EMG and Force Production Lab Report
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School
Utah Valley University *
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Course
3705
Subject
Health Science
Date
Jun 11, 2024
Type
docx
Pages
5
Uploaded by DPZVeg
EMG and Force Production Lab Report
Part 1: EMG
1.
What is a motor unit?
-
A motor unit is a muscle group that is made up of motor nerves and fibers. 2.
What does the EMG signal represent? Be specific.
-
An EMG signal represents when the electrodes record muscle contraction and motor units are firing. The heavier weight someone lifts with the electrodes attached, the larger the readings will be. The electrodes register how effected a muscle is during a certain movement.
3.
Describe motor recruitment - How is skeletal muscle force generation regulated? Please include the following terms: size principle, innervation ratio, recruitment pattern
-
Motor Recruitment is when the muscle group that is active requires more motor units because of muscle fatigue. -
Skeletal Muscle Force Generation is regulated by a dynamic process that involves the motor units and their recruitment based on the required force, and the rate which motor neurons fire action potentials. -
Recruitment pattern refers to the exercise type activity being performed. Low-force/endurance/lifting/ etc… It is the sequence which motor units are being used to produce muscle contractions.
-
Size principle works synergistically with motor units, and “sizes them up” in a sense that it orders small to large based on the force required.
-
The innervation ratio is what amount (#) of muscle fibers are being used by a singular motor neuron. Low/High innervation ratios.
4.
After watching the video, Describe the EMG activity observed during (a) the increasing workloads and (b) the fatigue trials in lab.
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The EMG activity would spike when the muscles were being worked, and the readings would also appear larger when larger weights were given to the participant, indicating more motor units were being used.
-
The motor unit recruitment were more and more as the time under tension increased. The readings would increase, thus showing more units were required.
5.
What is the relationship between fatigue and EMG activity? Why?
-
The relationship involves understanding when the body begins to compensate for declining muscle involvement, and gives the ability to accurately read energy reserves.
EMG and Force Production Lab Report
Part 2: Force Production
Data
Isometric Trials (Length-Tension)
Joint Angle (Degrees)
Torque (ft-lbs)
60
125
90
150
120
115
Isokinetic Trials (Force-Velocity)
Angular Velocity (degrees/sec)
Torque (Ft-lbs)
60
198
120
171
180
123
240
105
300
88
Length-Tension
1.
Graph
: Plot torque vs joint angle for knee extension. Use the highest recorded torque for each angle.
EMG and Force Production Lab Report
2.
What factors are responsible for the relationship between joint angle and torque? How do they affect torque?
-
First thing that comes to mind is the lever systems in the body that provide mechanical advantage or disadvantage. The advantage depends on the lengths of the moment arm and the resistance.
-
These affect torque is that there is a greater and lesser advantage; where certain joint angles allow for more weight to be lifted in certain positions that other joints cannot move in. Allowing for greater torque.
Force-Velocity
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EMG and Force Production Lab Report
1.
Graph
: Plot torque vs velocity of contraction for knee extension. Use the highest recorded torque at each angular velocity.
50
100
150
200
250
300
80
100
120
140
160
180
200
198
171
123
105
88
Torque Vs. Velocity of Contraction
Angular Velocity (deg/sec)
Torque (ft-lbs)
2.
Why does force production decrease with increasing velocity in these trials?
-
Muscle fatigue.
3.
Please explain why eccentric training can be better for strength gains and hypertrophy
-
In the eccentric phase, the muscle is undergoing the most
load with time under tension. In the force/length curve, when the muscle is in its most lengthened position, the sarcomeres have far more length to recover from, thus making them work the “most they can” in a sense. When working slowly into an eccentric contraction, you are forcing the sarcomeres to produce as much strength possible for them to control the weight on the way down, and this increases strength.
4.
Describe three applications or training principles derived from the force-
velocity curve that you learned from the Science for Sport article.
-
High/Low force velocity: Slow muscle contractions generating high force for heavy resistance exercise, and fast contractions generating low force because the speed output is so great, the muscles do not “have time” to react – this is mainly from exercises like sprinting.
EMG and Force Production Lab Report
-
Application of forces in training: Most relatable to me was
referring to power training; balancing force and velocity to improve strength and speed.
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Tailoring needs: understanding and improving how I can incorporate programs that enhance strength, power, and endurance to patient care will provide outcomes not previously thought of.