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1. Electromyogram Dr. Maheshkumar H Kolekar Associate Professor Dept. of Electrical Engineering IIT Patna

2. Muscles Muscle is a soft tissue found in most animals.  Muscle cells contain protein filaments of actin and myosin that slide past one another, producing a contraction that changes both the length and the shape of the cell. Actin ,  protein  that is an important contributor to the contractile property of muscle  and other  cells . It exists in two forms :  G-actin  (monomeric globular actin) and  F-actin  (polymeric fibrous actin), the form involved in muscle contraction . Myosin: The main constituent of the thick filaments is myosin. Each thick filament is composed of about 250 molecules of myosin. They are primarily responsible for maintaining and changing posture, and locomotion, as well as movement of internal organs.

3. Peristalsis refers to involuntary movements of the longitudinal and circular muscles. Primarily occurs in the digestive tract but can also happen in other hollow tubes of the body. Movements occur in progressive, wavelike contractions. Peristaltic waves are found in the esophagus, stomach, and intestines. Waves can be short, local reflexes or long, continuous contractions. Gastrointestinal (GI) tract: The alimentary canal or alimentary tract is part of the digestive Peristalsis

4. Peristalsis Contd.

5. Types of Muscles Skeletal Muscle: Skeletal muscles are anchored to tendons Cardiac Muscle: Involuntary muscles found on heart Smooth Muscle: Involuntary muscles found in stomach .

6. Types of Muscles Contd.

7. Skeletal Muscle organization Muscle Fiber: The basic structural unit of skeletal muscle is the muscle fiber, also known as a muscle cell . Fascicle is a bundle of skeletal muscle fibers (cells) surrounded by a connective tissue sheath known as the perimysium. These bundles are grouped together to form a muscle, allowing coordinated contractions and movement. Epimysium: Dense Layer connective tissue that surrounds and encases the entire muscle , providing structural support and helping to transmit forces generated during muscle contraction. Tendons: At the ends of muscles, the connective tissue extends beyond the muscle fibers to form tendons. Tendons attach muscles to bones , allowing for movement when the muscle contracts. Perimysium is a connective tissue that surrounds and groups muscle fibers into fascicles, providing support and pathways for nerves and blood vessels.

8. Endomysium: A thin layer of connective tissue that surrounds individual muscle fibers within a muscle, providing support, insulation, and a pathway for blood vessels and nerves to reach each muscle fiber. Myofiber : Muscle fibers are composed of myofibrils, which are long, cylindrical structures that run parallel to the length of the muscle fiber. Nucleus is a membrane-bound organelle in cells that contains genetic material (DNA) and controls cellular activities such as growth, metabolism, and reproduction.

9. Cardiac Muscle Structure: Composed of cardio myocytes, each with a centrally located nucleus, myofibrils, and sarcomeres, giving it a striated appearance. Cardiac Muscle Organization Capillaries: These are the smallest blood vessels in the body. Intercalated Discs: Its contain desmosomes and gap junctions, allowing for rapid electrical and mechanical coupling between cardio myocytes. Desmosomes: Cell junctions that provide strong adhesion between cells. Play a key role in maintaining tissue integrity and mechanical stability.

10. Cardiac Muscle fiber: Desmosomes are prominent in cardiac muscle cells. They secure adjacent cardio myocytes, allowing synchronized contractions. Example: Myocardium (heart muscle) Gap junction: In cardiac muscle allows direct communication between cells for rapid electrical impulse transmission, enabling synchronized heart contractions.

11. Smooth Muscle Organization Structure of Smooth Muscle Lacks visible striations like skeletal or cardiac muscles due to different cell organization. Actin and myosin filaments are arranged in a "staircase" pattern across the cell. Actin filaments connect at dense bodies and the cell membrane, unlike skeletal and cardiac muscle where they attach to Z plates. Filaments are arranged at angles to each other within the cell.

12. Function of Smooth Muscle Primary function is contraction, but with notable differences from skeletal muscle. Controlled by the autonomic nervous system, not voluntarily by the somatic nervous system. Contracts persistently, unlike the quick contract-and-release mechanism of skeletal muscle. Calcium levels control the amount of ATP (Adenosine triphosphate) available for contraction, allowing for sustained tension. Smooth Muscle Location Found in the circulatory system, digestive system , and responsible for raising body hairs . In the circulatory system, smooth muscle regulates blood pressure and oxygen flow. In the digestive system, smooth muscle enables peristalsis, moving food through the gut. Also involved in functions like contracting the iris, raising arm hairs .

13. Electrical signals generated during muscle contraction. EMG records muscle electrical activity. Key role in understanding muscle function. Vital in diagnosing neuromuscular disorders. Enables precise muscle control in prosthetics. Used in sports science, biomechanics, and more. Key Application Areas: Medical diagnosis, research, sports science, biomechanics. Electromyography (EMG)

14. Measures muscle's electrical potentials. Reflects muscle contraction and relaxation. Provides insights into neuromuscular health. Captures motor unit activity.

15. EMG Signal Components Motor unit action potentials (MUAPs) detected. Amplitude reflects muscle force. Duration and frequency provide insights. Shape and timing reflect muscle coordination. Complex patterns during complex movements.

16. Characteristics of EMG signal Amplitude Variation: 0 to 10 mV (-5 to +5 mv) prior to amplification . Frequency Spectrum: 10 to 500 Hz Dominant Energy Range: 50Hz to 150 Hz

17. Motor units drive muscle contractions. Interaction of actin and myosin filaments. EMG captures action potentials of motor units. Summation of motor unit activity creates overall signal. Muscle Contraction Mechanism

18. Physiology of EMG signal The physiology of EMG (Electromyography) signal involves the following points: EMG captures electrical signals from muscles via electrodes, representing anatomical and physiological properties of the muscle during contraction and at rest. EMG measures muscle activity during rest, slight contraction, and forceful contraction. It records the electrical activity produced by skeletal muscles, which is the sum of multiple motor units' activity

19. Single Contraction : A twitch involves a single contraction phase followed by a relaxation phase. Response to Stimulation : Triggered by a single action potential from a motor neuron. Phases : Includes a latent period (time between stimulation and contraction), contraction phase, and relaxation phase. Twitch Tetanic force: Sustained contraction of a muscle that occurs when it is stimulated at a high frequency, leading to a continuous force output. Here’s a breakdown: Sustained Contraction : Results in a prolonged, steady muscle contraction. High-Frequency Stimulation : Triggered by rapid, repetitive action potentials from motor neurons. Fusion of Twitches : Individual twitches merge into a continuous force due to the high frequency of stimulation. Maximum Tension : Produces greater force compared to single twitches, as there is no relaxation between stimuli. Duration : Typically short and can vary based on the muscle type and conditions.

20. Type of EMG-signal capture Electrode Needle electrode , which is commonly used in intramuscular electromyography (EMG) . Here are some key points related to needle electrodes: It inserted directly into the muscle tissue to detect electrical activity within specific muscle fibers. They provide highly localized recordings , making them useful for detailed muscle studies. These electrodes are ideal for identifying neuromuscular disorders or assessing the functionality of individual motor units . Because of their invasive nature, needle electrodes are often used in clinical or diagnostic settings to monitor deep muscles where surface electrodes may not be effective. Microelectrode: A tiny electrode used to record or stimulate electrical activity in cells or tissues. It's crucial in fields like neuroscience for studying neurons and creating brain-computer interfaces.

21. Surface electrode: Monopolar Electrode : Detects or stimulates electrical activity at a specific site. Reference Electrode : Positioned away from the active electrode to provide a baseline measurement. Signal Measurement : The difference in electrical potential between the active and reference electrodes is recorded. Monopolar Electrode Placement : Positioned on the skin's surface. Function : Measures electrical activity or delivers stimulation. Common Use : Used in ECG for heart monitoring and EEG for brain activity. Non-Invasive : Does not penetrate the skin, making it less invasive compared to internal electrodes.

22. EMG-signal capture Use of a differential amplifier . Input from two different points of the muscle. Electrode alignment with the direction of muscle fibers increases the probability of detecting the same signal. The system subtracts the two inputs to remove noise or irrelevant signals. It then amplifies the difference for clear EMG signal detection. Reference electrode placed on electrically unrelated tissue to reduce interference. Signals detected by the electrodes (denoted as M1 + n and M2 + n ) where "n" represents noise. The differential amplifier calculates the difference between signals from the two points, removing common noise.

23. Electrodes placed on skin over muscles. Detect electrical signals produced by muscles. Amplification and filtering ensure accuracy. Recorded data analyzed for insights. EMG Electrodes and Recording

24. A motor unit comprises a motor neuron and the muscle fibers it controls. Motor neurons transmit signals from the nervous system to muscle fibers, initiating contractions. Motor units ensure coordinated muscle activation and control. The Motor Units

25. Underlying Physiological Issues Resting Membrane Potential: The resting membrane potential (RMP) is the electrical potential difference across the cell membrane of a non-excited, resting cell. Potential difference exists across the sarcomere Intra-cellular fluid has a high [K + ] Extra-cellular (interstitial) fluid has a high [Na + ] and [Cl - ]

26. Net Effect Concentration Gradients : Ions like sodium (Na⁺) and potassium (K⁺) are unevenly distributed across the sarcolemma. Sodium is more concentrated outside the cell, while potassium is more concentrated inside the cell. This creates a concentration gradient that drives ion movement across the membrane. Difference in Potential Across the Sarcolemma : The sarcolemma acts as a selective barrier, maintaining a voltage difference across the membrane. This potential difference, known as the resting membrane potential, is due to the unequal distribution of ions. At rest, the inside of the cell is negatively charged relative to the outside. Role of Active Na⁺ and K⁺ Pumps : The Na⁺/K⁺ pump actively transports 3 Na⁺ ions out of the cell and 2 K⁺ ions into the cell against their concentration gradients. This active transport mechanism consumes ATP and helps maintain the ion concentration gradients across the sarcolemma. Resting Membrane Potential (~ -80 mV)

27. Resting Membrane Potential System stays in equilibrium (~ -80mV) until an intra- or extra-cellular stimulus is applied AP causing liberation of Ca + from the sarcoplasmic reticulum Galvanic stimulation

28. Action Potentials (AP) Rapid, temporary change in the electrical membrane potential of a cell. Occurs primarily in neurons and muscle cells. Enables transmission of signals within the nervous system. Critical for communication between neurons. Essential for initiating muscle contractions. Cell Membrane at rest Na⁺ Cl- K⁺ Cl- K⁺ A- Outside of Cell Inside of Cell Potassium (K+) can pass through to equalize its concentration Sodium and Chlorine cannot pass through Result:- inside is negative relative to outside - 70 mv

29. Factors That Influence the Signal Information Content of EMG Factor Influence Neuroactivation - firing rate of motor unit AP’s - no. of motor units recruited - synchronization of motor units Muscle fiber physiology - conduction velocity of fibers Muscle anatomy - orientation & distribution of fibers - diameter of muscle fibers - total no. of motor units Electrode size/orientation - no. of fibers in pickup area

30. Factors That Influence the Signal Information Content of EMG Factor Influence Electrode-electrolyte - type of material and site interface - electrode impedance decreases with increasing frequency Bipolar electrode - distance between electrodes configuration - orientation of electrodes relative to the axis of muscle fibers

31. Motor Unit Recruitment Slow twitch motor units recruited first Postural control Finely graded movements Fast twitch units recruited last Rapid, powerful, impulsive movements EMG can be used to study fatigue by analyzing frequency (e.g., median power frequency) characteristics during spectral analysis

32. EMG during Fatigue Increased Amplitude : As muscles fatigue, the amplitude of the EMG signal tends to increase due to the recruitment of additional motor units to maintain force output . Decreased Frequency : The frequency of EMG signals decreases as fatigue progresses because of reduced motor neuron firing rates and slowing of muscle fiber conduction velocity. Signal Changes : Muscle fatigue is characterized by a shift towards lower frequency components in the EMG power spectrum, indicating reduced efficiency in electrical signal transmission. Force Decline : Despite increased EMG activity, the actual muscle force output decreases during fatigue as muscle fibers become less responsive . Force, EMG, and H‐reflexes measured during the fatigue task. Note that there is more fluctuation in force toward the end of the fatigue task, when peak‐to‐peak EMG is maximal.

33. Pre-processing techniques enhance data quality. Baseline correction eliminates signal drift. Filtering removes high-frequency noise. Rectification for envelope analysis. Calculation of RSM value of EMG signals. EMG Signal Processing

34. Clinical Applications Diagnosing neuromuscular disorders. Monitoring progress in rehabilitation. Assessing muscle activity in patients. Guiding personalized treatment plans. Vital tool in neurology and rehabilitation .

35. EMG aids in diagnosing various conditions. Identifies abnormal motor unit activity . Detects muscle denervation (muscle loss) and weakness . Supports diagnosis of myopathies . Neuromuscular Diseases

36. EMG assists in designing effective exercises. Monitors patient progress during rehab. Provides real-time feedback to patients. Tailors treatment plans to individual needs. Enhances muscle strength and coordination. Muscle Rehabilitation

37. EMG assesses muscle activation during movements. Insights into muscle coordination and function. Optimizes training and sports performance. Analyzes muscle fatigue and efficiency. Guides sports-specific training programs. Sports Science and Biomechanics

38. EMG detects motor neuron diseases. Identifies disruptions in motor unit activity. Supports diagnosis of ALS (Amyotrophic Lateral Sclerosis). Monitors disease progression. Aids in assessing treatment effectiveness. Motor Neuron Disorders

39. EMG signals control prosthetic limbs. Offers intuitive and natural movement. Facilitates tasks like grasping and walking. Enhances mobility and quality of life. Integrates with robotics for advanced applications. Prosthetics and Robotics

40. Advancements in wearable EMG technology. Integration with AI for real-time analysis. Enhanced portability and user-friendliness. Personalized healthcare interventions. Greater accessibility and convenience. Future Developments

41. Advancements in wearable EMG technology: As technology continues to evolve, wearable EMG devices are likely to become more sophisticated. Improved sensor technology, smaller form factors, and better signal processing techniques will enhance the capabilities of these devices. This could lead to more accurate and reliable EMG measurements, enabling a wide range of applications.

42. Integration with AI for real-time analysis: The integration of wearable EMG technology with artificial intelligence (AI) systems holds great potential. AI algorithms can process EMG data in real-time, providing instant insights into muscle activity patterns. This could lead to applications such as immediate feedback during exercise routines or real-time monitoring of neuromuscular disorders.

43. Enhanced portability and user-friendliness: Future wearable EMG devices are likely to focus on improving user experience. Smaller and more lightweight designs will make the devices more comfortable for users to wear for extended periods. Intuitive interfaces and wireless connectivity will enhance ease of use and data sharing.

44. Personalized healthcare interventions: Wearable EMG technology could play a significant role in personalized healthcare. By continuously monitoring muscle activity, these devices could provide insights into individual movement patterns and habits. Healthcare providers can tailor exercise programs and rehabilitation plans based on this personalized data.

45. Greater accessibility and convenience: With advancements in technology, wearable EMG devices are expected to become more accessible to a wider population. Reduced costs, increased availability, and ease of use will encourage more people to incorporate them into their health and fitness routines. This increased adoption could lead to better overall health awareness and management.

46. Cross-talk from neighboring muscles. Ensuring accurate electrode placement. Managing interference and noise. Complex interpretation of EMG patterns. Addressing ethical considerations in data collection. Limitations and Challenges

47. More Biomedical Signal Electroneurogram (ENG) Electrical Signal observed as a stimulus and associated nerve action potential propagating over the length of the nerve. Event-related potential (ERP): It includes ENG or EEG in response to light, sound, electrical potential. Electrogastrogram (EGG) Electrical activity of stomach consists of rhythmic waves of depolarization and repolarization of its stomach muscles. Originates at mid-corpus of stomach and always present. Not directly associated with contraction. (muscle movement i.e. contraction and expansion is such that food will move in one direction)

48. More Biomedical Signal Phonocardiogram (PCG) Vibration or sound related to contraction of cardio hemic system (the heart and blood together) Carotid Pulse (CP) Pressure signal recorded over carotid artery as it passes near the surface of body at neck.

49. Thank You !