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.
Many people have tight hip flexors, but not all people do. Stretch the psoas and the rectus femoris if need-be. It may also be wise to stretch the hip flexors for other reasons; you may be able to inhibit them a bit and create some slack to make things easier for the glutes. 3. Static Stretch the Hammies First.