One of the most common overuse injuries is the muscle strain. Muscle injuries account for 10% to 55% of all acute sports injuries , and the majority of those injuries are muscle strains or bruises . The treatment of muscle strains can be challenging because “muscle tissue is often unable to fully regenerate to its pre-injury state” . For example, people recovering from hamstring injuries have a re-injury rate of approximately 30% . Similarly, scar tissue starts to form in as little as six weeks after a muscle injury . These challenges are made more difficult in those over the age of 40, as increased age has been shown to predispose athletes to muscle injury . So the treatment modality considered should be one that not only achieves return-to-play, but also rejuvenates the muscle.
ESWT has been shown to improve muscle repair and recovery after a muscle strain. Clinical studies have shown that ESWT treatments alone  and in combination with other treatment modalities [6,7] facilitate muscle repair and rejuvenation. When ESWT is incorporated into the treatment regimen, athletes experience less pain after injury [6,7], improved muscle tone , improved muscle strength , less muscle tightness  and increased muscle elasticity , and are able to return to activity . In one clinical study, physical therapy improved muscle tightness transiently after muscle injury, but when physical therapy was combined with ESWT, long-term improvements in muscle tightness were achieved . ESWT has even been shown to decrease muscle spasticity in those suffering from a stroke . The exact biologic mechanisms responsible for these improvements are unknown, though ESWT has been shown to increase blood flow in muscle tissues .
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