Week 12 Lecture

Diagnosis of muscle injuries (general): -Clinical diagnosis usually adequate History, physical examination -Ultrasound imaging Defines magnitude and location of injury (esp. MTJ) May be important in relation to management -MRI More accurate, better detail of size of muscle lesion Better imaging of injuries near MTJ Can identify lesions at the central tendon Best at 24-72h days post-injury Hamstring: TOTAPS Field Assessment: Talk Observe injured area Touch injured area Active movement assessment Passive movement assessment Skills test Specific Clinical Investigation: Prone palpation Identify ischial tuberosity HS contraction isometric leg straight Palpate distal until highest pain level with some palpatory pressure High speed injury – Significant dysfunction initially – Tends to settle quicker Slow stretch injury – Less bothersome initially – Slower to return

Frequent injury involving high speed running or extensive lengthening of the hamstrings Most commonly injured at musculotendinous junction High re injury rate indicates inadequate rehab or premature return to sport 1.HIGH SPEED INJURY Terminal swing/early stance phase Eccentric lengthening. Great length change and negative work performed by biceps femoris Considerable lengthening under load in second half of swing phase Injury site proximal head long head biceps musculotendinous junction – Significant dysfunction initially – Tends to settle quicker 2.SLOW SPEED STRETCHING INJURY Semimembranosis prox tendon close to ischial tuberosity – Less bothersome initially – Slower to return

Extrinsic(environment related) risk factors -SPEED TRAINING Particularly susceptible as increased running speed requires a sig increase in cadence a 3% increase requires a 15% increase in HS eccentric strength -TRAINING ERRORS Inadequate warmup warm up increases amount of force & length a muscle can absorb prior to tearing Fatigue related to unsuitable structure and content of training Poor playing surfaces INTRINSIC FACTORS -Age(>25 increased risk of injury 4x 20 yo) -previous injury -flexibility, more length increased risk of injury -Strength imbalances HS:Q ratios suboptimal vs quads ratio

-Previous hamstring injury is the greatest risk factor - possible that scar tissue may alter local contraction mechanics, therby influencing reinjury risk. • Inadequate rehab • Premature return to sport • Decreased quadriceps flexibility as assessed by the modified Thomas test was an independent risk factor - however hamstring flexibility not been related to higher incidence of strain. • Muscle imbalance (hamstring to quadriceps) • Older age Research found that male college athletes were 62% more likely to sustain a hamstring injury than female athletes and more common in field sports than in court sports.

Muscle Strains • Common in two joint muscles • Eccentric Contraction (dynamic overload) – Rapid sarcomere elongation – Frictional resistance within the muscle framework – Rate of lengthening (strain) possibly important • Common at musculotendinous junction (MTJ) – Due to organisation of CT at MT junction – Related load orientation & distribution across the MT junction

It’s positive prophylactic effect strongly suggest that it should be a component of a reconditioning program upon return to sport.

Initial Stage Goals Protect Healing Tissue Minimize atrophy and strength loss Prevent motion loss • Rest or relative rest – Immobilise vs gentle movement • Ice • Compression • Elevation No HARM

Muscle Injury – Acute Response • Peritrauma (0‐6hrs) – Fibre degeneration – Myonuclear death & dissolution – Impaired continuity of sarcolemma – Myofibrils break up into sarcomere units • Rupture of small vessels, focal nerve axon damage‐> Haematoma forms at injury site • Chemataxic stimuli from damaged cells attract WBC’s – espec. Neutrophils & Macrophages • Phagocytosis of damaged muscle fibres & breakdown metaboles – eg. Prostaglandin Early Healing (1‐6 days) • Satellite cells proliferate • Satellite cells transformed into myoblasts which fuse onto myotubes – Myo‐tube growth factors (interleukins etc.) released – Enhanced by (gentle) stretching & mechanical loading • Myotubes extend from torn ends of muscle fibres • Basal lamina – Acts as a scaffold for the new muscle fibre (also important for re‐ innervation) – Maintains a favourable environment for regeneration • Grow towards intervening scar tissue Early Healing (1‐6 days) • Attempt to grow through scar tissue but not usually possible • Fibre ends blend into scar tissue – New ‘mini‐musculotendinous junction’ • Scar tissue contracts to bring regenerated fibre ends closer together – Most injuries heal without excessive scar tissue

Prolonged rest (especially in shortened position) results in: – Decrease in muscle resting length – Decrease in number of sarcomeres in series – Decreased muscle volume (atrophy) – Decreased muscle fibre size and number – Increased intra‐muscular connective tissue – Increase muscle stiffness – Decrease muscle activation (50% in 4 weeks) – Responses less marked and slower in fast twitch muscles

Initial Stage Protect Healing Tissue Minimize atrophy and strength loss Prevent motion loss • Rest or relative rest– Immobilise vs gentle movement • Ice • Compression • Elevation No HARM Later Initial Stage Therapeutic Exercise • Stationary bike: spin • Isometrics of lumbo‐pelvic region Submax ISOMETRICs at 3 angles (90°60°30°) Early Proprioception • Single leg balance activities • Mini squats variable weight transfer Varied pain‐free angles Intermediate Stage Regain pain‐free HS strength, to full ROM Develop neuro‐muscular lumbo‐pelvic control Increase movement speed preparing for functional mvts Repair/Remodeling Phases Progressive fast walk /running program • twice daily from 1.5‐ 2.5 km/session • 100m run/100m walk Conditioning maintenance • swim, H2O run, bike programs Advanced Stages Symptom free all activities Improve neuro‐muscular lumbo‐pelvic control Normalize Conc:Ecc Ratio through full ROM Integrate postural control into Sports Later advanced stage Action specific exercise • Gym: Romanian dead lifts • Ball: H/S bridge, drop‐catches, glut stability bridge • Stretch/shortening exercises – Sport specific exercises • Kicking program • Sprint with direction changes, acceleration/deceleration • Running drills and run with ball pick‐up – Gym • Hypertrophy reps • Progress to strength then power reps over time

Prolonged rest (especially in shortened position) results in: – Decrease in muscle resting length – Decrease in number of sarcomeres in series – Decreased muscle volume (atrophy) – Decreased muscle fibre size and number – Increased intra‐muscular connective tissue – Increase muscle stiffness – Decrease muscle activation (50% in 4 weeks) – Responses less marked and slower in fast twitch muscles • Early Mobilisation results in – Better clearance of haematoma & inflammatory cells – More rapid regeneration of muscle fibres & connective tissue – Earlier restoration of contractile properties – More rapid restoration of tensile strength – Facilitates re‐vascularisation of damaged area • Regenerated muscle & young collagen fibres better oriented with the original muscle fibres

Muscle regeneration: Optimal Management • Aim to balance two competing processes – Optimise muscle regeneration – Minimise connective tissue (scar) proliferation - Fibroblasts appear at injury site within 48 hours - Early repair favours collagen synthesis over muscle - Reduce chances of re‐injury • Short period of reduced muscle load (3‐5 days) – Reduces bleeding and accelerated satellite cell activation – Accelerates appearance of Type‐1collagen in the injured area - Decreased chance of re‐injury – Limits the amount of connective tissue at the injury site – Better remodelling of connective tissue in the endo‐ and perimysium in the later stages of healing Influence on scarring and regeneration Early mobilisation • Regenerated muscle & young collagen fibres better oriented with the original muscle fibres Graduated loading process, similar to many other soft tissue injuries Factors to consider • Flexibility • Strength Consider 4 keys of muscle specificity 1) Muscle action 2) Muscle group 3) Velocity 4) Energy source (aerobic or anaerobic) • Speed • The sub‐qualities of speed: – Acceleration – Maximum velocity – Speed endurance – Agility (change of direction) – Reaction • Specifics • Proprioception

• Appears not to affect: – Tensile force to failure – Elongation (strain) to failure • Fatigue may decrease energy absorption during eccentric contraction – Decrease greatest in early phase of lengthening • Consequently – Greater elongation required to absorb tensile loads in the fatigued state • Heavier and slower gait pattern

• Passive then active SLR • Look for: – Apprehension – Deficits in speed or active range • Appears to be an accurate way to judge RTS Initial study demonstrated much lower reinjury rates • Comparison of speed and ROM of active vs.passive SLR • Based on feelings of apprehension