OVERUSE INJURIES IN RUNNING

CONTENTS Overview; Basic biomechanics of running; Epidemiology of running injuries; Causative factors; Dose-response relationship; and Prevention strategies Evaluation strategies

OVERVIEW Commonest type of sports in Hong Kong Mass entrants in the Tsing Ma Bridge Marathon and 98 New Airport International Marathon and 10 km. run

BENEFITS OF RUNNING Improve physical fitness level; Positive feeling of good health; Friendship and socialisation; Enjoyment; and Rewards

1. Establishing the extent of the sports injury problem Incidence Severity Sequence of Prevention 2. Establishing aetiology & mechanism of injuries 4. Assessing their effectiveness by repeating step 1 3. Introducing preventive measures

EPIDEMIOLOGY OF RUNNING INJURIES Knutzen and Hart (1996) A comprehensive review on running injuries Retrospective studies (16) Prospective studies (5) Annual incidence 48-65% (P); 24-60% (R)

EPIDEMIOLOGY OF RUNNING INJURIES Retrospective studies Marti et al. (1980) Surveillance study of 4,358 runners in a road race 1,994 injured (46%)

PROSPECTIVE STUDY Walter et al. (1989) Ontario Cohort study enrolled 1,680 runners at two races prospective survey for 12 months. 1,288 completed the follow-up data 48% were injury.

SITE OF INJURIES

Case series studies Clement et al. (1981) Review 1,650 patients between

EPIDEMIOLOGY OF INJURIES Data collection far from comprehensive Subjects selection bias Injuries ill-defined True incidence of injuries yet to be determined (for details, refer to Caine et al., (1996) epidemiology of sports injuries. Human Kinetics. Chapter 22)

ESTABLISHING AETIOLOGY & MECHANISM OF INJURIES

RUNNING EVENTS CHARACTERISTICS NEURO-MUSCULAR PREDOMINANCE (SPRINT & HURDLES) CARDIO-RESPIRATORY PREDOMINANCE (MIDDLE & LONG DISTANCE) CAPACITY BASED ON STRENGTH & ENDURANCE (AEROBIC & ANAEROBIC) PHYSIOLOGICAL ADAPTATION TAKING PRECEDENCE OVER TECHNIQUE

RUNNING CYCLE No double support phase Stance (40%) Float (30%) Swing (30%) Contact, midstance,propulsion forward swing & foot descent

Jogging: Stance > Swing Distance: Stance = Swing Sprinting: Stance < Swing

RUNNING BIOMECHANICS INITIAL GROUND REACTION FORCES VERTICAL GROUND REACTION FORCES VERTICAL GROUND REACTION FORCES 2-3 TIMES BODY WEIGHT 2-3 TIMES BODY WEIGHT ANTERIOR /POSTERIOR FORCES - 50% B.W. ANTERIOR /POSTERIOR FORCES - 50% B.W. MEDIAL /LATERAL SHEAR - 10% B.W. MEDIAL /LATERAL SHEAR - 10% B.W. DURATION ms. DURATION ms. PEAK IMPACT FORCES AT ms. PEAK IMPACT FORCES AT ms.

CAUSATIVE FACTORS IN RUNNING INJURIES EXTRINSIC Training error Running Terrain and Surfaces Running shoes

TRAINING ERROR Clement et al. (1981) Sudden increases in mileage or intensity High intensity without rest High level of competition

Marti et al. (1980) Increased association of injuries when mileage (>50 km./week) Ontario Cohort study > 40 km/week.

RUNNING TERRAIN AND SURFACES Clement et al Uneven, hardness, road camber Uphill and downhill

RUNNING SHOES FOOT MUST BE STABLE SHOCK ABSORBPTION – REDUCE THE INITIAL HEEL SPIKE RIGID LEVER FOR THE THRUST OF FORWARD MOTION

RUNNING SHOES SHOCK ABSORPTION EFFECT FACTS: The Shock absorption effect will easily lost 40% after Km. of running (After Cook et al 1985) FACTS: The Shock absorption effect will easily lost 40% after Km. of running (After Cook et al 1985)

CAUSATIVE FACTORS IN RUNNING INJURIES INTRINSIC IMPERFECT MUSCULOSKELTAL ALIGNMENT FLEXIBILITY

INTRINSIC FACTORS Cowan et al., 1996 Investigate effects of anatomic variation on risk of overuse injuries Prospective study Subjects: 294 army infantry for 12/52 training Risk of injury increase with Valgus knee (RR=1.9) and Q angle >15 degree (RR=5.4)

INTRODUCING PREVENTIVE MEASURE

PRINCIPLES OF TRAINING BIOLOGIC ADAPTATIONS TO IMPROVE PERFORMANCE IN SPECIFIC TASKS

TRAINING PROGRAM Yeung and Yeung 2001 Investigate the characteristics and training profile of marathon finishers and non- finishers Subjects: 113 runners from Standard Chartered Hong Kong Marathon 1998

Personal and training profile ProfilesFinishers (55) Non- finishers (58) P-value Marathon finished Weekly training Longest distance Warm-up Cool down Optimal mileage

TRAINING AND RECOVERY Warm (Cool) down Whirpools and Spas Massage Rest and Sleep Psychological Nutritional

COOL DOWN Lactate can be removed from blood and muscle more rapidly by light continuous aerobic exercise Optimal rate of removal % VO 2 max 50-65%

OVER TRAINING Sign of over training Fatigue and poor performance Increase resting heart rate Weight loss Irritability and sleep disturbance Elevated Serum Creatine Phosphokinase (CPK)

TRAINING TERRAIN TRACK vs ROAD CROSS TRAINING – UPHILL vs DOWNHILL TREADMILL

FUNCTIONAL ANATOMY OF FOOT Normal Foot arch, flat foot and Pes Cavas Effects of foot arch or weight bearing

SELECTION OF RUNNING SHOE

RUNNING SHOES Be Comfortable Protect the wearer from injury Not be a source in injury Facilitate athletic performance Be durable and economical

SHOE COMPONENTS

Last Straight / Curve Last Slip Last Board Last Shoe Upper Toe-box Heel Counter Achilles Tendon Pad Sole Outsole Midsole Insole

PRONATOR Needs stability and arch support Features: Straight last; Supportive heel counter; Extra support on medial side Increased medial wedging on insole Semirigid orthotic

NEUTRAL Need good fit, adequate arch and shock absorbing Features: Semicurved last; Extra cushioning & Medium heel counter

SUPINATOR Needs flexibility, maximum shock absorbing Features: Semicurved or curved last; Slip last Maximum cushioning

ASSESSING THE EFFECTIVENESS OF INTERVENTION

A systematic review of interventions to prevent lower- limb soft-tissue running injuries Yeung and Yeung, 2001a and 2001b

Randomised Controlled Trials Twelve studies, with a total of 8,806 subjects met the criteria for inclusion. three main preventive strategies for running injuries: modification of training schedule stretching exercises use of orthotics/support or footwear modification.

Modification of training schedule InterventionRelative risk Reduction of frequency of training 3/7 vs 5/ ( )* Reduction in duration of training vs 45per session 0.41 ( )* Reduction in running distance 280 km vs 82 km in 12 weeks 0.70 ( )*

STRETCHING Stretching outside training session Andrish et al.,1.27 ( ) Hartig and Henderson0.57 ( )* Stretching immediately before training session Pope et al.,0.85 ( ) Pope et al.,0.83 ( ) Van Mechelen et al.,1.19 ( )

EXTERNAL SUPPORT OR FOOTWEAR MODIFICATION Use of shocking absorbing insoles 0.87 ( ) Footwear modification0.83 ( )* Use of Knee brace0.35 ( )*

Injuries from running can be reduced by modifying training schedules, but now guidelines are available from trials on training load. Wearing a knee brace with a patellar support ring may be effective in preventing anterior knee pain provoked by running