Comparing The Effects of Singles vs. Doubles High-Intensity On-Court Tennis Training and Regular High-Intensity Interval Training on Aerobic and Anaerobic Performance Adaptations: A Randomized, Parallel-Controlled Study

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; VO_2max: 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.