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.
The Runner's Hamstring and Calf Stretch. You can do the runner's stretch to improve hamstring and calf flexibility. The runner's stretch is a common flexibility exercise for your hamstrings or calf muscles. Stand one foot from a wall and place your hands on the wall at shoulder height, shoulder-width apart. Take a step back with one leg while pushing into the wall. Keep your back straight and press your heels into the floor.