1. Psyc 552 Ergonomics & Biomechanics Lecture 7

2. Muscle Strength  Maximum voluntary exertion levels The maximum force that a muscle can produce under prescribed conditions. This force is well below the physiological tolerance of bones, tendons, and muscles

3. Strength  Dynamic…  Static…  Output can be Force produced at some point on the body Moment or torque produced about a given joint

4. Strength Measurements  Highly dependent on time…  Dynamic strength is highly influenced by velocity.

5. Strength testing criteria  Safe  Reliable  Practical

6. Factors Affecting Strength  Posture  Velocity  Acceleration

7. Using Static Strength Data

8. Electromyography (EMG)  Measures muscle action potentials and/or motor unit potentials  Recording methods…

9. Estimation of Force  F m =[G x NEMG x f(length) x f(vel)]+ F p

10. Psychophysical Strength Method  Kroemer (1982) liftest

11. Factors Affecting Strength (cont)  Gender  Age  Anthropometry

12. Other Measurements  Intradisc pressure Image from: http://www.spineuniverse.com/displayarticle.php/article1267.html

13. Other Measurements (cont)  Intra abdominal pressure  Stature  Vibration