Spring washers, sometimes called disc springs, are a subtype of washers. They lend their mechanical capabilities to the unique profile of the material: when subject to a load, the irregularities of the washer compress with a proportionate resistance to return to their predeflected shape.
You should never stretch a pulled muscle to the point of pain or you risk re-injuring it. Do not overstretch the pulled muscles. Too much stretching can retear injured muscle fibers. Gently stretching a pulled muscle may relax the surrounding muscle fibers, which may be tight in response to the injury.
This chronic inflammation leads to long-term pain. As any stretching of the tendon is very painful, the body reacts by hardening and shortening the calf muscles. This in turn stretches the tendon further and keeps the cycle of pain going. Pain-free thanks to eccentric strength training.