Table 2. Pre- and post-intervention values for all measured variables, along with inferential statistics.
Group n Outcome Pre-test (mean ± SD) Post-test (mean ± SD) Δ (post—pre) 95% CI for Δ p-value d (magnitude) SMD (Hedges’ g, post SD)
singlesHIIT 12 Peak Power (W·kg-1) 8.43 ± 0.51 10.25 ± 0.52 1.82 1.52 to 2.11 p < 0.001 3.90
very large		 1.74
(large)
singlesHIIT 12 Mean Power (W·kg-1) 6.12 ± 0.51 8.08 ± 0.57 1.96 1.79 to 2.13 p < 0.001 7.45
very large		 1.71
(large)
singlesHIIT 12 Fatigue index (%) 61.81 ± 6.91 49.20 ± 7.84 -12.60 -18.11 to -7.10 p < 0.001 -1.45
Large		 —0.86
(moderate)
singlesHIIT 12 VO2max (mL·kg-1·min-1) 50.14 ± 2.58 52.46 ± 1.90 2.32 1.61 to 3.03 p < 0.001 2.07
very large		 1.00
(large)
singlesHIIT 12 VIFT (km·h-1) 16.88 ± 0.43 17.79 ± 0.66 0.92 0.62 to 1.21 p < 0.001 1.96
Large		 0.92
(large)
doublesHIIT 12 Peak Power (W·kg-1) 7.93 ± 0.73 8.92 ± 0.77 1.00 0.86 to 1.13 p < 0.001 4.62
very large		 1.29
(large)
doublesHIIT 12 Mean Power (W·kg-1) 5.64 ± 0.65 6.60 ± 0.58 0.96 0.80 to 1.13 p < 0.001 3.70
very large		 1.40 (large)
doublesHIIT 12 Fatigue index (%) 62.78 ± 6.65 57.08 ± 7.73 -5.70 -11.34 to -0.07 p = 0.048 -0.64
moderate		 —0.46
(moderate)
doublesHIIT 12 VO2max (mL·kg-1·min-1) 50.01 ± 2.20 52.37 ± 1.13 2.36 1.52 to 3.20 p < 0.001 1.78
large		 0.98
(large)
doublesHIIT 12 VIFT (km·h-1) 16.54 ± 0.45 17.54 ± 0.62 1.00 0.73 to 1.27 p < 0.001 2.35
very large		 0.96
(large)
regHIIT 12 Peak Power (W·kg-1) 8.21 ± 0.66 9.24 ± 0.68 1.03 0.91 to 1.16 p < 0.001 5.29
very large		 1.52
(large)
regHIIT 12 Mean Power (W·kg-1) 5.90 ± 0.57 6.89 ± 0.56 0.99 0.85 to 1.12 p < 0.001 4.64
very large		 1.48
(large)
regHIIT 12 Fatigue index (%) 61.65 ± 7.66 55.37 ± 5.99 -6.28 -10.20 to -2.35 p = 0.005 -1.02
moderate		 —0.58
(moderate)
regHIIT 12 VO2max (mL·kg-1·min-1) 50.17 ± 1.74 52.50 ± 1.12 2.32 1.53 to 3.12 p < 0.001 1.86
large		 0.91
(large)
regHIIT 12 VIFT (km·h-1) 16.67 ± 0.49 17.62 ± 0.68 0.96 0.64 to 1.27 p < 0.001 1.92
large		 0.87
(large)
control 12 Peak Power (W·kg-1) 8.12 ± 0.67 8.16 ± 0.68 0.04 -0.07 to 0.15 p = 0.412 0.25
small		 0.06
(trivial)
control 12 Mean Power (W·kg-1) 5.73 ± 0.57 6.15 ± 0.66 0.42 0.07 to 0.77 p = 0.024 0.75
moderate		 0.40
(moderate)
control 12 Fatigue index (%) 63.35 ± 4.38 53.76 ± 13.59 -9.59 -17.47 to -1.71 p = 0.021 -0.77
moderate		 —0.39
(moderate)
control 12 VO2max (mL·kg-1·min-1) 49.86 ± 1.86 50.18 ± 1.56 0.32 0.00 to 0.63 p = 0.048 0.64
moderate		 0.17
(small)
control 12 VIFT (km·h-1) 16.75 ± 0.58 16.71 ± 0.58 -0.04 -0.39 to 0.30 p = 0.795 -0.08
trivial		 —0.02
(trivial)
regHIIT: running-based HIIT; HIIT: high-intensity interval training; VO2max: maximal oxygen uptake. VIFT: velocity at 30-15 intermittent fitness test. Notes. Values are mean±SD. Δ is post—pre. p-values are from paired t-tests. Within-group effect size is Cohen’s dz computed from the pre–post difference scores; qualitative thresholds: trivial <0.20, small 0.20-0.59, moderate 0.60-1.19, large 1.20-1.99, very large ≥2.00.