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.
Athletes who sustain a groin strain will want to incorporate a stretching program as part of their rehabilitation. Some simple stretches can help ease the symptoms of a groin strain. Furthermore, stretching can be a useful part of preventing groin injuries from occurring. As a general rule, the stretches should not hurt. There should be a gentle pulling sensation of the muscle, but this should not be painful. The first stretch is the squatting adductor stretch: Squat to the ground with your arms between your legs.