ATHLETIC STRETCHING By: Jesse DeLuca D.O. Primary Care Sports Medicine Fellow
Objectives • Review the pathophysiology • Discuss the literature and study findings pertaining to soreness, performance and injury risk. • Identify Guidelines on stretching.
OUTLINE • Muscle Structure and Mechanics • Vocabulary and Types of Stretching • Clinically Relevant Questions/Evidence • Guidelines
Definitions • Stretching – activity to increase ROM • Effects • Elastic – temporary • Viscous – reversible over time • Plastic – permanent • Stretch Reflex – muscle spindles cause contraction (not DTR’s/GTO)
Definitions • Intrafusal Fibers – proprioceptor (gamma motor neurons) • Rate of Change • Position • Extrafusal Fibers - movement (alpha motor neurons) • Pennate Angle – fiber angle to the primary tendon(the larger the pennate angle the slower and weaker the contraction)
Definitions • Stretching Techniques • Static – held position • Active – antangonist contraction • Proprio-Neuro-Facilitory (PNF) – combination • Ballistic – bouncing • Dynamic – propelling to end ROM but not past
Does stretching reduce soreness? • BMJ 2002 no support for reduction in soreness or for reduction in injury. Insufficient evidence for performance. • 5 studies (PEDro scale) • Decrease of 1 point out of 100 on VAS for post exercise soreness 24-72hrs • 2002 BMJ “Effects of stretching before and after exercising on muscle soreness and risk of injury systematic review”
Reduction of Soreness • The evidence from randomized studies suggests that muscle stretching, whether conducted before, after, or before and after exercise, does not produce clinically important reductions in delayed-onset muscle soreness in healthy adults. • Cochrane Database Syst Rev. 2011 Jul 6;(7):CD004577
Reduction of Soreness • 1 study showing stretching does not increase vascular blood flow. • Control group • Middle aged sedentary individuals • Supervised stretching vs supervised strength training • Journal of Applied Physicology, ‘Resistance training increases basal limb blood flow and vascular conductance in aging humans’
Does stretching decrease risk of injury? • Anterior Knee Pain Prevention • RCT • UK army recruits • 14 week exercise intervention during training (basic phase 1 recruit training) • 39 male units/11 female units , median 19.7 yo • ~750 recruits per study-arm • Intervention = 4 stretching and 4 strengthening exercises (supervised) • Control = warm-up (supervised) • 46 = AKP, 36 controls, 10 intervention • Discharged 25 control, 3 intervention • Am J Sports Med. 2011 May;39(5):940-8. Epub 2011 Jan 6.
Reduction in Injury • Lower limb injuries in Australian Army Recruits • Med Sci Sports Exerc. 2000 Feb;32(2):271-7 • Effect of muscle stretching during warm-up on the risk of exercise-related injury. • 1538 male army • stretch or control groups over 12 weeks • stretch group -1, 20-s static stretch under supervision for each of six major leg muscle groups during every warm-up. • Control group did not stretch. • 333 lower-limb injuries, 214 soft-tissue injuries • 158 injuries in the stretch group • 175 in the control group • no significant effect of preexercise stretching on all-injuries risk, soft-tissue injury risk or bone injury • Fitness (20-m progressive shuttle run test score), age, and enlistment date all significantly predicted injury risk (P < 0.01 for each) • height, weight, and body mass index did not.
Reduction in Injury • Effects of ankle dorsiflexion range and pre-exercise calf muscle stretching on injury risk in Army recruits. • reduced ankle dorsiflexion was a strong predictor of risk of injury. • control and ankle stretching groups did not have significant differences in injury. • AustJ Physiother. 1998;44(3):165-172.
Reduction in Injury • Cohort Study of Recreational Basketball Players • Courtside observation and questionairre • 40 ankle injuries at 3.85/1000 • ½ did not seek treatment • 3 risk factors identified • Previous injury • Air cell in shoes • Non-stretchers • BJSM 2001 “Ankle injuries in basketball: injury rate and risk factors “
Reduction in Injury • Cochrane 2001 but assessed as up to date 2011 • 6 trials • 5130 participants • NO evidence stretching reduces soft tissue injuries
Does stretching improve performance? • The effects of dynamic stretching on plantar flexor muscle-tendon tissue properties. • 20 males • Dynamic stretching of plantar flexors for 30 s and to repeat for 5 sets. • Ankle dorsiflexion ROM measured before and after the dynamic stretching. • Changes in the displacement of the myotendinous junction (MTJ), pennation angle, and fascicle length were also determined by using ultrasonography. • Ankle dorsiflexion ROM increased significantly after the dynamic stretching • A significant distal displacement of the MTJ was observed in first stretching set • Pennationangle, and fascicle length were unaffected by the dynamic stretching. Dynamic stretching was shown to be effective in increasing ankle joint flexibility. • dynamic stretching of the plantar flexors was considered an effective means of lengthening the tendon tissues. • Man Ther. 2011 Aug 2
Performance • Med Sci Sports Exerc. 2011 Jun 8 • Review of RCT’s • Effect of Acute Static Stretch on Maximal Muscle Performance: A Systematic Review. • Clear evidence exists indicating that short-duration acute static stretch (<30 s) has no detrimental effect • stretch durations of 30-45 s also imparted no significant effect • A sigmoidal dose-response effect was evident between stretch duration and both the likelihood and magnitude of significant decrements, with a significant reduction likely to occur with stretches ≥60 s. • This strong evidence for a dose-response effect was independent of performance task, contraction mode or muscle group. • Studies have only examined changes in eccentric strength when the stretch durations were>60 s, with limited evidence for an effect on eccentric strength. • The detrimental effects of static stretch are mainly limited to longer durations (≥60 s) which may not be typically used during pre-exercise routines in clinical, healthy or athletic populations. Shorter durations of stretch (<60 s) can be performed in a pre-exercise routine without compromising maximal muscle performance.
Performance • ClinicalJournalofSportsMedicine • 2004 • Acuteboutsofstretching • 22 outof 23 articles NO benefit on isometricforce, isokinetictorqueor jumping height. • Speed = 1 beneficial, 1 detrimental, 2 equivocal
Performance • Journal of Strength and Conditioning Research • 2006 • Dynamic vs. Static Stretch vs. none • USMA (14 f, 16 m) • 3 days • 3 power or agility tests • T shuttle run • Underhand medicine ball throw • 5 step jump • 1-2 minutes of recovery • Dynamic – improvement in all 3 • Static – improved 5 step jump • Of note 2007 study showed vertical countermovement jump negatively impacted by static stretching
Performance • Toughest Sport in the World • 2008 • Dynamic vs. Static exercises prior to all preseason practices • Long term (4 weeks) • Tested before and after in • Peak Torque of Quads • Underhand medicine ball throw • 300yd shuttle • Push-ups • Sit-ups • Broad Jump • 600 m run • Dynamic Stretching improved all aspects
Guidelines • Navy Seal Physical Fitness Guide • Dynamic stretching just before activity • Static stretching after • Ballistic NEVER • Warm-up before ALWAYS
Guidelines • FM 21-20 • Stretching types • Static • Passive • Ballistic • PNF
Guidelines • The ACSM recommends stretching muscle groups or joints throughout the body 2 to 3 days per week, and preferably 5 to 7 days per week, and to hold each stretch for 15 - 30 seconds. For optimal flexibility they recommend repeating each stretch 2 to 4 times each. • This guideline is for achievement of minimal fitness and conditioning guidelines.
Guidelines • ECSS 2007 Position Statement • During passive static stretching stress relaxation occurs, i.e. the mechanical properties of the muscle-tendon unit are affected during the actual stretch maneuver, however, this mechanical effect appears to rapidly (minutes) disappear. • Stretching produces gains in maximal joint range of motion: the mechanism for the augmented joint range of motion is an increased tolerance to applied stretch, rather than a change in the mechanical properties of the muscle-tendon unit. • The currently available evidence does not sup- port the notion that stretching prior to exercise can effectively reduce injury risk.
Guidelines • ECSS 2007 Position Statement • There is no evidence that muscle strength or jump performance will improve with an acute bout stretching. In fact, there is firm evidence that muscle strength and jump performance is diminished immediately after stretching. • Habitual stretching may improve maximal muscle strength and jump height. • Habitual stretching is unlikely to improve run- ning economy.
Guidelines • AAOS position statement for healthy living • Stretch. Begin stretches slowly and carefully until reaching a point of muscle tension. Hold each stretch for 10 to 20 seconds, then slowly and carefully release it. Inhale before each stretch and exhale as you release. Do each stretch several times. Never stretch to the point of pain, always maintain control, and never bounce on a muscle that is fully stretched.
Conclusion • In General • Stretching that is beneficial is likely sport, joint and possibly athlete specific. • There is a chance of harm and decrease in performance from good intentioned stretching especially in the short term. • Sport specific movements should be considered when determining a stretching program. • Stretching may only be beneficial in conjunction with other modalities. • Stretching over the long term is likely more important than pre-competition stretching. • Further studies need to be done.