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APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 1 Mario Lamontagne, PhD 1,2,3 Professor in Biomechanics 1- School of Human Kinetics, Faculty.

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Presentation on theme: "APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 1 Mario Lamontagne, PhD 1,2,3 Professor in Biomechanics 1- School of Human Kinetics, Faculty."— Presentation transcript:

1 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 1 Mario Lamontagne, PhD 1,2,3 Professor in Biomechanics 1- School of Human Kinetics, Faculty of Health Sciences, U. of Ottawa 2- Dept. of Mechanical Engineering, University of Ottawa, Ottawa, Canada; 3- Let People Move, Biomechanics Laboratory, Perugia, Italy FUNCTIONAL ROLE OF EMG IN ORTHOPAEDICS

2 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 2  Introduction  Background on the Electromyography  Recording Technique  Analysis of the EMG signal  Applications in Orthopaedics Scope of this presentation

3 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 3 IntroductionIntroduction  The electromyographic (EMG) signal offers a great source of information to both clinicians and researchers  EMG can be used to detect gait or joints pathologies, to assess a rehabilitation program, to measure the functionality of sport equipment and to implement an effective biofeedback therapy.

4 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 4 IntroductionIntroduction Surface EMG is also widely used in an effort to understand a number of research issues:  Muscles coordination around a joint  Relationship between muscular force and muscle electrical activity  Neuromuscular adaptations after joint surgery following a rehabilitation program.

5 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 5 Background on the EMG The muscle unit action potential detected by electrodes in the muscle tissue or on the surface of the skin. Central nervous system (CNS) activity initiates a depolarisation in the motoneuron.

6 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 6 A single axon leading to a muscle is responsible for the innervation of as few as 3 or as many as 2000 individual muscle fibres. A neuron and the muscle fibres are referred to as motor unit Background on the EMG

7 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 7 Background on the EMG A neuron and the muscle fibers are referred to as motor unit (MU)

8 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 8 Background on the EMG The nerve impulse is transmitted in a nerve axon as schematically shown down below + - AB

9 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 9 A dipole is moving along a volume conductor. A differential amplifier records the difference between the potentials at point A and B on the conductor. + - AB Background on the EMG + -

10 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 10 Background on the EMG + - AB The dipole is moving along the conductor. The potential A is getting more negative.

11 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 11 Background on the EMG More the dipole is moving between the potentials more the signal is positive + - AB

12 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 12 Background on the EMG + - AB Finally, the connector B registers the positive end of the dipole and the connector A is returning to zero. The result of the amplification becomes negative

13 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics AB The triphasic curve has some similarity with an action potential which passes through a nerve axon. Background on the EMG

14 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 14 Background on the EMG Number of MU varies with the type and function of muscles. MusclesNumber of muscle’s fibers/Neuron Platysmus25 Long Digital Flexor95 Tibialis Anterior609 Gastrocnemius1775

15 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 15 Motor Unit Recruitment Once an action potential reaches a muscle fiber, it propagates proximally and distally. This is called motor action potential (MAP). A motor unit action potential (MUAP) is spatiotemporal summation of MAPs for an entire MU. Background on the EMG

16 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 16 Background on the EMG An EMG signal is the algebraic summation of many repetitive sequences of MUAPs for all active motor units in the vicinity of the recording electrodes MUAP1 MUAP2 MUAP3 MUAP4

17 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 17 Background on the EMG MU 1 MU 2 MU 3 MU 4 Muscle tension MU 1 MU 2 MU 3 MU 4 MU Recruitment The order of MU recruitment is according to their sizes. The smaller ones are active first and the bigger ones are active last.

18 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 18 Background on the EMG MUAP vs. Force –For a voluntary contraction, muscle’s force depends on the number of MU and the frequency of activation –Muscle’s force is proportional of the cross- sectional area of the active muscle fibers. –Muscle force during isometric action is around 30 N/cm 2

19 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 19 Recording Techniques A wide variety of electrodes are available to measure the electrical muscle output  microelectrode and needle electrode (not practical for movement studies)  Surface electrodes (SE) and Intramuscular wire electrodes (IWE) are commonly used in movement studies The differential preamplifier increases the amplitude of the difference signal between each of detecting electrode and the common ground. The advantage of the differential preamplifier is to improve the signal- to-noise ratio of the measurement.

20 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 20 Recording Techniques EMG Signal Detection Summary Bipolar electrodes (active electrode rather than passive electrodes Distance between electrodes 10 to 20 mm apart Bandwidth of Hz CMRR greater than 100 dB Noise less than 2mV Electrode located on the midline of the muscle belly

21 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 21 Analysis of the EMG signal RAW Onset Peak In the time domain: the root-mean squared (RMS) value or also called Linear Envelop) the average rectified value Both are appropriate and provide useful measurements of the signal amplitude Muscle onset (time) Peak amplitude of RMS

22 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 22 Analysis of the EMG signal In the Frequency domain: Spectral Density –Median Frequency –Mean Frequency Wavelet This represents the frequency contents of EMG signal.

23 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 23 Interpretation of the EMG signal  EMG is a tool not without its hidden weaknesses  These problems have the potential to mask any benefit obtained from the recorded information.

24 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 24 Anecdotal Demonstration Adrian R. M. Upton conducted an anecdotal demonstration of the difficulty of documenting brain death by placing EEG electrodes in an upside-down bowl of lime Jell-O (reported in The New York Times, March 6, 1976, p. 50).

25 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 25 Interpretation of EMG  As with EEG traces, the interpretation of the recorded EMG should be conducted with care.  However, with proper use, the surface electromyogram is a powerful and effective tool for both clinical evaluation and research.

26 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 26 Applications in Orthopaedics Most of the applications of sEMG and imEMG are based on:  Muscle activation and timing  Muscle contraction profile  Muscle strength of contraction  Muscle fatigue. Recent technological development in sEMG moved research from the laboratory to the field applications. Few orthopaedic applications will be presented in sports, rehabilitation and sport medicine.

27 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 27 Objective:  Examine the neuromuscular response to functional knee bracing relative to anterior tibial translations. Design:  During randomized brace conditions, electromyographic data with simultaneous skeletal tibiofemoral kinematics and GRF were recorded from four ACL deficient subjects to investigate the effect of the functional brace during activity. Ramsey, D. K., Lamontagne, M., Wretenberg, P., Valentin, A., Engström, B., & Németh, G. (2003). Electromyographic and biomechanics analysis of anterior cruciate ligament deficiency and functional knee bracing. Clin Biomech (Bristol, Avon) Jan;18(1):28-34 APPLICATIONS IN SPORT MEDICINE Muscle Activation and Timing 1

28 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 28 APPLICATIONS IN SPORT MEDICINE Methods:  Kinematic and kinetic measure-ments were synchronously recorded with the EMG signal. The EMG data from the RF, S, BF, and LG were integrated for each subject in three separate time periods: 250 ms preceding foot-strike and two consecutive 125 ms time intervals following foot-strike. Muscle Activation and Timing 1

29 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 29 Results: WWith brace, ST activity significantly decreased 17% prior to footstrike wwhereas BF significantly decreased 44% during A2, (P<0.05). RRF activity significantly increased 21% in A2 (P<0.05). NNo consistent reductions in anterior translations were evident. APPLICATIONS IN SPORT MEDICINE Muscle Activation and Timing 1

30 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 30 APPLICATIONS IN SPORT MEDICINE Conclusion:  Joint stability may result from proprioceptive feedback rather than the mechanical stabilising effect of the brace. As a result of bracing, we observed decreased S and BF activity but increased RF activity. We suggest increased afferent input from knee proprioceptors and brace-skin-bone interface modifies EMG activity. Muscle Activation and Timing 1

31 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 31 Applications in Orthopaedics To better understand the neuromuscular control of the hamstrings to protect the ACL strain using an in vivo experimentation. PURPOSESPURPOSES

32 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 32 Applications in Orthopaedics  Five healthy males (mean: age; 25yrs; height: 167cm; weight: 71.5kg)  No previous knee joint injuries.  Prior the in vivo data collection, participants was instructed to the implantation procedure and testing protocol including training of the tasks METHODS: METHODS: Participants

33 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 33 Applications in Orthopaedics  DVRT arthroscopically implanted on the antero- medial band of the intact ACL under local anesthesia.  The barbed ends of the DVRT are inserted into the ligament bundle and fixed in place.  The surgical instruments were removed and the wounds were closed and sutured around the exiting instrument wire. METHODS: METHODS: Surgical Procedure

34 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 34 Applications in Orthopaedics  Kinematics was recorded with 4 H-S cameras (50 Hz) using SIMI Motion System.  EMG, force plate, and DVRT signals was collected for 8 s at 1000Hz synchronously with kinematic data  A total of five trials per movements were collected METHODS: METHODS: Testing Protocol

35 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 35 Applications in Orthopaedics  Rectified EMG signals were normalised by peak amplitude for the dynamic contractions of the three manoeuvres using the stopping motion EMG data as normalisation basis.  The data from all five trials was ensemble averaged over the cycle METHODS: METHODS: Data Analysis

36 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 36 Applications in Orthopaedics RESULTS: RESULTS: IN-VIVO ACL STRAIN Knee Angle DVRT GRF Vastii Hamstrings Gastroc.

37 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 37 Applications in Orthopaedics  Almost 80% of ACL injuries are non-contact in nature.  Neuromuscular strategy anticipated the landing impact during all motions 1-2  Strategy to position Lower-limb segment before landing 3  Joint coordination might play a role for injury prevention DISCUSSIONDISCUSSION 1- Besier, T.F., Lloyd, D.G., Ackland, T.R., Muscle activation strategies at the knee during running and cutting maneuvers. Med. Sci. Sports Exerc. 35, 119– Cowling, E.J., Steele, J.R., Is lower limb muscle synchrony during landing affected by gender? Implications for variations in ACL injury rates. J. Electromyogr. Kinesiol. 11, 263– McLean, SG, X. Huang, A. Su, and A. v d Bogert, Sagittal plane biomechanics cannot injure the ACL during sidestep cutting. Clinical Biomechanics ACL rupture during the Canadian badmington Championship: UO Student

38 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 38 Applications in Orthopaedics  The anticipatory muscle contraction of the hamstrings and Gastrocnemius play an important role of protecting excessive ACL elongation.  The Hamstrings and Gastrocnemius are more associated with ACL elongation than Knee joint Torque. DISCUSSIONDISCUSSION

39 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 39 Applications in Orthopaedics Gender Difference for a cut motion  Male and Female elite football players  Control speed  Cue given at 1.2m from the FP See EMG Data C C

40 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 40 Applications in Orthopaedics We investigated possible differences in muscle fatigue and recovery of knee flexor and extensor muscles in patients with a deficient anterior cruciate ligament compared with patients with a normal anterior cruciate ligament. Muscle Fatigue 1 Surface EMG can be used as muscle fatigue indicator Tho, K., Németh, G., Lamontagne, M., & Eriksson, E. (1997). Electromyographic Analysis of Muscle Fatigue in Anterior Cruciate Ligament Deficient Knees. Clinical Orthopaedics & Related Research(340),

41 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 41 Applications in Orthopaedics  SEMG of 15 patients with ACL deficiency was measured while the muscles were under 80% of MVC for 60 s and remeasured after 1, 2, 3, and 5 minutes of rest  Knee joint was at 45 degrees of flexion. Muscle Fatigue 1

42 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 42 Applications in Orthopaedics  Findings showed that:  First 60 s of contraction all muscles recorded significantly decreased MPF an increase in LEEMG amplitude.  Rate of decrease of MPF was significantly greater in the injured quadriceps and normal hamstrings.  All muscles recovered to the initial MPF level after 1 min of rest but two muscles in the injured and normal limb recorded an overshoot of mean power frequency during the recovery phase. Muscle Fatigue 1

43 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 43 Applications in Orthopaedics The findings confirmed  the fatigue state in all the muscles, suggest recruitment of more Type II fibers as the muscle fatigue  show the physiological adaptation of the quadriceps and hamstrings to ACL deficiency.  dissociation between low intramuscular pH and mean power frequency during the recovery phase. Muscle Fatigue 1

44 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 44 Applications in Orthopaedics We investigated the possible influence of wearing functional knee braces on various factors of muscle fatigue.  Measured parameters were; MVC, Peak Velocity (PK), power and number of repetition to muscle fatigue during isokinetic exercise, and also muscle fatigue during 50s isometric contraction Muscle Fatigue 2 Lamontagne, M. & Sabagh-Yazdi, F. (1999). The Influence of Functional Knee Braces on Muscle Fatigue. Paper presented at the XVIth of the International Society of Biomechanics, Calgary, Canada.

45 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 45 Applications in Orthopaedics  Two groups of healthy and ACL-deficient knee joint subjects with an average age of 28.8 years and 26,6 years respectively volunteered to this study.  All tests were performed on an isokinetic device (Kin- Com 500H) while the EMG signal was collected at 1000 Hz for six muscles (RF), (VL), (VM), (G), (MH) and (LH). Muscle Fatigue 2

46 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 46 Applications in Orthopaedics Analysis of EMG data revealed that  no significant differences were obtained for the EMG amplitude or the integral of the linear envelope EMG between the groups and conditions  During the 50s isometric exercise at 80% MVC, the fatigue state is represented by decline of MF value of EMG signal greater than 10 Hz  Muscle fatigue state was obtained in all muscles Muscle Fatigue 2

47 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 47 Applications in Orthopaedics  Percentage of decline of MF in the Gastrocnemius was significantly different between the groups (p<0.05).  Percentage of decline of median frequency in VM and G of ACL group and VL and G of healthy group was found statistically different (p<0.05) between conditions.  the outcomes showed a high correlation between the subjective perception of fatigue and percentage of decline of the MF (r = 0.64) for VL and RF muscles during the brace condition.  All other muscles showed very low correlation. Muscle Fatigue 2

48 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 48 CONCLUSIONCONCLUSION Factors like signal reliability, muscle synergy, mechanisms of proprioception, muscle fatigue mechanisms have been a great deal of interest in movement studies but these topics certainly need more research in order to understand muscle function and adaptation for ordinary people and athletes. Lamontagne, M. (2000). Electromyography in sport medicine (Chapter 4). In Rehabilitation of Sports Injuries (Ed. G. Puddu, A. Giombini, A. Selvanetti ), Springer-Verlag, Berlin, Heidelberg, New York

49 APA 6903 /05 Mario Lamontagne PhD School of Human Kinetics 49 Partly funded by: Natural Sciences and Engineering Council of Canada and Let People Move Partly funded by: Natural Sciences and Engineering Council of Canada and Let People Move


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