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Muscle Strains

Discussion in 'Biomechanics, Sports and Foot orthoses' started by RSThorogood, Mar 21, 2013.

  1. RSThorogood

    RSThorogood Member

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    Hi all,

    I was looking for some clarification regarding what occurs at a cellular level in muscle strains in comparison to reactive tendon pathology (location aside) and how to diagnose the different stages of muscle strain. A patient presented yesterday with an awkward trauma moment, that appears to have strained the Peroneus Longus muscle, and is painful in the muscle belly rather than at the origin or insertion. It could be a case of reactive tendinopathy due to trauma, or due to the location, possibly a case of a muscle strain.

    Unfortunately muscle strains/tears weren't spoken about at any length at university and despite quite a lot of searching, I'm yet to find any great recent research that can help me out. Is there any literature out there that can help me devise a treatment protocol for Muscle Strains similar to how Jill Cook's Tendon Continuum has helped me devise one for Tendon Pathology & to recognize different stages.

    Thanks in advance,
  2. Griff

    Griff Moderator

  3. Lorcan

    Lorcan Active Member

  4. toomoon

    toomoon Well-Known Member

    This is an extract from my website, which is in fact an extract from my upcoming book, The Foot and Leg in Sport, which in fact will be published on my website! Anyway I digress. If you want the full overview of muscle physiology and injury from a cellular level up, you will find it at www.bartoldbiomechanics.com.
    I hope the following helps a bit.
    Skeletal Muscle
    Skeletal muscle is composed of contractile tissue, muscle cells or fibres, and a network of connective tissue. The connective tissue is responsible for transmitting the pull of the muscle cells, and whilst not contractile in structure these connective tissue structures are contractile in function. The majority of skeletal muscle is under voluntary control and the tissue is comprised of long multinucleated cells called muscle fibres. These are derived from the embryonic myoblast cells by end to end fusion. This fusion results in myotubes during development. Muscle fibre end insert into tendons, that in turn attach to bone and effect movement of the relevant segment. The connective tissue sheaths surrounding the entire muscle is called the epimysium. Connective tissue infiltrates the entire internal structure of muscle tissue, to manifest at every level of muscle organisation. The connective tissue layer dividing the muscle into fascicles is called the perimysium. Each fascicle contains several muscle fibres. These individual muscle fibres are separated from each other by the endomysium. The basal lamina, or basement membrane is a thin layer of specialised connective tissue comprised of type IV collagen which invests each muscle fibre. The basement membrane has an important role within neuromuscular apparatus in terms of development and differentiation. Undifferentiated myoblasts are contained within the basement membrane and are thought to be a part of the regeneration process by their ability to fuse with damaged muscle fibres. The unit responsible for contractile muscle force is the muscle fibre (fig 3.1). A skeletal muscle fibre is comprised of contractile proteins called myofibrils. These are longitudinally oriented into bundles of thick and thin filaments called myosin and actin respectively (fig 3.2). These filaments effect contraction through their ability to slide past each other. The myofibril is striated in appearance, with transverse bands of repeated units called sarcomeres (fig 3.3). The acting filament is anchored at one end to a mesh of protein oriented at right angles to the filaments. This can be observed microscopically as a thick dense band or disc and is called the Z-band (Zwischenscheibe). This Z-band links the actin filaments and serves as a boundary between sarcomeres. They occur at regular intervals throughout the myofibril. The sarcomere is the basic unit of contractile tissue. Myofibrils are made up of many sarcomeres linked end to end. The myosin or thick filaments are located on the centre of the sarcomere. This filament rotates polarised light and can be identified microscopically as the anisotropic or A-band on longitudinal section. A muscle contraction occurs with shortening when myosin structure changes. There is successive making and breaking of cross-bridges between actin and myosin which promotes various changes of overlap of the fibres. Cross-bridges are located along the length of the myosin filament and slant away from the centre of the unit towards the near Z-band. Myosin filaments in series create an M-band at their thickest portion. The actin filaments are visible in relaxed muscle, as a zone on either side of the Z-band where they are not overlapped by the myosin filaments. This region is called the isotropic or I-band. The actin filaments point to each other but do not touch in relaxed muscle. There is therefore a region where myosin is not overlapped by actin and this is called Hensen’s disc or the H-zone.
    Sarcomeric structure is very predictable and regular and cross-sectionally each myosin filament is surrounded by six actin filaments, with each actin filament equidistant to three myosin filaments.
    Muscle Injury and Healing
    Injury to muscle including contusions, lacerations and strains, represents one of the most common traumas in sports medicine. Later chapters will address specific muscle injury, however it is important to be familiar with general principles of muscle injury and repair. In the literature, muscle injury frequency has been reported from 10-55% of all injuries in sport (Franke 1980; Zarins and Ciullo 1983; Sanderlin 1988). Muscle contusion is the result of an excessive compressive force such as a direct blow that results in intramuscular bleeding and disruption of muscle fibres (Zarins 1982). Muscle contusions are common in contact sport. Muscle strains occur when the muscle is stretched beyond its normal physiological load by an extrinsic, excessive tensile force. Muscle strain can occur when a muscle that acts across two joints has its normal sensitive neuromuscular coordination mechanism momentarily interrupted. This is especially precipitated by fatigue. An example of this type of injury is in the quadriceps muscle, which flexes the hip and extends the knee. A muscle strain may tear collagen fibres as well as muscle tissue itself if the failure point for the tissue is reached. It is important to recognise that muscle tissue has limited ability to regenerate and so any defect is usually filled with connective tissue scar. As a result of this muscle strength may be lost along with contractile function of the muscle. The most common muscle strains are not complete but partial ruptures of the muscular tissue and most commonly these lesions are seen near the myotendinous junction (Millar 1979; Almekinders and Gilbert 1986; Garrett et al 1987). When a muscle strain does occur the ability of the muscle tendon unit to resist stretch will play an important role. The failure load before rupture is lower in relaxed muscle than when contracted muscle is stretched. Garrett et al (1987) has reported that all factors decreasing the tensile properties of muscle increase the risk of strain under stretching. In Chapter 2 we investigated the cause of overuse injury in tendon and looked at extrinsic and intrinsic factors that may impact on injury. These risk factors hold true for any soft tissue injury and can be applied equally to muscle injury. In order to successfully manage injury we must have a secure understanding of the etiology of injury and biology of healing tissue.
  5. Ian Drakard

    Ian Drakard Active Member

    With traumatic injury involving p longus I'd also rule out cuboid issues. Often mobilising the cuboid if there is any discomfort around the cuboid articulations will resolve the peroneal pain. In acute cases doing this once or twice maybe enough. More chronic cases may benefit from lateral arch support/cuboid pad or similar. Hope this helps
  6. RSThorogood

    RSThorogood Member

    Thanks for the response so far. I've been reading through the Myofascial Pain & Dysfunction: Trigger Point Manual, which has been pretty helpful, but I'm also wary of the date of publication of the book and whether there are any more recent articles pertaining to muscle rehabilitation as opposed to tendon rehabilitation.
    Or are they classed under the same injury according to researchers?
  7. RSThorogood

    RSThorogood Member

    Thanks for the reply, I will have a look into the book, the website looks great.

    Are there any treatment protocols to follow to help reduce the amount of connective tissue scarring and promote normal healing rather than dysrepair?
    And do those treatment protocols differ from those of a tendon?
  8. Lorcan

    Lorcan Active Member

    You could use the technique Soft tissue release whereby the patient is and Active release whereby the patient is involved the treatment.
    The concept is whereby the muscle is shortened, the tissue is locked by fingers etc and the practitioner vectors away from the moving joint and the muscle is stretched/lengthened either passively or actively. This breaks down the scar tissue and encourages the collagen to be laid down in the direction of pull, following the fassicular arrangement.

    If your interested let me know and I'll give you link for a good and cheap manual on it.

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