Force generated by a muscle Essays

Force generated by a muscle Essays Force generated by a muscle Essay Force generated by a muscle Essay Evaluate Force-Angle Relationships utilizing EMG and Force Measurements Q1. From the single natural informations [ table 1 ] we obtained by standardization ( As % of Maximum utilizing as soap values: FORCEmax=117.2 N, EMGmax=306.8 millivolt ) the adjusted single informations [ table 2 ] . Q2. Electromyography is the technique for entering alterations in the electrical potency of a musculus when it is caused to contract by a motor nervus urge ( Barlett, R.1997 ; 228 ) The EMG signal profile and in effect the EMG is the electrical signal profile detected by an electrode on a musculus. In other words is the step of the action potency of the outer muscle-fiber membrane ( the sarcolemma ) . [ 3 ] : Force generated by a musculus is determined by two chief factors: the figure of motor units ( MUs ) actively stimulated at the same clip and the frequence ( firing rate ) at which the MUs are firing. Besides the amplitude of the EMG signal depends on both the figure of active MUs and their fire rates. Since both EMG amplitude and force addition as a effect of the same mechanisms, it is expected that musculus force can be estimated from surface EMG analysis. This is non rather true but merely in isometric contractions, where musculus electrical activity and musculus force have a comparatively additive relationship. [ 3 ] This is the chief ground why EMG is the method of pick for force appraisal. Q3. Using Normalised EMG and Joint Angle information from [ table 2 ] , the requested graph is shown below [ graph 2 ] Evaluate Force-Angle Relationships utilizing EMG and Force Measurements Q4. From the row informations for the whole group we calculate the average normalized values as in [ table 3 ] . Using informations for Max isometric force and EMG from [ table 3 ] , the requested graph is graph 3 below. Q5. Evaluate Force-Angle Relationships utilizing EMG and Force Measurements Evaluate Force-Angle Relationships utilizing EMG and Force Measurements Q6. Using the free-body diagram ( fig. 1 ) at a generic angle? we sketch the forces moving on the forearm during flexure against a known opposition. These forces are the opposition R, the mass of the forearm G, the attempt E of the musculus and the joint reaction force Fj. The joint reaction force as go throughing from the centre of rotary motion has no part to the minute at the joint and therefore is neglected. Assuming inactive equilibrium at each angle, the amount of minutes moving on the forearm at the cubitus peers zero: SMj = 0 Mj = ME MR MG [ 1 ] MR = R Lf wickedness? [ 2 ] , where Lf is the length of the forearm. MG = medium frequency g LCM wickedness? [ 3 ] , where LCM is the distance of the forearm s centre of mass from the joint and medium frequency is the mass of the forearm and manus. ME = E? LE where E? is the rotational constituent of the attempt E. ME = E LE sinf [ 4 ] , where degree Fahrenheit is the angle between the long axis of the forearm and the line of application of the attempt force and LE is the attempt arm ( normal distance between the point of interpolation of the musculus on forearm and the joint ) . Substituting the assorted minutes [ 2 ] , [ 3 ] , [ 4 ] in equation [ 1 ] we obtain, utilizing the conventions of the marks: Mj = E LE sinf Roentgen Lf wickedness? medium frequency g LCM wickedness? [ 5 ] To cipher the Torque utilizing equation [ 5 ] we must cognize Lf, LE, LCM, degree Fahrenheit, medium frequency ( R, E and? known, g = 9.81 ms-2 ) . Equation [ 5 ] calculates the torsion utilizing inactive equilibrium at each angle and presuming that the length of the musculus remain changeless as joint angle alterations, which is non true. For a more accurate computation we besides need to cognize the relationship between contraction force and constrained musculus length. Evaluate Force-Angle Relationships utilizing EMG and Force Measurements Q7. Standardization is the mathematical look of the amplitude of the EMG signal as a ratio to the amplitude of a contraction deemed to be maximal ( peak EMG from an isometric maximal voluntary contraction ( MVC ) of the same musculus ) . EMG signal has a complex nature and the account that merely the figure of active motor units and their fire rates can impact it is semplicistic. In world anatomical, physiological and proficient factors have influence on the electromyographical signal. In a reappraisal of such factors ( De Luca, 1997 ) grouped them as causative, intermediate and deterministic. Some of these factors are: musculus fibre diameter, figure of musculus fibres, electrode-skin interface, signal conditioning, figure of active motor units, tissue sum, distance from skin surface to muscle fibre, musculus fibre conductivity speed, musculus blood flow, common electrode spacing, fiber type and location, motor unit firing rate. [ 2 ] Because of the above factors and besides for grounds of direct comparing of EMG signals recorded with signals from the same musculus on different occasions or from different musculuss and different persons we use normalised EMG signals instead than absolute values. Mentions Barlett, R. ( 1997 ) Introduction to Sports Biomechanics, Taylor A ; Francis e-Library, 2002. Carl J. Payton, Biomechanical Evaluation of Movement in Sport and Exercise, Taylor A ; Francis e-Library, 2007. Hamill, Joseph ; Knutzen, Kathleen M. , Biomechanical Basis of Human Movement, 3rd Ed, Lippincot A ; Wilkins, 2009.