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.
Treatment. Pulled muscles mostly heal independently without particular medical treatment. The pain may begin to dissipate within two or three weeks, yet the injury can be two months before it is thoroughly recovered. Within the first 48 hours of pulling your back muscle, apply ice to the injured area. It should be applied every four hours for 15 to 20 minutes each time. This helps decrease the pain and inflammation, which can contribute to the pain too.