TY - JOUR

T1 - Despite Good Correlations, There Is No Exact Coincidence between Isometric and Dynamic Strength Measurements in Elite Youth Soccer Players

AU - Wagner, Carl M.

AU - Warneke, Konstantin

AU - Bächer, Christoph

AU - Liefke, Christian

AU - Paintner, Philipp

AU - Kuhn, Larissa

AU - Brauner, Torsten

AU - Wirth, Klaus

AU - Keiner, Michael

N1 - Publisher Copyright: © 2022 by the authors.

PY - 2022/11/10

Y1 - 2022/11/10

N2 - Speed strength performances are substantially dependent on maximum strength. Due to their importance, various methods have been utilized to measure maximum strength (e.g., isometric or dynamic) with discussed differences regarding transferability to sport-specific movements dependent upon the testing procedure. The aim of this study was to analyze whether maximum isometric force (MIF) during isometric back squats correlates with maximum strength measurements of the one repetition maximum (1RM) in the squat, with countermovement jump (CMJ) performance, and with drop jump (DJ) performances in elite youth soccer players (n = 16, 18.4 +/- 1.5 [range: 17-23] years old). Additionally, concordance correlation coefficients (CCC, [rho(c)]) between isometric and dynamic measurements were calculated to verify whether one measurement can actually reproduce the results of the other. To improve comprehension, differences between isometric and dynamic testing values were illustrated by providing differences between both testing conditions. For this, the mean absolute error (MAE) and the mean absolute percentage error (MAPE) were calculated. To reach equality in scale, the 1RM measures were multiplicated by 9.81 to obtain a value of N. The 1RM demonstrated correlations of tau = |0.38| to |0.52| with SJ and CMJ performances, while MIF demonstrated correlations of tau = |0.21| to |0.32|. However, the correlations of both 1RM and MIF with the DJ reactive strength index (RSI = jump height/contact time) from different falling heights were of no statistical significance. The data showed significant correlations between both the absolute (tau = |0.54|) and the relative (tau = |0.40|) performances of 1RM and MIF, which were confirmed by CCC of rho(c)= |0.56| to |0.66|, respectively. Furthermore, the MAE and MAPE showed values of 2080.87 N and 67.4%, respectively. The data in this study show that, despite good correlations, there is no exact coincidence between isometric and dynamic strength measurements. Accordingly, both measurements may only represent an estimation of maximal strength capacity and cannot be substituted for each other. Therefore, maximal strength should be tested by using high similarity in the contraction condition, as it is used in the training process to counteract underestimation in strength because of unfamiliarity with the testing condition.

AB - Speed strength performances are substantially dependent on maximum strength. Due to their importance, various methods have been utilized to measure maximum strength (e.g., isometric or dynamic) with discussed differences regarding transferability to sport-specific movements dependent upon the testing procedure. The aim of this study was to analyze whether maximum isometric force (MIF) during isometric back squats correlates with maximum strength measurements of the one repetition maximum (1RM) in the squat, with countermovement jump (CMJ) performance, and with drop jump (DJ) performances in elite youth soccer players (n = 16, 18.4 +/- 1.5 [range: 17-23] years old). Additionally, concordance correlation coefficients (CCC, [rho(c)]) between isometric and dynamic measurements were calculated to verify whether one measurement can actually reproduce the results of the other. To improve comprehension, differences between isometric and dynamic testing values were illustrated by providing differences between both testing conditions. For this, the mean absolute error (MAE) and the mean absolute percentage error (MAPE) were calculated. To reach equality in scale, the 1RM measures were multiplicated by 9.81 to obtain a value of N. The 1RM demonstrated correlations of tau = |0.38| to |0.52| with SJ and CMJ performances, while MIF demonstrated correlations of tau = |0.21| to |0.32|. However, the correlations of both 1RM and MIF with the DJ reactive strength index (RSI = jump height/contact time) from different falling heights were of no statistical significance. The data showed significant correlations between both the absolute (tau = |0.54|) and the relative (tau = |0.40|) performances of 1RM and MIF, which were confirmed by CCC of rho(c)= |0.56| to |0.66|, respectively. Furthermore, the MAE and MAPE showed values of 2080.87 N and 67.4%, respectively. The data in this study show that, despite good correlations, there is no exact coincidence between isometric and dynamic strength measurements. Accordingly, both measurements may only represent an estimation of maximal strength capacity and cannot be substituted for each other. Therefore, maximal strength should be tested by using high similarity in the contraction condition, as it is used in the training process to counteract underestimation in strength because of unfamiliarity with the testing condition.

KW - Physical education and sports

KW - squat

KW - maximal strenght

KW - 1rm

KW - isometrics

KW - jump

KW - speed-strenghth

KW - soccer

UR - https://www.mendeley.com/catalogue/eeaa3a90-3d4c-379e-b56a-5af69dbed0c8/

UR - http://www.scopus.com/inward/record.url?scp=85149455143&partnerID=8YFLogxK

U2 - 10.3390/sports10110175

DO - 10.3390/sports10110175

M3 - Journal articles

C2 - 36355825

VL - 10

JO - Sports

JF - Sports

SN - 2075-4663

IS - 11

M1 - 175

ER -