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Supplemental material, sj-docx-1-sph-10.1177_19417381221116345 for Norm Values of Muscular Strength Across the Life Span in a Healthy Swiss Population: The COmPLETE Study by Eric Lichtenstein, Jonathan Wagner, Raphael Knaier, Denis Infanger, Ralf Roth, Timo Hinrichs, Arno Schmidt-Trucksaess and Oliver Faude in Sports Health: A Multidisciplinary Approach

Background. It has been proposed that muscle architecture can be associated with sprint performance and the risk of sustaining a muscle injury. During puberty, sprint performance as well as muscle injury risk increases in young soccer players. In this study, we investigated the changes in m. biceps femoris long head (BFlh) cross-sectional area (ACSA), fascicle length (FL) and pennation angle (PA) and sprint performance as well as their relationship in under 13 to 15 youth soccer players. Methods. In total, we measured 85 youth soccer players in under 13 (n=29, age=12.5 y (SD=0.1), height=155.3 cm (6.2), weight=43.9 kg (7.6)), under 14 (n=25, age=13.5 y (0.3), height=160.6 y (7.7), weight=47.0 kg (6.8)) and under 15 (n=31, age=14.4 y (0.3) , height=170.0 cm (7.7), weight=58.1 kg (8.8) ) teams of three high level soccer clubs. We used ultrasound to measure BFlh ACSA, FL and PA. We performed sprint tests to assess 10m and 30m sprint time, maximal velocity (vmax) and maximal acceleration (amax). We calculated Pearson’s r and 95% compatibility intervals to assess the relationship between sprint ability, maturity ratio, chronological age and architectural parameters. In addition, we calculated the best set of predictors for sprint ability using multiple regression models.Results. All muscle architectural parameters increased from the under 13 to the under 15 age group (BFlh ACSA: 37%, BFlh FL: 11%, BFlh PA: 8%). All sprint performance parameters improved from the under 13 to under 15 age categories (30m time: 7%, 10m time: 4%, vmax: 9%, amax: 7%). BFlh ACSA was correlated with 30m sprint time (r = -0.61 (95% CI = -0.73, -0.45)) and vmax (r= 0.61 (0.45, 0.72)). The correlation for maturity ratio with assessed parameters were larger compared to the correlation for chronological age. A combination of BFlh ACSA, FL, chronological age and height best predicted sprint parameters. Discussion. Parallel to improvements in sprint performance, muscle architectural parame-ters increase from the under 13 to under 15 age groups. BFlh ACSA seems to be related to sprint performance in youth soccer players. BFlh ACSA and chronological age are the main predictors of most sprint parameters.