Publications

Study aim: This pilot study aimed to quantify acute and short-term pre- to post-session changes in the mechanical properties of shoulder girdle muscles in volleyball players during an in-season preparatory mesocycle.

Material and methods: Eight male volleyball athletes competing at the national academic level underwent assessments once per week across a 3-week in-season preparatory mesocycle immediately preceding the Polish Academic Volleyball Championships. At each session, MyotonPRO was used to measure tone (Hz), stiffness (N/m), and elasticity (log. decrement, D) before and after standardized 120-min training. Upper-body explosive power was assessed via the seated medicine-ball throw. Week-specific pre–post comparisons were tested with paired t-tests (Cohen’s dz, 95% CI). Two-way repeated-measures ANOVAs examined Time (pre/post) × Week effects.

Results: Upper trapezius tone increased significantly post-training across all weeks (dz = 0.90–1.01, p < 0.05). Lower trapezius elasticity improved consistently (Δ = –0.13 to –0.17, dz ≈ –1.0, p < 0.05), while infraspinatus elasticity improved only in Week 3 (dz = –1.13, p = 0.015). Exploratory repeated-measures ANOVA also identified a Time effect for upper trapezius tone (F(1,7)= 12.1, p= 0.010, ηp2 = 0.634), although ANOVA-based effect sizes should be interpreted cautiously given the pilot sample.

Conclusions: Preliminary data suggest that selected shoulder stabilizers exhibited short-term pre- to post-session changes in tone and elasticity during the monitored in-season preparatory mesocycle. Given the pilot sample, these localized changes should be interpreted cautiously.

Keywords: volleyball, shoulder joint, muscle, skeletal, elasticity, performance

Consistent pre- to post-session increases in upper trapezius tone, together with reductions in logarithmic decrement in the lower trapezius and infraspinatus, indicate that selected shoulder stabilizers exhibited measurable short-term mechanical changes across the monitored volleyball sessions. These findings support the feasibility of handheld myotonometry for detecting localized muscle mechanical responses in an ecologically valid training context. Given the pilot sample, lack of a control group, and absence of quantified external load, these findings should be interpreted cautiously. At present, myotonometry should be viewed as a complementary monitoring method for describing session-related muscle responses rather than as a stand-alone tool for guiding load management, optimizing performance, or inferring injury risk. Future studies with larger cohorts, longer follow-up, and integrated load, functional, and clinical measures are needed to determine its practical value in volleyball settings.