Characteristics of the study participants
Irrespective of outcome, we did not detect statistically significant differences in participants’ characteristics, neither in study 1 nor in study 2 (Table 1).
Discriminative validity of Lower Quarter Y Balance Test performance (study 1)
Statistical data on the discriminative validity for YBT-LQ performance between young male soccer players and age-matched male untrained subjects are displayed in Table 2. With regard to the absolute values (i.e., reach distance in cm), the soccer players compared to the controls achieved small- to medium-sized and significantly better values for AT (p ≤ 0.009; d = 0.45-0.49), PM (p < 0.001; d = 0.64), and PL (p < 0.001; d = 0.65-0.69) directions, irrespective of the reaching leg. In addition, we detected significant differences between the three reach directions (PM > PL > AT) for the right and left leg reach, irrespective of training status (i.e., soccer players or untrained subjects). Further, AUC-values were 0.63 (AT), 0.67 (PM), and 0.69 (PL) for the right and 0.64 (AT), 0.66 (PM), and 0.68 (PL) for the left leg reach, respectively. Results indicate that there is a chance of 63-69% that the YBT-LQ is possible to differentiate between soccer players and age-matched untrained individuals.
Concerning the relative values (i.e., reach distance in % LL), the soccer players achieved large-sized and significantly better values for AT (p < 0.001; d = 0.86-0.87), PM (p < 0.001; d = 1.11-1.17), and PL (p < 0.001; d = 1.08-1.10) directions as well as for the CS (p < 0.001; d = 1.16-1.21) compared to the controls, irrespective of the reaching leg. Additionally, we found significant differences between the three reach directions (PM > PL > AT) for the right and the left leg reach, irrespective of training status (i.e., soccer players or untrained subjects). Further, AUC-values were 0.74 (AT), 0.78 (PM), 0.78 (PL), and 0.80 (CS) for the right and 0.74 (AT), 0.79 (PM), 0.77 (PL), and 0.81 (CS) for the left leg reach, respectively. Results indicate that there is a chance of 74-81% that the YBT-LQ is possible to differentiate between soccer players and age-matched untrained individuals.
Discriminative validity of Upper Quarter Y Balance Test performance (study 2)
Table 3 shows the statistics on the discriminative validity for YBT-UQ performance between young female and male swimmers and age-/sex-matched untrained subjects. With regard to the absolute values (i.e., reach distance in cm), we detected significant, large-sized differences in favour of swimmers for the MD (p < 0.001, d = 0.87-0.91), IL (p < 0.001, d = 1.19-1.30), and SL (p < 0.001, d = 1.46-1.78) directions. Further, we found significant differences between the three reach directions (MD > IL > SL) for the right and left arm reach, irrespective of training status (i.e., swimmers or untrained subjects). In addition, AUC-values were 0.75 (MD), 0.83 (IL), and 0.90 (SL) for the right and 0.75 (MD), 0.79 (IL), and 0.84 (SL) for the left arm reach, respectively. In other words, there is a chance of 75-90% that the YBT-UQ is possible to distinguish between swimmers and age-/sex-matched untrained subjects.
With respect to the relative values (i.e., reach distance in % AL), we observed significant, large-sized differences in favour of swimmers for the MD (p < 0.001, d = 0.92-1.09), IL (p < 0.001, d = 0.88-0.99), and SL (p < 0.001, d = 1.11-1.48) directions as well as for the CS (p < 0.001, d = 1.17-1.28). In addition, AUC-values were 0.73 (MD), 0.76 (IL), 0.85 (SL), and 0.80 (CS) for the right and 0.78 (MD), 0.71 (IL), 0.77 (SL), and 0.79 (CS) for the left arm reach, respectively. In other words, there is a chance of 71-85% that the YBT-UQ is possible to distinguish between swimmers and age-/sex-matched untrained subjects.