Structure and Motion Laboratory

Research Interests

The Relationship Between the Contractile Element and Elasticity in the Muscle-tendon Unit

Muscle can only achieve optimum efficiency over a narrow range of contraction velocities and peak power over a somewhat higher and wider range of velocities. Locomotion however requires the absorption and generation of power at a wide range of velocities. Whilst alterations in fibre length and skeletal lever arms can account for changes in gearing of the whole locomotor system there is still the requirement for varying the velocity of power generation as a function of activity. Muscle fibres are constrained for this function but when placed in series with an elastic element greater mechanical versatility results. The elasticity has two functions in addition to the energetic benefits discussed above:

To regulate force as a function of length - this is critical in decelerating a mass, either that of a limb or the trunk during locomotion, and accounts for the characteristic sinusoidal shape of the vertical force - time curve in animal locomotion.
To accelerate masses during locomotion using elastic energy stored in the tissue in a previous phase of the gait cycle (above). This achieves a higher power output/higher velocity than could be achieved by muscle contraction.

There is therefore a balance between having elastic tendons that store and return energy and long muscles that are versatile but heavy and require a lot of energy to generate force or achieve a length change. Muscles are however required to drive, tune and damp the spring system.

Projects

Structure and Motion Lab These pages maintained by the SML Contact: Alan Wilson