Table 1. Descriptive statistics (mean ± one standard deviation - 1SD) of the swim speed and dv as discrete variables in the three tiers groups by sex. It is also presented the anthropometric features by tier and sex. Boys Girls Mean ± 1SD (Tier #1) Mean ± 1SD (Tier #2) Mean ± 1SD (Tier #3) Mean ± 1SD (Tier #1) Mean ± 1SD (Tier #2) Mean ± 1SD (Tier #3) Speed [m/s] 1.56 ± 0.06 1.41 ± 0.03 1.21 ± 0.05 1.41 ± 0.03 1.30 ± 0.02 1.16 ± 0.07 dv [%] 7.91 ± 2.19 7.91 ± 1.83 8.81 ± 2.15 8.05 ± 3.01 7.65 ± 2.04 10.01 ± 2.56 Stroke frequency [Hz] 0.90 ± 0.10 0.89 ± 0.11 0.86 ± 0.11 0.81 ± 0.07 0.83 ± 0.08 0.79 ± 0.07 Stroke length [m] 1.77 ± 0.20 1.60 ± 0.17 1.43 ± 0.19 1.75 ± 0.13 1.58 ± 0.14 1.48 ± 0.13 Body mass [kg] 59.74 ± 7.24 48.33 ± 7.04 45.62 ± 5.65 51.51 ± 3.20 48.21 ± 7.90 48.81 ± 9.20 Height [cm] 170.70 ± 6.99 159.75 ± 6.87 155.55 ± 7.17 162.35 ± 4.04 156.78 ± 4.56 156.03 ± 6.77 Arm span [cm] 177.28 ± 9.17 165.21 ± 6.83 159.75 ± 8.74 163.50 ± 4.89 159.25 ± 6.15 160.50 ± 6.64 dv – intra-cyclic variations of horizontal speed.