Running is, maybe, the most ancient physical activity. Nevertheless, it has been on the spot in the last years, and actually is a trending exercise around the world. Running is a whole body activity that stresses our systems both in metabolic and mechanistic way. This stress, repeated continuously, could lead into an overuse injury in muscle, tendon or even bone, being running one of the sports in which overuse injuries develop more frequently, in around 59.4% of the cases. As Videbæk found in their study, the incidence of injury is higher in beginners than in recreational runners, which could be explain, at least partially, in the adaptations reached along their physical training period.

Different exercises have been proposed to prevent all these overuse injuries related to running, being eccentric overload training one of the most accepted in the last years because its ability to improve the state of tendons without a great metabolic impact. Eccentric overload means that the eccentric phase of the movement is performed with higher loads and velocity than the concentric. For example, squat movement combined with eccentric is the “gold standard” for the patellar tendon, and it is commonly used to cause beneficial changes in the tissues. The protocol most widely used  consists in 12–15 weeks of treatment for patellar tendinosis injuries. For the Achilles tendon, a number of studies have used eccentric overload to improve the state of tendon and muscle in reduced time. These (patellar and Achilles) are the tendons that support more loads during running, and we must take this in account when we plan specific training or therapy for runners, even more if they are beginners.

During running, not only tendons suffer a bigger stress. Muscles are contracting both in concentric, isometric and eccentric manner, with more implications of each one depending on the terrain (uphill or downhill running),  so it could be interesting to train muscles to face concentric and eccentric contractions safely.