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Thimo Wiewelhove, Christian Raeder, Rauno Álvaro de Paula Simola, Christoph Schneider, Alexander Döweling, Alexander Ferrauti

• \(\textbf {Objective:}\) Tensiomyography (TMG) is an indirect measure of a muscle’s contractile properties and has the potential as a technique for detecting exercise-induced skeletal muscle fatigue. Therefore, the aim of this study was to assess the sensitivity of tensiomyographic markers to identify reduced muscular performance in elite youth athletes. \(\textbf {Methods:}\) Fourteen male junior tennis players (age: 14.9 \(\pm\) 1.2 years) with an international (International Tennis Federation) ranking position participated in this pre-post single group trial. They completed a 4-day high-intensity interval training (HIT) microcycle, which was composed of seven training sessions. TMG markers; countermovement jump (CMJ) performance (criterion measure of fatigue); delayed onset muscle soreness; and perceived recovery and stress were measured 24 h before and after the training program. The TMG measures included maximal radial deformation of the rectus femoris muscle belly (Dm), contraction time between 10 and 90%Dm(Tc) and the rate of deformation until 10% (V10) and 90% Dm (V90), respectively. Diagnostic characteristics were assessed with a receiver-operating curve (ROC) analysis and a contingency table, in which the area under the curve (AUC), Youden’s index, sensitivity, specificity, and the diagnostic effectiveness (DE) of TMG measures were reported. A minimum AUC of 0.70 and a lower confidence interval (CI) >0.50 classified "good" diagnostic markers to assess performance changes. \(\textbf {Results:}\) Twenty-four hours after the microcycle, CMJ performance was observed to be significantly (\(\it p\) < 0.001) reduced (Effect Size [ES] = −0.68), and DOMS (ES = 3.62) as well as perceived stress were significantly (\(\it p\) < 0.001) increased. In contrast, Dm (ES = −0.35), Tc (ES = 0.04), V10 (ES = −0.32), and V90 (ES = −0.33) remained unchanged (\(\it p\) > 0.05) throughout the study. ROC analysis and the data derived from the contingency table revealed that none of the tensiomyographic markers were effective diagnostic tools for detecting impaired muscular performance in elite youth athletes (AUC, 95% CI, DE%; Dm: 0.46, 0.15–0.77, 35.7%; Tc: 0.29, 0.03–0.59, 35.7%; V10: 0.71, 0.27–1.00, 35.7%; V90: 0.37, 0.10–0.65, 35.7%). \(\textbf {Conclusion:}\) The tensiomyographic parameters that were assessed in this study were not sensitive enough to detect muscular performance changes in elite youth athletes. However, due to the preliminary nature of the study, further research is needed to investigate the sensitivity of TMG in this population.