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The Science Behind Muscle Injuries

Muscle injuries comprise of 10%-55% of all sustained sport related injuries. Contusions, strains or lacerations are the three main causes of muscle injuries with more than 90% of muscle injuries resulting from contusions and strains. A muscle contusion is where a muscle is subject to a sudden, strong compressive direct blow resulting in muscle tissue damage. Strains are most commonly caused during sprinting, jumping, or rapid muscular contraction or over stretching. This causes an excessive tensile (pulling) force subjected onto the muscle leading to overstraining of the myofibers (muscle fibers), typically at the point where the muscle joins with the attached tendon, called the myotendonous junction.
The way a skeletal muscle heals itself after sustaining a strain, contusion or laceration is quite different than how a bone heals itself after sustaining a fracture. A bone heals itself through exact regeneration of the identical tissue at fault, where as a skeletal muscle heals itself through a repair process. A skeletal muscle lays down connective scar tissue, which is a different tissue than that of its original state. The healing of a skeletal muscle follows a constant pattern regardless of its cause (contusion, strain or laceration). Three phases have been scientifically outlined within this pattern:
Destructive phase: Rupture and necrosis (cell death) of myofibers, and the formation of a hematoma between the ruptured myofiber end stumps, and the inflammatory cell reaction.
Repair phase: Phagocytosis (cleaning and riding) of the necrotized tissue, the regeneration of myofibers, the production of a connective tissue scar, as well as capillary (blood vessel) ingrowth into the injured area.
Remodeling phase: The maturation of the regenerated myofibers, contraction (shrinking) and reorganization of the connective tissue scar tissue, and recovery of the functional capacity of the muscle.


R.I.C.E: During this acute stage, patients should follow R.I.C.E principle which stands for Rest, Ice, Compression, and Elevation. All are used to help decrease blood flow, and inflammation.
Rest/Immobilize (2-3 days): Scientific research has confirmed that immobilization should be limited to the first few days post-injury. This is to prevent any excessive scar tissue being formed, reruptures of the injured muscle, and most importantly to allow for the new collagen tissue being laid down to secure itself to either end of the injured stumps in order to resist tensile stress caused by muscle contractions. However, if immobilization is continued longer than this, muscle atrophy (shrinking), excessive scar and collagen tissue is produced within the muscle tissue, and a retard in recovery of the strength of the injured skeletal muscle. With regards to ice and compression, it has been shown that early use of cryotherapy (ice therapy) with compression results in a smaller hematoma between the ruptured myofiber stumps, less inflammation, and accelerated early regeneration. A good rule of thumb for icing is applying ice 15-20 minutes in duration every 30-60 minutes. This allows your tissue temperature to decrease up to 3-7 degrees and a 50% reduction in the intramuscular blood flow. Lastly, elevation is used based on the physiological affect, where the injured extremity in placed above the heart resulting in a decrease in hydrostatic pressure and therefore reduces excessive interstitial fluid.
3-5 DAYS POST-INJURY: Once the above steps have been met and complied with, patients may progress into a more active and therapeutic treatment approach.
Active Mobilization: Active Mobilization induces more rapid and intensive capillary ingrowth (increase in blood flow and oxygen) into the injured area, better regeneration of muscle fibers, and more parallel orientation of the regenerating myofibers. Also, early mobilization of the injured muscle allows for biomechanical strength of the injured muscle to return to the level of uninjured muscle more rapidly than if immobilized. With active mobilization after the short period of immobilization enhances the penetrations of the newly formed muscle fibers through the connective tissue scars, which in turn helps decrease and shrink the scars overall size.
Manual Therapy: Various manual therapy techniques (i.e. Active Release Technique, Graston Technique, Acupuncture etc) help aid in the acceleration and efficiency of the healing cascade. By providing a mechanical stress/ stimulation through the healing structures allows for collagen producing cells to become stimulated and activated to help lay down the reparative tissue. These cells also are stimulated to lay down this new tissue in proper fiber orientation allowing for proper pre-injury muscle function. Manual therapy prevents and eliminates of adhesions and excessive scar tissue as well as allowing the formed scar tissue to shrink in size and increase its tensile strength, which helps restore proper muscle function.
When to return to sport/ activity: Patients should follow two basic principles before returning to pre-injury activities. They are
1) The ability to stretch the injured muscle as much as the uninjured contralateral muscle.
2) There is pain-free use of the injured muscle with 90% of its strength comparable to the contralateral uninjured muscle.

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