Introduction to Sports Biomechanics: Analysing Human Movement ...

torque output while the angular velocity is constant; computation of angular velocity
is, therefore, essential. Most isokinetic dynamometers output torque and angular
position data in digital form. Angular velocity and acceleration can be obtained by
differentiation of the angular position-time data after using appropriate noise reduction
techniques (see Chapter 4). Instantaneous joint power (P = T.ω) can be calculated
from the torque (T) and angular velocity (ω) when the preset angular velocity has been
reached.
Data processing in isokinetic dynamometry
The following parameters can normally be obtained from an isokinetic dynamometer
to assess muscle function (for further information, see Baltzopoulos, 2007; Further
Reading, page 280).
The maximum torque
The isokinetic maximum torque is used as an indicator of the muscle torque that can
be applied in dynamic conditions. It is usually evaluated from two to six maximal
repetitions and is taken as the maximum single torque measured during these
repetitions. The maximum torque depends on the angular position of the joint.
Maximum power can also be calculated.
The reciprocal muscle group ratio
The reciprocal muscle group ratio is an indicator of muscle strength balance around
a joint, which is affected by age, biological sex and physical fitness. It is the ratio of the
maximum torques recorded in antagonist movements, usually flexion and extension, for
example the quadriceps femoris to hamstrings muscle group ratio.
The maximum torque position
The maximum torque position is the joint angular position at maximum torque and
provides information about the mechanical properties of the activated muscle group. It
is affected by the angular velocity. As the angular velocity increases, this position tends
to occur later in the range of movement and not in the mechanically optimal joint
position. It is, therefore, crucial to specify the maximum torque position as well as the
maximum torque.
Muscular endurance under isokinetic conditions
THE ANATOMY OF HUMAN MOVEMENT
Muscular endurance under isokinetic conditions is usually assessed through a ‘fatigue
index’. It provides an indication of the muscle group’s ability to perform the movement
at the preset angular velocity over time. Although there is no standardised testing
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