Supplementary Table S2. Jump characteristics.
Period Sequence Pre Δ3′ Δ6′ Δ9′ Δ12′
JH [cm] (M±SD; 95%CI)
P1 ICA→VPA 39.99 ± 2.71 (37.48; 42.49) 2.04 ± 3.62 (−1.30; 5.39) −0.03 ± 3.10 (−2.89; 2.84) −0.91 ± 2.45 (−3.18; 1.35) 0.89 ± 2.69 (−1.60; 3.37)
VPA→ICA 38.96 ± 4.32 (34.96; 42.95) 0.74 ± 1.70 (−0.83; 2.31) −1.04 ± 2.49 (−3.35; 1.26) −0.80 ± 0.62 (−1.37; −0.23) −1.16 ± 2.95 (−3.89; 1.57)
P2 ICA→VPA 42.97 ± 3.23 (39.99; 45.96) −1.69 ± 0.79 (−2.41; −0.96) −0.93 ± 1.61 (−2.42; 0.56) −1.69 ± 1.64 (−3.21; −0.17) −0.99 ± 2.57 (−3.37; 1.40)
VPA→ICA 39.10 ± 5.35 (34.15; 44.05) 0.73 ± 1.07 (−0.26; 1.72) 1.33 ± 1.17 (0.25; 2.41) 1.39 ± 1.49
(0.01; 2.76)		 2.01 ± 2.92 (−0.69; 4.72)
PP [W/kg] (M±SD; 95%CI)
P1 ICA→VPA 53.27 ± 3.73 (49.82; 56.72) 2.04 ± 3.63 (−1.31; 5.40) 0.16 ± 2.06 (−1.75; 2.06) −1.11 ± 1.65 (−2.64; 0.41) 0.76 ± 3.23 (−2.23; 3.74)
VPA→ICA 51.69 ± 5.78 (46.34; 57.03) 0.24 ± 2.77 (−2.31; 2.80) −1.29 ± 2.61 (−3.70; 1.13) −0.73 ± 2.29 (−2.84; 1.39) −1.80 ± 3.65 (−5.18; 1.58)
P2 ICA→VPA 56.27 ± 4.44 (52.16; 60.38) −1.13 ± 1.87 (−2.86; 0.60) −1.11 ± 1.87 (−2.85; 0.62) −1.73 ± 2.35 (−3.90; 0.45) −1.87 ± 2.52 (−4.20; 0.46)
VPA→ICA 52.11 ± 5.94 (46.62; 57.61) 1.09 ± 1.93 (−0.70; 2.87) 1.51 ± 1.38 (0.23; 2.79) 1.19 ± 2.00 (−0.67; 3.04) 1.29 ± 3.54 (−1.99; 4.56)
RSImod (M±SD; 95%CI)
P1 ICA→VPA 0.46 ± 0.04 (0.42; 0.51) 0.02 ± 0.04 (−0.01; 0.06) 0.00 ± 0.04 (−0.04; 0.04) −0.01 ± 0.04 (−0.05; 0.03) 0.00 ± 0.06 (−0.06; 0.06)
VPA→ICA 0.44 ± 0.07 (0.37; 0.50) −0.02 ± 0.02 (−0.04; 0.00) 0.00 ± 0.02 (−0.02; 0.02) 0.00 ± 0.05 (−0.04; 0.05) −0.01 ± 0.06 (−0.06; 0.04)
P2 ICA→VPA 0.55 ± 0.14 (0.43; 0.68) −0.08 ± 0.16 (−0.22; 0.07) −0.07 ± 0.17 (−0.22; 0.08) −0.08 ± 0.17 (−0.24; 0.07) −0.05 ± 0.15 (−0.19; 0.08)
VPA→ICA 0.43 ± 0.07 (0.37; 0.50) 0.05 ± 0.07 (−0.02; 0.11) 0.07 ± 0.07 (0.00; 0.13) 0.07 ± 0.08
(0.00; 0.14)		 0.08 ± 0.07
(0.01; 0.15)
CT [ms] (M±SD; 95%CI)
P1 ICA→VPA 862.29 ± 72.38 (795.34; 929.23) 2.86 ± 61.62 (−54.13; 59.84) −3.00 ± 53.74 (−52.70; 46.70) 4.57 ± 63.92 (−54.55; 63.69) 27.14 ± 83.46 (−50.04; 104.33)
VPA→ICA 943.00 ± 129.95 (822.82; 1063.18) 24.00 ± 45.96 (−18.51; 66.51) −62.29 ± 67.47 (−124.68; 0.11) −51.43 ± 67.24 (−113.61; 10.76) −36.86 ± 89.01 (−119.18; 45.46)
P2 ICA→VPA 808.14 ± 157.14 (662.82; 953.47) 62.00 ± 173.24 (−98.22; 222.22) 71.29 ± 176.68 (−92.11; 234.68) 79.57 ± 195.79 (−101.51; 260.65) 39.29 ± 180.83 (−127.95; 206.53)
VPA→ICA 908.00 ± 87.91 (826.69; 989.31) −64.71 ± 109.27 (−165.77; 6.34) −89.00 ± 116.20 (−196.46; 18.46) −98.14 ± 129.80 (−218.18; 21.90) −107.29 ± 115.11 (−213.74; −0.83)

Values are mean ± SD (95% CI), with CI in round brackets using a semicolon (e.g., (lower; upper). Pre: measurement after the standardized general warm-up in that period. Δ3′/Δ6′/Δ9′/Δ12′: change from Pre at 3/6/9/12 min (positive = increase; negative = decrease). Period: P1 and P2 in the crossover design. Sequence: order of conditions—ICA→VPA (P1: isometric squat ICA; P2: volleyball activation without ICA) and VPA→ICA (reverse). Conditions: ICA = isometric conditioning activity (3×5×3 s; total 45 s; 3-min interset rest); VPA— standardized volleyball pre-training activation condition. JH—Jump Height (cm); CT—Contraction time (s); PP—Peak Power (W/kg); RSImod—modified reactive strength index; Frequency—natural oscillation frequency (Hz); Decrement—logarithmic decrement (dimensionless); P1/P2—crossover periods 1/2; Sequence—order of VPA— standardized volleyball pre-training activation condition.

Values are mean ± SD (95% CI), with CI in round brackets using a semicolon (e.g., (lower; upper). Pre: measurement after the standardized general warm-up in that period. Δ3′/Δ6′/Δ9′/Δ12′: change from Pre at 3/6/9/12 min (positive = increase; negative = decrease). Period: P1 and P2 in the crossover design. Sequence: order of conditions—ICA→VPA (P1: isometric squat ICA; P2: volleyball activation without ICA) and VPA→ICA (reverse). Conditions: ICA = isometric conditioning activity (3×5×3 s; total 45 s; 3-min interset rest); VPA— standardized volleyball pre-training activation condition. JH—Jump Height (cm); CT—Contraction time (s); PP—Peak Power (W/kg); RSImod—modified reactive strength index; Frequency—natural oscillation frequency (Hz); Decrement—logarithmic decrement (dimensionless); P1/P2—crossover periods 1/2; Sequence—order of VPA— standardized volleyball pre-training activation condition.