Muscle Force Experiment

1
Muscle Force Experiment

• Melissa Read
• Lab Partner Dylan Chavez
• March 18, 2003

2
Setup

• Optical table with crossbar mounted on load cells
• HP 973A DMM (2)
• One measured Load cell voltage
• Other measured EMG
• HP 3610A Power Supplies (2)
• Tektronix CFG253 Function Generator
• Gemini PM-100 active speaker
• Other Electronics

3
Calibration of Load Cell
Voltage(V) 0.015Force(N) 0.358
4
Maximal Voluntary Contraction (MVC)
Left Arm Diameter 92.66 mm MVC 907
N Pressure 133.5 kPa
Right Arm Diameter 95.86 mm MVC 1134
N Pressure 156.7 kPa

• These values assume a lever ratio of 10.
• A strong man can have an MVC value of
  approximately 3500 N.

5
Relationship between Force and EMG

• Force ranges from 1 MVC (15 N) to 56 MVC (639
  N).
• Appears to be linear until around 30 MVC (340
  N).

6
Force and EMG during Fatigue Testing

• Force remains constant.
• Average EMG remains constant.

7
Standard Deviation of EMG during Fatigue Testing

• Standard deviation increases over time.
• Suggests that EMG varies with fatigue.
• Accounts for non-linearities seen when force
  applied is greater than 30 MVC.
  

8
Errors

• Errors come from two main areas
• Errors regarding linear scale chosen to equate
  load cell voltage to force.
• Human error in attempting to read the EMG and
  load cell measuring multimeters simultaneously.

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Questions?