PATHOPHYSIOLOGY OF SKELETAL MUSCLE INJURIES Dr. Muhammad Mustafa Qamar mustafaqamar.com

Discuss the structure & function of skeletal muscle, progressing on to the Pathophysiology of skeletal muscle injury and repair.

Anatomy of skeletal muscles

Physiology of skeletal muscles

Pathophysiology of skeletal muscles There are a number of types of muscle injury that can occur such as: LACERATION CONTUSION STRAIN

Pathophysiology of skeletal muscles Strains most commonly occur in muscles working across two joints e.g. hamstrings, gastrocnemius (Jarvinen et al. 2005)

Pathophysiology of skeletal muscles When the muscle is strained the initial injury is usually associated with disruption of the distal myotendinous junction. Injuries to the muscle belly only occur with the application of very high forces. The contractile elements are the first tissues to be disrupted; with the surrounding connective tissue not being damage until high forces are applied.

Pathophysiology of skeletal muscles Muscles heal by a repair process that can be divided into two phases: The destruction/injury phase Repair and regeneration

Pathophysiology of skeletal muscles Destruction/injury phase This phase results in damage to the vascular supply and as Oxygen can no longer reach the cells, they die and release lysosomes. Within 15 minutes of injury the damaged tissue release powerful enzymes such as thrombin thereby setting off an inflammatory cascade. A haematoma is formed to fill the gap between ruptured muscle fibres. Clinically tissue inflammation presents as redness, heat, swelling and pain of the tissues.

Pathophysiology of skeletal muscles Repair and regeneration the injured tissues attract lymphocytes and macrophages to the area. The regeneration process starts within 3–6 days following injury, reaching a peak between day 7 and 14. The regenerative capacity of skeletal muscle is provided by satellite cells, specialised cells underneath the basal lamina of each muscle fibre.

Pathophysiology of skeletal muscles Repair and regeneration This regeneration process can occur rapidly, within 10 days post injury the injured muscle can regain much of its contractile ability with progressively applied loading, set at levels below the pain threshold (Nikolaou et al. 1987). Muscle with its capacity for rapid regeneration due to the nature of its constituent tissues requires a modified approach (Peterson and Holmich 2005; Thorssonet al. 2007).

Treatment of muscle injuries The initial treatment of musculoskeletal injuries should be rest, ice, compression and elevation (RICE).

Treatment of muscle injuries Rest and mobilization Studies have shown early mobilization aids with regeneration of muscle fibres (stimulation of satellite cells and myotube formation improves capillary growth into the area and aids with more parallel orientation of collagen and muscle fibres (Nikolaou et al. 1987, Taylor et al. 1993; Goldspink 1999). Early weight bearing to help promote scar tissue re-alignment (Croisier 2004; Jarvinen et al. 2005)

Treatment of muscle injuries Ice (duration) Clinical studies have shown the optimal duration to apply ice is for 5–10 minutes in the initial stages and repeat every 60 minutes (Croisier 2004; Hubbard et al. 2004) within the first 24–48hours to reduce the inflammatory effects.

Treatment of muscle injuries Compression Compression is an area where research is lacking. A recent clinical study by (Thorsson et al. 2007) utilising 40 athletes with calf injuries found compression resulted in no significant difference in reducing muscle haematoma, or speed of recovery of the injury using compression

Treatment of muscle injuries Elevation It simply relies on the use of gravity to promote venous return and lymphatic flow to drive swelling/oedema from the area (Hergenroeder 1998). Greatest benefit that comes from compression and elevation is that it ensures that the athlete rests during the acute inflammatory phase of the first 72 hours following injury.

Treatment of muscle injuries Strengthening exercise Isometric exercise can begin after 2–5 days and should be performed within the limits of pain (Jarvinen et al. 2 Three sets of 10 repetitions using 5–10 second holds to begin with at intensity within pain tolerance (Pull and Ranson 2007).

Treatment of muscle injuries Strengthening exercise These then are undertaken at multiple angles, beginning in mid range then progressing to inner range (shortened position) then outer range (lengthened position). Once these can be undertaken in a pain-free manner throughout the available range, then isotonic exercises can commence.

Treatment of muscle injuries Strengthening exercise Endurance based programme (three sets of 15 repetitions at 40–60% of one repetition maximum) Strength (4–6 sets of 3–6 repetitions at 85–95% of one repetition maximum Power training (3–5 sets of 3-5 repetitions at 75–85% of one repetition maximum) (Kraemer et al. 2002),

Treatment of muscle injuries Strengthening exercise Mobiliser muscles Hamstrings Quadriceps Gastrocnemius Pectorialis major Latissimus dorsi Stabiliser muscles Gluteus medius/minimus Adductor longus Tibialis posterior Infraspinatus Subscapularis

Treatment of muscle injuries Stretching Passive stretching (at the end of available range) should be avoided for the first 72 hours as a minimal period, possibly the athlete should not stretch for the first 7–10 days following injury (Neidlinger W Time, frequency, duration and intensity of stretch ???

Treatment of muscle injuries Stretching passive stretching should be held for a minimum of 15 seconds with 6–8 sets per day (Roberts andWilson 1999).

Treatment of muscle injuries Electrotherapy Pulsed shortwave diathermy Therapeutic ultrasound EMS

Example of muscle injury (hamstring) Anatomy and function

Example of muscle injury (hamstring) The strain is most likely to occur during two phases of the running cycle; late forward swing and toe off (Stanton 1989) as during this phase the hamstrings decelerate hip flexion and knee extension (Hoskins and Pollard 2005) resulting in large eccentric loads.

Example of muscle injury (hamstring) Predisposing factors previous injury lack of flexibility Inadequate warm up fatigue strength imbalance and inadequate quadriceps to hamstring ratio poor coordination

Example of muscle injury (hamstring) Symptoms ???

Example of muscle injury (hamstring) Treatment ???

Rehabilitation A rehab program should include: Flexibility exercises. Strengthening exercises. Endurance activities. Coordination and agility training (for competitive athletes).

Rehabilitation Five phases Phase I (Acute phase) - (1-5 d) Phase II- Sub acute phase - (5 d to 3 wk) Phase III- Remodeling phase - (1-6 wk)  Phase IV- Functional stage – (2 weeks to 6 months) Phase V- Return to Sport (6 months)