Strength assessment is an integral part of many clinical tests and some outcome measures. However, shoulder strength may not only be influenced by pathology or treatment effect, but also by scapular position. The present study aimed to examine the influence of scapular positioning on shoulder strength.
Methods
Sixteen normal volunteers (seven males and nine females; mean age 35 years) conducted maximal isometric elevation strength tests in scapular positions of self-selected neutral (SN), maximal protraction (SP), maximal retraction (SR) and posterior tilt (ST), with all of these being assessed in the scapular plane. A prospective, repeated measure, balanced protocol was employed.
Results
Resultant strengths were SN = 6.5 kg, SP = 5.0 kg, SR = 5.3 kg and ST = 5.0 kg. Analysis of variance was significant (p = 0.002) with post-hoc analysis revealing SN as being significantly stronger than SP (p = 0.002), SR (p = 0.004) and ST (p = 0.001). There were no significant differences between SP, SR and ST. Test – retest analysis yielded intraclass correlation coefficients exceeding 0.85.
Conclusions
Altering scapula position may affect shoulder strength in asymptomatic individuals. This has implications for the validity and reliability of shoulder tests and outcome measures that are reliant upon shoulder strength, at the same time as supporting the premise that the application of scapula correction exercises should be based upon individual assessment rather than general prescription.
HegedusEJ, GoodeA., CampbellS.. Physical examination tests of the shoulder: a systematic review with meta-analysis of individual tests.Br J Sports Med2008; 42: 80-92.
2.
BrainG. Aids to the examination of the peripheral nervous system.4th edition.Edinburgh: WB Saunders, 2000.
3.
ConstantC., MurleyA. A clinical method of functional assessment of the shoulder.Clin Orthop1987; 214: 160-4.
4.
SmithJ., DietrichCT, KotajarviBR, KaufmanKR. The effect of scapular protraction on isometric shoulder rotation strength in normal subjects.J Shoulder Elbow Surg2006; 15: 339-43.
5.
SmithJ., KotajarviBR, PadgettDJ, EischenJJ. Effect of scapular protraction and retraction on isometric shoulder elevation strength.Arch Phys Med Rehabil2002; 83: 367-70.
6.
KiblerWB, SciasciaA., DomeD. Evaluation of apparent and absolute supraspinatus strength in patients with shoulder injury using the scapular retraction test.Am J Sports Med2006; 34: 1643-7.
7.
CathcartCW. Movement of the shoulder girdle involved in those of the arm on the trunk.J Anat Physiol1884; 18: 211-8.
8.
LukasiewiczAC, McClureP., MichenerL., PrattN., SennettB. Comparison of 3-dimensional scapular position and orientation between subjects with and without shoulder impingement.J Orthop Sports Phys Ther1999; 29: 574-83.
9.
LudewigPM, CookTM. Alterations in shoulder kinematics and associated muscle activity in people with symptoms of shoulder impingement.Phys Ther2000; 80: 276-91.
10.
LewisJS, GreenA., WrightC. Subacromial impingement syndrome: the role of posture and muscle imbalance.J Shoulder Elbow Surg2005; 14: 385-92.
11.
BorsaPA, TimmonsMK, SauersEL. Scapular-positioning patterns during humeral elevation in unimpaired shoulders.J Athl Train2003; 38: 12-7.
12.
LewisJS. Rotator cuff tendinopathy/subacromial impingement syndrome: is it time for a new method of assessment?Br J Sports Med2009; 43: 259-64.
13.
DvirZ., BermeN. The shoulder complex in elevation of the arm: a mechanism approach.J Biomech1978; 11: 219-25.
14.
LeeHM, BhatA., ScholzJP, GallowayJC. Toy-oriented changes during early arm movements: IV: shoulder-elbow coordination.Infant Behav Dev2008; 31: 447-69.
AlexanderCM, MileyR., HarrisonPJ. Functional modulation of shoulder girdle stability. Exp Brain ResExperimentelle Hirnforschung. Experimentation Cerebrale [Comparative Study Research Support, Non-U.S.Gov't]2005; 161: 417-22.
17.
BullockMP, FosterNE, WrightCC. Shoulder impingement: the effect of sitting posture on shoulder pain and range of motion.Man Ther2005; 10: 28-37.
18.
KebaetseM., McClureP., PrattNA. Thoracic position effect on shoulder range of motion, strength, and three-dimensional scapular kinematics.Arch Phys Med Rehabil1999; 80: 945-50.
19.
MyersJB, WassingerCA, LephartSM. Sensorimotor contribution to shoulder stability: effect of injury and rehabilitation.Man Ther2006; 11: 197-201.
20.
LinJJ, HungCJ, YangPL. The effects of scapular taping on electromyographic muscle activity and proprioception feedback in healthy shoulders.J Orthop Res2011; 29: 53-7.
21.
AlexanderCM, StynesS., ThomasA., LewisJ., HarrisonPJ. Does tape facilitate or inhibit the lower fibres of trapezius?Man Ther2003; 8: 37-41.
22.
McClurePW, MichenerLA, SennettBJ, KardunaAR. Direct 3-dimensional measurement of scapular kinematics during dynamic movements in vivo.J Shoulder Elbow Surg2001; 10: 269-77.
23.
MottramSL. Dynamic stability of the scapula.Man Ther1997; 2: 123-31.
24.
MottramSL, WoledgeRC, MorrisseyD. Motion analysis study of a scapular orientation exercise and subjects ability to learn the exercise.Man Ther2009; 14: 13-8.
25.
HughesRE, JohnsonME, O'DriscollSW, AnKN. Normative values of agonist-antagonist shoulder strength ratios of adults aged 20 to 78 years.Arch Phys Med Rehabil1999; 80: 1324-6.
26.
BeightonP., HoranF. Orthopaedic aspects of the Ehlers Danlos syndrome.J Bone Joint Surg (British Volume)1969; 51B: 444-53.
27.
BarnettND, DuncanRDD, JohnsonGR. The measurement of three dimensional scapulohumeral kinematics–a study of reliability.Clin Biomech1999; 14: 287-90.
28.
PopperN., PeterW. Normal and abnormal motion of the shoulder.J Bone Joint Surg1976; 58: 195-201.
29.
BankesMJK, CrossmanJE, EmeryRJH. A standard method of shoulder strength measurement for the Constant score with a spring balance.J Shoulder Elbow Surg1998; 7: 116-21.
30.
KatolikLI, RomeoAA, ColeBJ, VermaNN, HaydenJK, BachBR. Normalization of the Constant score.J Shoulder Elbow Surg2005; 14: 279-85.
31.
BlonnaD., ScelsiM., MariniE.. Can we improve the reliability of the Constant–Murley score?J Shoulder Elbow Surg2012; 21: 4-12.
MunroBH. Statistical methods for health care research.3rd edition.Philadelphia, PA: Lippincott, 1997.
34.
KiblerWB, ChandlerTJ, LivingstonBP, RoetertEP. Shoulder range of motion in elite tennis players. Effect of age and years of tournament play.Am J Sports Med1996; 24: 279-85.
35.
JenpYN, MalangaGA, GrowneyES, AnKN. Activation of the rotator cuff in generating isometric shoulder rotation torque.Am J Sports Med1996; 24: 477-85.
36.
YianEH, RamappaAJ, ArnebergO., GerberC. The constant score in normal shoulders.J Shoulder Elbow Surg2005; 14: 128-33.
37.
HirschmannM., WindB., AmslerF., GrossT. Reliability of shoulder abduction strength measure for the Constant–Murley score.Clin Orthop Relat Res2010; 468: 1565-71.
38.
PodolskyRJ, SchoenbergM. Force generation and shortening in skeletal muscle.Comprehensive PhysiologyHoboken, NJ: John Wiley, 2010.
39.
GordonAM, HuxleyAF, JulianFJ. The variation in isometric tension with sarcomere length in vertebrate muscle fibres.J Physiol1966; 184: 170-92.
40.
LieberRL. Skeletal muscle structure, function and plasticity: the physiological basis of rehabilitation.3rd edition.Philadelphia. PA: Lippincott Williams & Wilkins, 2009.
41.
LudewigPM, ReynoldsJ. Association of scapular kinematics and glenohumeral joint pathologies.J Orthop Sports Phys Ther2009; 39: 90-104.
42.
KiblerWB, SciasciaAD, UhlTL, TambayN., CunninghamT. Electromyographic analysis of specific exercises for scapular control in early phases of shoulder rehabilitation.Am J Sports Med2008; 36: 1789-98.
43.
JSR., MacDermidJC, WoodhouseLJ. A systematic review of the psychometric properties of the Constant–Murley score.J Shoulder Elbow Surg2010; 19: 157-64.
44.
WaltonMJ, WaltonJC, HonorezLAM, HardingVF, WallaceWA. A comparison of methods for shoulder strength assessment and analysis of Constant score change in patients aged over fifty years in the United Kingdom.J Shoulder Elbow Surg2007; 16: 285-9.
45.
OgstonJB, LudewigPM. Differences in 3-dimensional shoulder kinematics between persons with multidirectional instability and asymptomatic controls.Am J Sports Med2007; 35: 1361-70.
46.
von Eisenhart-RotheR., MatsenFAI, EcksteinF., VoglT., GraichenH. Pathomechanics in atraumatic shoulder instability: scapular positioning correlates with humeral head centering.Clin Orthop2005; 433: 82-9.
