Introduction. Monitoring muscle stiffness in athletes can be a good method of assessing fatigue caused by high training loads, and the early detection of fatigue can help prevent the occurrence of micro-trauma in the muscles that can cause contusions. The research carried out by Wilson et al.  confirmed that an optimal level of muscle stiffness is significantly correlated with high muscle loads. The aim of the current study was to determine changes in muscle stiffness of the left and right thighs during six weeks of plyometric training (PT) in volleyball players.
Material and methods. The study involved 16 volleyball players from the second-league Opole University of Technology Club (age = 21.12 ± 1.66 years, height = 191.62 ± 5.73 cm, and weight = 86.25 ± 6.66 kg) with at least five years of competitive experience (7.5 ± 2.44 years). Muscle stiffness was measured during three stages of the plyometric training using a MYOTON PRO device (Estonia).
Results. An RM-ANOVA analysis showed a significant difference in the resting stiffness of the semitendinosus (posterior thigh) muscles of the left and right limbs before the plyometric training began, but no significant differences were found in the stiffness of these muscles in the fourth or sixth weeks of training. The results of the measurement performed for the anterior muscles of the thigh did not reveal a significant difference in the stiffness of the left limb compared to that of the right limb in subsequent weeks of training.
Conclusion. The loads used in plyometric training in volleyball players caused a decrease in the differences in muscle stiffness between the left and right limbs, and in both limbs, adaptation trended towards an increase or a decrease in stiffness.
female volleyball players. Modelowanie Inżynierskie 44, 302-306. [in Polish] 23. Friedrich H., Vetter K. (2003). The value of strength-diagnostic for the structure of jumptraininginvolleyball. European Journal of Sport Science 3, 1-10. 24. Sheppard J.M., Newton R.U. (2012). Long-term training adaptations in elite male volleyball players. Journal of Strength and Conditioning Research 26(8), 2180-2184. 25. Häkkinen K., Komi P.V., Alén M., Kauhanen H. (1987). EMG, muscle fiber and force production characteristics during a 1 year training period in elite weight
1993 33 400 404 Voigt HF, Vetter K. The value of strength-diagnostic for the structure of jumptraininginvolleyball. Eur J Sport Sci , 2003; 3(3): 1-10 10.1080/17461390300073310 Voigt HF Vetter K The value of strength-diagnostic for the structure of jumptraininginvolleyball Eur J Sport Sci 2003 3 3 1 10 Zhang R. Features of the women volleyball player's body shape and bounce quality in the 26th Olympic game-analyzing the present situation of Asian women volleyball teams. Journal of Guangzhou Physical Education Institute 1998; 18: 99-103 Zhang R Features of
strength-diagnostic for the structure of jumptraininginvolleyball. Eur J Sport Sci 2003; 3(3): 1–10 10.1080/17461390300073310 Voigt H Vetter K The value of strength-diagnostic for the structure of jumptraininginvolleyball Eur J Sport Sci 2003 3 3 1 – 10 Wnorowski K, Aschenbrenner P, Skrobecki J, Stech M. An assessment of a volleyball player’s loads in a match on the basis of the number and height of jumps measured in real-time conditions. Balt J Heal Phys Act , 2013; 5(3): 199–206. Available from: http