Table 4.

Subgroup analysis of overall effects of interval training on immune outcomes.

Outcome (Subgroup)	N° of Studies	MD (95% CI)	p-Value	Heterogeneity
				I2 (%)	p-Value
IgA concentration (µg·mL−1)
IT type: SIT	5	46.98 (56.73 to 150.68)	0.37	94	<0.001
IT type: HIIT	4	39.54 (19.92 to 59.16)	<0.001	0	1
Sex: men	6	65.62 (−6.43 to 137.66)	0.07	91	<0.001
Sex: women	3	−18.91 (−66.24 to 28.42)	0.43	0	0.59
Modality: cycling	5	53.22 (−33.53 to 139.96)	0.23	94	<0.001
Modality: running	4	22.07 (−17.34 to 61.47)	0.27	0	0.92
IgA secretory rate (µg·min−1)
IT type: SIT	6	−17.33 (−33.68 to −0.98)	0.03	68	0.007
IT type: HIIT	2	−7.29 (−23.95 to 9.36)	0.39	0	0.73
Sex: men	5	−13.17 (−35.03 to 8.70)	0.24	74	0.004
Sex: women	2	−19.34 (−29.11 to −9.58)	<0.001	0	0.74
Modality: cycling	-	-	-	-	-
Modality: running	-	-	-	-	-
Leucocyte count (103 µL−1)
IT type: SIT	5	3.14 (1.83 to 4.44)	<0.01	80	<0.001
IT type: HIIT	9	2.31 (1.30 to 3.32)	<0.001	78	<0.001
Sex: men	-	-	-	-	-
Sex: women	-	-	-	-	-
Modality: cycling	9	2.40 (1.47 to 3.33)	<0.001	84	<0.001
Modality: running	3	2.46 (1.30 to 3.62)	<0.001	21	0.28
Lymphocyte count (103 µL−1)
IT type: SIT	3	1.62 (0.89 to 2.35)	<0.001	66	0.05
IT type: HIIT	9	1.21 (0.67 to 1.74)	<0.001	81	<0.001
Sex: men	-	-	-	-	-
Sex: women		-	-	-	-
Modality: cycling	8	1.17 (0.65 to 1.70)	<0.001	82	<0.001
Modality: running	3	1.14 (0.67 to 1.61)	<0.001	10	0.33
Lymphocyte count (103 µL−1) recovery
IT type: SIT	3	−0.51 (−0.77 to −0.26)	<0.001	18	0.30
IT type: HIIT	9	−0.29 (−0.56 to 0.03)	0.03	66	0.003
Sex: men	-	-	-	-	-
Sex: women	-	-	-	-	-
Modality: cycling	8	−0.47 (−0.62 to −0.32)	<0.001	0	0.55
Modality: running	3	0.04 (−0.63, 0.72)	0.9	85	0.001

SIT, sprint interval training; HIIT, high-intensity interval training. Significant p-values are indicated in bold.