Seems that working out with weights in order to grow muscle doesn't apply to workouts aimed only at humans.

Researchers at Hokkaido University in Japan have come up with a way to manufacture materials that grow stronger as a result to exposure to mechanical stress, a process that parallels that of skeletal development.

The discovery could open the door to the creation of durable substances that can change and strengthen depending on the surrounding environment.

The work grew out of studying processes that help human muscles gain strength -- when people work out at the gym, muscle fibers are stressed to the point of breaking down, which ushers in the creation of newer ones that are stronger. Amino acids from proteins must be present in order for this process to be a success.

The research team created a solution that replicated the process of blood transporting amino acids to human muscles.

According to a press release, applying pressure to a hydrogel, which the team placed within molecules in order to make larger molecules known as polymers, causes some of the polymers to break.

This creates a chemical group known as ‘mechanoradicals’ at the ends of the shattered polymer chains. The mechanoradicals can serve as catalysts to "the joining up of the monomer absorbed into the hydrogel from the surrounding solution into a polymer network, strengthening the material."

As more stretching occurs, more breaking down and rebuilding also happens. As a result of this material conditioning, the polymers increase in weight; when heated at elevated temperatures, the surface of the hydrogel also becomes more resistant to water.

One potential use for the discovery: Making exoskeletal suits for people with bone injuries.