Eccentric exercises for the calf muscles have been shown to be effective for chronic non-insertional Achilles tendinopathy (AT). However, the relative effectiveness of various dosages is unknown. A systematic review of randomized-controlled trials (RCTs) was designed to determine whether an optimum dose of eccentric exercises could be recommended. Three selected RCTs showed positive effects of very similar eccentric exercise protocols for chronic non-insertional AT. Owing to insufficient reported compliance data, a conclusion on the relative effectiveness of various compliances was not feasible. According to our review, the relative effectiveness of various dosages of eccentric exercises for AT is still unclear. However, it appears that highly variable compliance rates result in similar positive outcomes; these findings, therefore, highlight the need for further investigations.