All data are presented as mean ± standard deviation (SD) (see S1 File for the raw data).
After verifying normality, a repeated-measures analysis of variance (ANOVA) was applied to the
physiological responses and tennis performance outcomes. When ANOVAs revealed a significant
difference, p-value and partial eta square (η2), and their interpretation according to
Cohen’s scale [16] (η2 = .01 for small effect, η2 = .06 for medium effect, and η2 = .14 for large
effect) were reported. If a significant interaction was found, a Bonferroni post-hoc test was performed.
A paired-t test was used to compare RPE between HIIT sessions. An effect size (ES)
was computed and interpreted according to Cohen’s scale [16] (ES = 0.2 for small effect,
ES = 0.5 for medium effect, and ES0.8 for large effect) for all pairwise comparisons. The level
of significance was set at p 0.05. All analyses were performed on SPSS 11.0 (SPSS, Inc., Chicago,
IL.).