Table 4.
Correlations between all variables according to age ranges.
| U12 | Ball speed (km/h) | BVE (m) | MVM (m/s) | FED | FEV | DFAD | DFAV | |
| MRE | −0.112 | 0.178 | −0.176 | −0.248 | −0.115 | 0.163 | −0.205 | |
| Ball speed | -- | 0.166 | 0.157 | 0.184 | 0.380* | −0.350* | −0.077 | |
| BVE | -- | -- | 0.300 | −0.043 | −0.046 | 0.128 | 0.065 | |
| MVM | -- | -- | -- | 0.851** | 0.423** | −0.506** | −0.016 | |
| FED | -- | -- | -- | -- | 0.678** | −0.694** | −0.073 | |
| FEV | -- | -- | -- | -- | -- | −0.657** | −0.162 | |
| DFAD | -- | -- | -- | -- | -- | -- | 0.116 | |
| U16 | Ball speed (km/h) | BVE (m) | MVM (m/s) | FED | FEV | DFAD | DFAV | |
| MRE | 0.189 | 0.320 | 0.034 | −0.248 | −0.133 | 0.249 | −0.007 | |
| Ball speed | -- | 0.328 | 0.427* | 0.228 | −0.061 | 0.347 | −0.050 | |
| BVE | -- | -- | 0.593** | −0.106 | −0.352 | 0.077 | 0.247 | |
| MVM | -- | -- | -- | 0.706** | 0.263 | −0.534** | −0.389* | |
| FED | -- | -- | -- | -- | 0.582** | −0.767** | −0.314 | |
| FEV | -- | -- | -- | -- | -- | −0.228 | −0.298 | |
| DFAD | -- | -- | -- | -- | -- | -- | 0.275 | |
| 18+ | Ball speed (km/h) | BVE (m) | MVM (m/s) | FED | FEV | DFAD | DFAV | |
| MRE | −0.156 | −0.157 | −0.357* | −0.343* | −0.085 | 0.176 | −0.055 | |
| Ball speed | -- | −0.281 | 0.015 | 0.227 | 0.050 | −0.102 | −0.308* | |
| BVE | -- | -- | 0.542** | −0.146 | −0.180 | 0.114 | 0.041 | |
| MVM | -- | -- | -- | 0.613** | 0.225 | −0.261 | −0.068 | |
| FED | -- | -- | -- | -- | 0.444** | −0.482** | −0.030 | |
| FEV | -- | -- | -- | -- | -- | 0.000 | −0.294 | |
| DFAD | -- | -- | -- | -- | -- | -- | 0.220 | |
| * p < .05; ** p < .01 | ||||||||
MRE: mean radial error (m); ball speed (km/h); BVE: bivariate variable error (m); MVM: mean velocity magnitude (m/s); FED: fuzzy entropy of the displacement of COP (unitless); FEV: fuzzy entropy of the velocity of COP (unitless); DFAD: detrended fluctuation analysis of the displacement of COP (unitless); DFAV: detrended fluctuation analysis of the velocity of COP (unitless).