Chains, trains and contractile fields
2010; Elsevier BV; Volume: 14; Issue: 4 Linguagem: Inglês
10.1016/j.jbmt.2010.07.001
ISSN1532-9283
Autores Tópico(s)Tribology and Wear Analysis
ResumoIn the film, Planes, Trains and Automobiles, the underlying theme is that two men are trying to get home in time for a major social celebration. The story is focused around the challenges these men face as the route from a to b became increasingly convoluted and indirect. In animal locomotion, this same theme of getting from a to b in the most efficient way is often a key aspect of organismal evolutionary fitness. However, there may be some cases in which a more convoluted, indirect route may be of survival benefit; for example, if you were to track a course of musculature around the body in a spiral fashion (Beach, 2007Beach P. The contractile field – a new model of human movement.Journal of Bodywork and Movement Therapies. 2007; 11: 308-317Abstract Full Text Full Text PDF Scopus (6) Google Scholar; Wallden, 2008Wallden M. Rehabilitation and Movement Re-education Approaches. Naturopathic Physical Medicine. Elsevier, 2008Google Scholar; Myers, 2001Myers T. The Anatomy Trains. Churchill Livingstone, 2001Google Scholar), the longer your route from a to b, the more muscle fibres can be utilised, and therefore the more power can be generated. This is why when power generation occurs in sports, such as when hitting, throwing, kicking or punching, it typically involves a rotary twist of the body; to access this fast twitch spiral musculature coursing from the lower limb through and around the trunk, and back out via a different limb to its extremity. Of course, the more powerful a movement, the less efficient it generally is; this applies as much to the human body as it does to planes trains and automobiles. If a Ferrari competes with smart car, the Ferrari may win, but in the long run, the Smart car will go further on the same amount of fuel. Equally, there is little sense in a creature retaining fuel if it is to be some other creatures dinner as a result. Organismal biological design still seems to have the edge on synthetic counterparts; especially in terms of versatility. Going even further back, prior to human evolution, may provide even deeper insight; for this, it is necessary to look back into deep time. Early life on Earth exhibited poor or limited motility; nevertheless, such motility was sufficient to satisfy survival within the presenting ecological niche that single-celled, photosynthesising organisms found themselves in. Early animal forms, such as sponges, anemones and jellyfish all showed very primitive circumferential movement patterns. These movement patterns have been described as the “radial chain” musculature (Beach, 1989Beach, P., 1989. Development of muscle chains theory. Personal communication.Google Scholar, Personal Communication) or “radial contractile field” (Beach, 2008Beach P. The contractile field – a new model of human movement – part 3.Journal of Bodywork and Movement Therapies. 2008; 12: 158-165Abstract Full Text Full Text PDF PubMed Scopus (2) Google Scholar; Wallden, 2008Wallden M. Rehabilitation and Movement Re-education Approaches. Naturopathic Physical Medicine. Elsevier, 2008Google Scholar). Later animal forms, such as flat worms and round worms also exhibit this circumferential movement pattern, but do so sequentially across body segments. It was not until the evolution of vertebrates in the form of fish that effective longitudinal contraction down the body wall could take place (Kardong, 2002Kardong, K., 2002. Vertebrates. McGraw-Hill, New York.Google Scholar; Wallden, 2008Wallden M. Rehabilitation and Movement Re-education Approaches. Naturopathic Physical Medicine. Elsevier, 2008Google Scholar). Subsequent development merely elaborated on the established fish-based body plan (Erwin et al., 1997Erwin D. Valentine J. Jablonski D. The origin of animal body plans.American Scientist. 1997; 85: 126-137Google Scholar); this was the premise of Gracovetsky, 1988Gracovetsky S. The Spinal Engine. Springer, Vienna1988Crossref Google Scholar Spinal Engine theory, the concept that the spine is what drives the legs forward; the limbs simply amplifying spinal motion in steady-state gait. Various thinkers from the exercise and rehabilitation fields have made attempts to understand these developments in the musculoskeletal function of organisms; among them early pioneers including Raymond A. Dart’s Double Helix Mechanism of the Spine, Phillip Beach’s Muscle Chains (1989), which evolved into a concept now called Contractile Fields (2007/2008), Andry Vleeming’s and Diane Lee’s Slings (Vleeming et al., 1997Vleeming, A., Snijders, C., Stoeckart, R., Mens, J., 1997. The role of the sacroiliac joins in coupling between spine, pelvis, legs and arms. In: Vleeming et al. (Eds.), Movemen, Stability & Low Back Pain. Churchill Livingstone, 53--71.Google Scholar) and Thomas Myer’s Anatomy Trains (2001). In short, these people – and many others alongside – were all doing “joined-up-thinking” in the field of human locomotor anatomy. In the last issue of this Journal, the co-editor of this section of JBMT, Warrick McNeill PT, included a paper on the importance of the deep longitudinal sling in hamstring strain (Panayi, 2010Panayi S. The need for lumbar-pelvic assessment in resolution of chronic hamstring strain.Journal of Bodywork and Movement Therapies. 2010; 14: 294-298Abstract Full Text Full Text PDF PubMed Scopus (29) Google Scholar). This sling, described by van Wingerden et al., 1996van Wingerden, J.P., Vleeming, A., Stoeckart, R., Raissadad, K., Snijders, C.J., 1996. Force transfer between biceps femoris and peroneus muscle; a proposal for a longitudinal spring mechanism in the leg.Google Scholar, Vleeming et al., 1997Vleeming, A., Snijders, C., Stoeckart, R., Mens, J., 1997. The role of the sacroiliac joins in coupling between spine, pelvis, legs and arms. In: Vleeming et al. (Eds.), Movemen, Stability & Low Back Pain. Churchill Livingstone, 53--71.Google Scholar and Gracovetsky, 1997Gracovetsky S. Linking the spinal engine with the legs: a theory of human gait.in: Vleeming A. Mooney V. Dorman T. Snijders C. Stoeckart R. Movement, Stability and Low Back Pain – The Essential Role of the Pelvis. Churchill Livingstone, New York1997: 243-252Google Scholar is key in both stabilization of the lumbopelvic complex and, Gracovetsky argues, in utilising ground reaction force to de-rotate the spine in gait. Further research, such as Hungerford et al., 2003Hungerford B. Gilleard W. Hodges P. Evidence of altered lumbopelvic muscle recruitment in the presence of sacroiliac joint pain.Spine. 2003; 28: 1593-1600PubMed Google Scholar paper suggest that this sling may also become facilitated as a result of sacroiliac joint (SIJ) pain; the deeper, intrinsic or “inner unit” musculature being somewhat inhibited or delayed in response in SIJ pain patients – when compared with controls – and the biceps femoris firing ahead of these muscles in a feed-forward mechanism. This may have a logical cross-over to the issues discussed in the paper in this section, by Hashemirad et al., 2010Hashemirad F. Talebian S. Olyaei G. Hatef B. Compensatory behaviour of the postural control system to flexion-relaxation phenomena.Journal of Bodywork and Movement Therapies. 2010; 14PubMed Google Scholar, on the flexor-relaxation phenomenon. They describe how a lumbar spine which has undergone creep due to prolonged flexion (for just 7 min or more) will create a statistically significant delayed flexor-relaxation phenomenon. For those unfamiliar with this response, the typical clinical response being observed is a switch from a “muscular” trunk strategy (erector spinae) to a “ligamentous” trunk strategy (transversus abdominis pulls on the thoracolumbar fascia and whole posterior ligamentous system of the spine tightens) at around 45 degrees of trunk flexion or around 90% of lumbar flexion. This reflex is stimulated by mechanoreceptors in the posterior ligamentous system of the spine inhibiting the lumbar erectors. An implication of Hashemirad et al.’s findings, is that the normal stretch does not activate the flexor-relaxation of the lumbar erectors at the usual time; this means that the hamstrings, the transversus abdominis (and it’s tensioning of the deep layer of the thoracolumbar fascia) which normally become dominant at this point in the movement, are delayed in their action. The upshot is decreased intra-abdominal pressure (due to delayed TrA contraction), decreased force closure at the sacroiliac joints (due to TrA not activating the nut-cracker phenomenon of force closure at the SIJ), decreased extensor moment action of the diamond-shaped middle layer of the thoracolumbar fascia, extended lumbar erector contraction in a position of increased flexion and therefore greater risk of posterior annular loading and potential injury. In short, from one simple act of flexing the lumbar spine for a little too long, the ability of the body to effectively transfer loads during lifting or squatting, via a posterior myofascial chain incorporating the hamstrings, sacrotuberous ligaments, thoracolumbar fascia, posterior ligamentous system, lumbar erectors and transversus abdominis, is compromised. This means that the SIJ’s and the discs become more vulnerable to injury; and the ramifications may be greater than that. The later that the hamstrings become dominant in this movement pattern, for example, the greater the leverage on their proximal insertion due to the angle of trunk inclination. Might this influence their risk for becoming strained? If the loading on the hamstring changes its real-time orientation based on the body’s long-established reflex mechanisms, could this have ramifications further down the deep longitudinal sling – as far as the arch of the foot and its role in absorption, storage and recoil of ground reaction forces? At this point the answers are unclear, but what is known is that a change in the spatiotemporal relationships of the body; especially if this occurs under load or velocity, such as in a sporting event, creates significant computational stress onto the nervous system, to adapt to a situation that it isn’t reflexively equipped for. Perhaps a clinical realisation arising from this is that not only are ergonomics key, but also paying attention to other causes of creep on the ligamentous system, such as the hypnotic effect of computer and TV screens, the sedative effects of alcohol consumption or of chronic sleep deprivation; potentially switching the body off from its own mechanoreceptive feedback, may offer greater understanding in preventing low back injury. A second paper appearing in this edition’s Rehabilitation and Prevention section is titled “Muscle fascia and force transmission” by Peter Purslow, 2010aPurslow P. Muscle, fascia and force transmission.Journal of Bodywork and Movement Therapies. 2010; 14PubMed Google Scholar PhD. This paper explains in great detail how the inner fascial components of the muscle; the endomysium, which surrounds the myofibril, and the perimysium, which surrounds the muscle fibre bundles, form a network to create fascial continuity between different contractile units; even if one unit is fatigued, damaged, being repaired or, indeed, is simply growing. A muscle can be imagined to behave a little like a bridge, connecting one piece of land (bone) to another piece of land (bone) while traversing some kind of ditch or gap (joint). In this way the bridge (muscle) would be built of hundreds of units – perhaps bricks – (sarcomeres) placed both end to end (in series) and alongside each other (in parallel). These bricks (sarcomeres) are designed to both withhold and to generate great forces. In the structure of the bridge, this is a relatively static role, but in the structure of the muscle, this is a far more complex dynamic interplay between resting tone, and various contractile states (concentric, eccentric, isometric and so on). If one or more bricks were to become damaged, or be knocked out of the structure of the bridge, its integrity and ability to both withstand and to generate force would be significantly impaired. However, in both muscles and in bridges this happens regularly, and reconstruction and maintenance is an ongoing feature of such a functional load-bearing structure. In order to be able to safely repair the bridge while it can still allow loads to be taken, some kind of extrinsic scaffolding needs to be in place; probably across the whole bridge (the epimysium), and it is likely that a more focused brace (perimysium) will need to be placed under the section of bridge that is to be repaired; while, specifically, the bricks (sarcomeres) in contact with the actual brick to be repaired (damaged sarcomere) may need a very specific, localised brace to hold them, while the stone mason is doing his work. This allows replacement of the damaged brick (sarcomere) and effective force transmission between the adjacent bricks (sarcomeres) so that the bridge (muscle) doesn’t lose much, if any functional capacity. This is critical to maintain motility of the system of which the muscle (bridge) is a part (Fig. 1). As Purslow goes on to discuss, there is more to these systems than just biomechanics. He illustrates, for example that additional crosslinks may form through advanced glycation end products (AGEs); typical of the changes in connective tissues in those with blood sugar dysregulation, from smoking and from aging. Connective tissue function is not just, then, about how the body is used biomechanically, but what it is exposed to biochemically. Purslow’s work is also relevant to the concept of slings discussed by Panayi, 2010Panayi S. The need for lumbar-pelvic assessment in resolution of chronic hamstring strain.Journal of Bodywork and Movement Therapies. 2010; 14: 294-298Abstract Full Text Full Text PDF PubMed Scopus (29) Google Scholar in JBMT issue 14(1), by Myers, 1997aMyers T. The ‘anatomy trains’.Journal of Bodywork and Movement Therapies. 1997; 1: 91-101Abstract Full Text PDF Scopus (31) Google Scholar, Myers, 1997bMyers T. The ‘anatomy trains’: part 2.Journal of Bodywork and Movement Therapies. 1997; 1: 135-145Abstract Full Text PDF Scopus (11) Google Scholar many times in this Journal and in his book Anatomy Trains, as well as by Beach, 2008Beach P. The contractile field – a new model of human movement – part 3.Journal of Bodywork and Movement Therapies. 2008; 12: 158-165Abstract Full Text Full Text PDF PubMed Scopus (2) Google Scholar, Beach, 2007Beach P. The contractile field – a new model of human movement.Journal of Bodywork and Movement Therapies. 2007; 11: 308-317Abstract Full Text Full Text PDF Scopus (6) Google Scholar. These slings are, important in providing a whole-body appreciation of dysfunctional states, helping us to track back to where a problem may have arisen from and, indeed, as McNeill, 2010McNeill W. Journal of Bodywork and Movement Therapies. 2010; 13: 272-275Abstract Full Text Full Text PDF Scopus (2) Google Scholar and Chaitow, 2010Chaitow L. Clinical prediction rules.Journal of Bodywork and Movement Therapies. 2010; 14: 7-8Abstract Full Text Full Text PDF Scopus (6) Google Scholar have discussed, to predict where a future problem may arise. What Purslow’s work seems to indicate is that contractile forces passing through the sarcomeres and direct into the myotendinous junction are route-1 for force generation, but that if a given line of sarcomeres has a damaged unit in series (or “brick” in the line), then this doesn’t stop every other sarcomere in that series from working; but simply allows contractile forces to be transmitted laterally across to a parallel series of sarcomeres (line of bricks) allowing continued function of the muscle, without significant compromise to performance or to repair. Interestingly, Hunter, 2005Hunter, G., 2005. Hamstring strain in professional football. Football Association Medical Society Non- League Conference, Lilleshall, UK, October 2005.Google Scholar presented prospective research on English Premiership soccer players which demonstrated that those players with greater measurable stiffness in their hamstrings at the beginning of the season were the least likely to suffer a hamstring strain during that season. Muscle stiffness is known to be generated by the series elastic components, which act like springs in between each sarcomere (Sarhmann, 2002Sarhmann S. Diagnosis and Treatment of Movement Impairment Syndromes. Mosby, 2002Google Scholar). Therefore, the more sarcomeres (bricks) in parallel, the more series elastic components, the greater the stiffness, and the more possible pathways for force transmission – as well as for running repairs during play and across the season in general. As to whether these forces can pass out of the contracting muscle and into the surrounding fascia (epimysium), Purslow is uncertain, but explains that it would seem entirely feasible and that there is certainly evidence of a hydraulic amplifier mechanism occurring between agonist muscles within a compartment.Text box 1Evidence for hydraulic amplification between agonists in muscle compartments“…compartmentalisation increases the efficiency of muscle contraction. The contraction of one muscle within the group pressurises the compartment (from 15 mmHg in normal contractions up to approx. 80 mmHg in tetanic conditions), and even a small elevation in pressure raises the contractile efficiency of all members in the muscle group. Cutting the fascia releases 50% of this normal pressure generation and decreases contractile force for a given extension by 16% (Garfin et al., 1981Garfin S.R. Tipton C.M. Mubarak S.J. Woo S.L.Y. Hargens A.R. Akeson W.H. Role of fascia in maintenance of muscle tension and pressure.Journal of Applied Physiology. 1981; 51: 317-320PubMed Google Scholar).The interactions of the contractile proteins actin and myosin in muscle are known to be sensitive to high pressures, but very large pressures (10 MPa, or 100 atm) are required, and the effect of these are to reduce the active tension generated (Knight et al., 1993Knight P.J. Fortune N.S. Geeves M.A. Effects of pressure on equatorial X-ray fiber diffraction from skeletal muscle fibers.Biophysical Journal. 1993; 65: 814-822Abstract Full Text PDF PubMed Scopus (9) Google Scholar). Perhaps the more useful explanation of the effect observed at such low pressures is the lateral constraint effect proposed by Aspden (1990)Aspden R.M. Constraining the lateral dimensions of uniaxially loaded materials increases the calculated strength and stiffness-application to muscle and bone.J. Mater. Sci. Mater. Med. 1990; 1: 100-104Crossref Scopus (29) Google Scholar, which argues that the reduction in lateral expansion that pressurisation of neighbouring muscles may cause increases the effective muscle stiffness in active contraction, thus leading to increased force production for a given length of contraction.” “…compartmentalisation increases the efficiency of muscle contraction. The contraction of one muscle within the group pressurises the compartment (from 15 mmHg in normal contractions up to approx. 80 mmHg in tetanic conditions), and even a small elevation in pressure raises the contractile efficiency of all members in the muscle group. Cutting the fascia releases 50% of this normal pressure generation and decreases contractile force for a given extension by 16% (Garfin et al., 1981Garfin S.R. Tipton C.M. Mubarak S.J. Woo S.L.Y. Hargens A.R. Akeson W.H. Role of fascia in maintenance of muscle tension and pressure.Journal of Applied Physiology. 1981; 51: 317-320PubMed Google Scholar). The interactions of the contractile proteins actin and myosin in muscle are known to be sensitive to high pressures, but very large pressures (10 MPa, or 100 atm) are required, and the effect of these are to reduce the active tension generated (Knight et al., 1993Knight P.J. Fortune N.S. Geeves M.A. Effects of pressure on equatorial X-ray fiber diffraction from skeletal muscle fibers.Biophysical Journal. 1993; 65: 814-822Abstract Full Text PDF PubMed Scopus (9) Google Scholar). Perhaps the more useful explanation of the effect observed at such low pressures is the lateral constraint effect proposed by Aspden (1990)Aspden R.M. Constraining the lateral dimensions of uniaxially loaded materials increases the calculated strength and stiffness-application to muscle and bone.J. Mater. Sci. Mater. Med. 1990; 1: 100-104Crossref Scopus (29) Google Scholar, which argues that the reduction in lateral expansion that pressurisation of neighbouring muscles may cause increases the effective muscle stiffness in active contraction, thus leading to increased force production for a given length of contraction.” Purslow, 2010bPurslow, P., 2010b. Personal communication.Google Scholar states: “Whether epimysium in some muscles at least can also act in the same way to hydraulically stiffen the muscle so that it produces more force for a given length change is, as far as I know, not known, but in some muscles with heavy sheets of tendon-like epimysium it certainly looks a possibility.” Research conducted by Vleeming et al., 1997Vleeming, A., Snijders, C., Stoeckart, R., Mens, J., 1997. The role of the sacroiliac joins in coupling between spine, pelvis, legs and arms. In: Vleeming et al. (Eds.), Movemen, Stability & Low Back Pain. Churchill Livingstone, 53--71.Google Scholar supports this notion of the capacity of the epimysium to transfer load across compartments into adjoining muscle groups. Research conducted both on the transfer of load between the gluteus maximus and the contralateral latissimus dorsi via the thoracolumbar fascia, and on the peroneus longus through to the tendon of biceps femoris, showed that a percentage (approximately 18%) of forces applied to the cadaveric myofascial system were, indeed, transferred across muscle groups. The most likely explanation for this (as had been hypothesized by authors such as Myers, Beach and others) is the direct fascial attachments; but specifically of the epimysium (as opposed to contributions from the endomysium or perimysium). The limitations of these studies are clear, inasmuch as the subjects were not living, had been prepared as cadavers (factors which will both significantly alter tissue properties) and were assessed on a dissection table (ie not in a functional load-bearing or sports-specific position), and using extrinsic application of force rather than intrinsic myogenic contractile forces. Nevertheless, such research allows the bodyworker and movement therapist the possibility of making associations between the apparent “functional anatomy” and what they see clinically. One such example is the biomechanics of gait. For the last 10 years or so, the running community has been in debate about whether running with a heel strike is functional or not. Many running coaches have suspected that the natural state is to strike the ground with the forefoot since a higher proportion of elite distance runners forefoot strike, than those in the lower echelons of the sport. Yet, despite this, heel striking runners still outnumber the forefoot strikers by some significant margin (Downey, 2009Downey G. Lose your shoes. Is barefoot better?.http://neuroanthropology.net/2009/07/26/lose-your-shoes-is-barefoot-better/Date: 2009Google Scholar). This is why the research from Lieberman et al., 2010Lieberman D. Venkadesan M. Werbel William A.W. Daoud A. D’Andrea S. Davis I. Ojiambo Mang’Eni R. Pitsiladis Y. Foot strike patterns and collision forces in habitually barefoot versus shod runners.Nature. 2010; 463: 531-e536Crossref PubMed Scopus (939) Google Scholar published earlier this year met with so much interest from the world’s media and, in particular with the biomechanics and podiatry communities. What Lieberman et al., 2010Lieberman D. Venkadesan M. Werbel William A.W. Daoud A. D’Andrea S. Davis I. Ojiambo Mang’Eni R. Pitsiladis Y. Foot strike patterns and collision forces in habitually barefoot versus shod runners.Nature. 2010; 463: 531-e536Crossref PubMed Scopus (939) Google Scholar did, for the first time, was to assess groups of habitually unshod runners, versus habitually shod runners, from different cultures, comparing their running style both barefoot and in running shoes. Adults were sampled from three groups of individuals who run a minimum of 20 km per week: (1) habitually shod athletes from the USA; (2) athletes from the Rift Valley Province of Kenya (famed for endurance running), most of whom grew up barefoot but now wear cushioned shoes when running; and (3) US runners who grew up shod but now habitually run barefoot or in minimal footwear. Adolescents from two schools in the Rift Valley Province were also compared: one group (4) who have never worn shoes; and another group (5) who have been habitually shod most of their lives.Tabled 1SubjectConditionRFSMFSFFSHabitually shod adults, USABarefoot83170Shod10000Recently shod adults, KenyaBarefoot9091Shod291854Habitually barefoot adults, USABarefoot25075Shod501337Barefoot adolescents, Kenya (never)Barefoot122266Shod–––Shod adolescents, KenyaBarefoot621919Shod9730 Open table in a new tab RFS=Rearfoot strike. MFS=Midfoot strike. FFS=Forefoot strike. What these results seem to clearly demonstrate is that, while humans are able to rearfoot, midfoot or forefoot strike, it would appear that the primary discriminating factor in this behaviour, is more to do with whether they are shod, rather than their genetic or biomechanical heritage (Figure 2). At this early stage in the research, it would seem that the working conclusion is that the natural state for running appears to be a forefoot strike, while adorning the foot with a running shoe seems to be the primary causative factor in rearfoot strike behaviour. Assuming further ongoing research seems to support this notion, what may be the clinical implications for such an understanding? Firstly, of course, the biomechanics books may have to be re-written with respect to running gait. Interestingly, of course, most such texts have been written since people started wearing running shoes in 1970s and beyond; and therefore have used data from shod groups. Secondly, other findings, both within this research from Lieberman and from other groups suggest that barefoot running and shod running differ with respect to lower limb joint angles, muscle activation firing patterns, leg stiffness, joint torques, and so on (DeWit et al., 2000DeWit B. et al.Biomechanical anlaysis of the stance phase during barefoot and shod running.Journal of Biomechanics. 2000; 33: 269-278Abstract Full Text Full Text PDF PubMed Scopus (393) Google Scholar, Divert et al., 2005Divert C. et al.Stiffness adaptations in shod running.Journal of Applied Biomechanics. 2005; 21: 311-321PubMed Google Scholar, Kerrigan et al., 2010Kerrigan D. Casey M.D. Jason F. Geoffrey S. Keenan M. Dicharry J. Della U. CroceWilder R. The effect of running shoes on lower extremity joint torques.PM&R. 2010; 1: 1058-1063Abstract Full Text Full Text PDF Scopus (92) Google Scholar). Weaker epidemiological studies suggest the possibility that these factors may reduce injury profiles (Warburton, 2001Warburton M. Barefoot running.Sportscience. 2001; 5sportsci.orgGoogle Scholar). While research from the strength and conditioning field suggests that increasing leg stiffness; something that happens naturally when running barefoot, is a key way to increase top flight running speed (Peak Performance, 2009Peak Performance, 2009. Training for Sprinting, Speed & Acceleration.Google Scholar). If we are to place this research regarding the natural biomechanical state into the context of “joined-up-anatomy”, or the fusion of musculature hitherto regarded as “separate” entities, it may be possible to identify a dual speed system: one for low-speed gait (walking) and one for supra-walking pace gait (running, to include jogging, and sprinting). The reason for this is that there is a potential problem with the deep longitudinal system, as described by van Wingerden (2006), Vleeming et al., 1997Vleeming, A., Snijders, C., Stoeckart, R., Mens, J., 1997. The role of the sacroiliac joins in coupling between spine, pelvis, legs and arms. In: Vleeming et al. (Eds.), Movemen, Stability & Low Back Pain. Churchill Livingstone, 53--71.Google Scholar, Panayi, 2010Panayi S. The need for lumbar-pelvic assessment in resolution of chronic hamstring strain.Journal of Bodywork and Movement Therapies. 2010; 14: 294-298Abstract Full Text Full Text PDF PubMed Scopus (29) Google Scholar, in the context of this new research on the forefoot strike; it can only really work if you heel strike. Though it wasn’t explicitly discussed by Panayi, 2010Panayi S. The need for lumbar-pelvic assessment in resolution of chronic hamstring strain.Journal of Bodywork and Movement Therapies. 2010; 14: 294-298Abstract Full Text Full Text PDF PubMed Scopus (29) Google Scholar, the lower portion of the deep longitudinal sling, namely the tibialis anterior and the peroneus longus, which form a connective tissue stirrup around the arch of the foot, to control pronation of the medial longitudinal arch, will work very well if the foot is dorsiflexed before heel strike, as it means that the leverage of the ground reaction force against the heel, in tandem with the descending load of the bodyweight through the talocrural joint, will result in a very strong eccentric load through this lower portion of the sling (which is when a muscle is strongest); effectively controlling both plantar flexion of the ankle and pronation of the medial longitudinal arch. But, if the natural state of running is to plantarflex the foot and to forefoot strike, then this system suddenly becomes very inefficient; not serving to control pronation, nor to translate forces up the sling to provide force closure to th
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