“Electromyography Segmented Assessment for Lower Limb Muscle Transition to Fatigue During Isometric Contraction” By Jorge Garza-Ulloa, Pablo Rangel, Olatunde Adeoye Department of Electrical and Computer Engineering, University of Texas at El Paso, Laboratory for Human Motion Analysis and Neurorehabilitation, El Paso, USA 1 (#)
“ Electromyography Segmented Assessment for Lower Limb Muscle Transition to Fatigue During Isometric Contraction ” Outline 1. Abstract 2. Introduction and Background 3. Concept: Transition-to-fatigue 4. Methodolgy / Experimentation 6. Results 7. Conclusions ( 2
“ Electromyography Segmented Assessment for Lower Limb Muscle Transition to Fatigue During Isometric Contraction ” Abstract ( Olatunde Adeoye ) Surface Electromyography (sEMG) activity of the lower extremities Analyze muscle transition to fatigue on four leg muscles. Measured lower extremity muscles : • vastus lateralis (VL) • gastrocnemius lateralis (GL) • Tibialis anterior (TA) • Soleus (S) Data recorded when subjects performed an isometric exercise : • one minute test twice for energize muscles • two and three minutes for stimuli transition-to-fatigue Objective: determine and analyze the muscle transition to fatigue activity generated by muscle tension for a specified period of time. sEMG data of the subjects segmented for fast analysis and easy tracking of the changes observed on raw data without any filtering. 3
“ Electromyography Segmented Assessment for Lower Limb Muscle Transition to Fatigue During Isometric Contraction ” Abstract continue... Amplitude of the high frequency is correlated to force level Amplitude of the low frequency band is correlated to the muscle fatigue. Two methods were used: • Amplitude row data related with raw sEMG data , MNF during the segmentation • Analyzing the muscles with more activities on all test using segmentation. • Results show the effects of transition-to-fatigue phenomena contributed to: • Physiological fatigue • Muscle fatigue. 4
“ Electromyography Segmented Assessment for Lower Limb Muscle Transition to Fatigue During Isometric Contraction ” Introduction and Background Localized muscle fatigue occurs: • After a prolonged relatively muscle activity • When muscle or groups of muscles are unable to exert any more force or power. (Physiological fatigue). Three types of localized muscles are: • Non- fatigue • Transition-to-fatigue • Fatigue sEMG signal can be analyzed to detect Transition-to-Fatigue. Development in muscle fatigue correlates to: Changes in amplitude and Median Mean Frequency ( MNF ) The signal is analyzed in frequency-domain 5
“Electromyography Segmented Assessment for Lower Limb Muscle Transition to Fatigue During Isometric Contraction” Concept: Transition to fatigue Simple muscle twitch • Mechanical response of a single muscle fiber to a single action potential • Latent period (10 ms): Muscle tension is beginning. • Contraction period (40 ms): Muscle fibers shorten. • Relaxation period (50 ms): Ca 2+ renters the sarcoplasmic reticulum • Total duration -100 ms (varies) • Doesn’t have refractory period 6
“ Electromyograhic Segmented Assessment for Lower Limb Muscle Transition to Fatigue During Isometric Contraction” Concept: Transition-to-fatigue Summation Adding together of individual twitch contractions to increase the intensity of overall muscle contraction 1) Multiple fiber summation 2) Frequency summation 7
“Electromyograhic Segmented Assessment for Lower Limb Muscle Transition to Fatigue During Isometric Contraction” Concept: Transition-to-fatigue Multiple fiber summation • More the fibers (motor units) taking part in contraction more will be the force of contraction • For weak contraction, smaller and fewer motor units are stimulated • For stronger contractions more & more motor units are stimulated (recruitment) • Frequency summation, tetanus or tetanization • Sustained contraction due to repeated stimuli of high frequency 8
“ Electromyograhic Segmented Assessment for Lower Limb Muscle Transition to Fatigue During Isometric Contraction” Concept: Transition-to-fatigue Frequency summation • Incomplete tetanization • Muscle fiber is stimulated at such a frequency that every next stimulus falls during previous relaxation period • Subsequent contraction is superimposed on the previous relaxation • Force of subsequent contractions rises due to beneficial effect of Ca++ • Muscle fiber partially relaxes between stimuli • Complete tetanization • Muscle fiber is stimulated at such a frequency that every next stimulus falls during previous contraction period • Subsequent contractions merge with the previous ones • Smooth contraction of greater force is achieved • No relaxation phase • Leads to fatigue 9
“ Electromyograhic Segmented Assessment for Lower Limb Muscle Transition to Fatigue During Isometric Contraction” Concept: Transition-to-fatigue Muscle fatigue: Decrease in muscular activity due to repeated stimuli Causes: a. In muscle • Lack of nutrients and glycogen • Lack of oxygen • Accumulation of lactic acid • Conduction failure along ‘T’ tubules -blockage of Ca 2+ release for sarcoplasmic cistern b. In Neuromuscular junction • Depletion of Acetyl Choline c. In Central Neural System • CNS cannot send excitatory signals to the contracting muscles • Generally psychological • Fatigue reverses by taking rest 10
“ Electromyograhic Segmented Assessment for Lower Limb Muscle Transition to Fatigue During Isometric Contraction” Methodolgy / Experimentation Main objective : • Get the subjects into a state of incomplete tetanus to analyze the trends of how the Transition-to-Fatigue happens. • Dangerous to have them reach a state of complete tetanus so the exercises were design to keep them from any harm. 11
“ Electromyograhic Segmented Assessment for Lower Limb Muscle Transition to Fatigue During Isometric Contraction” Methodolgy / Experimentation Experimental Procedure • At detail the procedure was explained to every participant. • An IRB (Institutional Review Board) agreement was signed by each subject before proceeding with the experimentation. • Preliminary anthropometric, demographic, and clinical data was taken from each subject. • The Pocket EMG by BTS Bioengineering was properly calibrated and placed over the subjects. Software and System Set Up • The Pocket EMG by BTS Bioengineering sEMG System software was configure and initialized following the User’s Guide directions and the previous training provided to the laboratory staff. 12
“ Electromyograhic Segmented Assessment for Lower Limb Muscle Transition to Fatigue During Isometric Contraction” Methodolgy / Experimentation Sensor Placement • The Pocket EMG by BTS Bioengineering electrodes were allocated over the following muscles: • Vastus Lateralis (VL) by knee force, • Gastrocnemius Lateralis (LG) as flexion of knee • Soleus (Sol) as an antagonist plantarflexion • Tibialis Anterior (TA) as as Dorsiflexion Before placing the sensor areas where cleaned and shaved (if needed) to obtained a better and direct contact to the muscle. 13
“ Electromyograhic Segmented Assessment of Lower Limb Muscle Transition to Fatigue During Isometric Contraction” Methodolgy / Experimentation Trials Complete procedure took about thirty minutes. Subjects were able to dictate when they were ready to proceed They were given a rest period of at least 5 minutes between each trial. The experimental procedure consisted of one isometric exercise procedure been repeated four times in three different time ranges: • First (1MA), a sEMG reading of the legs at the assigned position was acquired for one minute. • Next, the subject was asked to do the same isometric exercise for one more minute (1MB), then two minutes (2M) and finally three minutes (3M). 14
“Electromyography Segmented Assessment for Lower Limb Muscle Transition to Fatigue During Isometric Contraction” Procedure Our goal analyze the sEMG with all possible detail of muscle change, huge files ! • Raw Data from Sample Frequency of 2000 Hz • Aprox. 120,000 samples per minute • No filter of any kind • The Raw data was segmented each 5,000 samples, this means each segment of 2.5 sec. to register any muscle variation. • Find Spectrum frequency using fast Fourier transform (FFT) • Calculate Mean Frequency (MNF) 15
“Electromyography Segmented Assessment for Lower Limb Muscle Transition to Fatigue During Isometric Contraction” Procedure: Anthropometric Data Tests: HEIGTH WEIGT SUBJECT AGE SEX (cm) H ( Kg) BMI 1MA 1MB 2M 3M SH1 22 MALE 177 95.34 30.4 Y Y i X SH2 32 MALE 177 93.07 29.7 Y Y Y i SH3 24 MALE 180 85.81 26.5 Y Y Y Y SH4 23 FEMALE 167 68.00 25.5 Y Y Y i SH5 26 FEMALE 162 70.00 26.8 Y Y Y Y SH6 19 FEMALE 168 71.00 25.2 Y Y Y Y SH7 21 MALE 155 65.83 27.4 Y Y Y Y SH8 27 MALE 177 88.53 28.2 Y Y Y Y SH9 29 MALE 177 90.80 29 Y Y Y i SH10 21 MALE 179 90.80 28.3 Y Y i x SH11 42 MALE 167 83.99 30.1 Y Y i x SH12 34 MALE 183 129.39 38.9 Y Y i x 12 subjects with IRB (Institutional Review Board) agreement signed 16
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