Table 2. Aerobic fitness variables assessed by the Yo-yo IR1 test, peak heart rate (HR) and vertical jump (CMJ) for all groups before and after the experimental and control periods. In the control period the group name remains, but no supplementary HIIT training was performed. Variable Group Pre Post p d Delta Delta p d Pre vs. Post Pre vs. Post change Change (%) Between deltas Between deltas Distance (m) 10s/10s 2083 ± 411 2434 ± 345 <0.001 0.92 (large) 351 ± 192 18.5 ± 11.7 0.039 0.85 (large) 15s/15s 2225 ± 262 2418 ± 275 0.005 0.72 (moderate) 194 ± 175 9.0 ± 8.5 Control period 10s/10s 2166 ± 418 2083 ± 349 0.587 0.22 (small) -83 ± 281 -2.2 ± 15.2 0.973 0.01 (trivial) 15s/15s 2317 ± 275 2231 ± 289 0.443 0.31 (small) -86 ± 162 -3.6 ± 7.1 V·O2max (ml/kg/min) 10s/10s 53.9 ± 3.5 56.8 ± 2.9 <0.001 0.92 (large) 2.9 ± 1.6 5.6 ± 3.2 0.039 0.85 (large) 15s/15s 55.1 ± 2.2 56.7 ± 2.3 0.005 0.72 (moderate) 1.6 ± 1.5 3.0 ± 2.7 Control period 10s/10s 54.6 ± 3.5 53.9 ± 2.9 0.587 0.22 (small) -0.7 ± 2.4 -1.1 ± 4.4 0.973 0.35 (small) 15s/15s 55.9 ± 2.3 55.1 ± 2.4 0.443 0.31 (small) -0.1 ± 0.4 -1.3 ± 2.4 vV·O2max (km/h) 10s/10s 16.6 ± 0.6 17.1 ± 0.5 <0.001 0.92 (large) 0.5 ± 0.3 3.3 ± 1.9 0.039 0.85 (large) 15s/15s 16.8 ± 0.4 17.1 ± 0.4 0.005 0.72 (moderate) 0.3 ± 0.3 1.8 ± 1.7 Control period 10s/10s 16.7 ± 0.7 16.6 ± 0.5 0.587 0.22 (small) -0.1 ± 0.4 -0.7 ± 2.7 0.973 0.00 (trivial) 15s/15s 16.9 ± 0.4 16.8 ± 0.5 0.443 0.31 (small) -0.1 ± 0.3 -0.8 ± 1.5 HR(bpm) 10s/10s 198 ± 5 198 ± 5 0.705 0.15 (trivial -0.7 ± 3.3 0.4 ± 1.7 0.152 0.58 (moderate) 15s/15s 194 ± 6 195 ± 5 0.683 0.16 (trivial) 0.8 ± 1.7 -0.4 ± 0.9 Control period 10s/10s 197 ± 5 197 ± 7 0.820 0.09 (trivial) 0.5 ± 2.5 -.02 ± 1.3 0.416 0.33 (small) 15s/15s 195. ± 6 195 ± 6 0.949 0.03 (trivial) -0.2 ± 1.6 0.1 ± 0.8 CMJ (cm) 10s/10s 37.8 ± 3.1 37.5 ± 3.8 0.993 0.08 (trivial) -0.3 ± 1.9 1.0 ± 5.0 0.893 0.06 (trivial) 15s/15s 38.1 ± 2.7 37.9 ± 2.6 0.974 0.07 (trivial) -0.2 ± 1.4 0.6 ± 3.8 Control period 10s/10s 37.9 ± 3.6 37.0 ± 3.1 0.498 0.27 (small) -0.9 ± 1.5 2.4 ± 4.3 0.896 0.05 (trivial) 15s/15s 38.0 ± 3.2 37.2 ± 1.9 0.449 0.30 (small) -0.8 ± 2.6 2.1 ± 7.3 Exp: experimental condition; Con: Control condition; Distance (m): Distance covered in the Yo-yo IR1 expressed in meters, V̇O2max (ml/kg/min): maximum oxygen consumption, vV̇O2max (km/h): running speed at V̇O2max, HR (bpm): Heart Rate, CMJ (cm): Counter movement jump; d: Effect size. Delta values were calculated from Pre-and post- training values. Data are means and standard deviations (mean±SD).