1992).

The TVA is the deepest of the abdominal muscles (Miller and Medeiros 1987; Jull, Richardson, Hodge and Hide, 1999) and is said to be used for trunk stabilization purposes (Reiman, Harris and Cleland, 2009). The anatomical attachment of the TVA was described by Gray (2008) graphically and verbally. The TVA arises, as fleshy fibres from the lateral third of the inguinal ligament, from the anterior three-fourths of the inner lip of the iliac crest, from the inner surfaces of the cartilages of the lower six ribs, integrating with the diaphragm, and from the lumbodorsal fascia.

The muscle ends interiorly in a broad aponeurosis, the lower fibres of which curve infer medially (medially and downward) and are inserted, together with those of the internal oblique muscle, into the crest of the pubis and pectineal line, forming the conjoint tendon. In layperson's terminology, the muscle ends in the middle line of the linear Alba, in conjunction with the rectus abdomens and the internal and external oblique.

Functioning like a corset (within a serape effect; Konin, Beil and Werner, 2003) due to its orientation to the linear Alba, the TVA (according to Bliss, 2005) function is to stabilize the lower back before movement of the arms and/or legs occurs. This function is critical if wear and tear of the joints in your low back is to be prevented. Richardson, Sniijders, Hides, Damen, Pas and Storm (2002) also highlight that one of the most important actions of the TVA that achieves the most stabilisation is to draw-in the abdominal (hollow) or to brace in activating this corset. This in turn forms a relationship with the process of intra-abdominal pressure and its numerous correlated mechanical principles (Porter, 1986).

Hodges and Richardson (1997) undertook a study which used needle electrodes on the TVA, deltoid and upper legs in attempt to establish the activation timing sequence of the TVA prior to limb movements. They suggested that when arm movement is performed, the onset of TVA activity precedes that of deltoid by approximately 30 milliseconds. In contrast, when the leg is moved (producing reactive forces of greater magnitude due to the increased mass), activation of TVA precedes that of deltoid by more than 100 milliseconds. This supports the proposal that the contraction of the TVA muscle prior to the movement of a limb may contribute to the control of stability of the adjacent joints in addition to controlling the position of the centre of gravity within the base of support, especially when the stability of the lumbar spine is challenged by rapid motion of the upper limb. They continued and suggested that the TVA is the first trunk muscle to activate, and the onset of its activity is not significantly affected by the direction of the reactive forces.

A few years before the Hodges and Richardson (1997) findings, Creswell, Oddsson and Thorstensson (1994) reported a similar trend with self-induced ventral perturbations trunk loading and where the time of arrival of the insult could be predicted. These authors reported activity of TVA to proceed that of the rectus abdominals and internal and external obliques by 65-120 ms, which is comparable to the range reported in the Hodges and Richardson (1997) study of 10-117 milliseconds. With such contrasting values a look at the possible reason for this is worth investigating.

The Richardson and Hodges (1997) study involved the identification of the sequence of contraction of the trunk and limb muscles during hip flexion, abduction, and extension, with no external resistance, and with no initial motion of the spine. However, the Creswell et al (1999) study looked at ventral or dorsal (spine) load when sudden loading was applied to the trunk which had attached to it a 5 kg resistance. It is possible that activity of the TVA prior to that of the rectus abdominals, internal and external oblique's may have been in perturbation to the expected ventral loading condition which may indicates a feed-forward postural strategy designed to increase the stability of the TVA for the ensuing sudden load (Cresswell, 1993) and which may be partly contributed by the effect of hollowing or bracing the TVA.

A study by Richardson et al (2002), the same group who identified the above timing sequencing of the TVA, compared the effect of abdominal hollowing against abdominal bracing in lower back stabilization efficacy. They found hollowing increased the stability significantly more than bracing, suggesting that hollowing is both more functionally effective and more energy efficient. Abdominal hollowing using predominantly TVA contraction leaves the prime movers of trunk rotation; the internal and external oblique free to mobilise the trunk in the rotary fashion, (Gracovetsky, 1988). This something which may contribute to the differences in the timing of the TVA in the Richardson and Hodges (1997) and Creswell et al ( 1999) studies.

A few years later Hides, Wilson, Stanton; McMahon, Keto, McMahon, Bryant, and Richardson (2006) investigated this corset effect using magnetic resonance imaging (MRI), of the bilateral function of the TVA during a drawing-in of the abdominal wall. They validated the study with the use of real-time ultrasound imaging as a measure of the deep abdominal muscle during a drawing-in of the abdominal wall. They demonstrated that the MRI results indicated that during a drawing-in action, the TVA contracts bilaterally to form a musculofascial band that appears to tighten (a corset) and most likely improves the stabilization of the lower back region.

However, with all theories and beliefs, counter theories and beliefs occur. Siff (2003) discerned that the combined force directions of the external and internal obliques can produce the force direction of the TVA, thereby carrying out roles like those of TVA. In other words, if active internal oblique muscles pull along one diagonal across the trunk and active external obliques pulling along the inverse diagonal, the resultant force will exerted roughly parallel to the floor (if you are standing), in other words in the same direction as tension in the TVA.

This vector resultant alone may be more than adequate to compensate for any apparently undesirable TVA malingering. Moreover, activation of a muscle still does not prove its function. McGill (2001) also found similar findings regarding Siff's (2003) work by stating that some confusion exists in the interpretation of the literature regarding the issue of abdominal hollowing and abdominal bracing. McGill (2001) said that Richardson et al (2009) observed that the hollowing of the abdominal wall recruits the transverse abdominals. On the other hand, an isometric abdominal brace co-activates the transverse abdominals with the external and internal oblique's to ensure stability in virtually all modes of possible instability (Juker, McGill, Kropf and Steffen, 1998). McGill (2001) then neither finished by stating that in bracing the wall is neither hollowed in nor pushed out. In this way, abdominal bracing is superior to abdominal hollowing in ensuring stability.

This said, the former studies by Richardson et al (1991) and Hides et al (2006) support the findings by Teyhen, Miltenberger, Deiters, Del Toro, Pulliam, Childs, Boyes and Flynn (2005) who looked at patients with LBP to determine the characteristics and the extent to which the abdominal drawing-in manoeuvre (hollowing) results in preferential activation of the TVA. On average, LBP patients demonstrated a two-fold increase in the thickness of the TVA during the hollowing manoeuvre. This provided validity for the notion that hollowing results in preferential activation of the TVA in patients with LBP.

Supporting the hollowing hypothesis is the concept that the TVA has a higher level of slow twitch muscle fibres (Fredericson and Moore, 2005) with a suggestion that the TVA pre-contracts, supporting the visceral fulcrum theory and the ethos that the TVA contracts prior to any limb movement (Hodges, 1999). The visceral fulcrum theory is a counter force generated by the visceral when the TVA contracts and provides a functional cylinder around the spine (Hodges, 1999). Hodges (1999) also mentions a further contribution of the TVA to spinal stability regarding intra abdominal pressure. In the original Creswell et al (1994) study which identified TVA activation prior to other abdominal muscularity in loading, they also identified IAP in relation to spinal stability.

Creswell et al (1994) positioned intra-abdominal pressure (IAP) transducer in the gastric ventricle with intra-muscular electromyography electrode placed the TVA, what they summarised was IAP and TVA muscle contractions may result in an increased stiffening of the inter-vertebral joints within the lumbar spine and thereby simplify the control of subsequent extensor torque development by dorsal musculature. Additionally, a trunk extensor moment, although low in magnitude, may be developed through the increased IAP.

The development of techniques such as fine wire electromyography (EMG) activity along with the guidance of ultrasound imaging has allowed the direct investigation of the recruitment of the TVA muscle (Goldman, Lehr, Millar and Silver, 1987; De Troyer, Estenne, Ninane, VanGansbeke and Gorini, 1990; Creswell, Grundstrom and Thorstensson, 1992). According to Hodges (1999) the first investigations of the TVA as a possible contributor to spinal control were performed by Creswell et al (1992). These studies were stimulated by the observation that high intra-abdominal pressure was present during isometric trunk extension, measured with surface EMG electrodes. However, little activity of Rectus Abdominals, along with External and Internal Obliques could be detected with surface EMG electrodes (Creswell and Thorstensson, 1989). Thus the TVA was postulated to be responsible for this pressure increase since it can generate pressure without opposing the trunk extensor moment (Creswell et al, 1992). Creswell (1993) stated this as being unexpected with the continuous (but varying) activity of TVA and its close relationship to intra-abdominal pressure leading the authors to conclude that TVA may contribute to a general mechanism for trunk stabilization rather than the production of torque or control of orientation of the spine.

This close relationship of intra abdominal pressure and TVA activation is seen to be vital as intra-abdominal pressure produces what is defined as 'hoop tension'; a force applied circumferentially to the spine that creates hoop stress, which serves to stabilize the lumbar spine, by the generating of lateral tension on the thoracolumbar fascia. The superficial lamina of the posterior layer of thoracolumbar fascia generates tension downward via its attachments at the lumbar vertebrae two (L2) and three (L3), while the deep lamina generates tension upward through its attachments at lumber vertebrae four (L3) and five (L5). These mutually opposing vectors tend to approximate or oppose separation of the L2 and L4 vertebra and the L3 and L5 vertebra, creating what is referred to as "Thoracolumbar Fascia Gain" (Gracovetsky, 1988; White & Panjabi, 1990 and Bogduk & Towmey, 1991).

This occurs due to the lateral raphe of the thoracolumbar fascia passing medially to the linear
Alba (Bogduk and MacIntosh, 1984). Due to this horizontal Fibre orientation, contraction of TVA results in a reduction of abdominal circumference with a resultant increase in tension in the thoracolumbar fascia and an increase in intra-abdominal pressure. This according to (McGill, 2001) provides evidence of the TVA being a strong spinal stabilizer as it has only a limited ability to produce trunk motion.

One final point regarding the workings of the TVA is the mathematical model originally described by Gracovetsky (1988). This model is induced by the process of intra-abdominal pressure and is known as "The mechanical Amplifier Affect". Gracovetsky (1988) demonstrated the extension force produced by expansion of the erector spine muscles within the compartment created by the thoracolumbar fascia and lamina groove of the spine to be a significant contributor to one's ability to lift a load. The expansion of the muscles within the thoracolumbar fascia produces intra-compartmental pressure (ICP). The cylinder is stabilized by synergistic activation of the transverses abdominals (TVA) and posterior fibres of the internal oblique (IO). The results indicated that intra-abdominal pressure increased following the activation of TVA and was early enough to precede the onset of limb movement and could contribute mechanically to the preparatory process occurring prior to limb movement as previously mentioned (Creswell, et al 1994; Hodges and Richardson. 1999).

Throughout this essay, cases for and against the role regarding the TVA activation in the stabilisation of the lower back have been documented. This essay accepts that there was no focus on breathing mechanics and the functioning of the diaphragm, which may contribute to spinal stability. This said, future endeavours regarding breathing and the diaphragm need investigating. Regarding future studies, this essay only focused on those individuals who are able bodied and not with any form of disability which brings up the following questions: Firstly, does the activation of the TVA become more important if a disability has occurred? Secondly, would some of the above findings contribute to making the rehabilitation process quicker and smoother when recovering from an accident? Finally, does activation of the TVA enhance ability to use prosthesis or a wheelchair easier with less lower back discomfort which may occur due to the change in skeletal, muscular and neurone motion? In conclusions these are all valid questions that would need further investigation and are beyond the limitations of this essay.

References

Back Pain Association. Backfacts. Available: www.backpain.org/pdfs/backfacts-uk-2005.pdf 2006.
Bliss LS. Core Stability: The Centrepiece of Any Training Program. Current Sports Medicine Reports, 4 (3) pp 179-183. 2005.
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Answering the Question from Daniel

Hi Daniel

 
I hope you are well. Thank you for reading my blog and asking a question. You question seem to have main points.

1. The hypothesis of Natural

 

2. The subjective view of observation

1. Natural movement is a continuum regarding the reaction to an action event of the sequential algorithm to the desired outcome. This occurs through the internalisation and externalisation reference frame for survival in accordance and organisation with the laws of mechanical physics and human engineering. These observations are postulated based upon the subdued and full- field human responses.

2. It is worth stating that I see myself as a philosopher and not a scientist (though I have a science background). In my opinion observations are subjective and once quantified natural movement no longer becomes natural. Thus any attempt to quantify natural human movement goes against naturality. It is good to remember that for every one objective answer births the dawn of a magnitude of subjective dreams, and it is this dream which brings scientific evolution.

‘’ There are those who are trying to find answers to a question- they are called scientist. There are those who are questions such answers- we are called dreamer’s ’’

WHICH ONE ARE YOU

I hope this answers your questions; please ask more regarding any blog article

Yours

Steve Braybrook

Bsc, Msc, Mpt

The Re-Act Principle: A new principle in Movement Dynamics.

All sporting and non- sporting actions have one thing in common; they are all based upon principles of natural human movement. The only difference is the end outcome that is to be accomplished. In the sporting world numerous documented specific drills and training protocols have been devised in an attempt to enhance these natural movements and although the majority of these drills and protocols have been developed through scientific evaluation of the sport in question resulting in specific coaching techniques, actual natural human movement principles themselves appear to be very scarce.

These natural human movement principles I refer to as being the Re-Act principle, which is the reaction to the initial action sequencing and may provide coaches with additional knowledge to pass onto their participants. The following are a very small selection of questions that I would like to share in response to hypothesising Re-Act Principle

A.    How many times does a single foot touch the ground before an internal reference frame requires a Re-Act?

B.     How many times does a single foot touch the ground before an external reference frame requires a Re-Act?

C.     How many times do both feet touch the ground during the Re-Act sequence?

D.    Why are we attempting to control our centre of mass and base of support when loading response needs minimising?

E.     Why do we attempt to control gravity, ground reaction principles and the principles of linear and rotation mechanics when these are given to us for free?

F.   Finally, when implementing the Re-Act, where and when does the initial chain reaction occur from? and where and when does it end?

The Re-Act principle is based upon observation of natural human movement, both from sporting and non-sporting activities and attempts to give those who want to optimise their own actions a new perspective to both training and life.

Introduction to Kicking

The mature form of the kicking skill has been characterized by an approach to the ball of one or more strides with the final stride being that of a jump, step or lunge. The placement of the supporting foot is at the side, and slightly behind the stationary ball. The kicking leg is first taken backwards and the leg flexes at the knee (called leg cocking). The motion of the swing leg initiates an action-reaction of the opposite arm (Newton’s third law of motion: if a body exerts a force on another, there is an equal and opposite force, called a reaction on the first body by the second). Forward motion is initiated by rotating the pelvis around the vertical axis (the supporting leg) and by bringing the thigh of the kicking leg forwards while the knee continues to extend. Once this initial action has taken place, the thigh begins to decelerate until it is essentially motionless at ball contact and the action-reaction causes the opposite arm to the kicking leg to reverse their rotations around its vertical axis. During this deceleration, the shank vigorously extends about the knee to almost full extension at ball contact the leg remains straight through ball contact and begins to extend during the long follow-through. The foot often reaches above the level of the hip during the follow-through and a final jump or hop can be seen when conservation of momentum continues past its point of impact.

Abstact:Introduction to impact force and muscle turning

Researcher's such as Dekel and Weissman, 1978; Radin et al., 1973, 1978 and Serink et al., 1977) state that If the joints are regularly submitted to such high-frequency impact force peaks, subchondral bone and articular cartilage begin to degenerate with speculation that these ‘impact force peaks’ are the causative factors in the development of lower back pain and running injuries in runners (Clement et al., 1981; James et al., 1978).

In an attempt to minimise these impact forces, changing the foot and leg geometry along with ankle and knee joint stiffness have been described by Lafortune, Hennig and Lake (1995) as being important developmentally both individually as well as collectively. Nigg (1997) suggested that the strategy of changing the coupling between the soft and rigid structures of the individuals’ leg termed ''Muscle Tuning'', may also be of much importance.

Nigg (1997) spoke of the muscle turning as a concept suggesting that the impact forces during heel strike should be considered as an input signal, characterized by amplitude and frequency. This impact force signal could produce bone vibrations at high frequencies and soft tissue vibrations of the human leg (e.g., triceps surae, quadriceps, or hamstrings muscles) at frequencies that might concur with the frequencies of the input signal.

Abstract on windlass mechanics

It is during the action of dorsiflexion of the toes, which occurs in late stance phase that the plantar aponeurosis is stretched as it wraps around the metatarsal heads. This is the so-called windlass mechanism. Windlass is the tightening of a rope or cable (Viel and Esnault, 1989), which according to Hicks (1954) is like a triangular structure or truss, which occurs in the late phase of stance. This windlass is responsible for the stretch tension from the plantar fascia preventing the spreading of the calcaneus and the metatarsals and maintainsing the medial longitudinal arch (Fuller, 2000), which contributes to stiffening of the foot by pulling on the heel, causing inversion at the subtalar joint and `locking' the midtarsal joint (Briggs and Tansey, 2001). This occurs by shortening the distance between the calcaneus and metatarsals with the plantar fascia forming the tie-rod that runs from the calcaneus to the phalanges via the midtarsal joint, which carries as much as 14% of the total load on the foot whilst lowering the arch degenerates the load bearing capacity of the foot (Kim and  Voloshin,1985).

Abstract on the proximal to distal sequencing

There are currently two explanations for the proximal-to-distal sequence, both based on the principle of conservation of angular momentum. Theory One ''external moment'' states that once the motion of the system begins, an angular momentum is developed in the system and the distal segment lags behind. As the proximal segment approaches maximum velocity, an external force opposes this motion, which negatively accelerates the proximal segment, allowing inertia to propel the distal segment forward (Ford, 1998; Marshal and Elliott, 1999). Theory Two '' internal moment'' contends that no external torque is applied to the system after the initial acceleration of the system takes place. The system with some mass, is said to move with a given angular velocity, thus having an angular momentum, which is conserved throughout the action (Putnam ,1983: Ford, 1998).

However, these theorys may not  tell the full story and may infact only explain partial representation.