The effects of a six-week plyometric training program on the stiffness of anterior and posterior muscles of the lower leg in male volleyball players - Mroczek, D.; Superlak, E.; Seweryniak, T.; Mackala, K.; Konefal, M.; Chmura, P.; Borzucka, D.; Rektor, Z. (Central European Journal of Sport Sciences and Medicine, 2017)