Applied Biomechanical Analysis- lecture 7- Isokinetic dynamometry
Dynamometry= measurement of strength
Isokinetic= constant speed
The basic theory centres on balanced torques- the torque produced by the machine
is equal to the torque made by the participant. Isokinetic means no angular
acceleration & no net torque/moment.
Joint function
The joint torque is the sum of the torques from various muscle-tendon units that
cross the joint. It is not possible to measure torque produced by a single muscle, as
the torque at any moment is affected by many factors. The factors affecting torque
include:
The inherent muscle ‘strength’
The level of muscle activation
The current joint angle
The joint angular velocity
The muscles recent history (including fatigue)
Muscle strength- the maximum force a muscle can produce is affected by muscle
size, and fibre arrangement (parallel vs pennate).
Muscle activation- corresponds to level of ‘neural drive’ arriving at motor units. The
most common level is the maximum voluntary contraction (MVC). % of MVC can be
dfined but isn’t easy.
Joint angle- changes in joint angle can cause changes in the muscles moment arm.
Recent history- fatigue?- inability to maintain level of joint torque over a sustained
contraction & repeated contractions.
Steps in IKD analysis
Create a protocol
Enter participant details
Set-up dynamometer
Explain process to participant
Warm-up
Run tests
Analyse results & give feedback
Safety issues
Dynamometry= measurement of strength
Isokinetic= constant speed
The basic theory centres on balanced torques- the torque produced by the machine
is equal to the torque made by the participant. Isokinetic means no angular
acceleration & no net torque/moment.
Joint function
The joint torque is the sum of the torques from various muscle-tendon units that
cross the joint. It is not possible to measure torque produced by a single muscle, as
the torque at any moment is affected by many factors. The factors affecting torque
include:
The inherent muscle ‘strength’
The level of muscle activation
The current joint angle
The joint angular velocity
The muscles recent history (including fatigue)
Muscle strength- the maximum force a muscle can produce is affected by muscle
size, and fibre arrangement (parallel vs pennate).
Muscle activation- corresponds to level of ‘neural drive’ arriving at motor units. The
most common level is the maximum voluntary contraction (MVC). % of MVC can be
dfined but isn’t easy.
Joint angle- changes in joint angle can cause changes in the muscles moment arm.
Recent history- fatigue?- inability to maintain level of joint torque over a sustained
contraction & repeated contractions.
Steps in IKD analysis
Create a protocol
Enter participant details
Set-up dynamometer
Explain process to participant
Warm-up
Run tests
Analyse results & give feedback
Safety issues
