Context An Exercise Progression from for Shoulder • Therapeutic exercises are prescribed along Rehabilitation based on Rehabilitation based on a continuum a continuum the available EMG • A common goal to increase neuromuscular Literature activity • In order to stimulate neuromuscular & musculotendinous adaptations musculotendinous adaptations Ti Tim L. Uhl PhD ATC PT FNATA L Uhl PhD ATC PT FNATA • Thereby allowing the patient to return to Department of Rehabilitation Sciences “normal” physical College of Health Sciences University of Kentucky Context Objectives • Describe Electromyography data collection and • Better understanding the neuromuscular interpretation activity levels of therapeutic exercise allows y p • Outline an exercise progression through a phased us to match the exercise selected to the rehabilitation process keeping physiological healing patient’s state of healing response and tissue reactivity in mind • This knowledge also allows us to titrate the – Higher EMG activity greater muscular recruitment exercises prescribed up or down the • Rehabilitation exercises are often selected based on continuum based on the patient’s response continuum based on the patient’s response EMG research to facilitate specific muscle activation – Therapeutic exercises rarely isolate “The whole of science is nothing more than a refinement of everyday thinking.” – Albert Einstein (1879 - 1955), Physics and Reality 1936 1
Electromyography Electromyography (EMG) • The recording and • A technique to • A technique to analysis of myoelectrical l i f l t i l evaluate and record signals derived from electrical activity motor unit activity from skeletal muscle – EKG/ECG – cardiac • Motor Unit muscle muscle – Nerve cell body in the spinal • Device is cord electromyograph – The motor nerve (axillary) – The muscle fibers that the • Generates an nerve innervates electromyogram When a Muscle Contracts Set-up for collecting EMG data • Action potential travels d down motor nerve to t t neuromuscular junction • ACh causes breakdown of membrane to produce motor action potential (endplate potential) (endplate potential) • Potential is propagated along sarcolemma 2
Set up for Indwelling Electrodes Action Potential Propagation (Fine Wire) • The recording electrodes (surface or electrodes (surface or indwelling) placed in parallel to the muscle fibers detect the relative voltage difference between the two electrodes as the action potential propagates along the muscle fibers Utilization of EMG in Which Muscle Turned on First? Rehabilitation and Research 0 .0 0 m s e c . 1 0 0 .0 0 • Initiation of muscle activation (Onset) Force to rq u e (2 0 4 8 x ) (3 2 x ) • How long is a muscle activated (Duration) (3 2 x ) v e lo c ity (3 2 0 x ) Velocity • Amount of muscle activation (Amplitude) s u p ra (0 .5 x ) (3 2 x ) • Measures level of fatigue occurring in a Supraspinatus i in fra (0 .5 x ) f (0 5 ) muscle (Frequency shifts) (2 5 x ) Infraspinatus p o s td e lt(3 2 x ) (3 2 x ) Posterior Deltoid 2 0 0 .0 0 m s e c . 3
Utilization of EMG in Relative Amount of Muscular Rehabilitation and Research Activity • Measure of EMG Amplitude • Normalization of EMG signal to an event or to a – To determine how much muscular activity was T d t i h h l ti it specific task recruited for a particular exercise • Allows for comparison between subjects, days, • EMG activity is translated from Volts to muscles or studies percentage of muscle activity – Soderberg & Knutson, Phys Ther 2000 – MVC – maximal voluntary contraction y – RVC – reference voluntary contraction (task, set load) Normalization EMG Amplitude Categorization • Specific positions identified for • 0 – 20% Low activity • 15%MVIC= 30N force shoulder or MMT positions • 21 – 40% Moderate activity y conservative estimate to conservative estimate to • Rotator cuff • Rotator cuff • 41 – 60% High activity – Kelly, J Ortho Res 1996 protect repair • >61% Very High activity • Scapular musculature – Long, JOSPT 2010 – DiGivone, JSES 1990 – Michener, Phy Ther 2005 – Assumptions: fraction of • 100% isometric contraction (MVIC) – 0 – 5% Minimal EMG activity MVIC, CSA, specific – Most commonly used (background noise) tension, & fiber pennation – Need to perform for 3-5 sec duration with – Perry, Gait Analysis 1992 Perry, Gait Analysis 1992 2-3 repetition with at least 30-90 sec. rest 2 3 repetition with at least 30 90 sec rest – 44±15N load for 206 ±88 • <20% = Minimal activity – Hagberg. Am J Phys Med 1981 cycles generated 50% • The highest amplitude obtained • 20-50% = Moderate activity loss of rotator cuff repair during time interval is considered 100% (1 or ½ second) • >50% = Marked activity – Bicknell, Arthroscopy 2005 • EMG data is expressed as a %MVIC – McCann, Clin Orth Rel Res or %RVC 1993 4
Limitations of EMG Rotator Cuff Tendon Rupture • Sources of interference • Not typically traumatic – Movement artifact • Degenerative overuse • Degenerative overuse – External electrical noise (electrical outlets, ECG) mechanism most – Possibility of “cross-talk” from other muscles (surface) common • Reducing interference by use good • Combination of equipment, small electrodes, and careful compression and p electrode placement electrode placement eccentric overload • Not a measure of force or strength – Lin et al., J Biom 2004 – Moderate correlation in an isometric conditions – Inman, EEG Clin Neurophysiol 1952 Biomechanical Properties of Rehabilitation Implications Healing Tendon • Following tendon repair first 3- 6 • Human tendon maximal wks loads across the tendon strength ranges from 50 – have to be minimal 150MPa • Animal model suggest – Gelberman et al., Injury and Immobilization is beneficial over Repair Musculoskeletal Soft early mobilization Tissues 1987 • Rat maximal tensile load – Increased organization =25 + 9 MPa – Less scar formation – 6wks = 8% 6wks = 8% – Mechanically stronger – Mechanically stronger – Thomopoulos, J Biom Eng, 2003 – 12 wks = 12% • Gradual introduction of stresses – Repaired supraspinatus post- during the maturation process op does not approach intact values – Lower EMG activity – Carpenter et al., JSES 1998 5
Rehabilitation Progression Immobilization ≠ Inactivity • EMG activity is present in Functional Sport immobilizer S Specific ifi • Caution for certain activities to protect of rotator cuff Power – Bimanual tasks increases Biceps (7- Kinetic Recovery 16%) [SLAP] Chain breakage – Pulling open door activated Strength Supraspinatus (10-20%) [Rot Cuff Endurance Kibler, Functional Rehabilitation Rehabilitation Repairs] Repairs] Neuromuscular Control 1998 – Pushing open a door quicky activate Infra. (60±45%) [Rot Cuff Repairs] Rest Wound care Acute Modalities – Reaching task with contralateral limb facilitate scapular musculature (20-60%) Injection ROM in the immobilized limb Bracing – Smith, J Sh Elb Surg 2004 Quick Motions of Contralateral Other Precautions in Sling Arm Increase Activity • Post-operatively to • Post-operatively to protect healing rotator cuff avoiding drinking with involved side while in sling – Long, JOSPT 2010 6
Respect Physiological Healing when Acute Phase Rehabilitation Prescribing Exercises 100 • For proper healing need some 90 period of immobilization period of immobilization 80 70 • Initiate ROM within physiological 60 % MVIC healing restraints and pain 50 tolerances 40 • Can we find a balance Hugh Owen Thomas 30 Father of Immobilization 20 10 10 Adhesions 0 Communication What level of muscle activity is Pendulum associated with PROM? • Pendulum • Pendulum • Small vs large circle • Small vs large circle • Supine Passive • Correct vs incorrect elevation • 13 Healthy subjects – w/ or without • Concluded small therapist circles (20cm) circles (20cm) • Forward Bow generated lowest • CPM EMG activity – Long, JOSPT 2010 7
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