Today, the isokinetic mode with its means of quantification is routinely used in functional rehabilitation or training to restore the function of injured muscles and limbs or to increase muscular performance, respectively.

Nevertheless, muscular performance is not only linked to the force production capacities of muscles, but also to its elastic characteristics. In fact, skeletal muscles generate force that must be transmitted to a joint via the muscle-tendon complex. The properties of these structural elements can affect the force a muscle can develop and the role it plays in joint mechanics.

Elastic structures - like muscles, tendons and articular structures - play a part in:

    -the transmission of the generated force via tendinous structures to the joint
    -the storage an reutilization of elastic energy during movement
    -the improvement in the output of muscle contraction
    -the integrity and maintenance of muscular structures and joint stability

Muscle and joint stiffness are therefore parameters of special interest, because their value determines the resistance to an external perturbation and thus they are important for posture and movement control. In this conjunction, a stiff structure allows immediate response and precise movement control, but it reduces the range of movement over which forces can be applied.

Elastic properties of the muscle-tendon complex can be quantified in terms of musculotendinous stiffness by means of a quick-release technique. Elastic properties of the muscle-joint system can be quantified in terms of musculoarticular stiffness by means of sinusoidal perturbations.