Psyc 552 Ergonomics & Biomechanics Lecture 7

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

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

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

Strength testing criteria  Safe  Reliable  Practical

Factors Affecting Strength  Posture  Velocity  Acceleration

Using Static Strength Data

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

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

Psychophysical Strength Method  Kroemer (1982) liftest

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

Other Measurements  Intradisc pressure Image from:

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