Fig. 10

Force in the cat medial gastrocnemius as a function of changes in tendon and aponeuroses lengths obtained by subtracting fibre lengths from the total muscle tendon unit lengths. Note that plotting the muscle force against this length (defined incorrectly as the series elastic element of the muscle -[61]) results in the appearance of net work by the (incorrectly) defined series elastic element, a thermodynamic impossibility. This example illustrates that the nature of the series elastic element is difficult to define, and is often used incorrectly leading to conclusions on the storage and release of energy in muscle contraction by series elastic elements (such as aponeuroses) that are incorrect