When an initially stretched rubber band contracts (isothermally) and lifts a weight, it does work (for us) at the expense of heat absorbed from the surroundings, just like an initially compressed gas which expands (isothermally). How the work-producing force of contraction stems from thermal motion is nicely explained he

http://scifun.chem.wisc.edu/homeexpts/rubberband.html
"This occurs because as a material is heated, its molecules move about more energetically. In materials made up of small, compact molecules, e.g., the liquid in a thermometer, as the molecules move about more, they push their neighboring molecules away. Rubber, on the other hand, contains very large, threadlike molecules. When rubber is heated, the sections of the molecules move about more vigorously. In order for one part of the molecule to move more vigorously as it is heated, it must pull its neighboring parts closer.. To visualize this, think of a molecule of the stretched rubber band as a piece of string laid out straight on a table. Heating the stretched rubber band causes segments of the molecules to move more vigorously, which can be represented by wiggling the middle of the string back and forth. As the middle of the string moves, the ends of the string get closer together. In a similar fashion, the molecules of rubber become shorter as the rubber is heated, causing the stretched rubber band to contract."

Yet, despite the analogy between the contraction force (in rubber-like materials) and the gas pressure, there is an essential difference. Under isothermal conditions, we can only restore the initial (compressed) state of the gas system by doing work against the unaltered work-producing force, that is, by spending back the work we have just gained. Clearly, in this case, net work gained at the end of the operations expansion/compression has nowhere to come from.

In contrast, the restoration of the initial (stretched) state of contractile materials could involve some preliminary loosening of the work-producing contraction force so that more weight is lifted during contraction than dropped during stretching (the net work extracted from the operations contraction/stretching is positive). The following example shows that the work-producing force of contraction can be increased by adding hydrogen ions to the system and subsequently decreased by removing the hydrogen ions:

http://www.ncbi.nlm.nih.gov/pmc/arti...00645-0017.pdf
POLYELECTROLYTES AND THEIR BIOLOGICAL INTERACTIONS, A. KATCHALSKY, pp. 13-15: "Let the polymolecule be a negatively charged polyacid in a stretched state and have a length L. Now let us add to the molecule a mineral acid to provide hydrogen ions to combine with the ionized carboxylate groups and transform them into undissociated carboxylic groups according to the reaction RCOO- + H+ = RCOOH. By means of this reaction, the electrostatic repulsion which kept the macromolecule in a highly stretched state vanishes and instead the Brownian motion and intramolecular attraction cause a coiling up of the polymeric chains. Upon coiling, the polymolecule contracts and lifts the attached weight through a distance deltaL. On lifting the weight, mechanical work f*deltaL was performed... (...) FIGURE 4: Polyacid gel in sodium hydroxide solution: expanded. Polyacid gel in acid solution: contracted; weight is lifted."

Although the net work extracted from the operations contraction/stretching can be made positive (by means of hydrogen ions), there is still no proof that the second law of thermodynamics is violated since the work involved in the operations adding_hyrogen_ions/removing_hydrogen_ions is still not evaluated. Yet scientists free from the strangling hold of the dogma would see that the violation is by no means improbable.

Pentcho Valev