International Journal of Clinical Case Reports, 2026, Vol.16, No.2, 84-91 http://medscipublisher.com/index.php/ijccr 88 Table 2 Descriptive Statistics Group VO₂ Pre (ml/kg/min) VO₂ Post (ml/kg/min) Sprint Pre (s) Sprint Post (s) HIIT 45.6 ±4.8 (36-55) 50.8 ±5.0 (42-60) 5.47±0.39 (4.9-6.3) 5.05±0.40 (4.4-5.8) Control 44.9 ±5.1 (35-55) 46.0 ±5.2 (36-56) 5.53±0.38 (4.9-6.2) 5.48±0.38 (4.9-6.2) The normality of change scores was evaluated using Shapiro-Wilk tests (Table 3). Changes in sprint time and VO₂ max were roughly normally distributed in both groups, as seen by the non-significant nature of all distributions (p>0.05). This met the parametric testing assumptions. Table 3 Shapiro-Wilk Normality Tests Variable W p-value HIIT VO₂ Change 0.96 0.58 Control VO₂ Change 0.95 0.42 HIIT Sprint Change 0.97 0.71 Control Sprint Change 0.96 0.55 Table caption: All p>0.05→data approximately normal The HIIT group showed significant pre-post improvements in both sprint performance (t(19)=-10.5, p<0.001) and VO₂ max (t(19)=13.1, p<0.001), according to paired t-tests (Table 4). There was no discernible change in sprint performance (t(19)=-1.3, p=0.20), however the control group's VO₂ max improved little but statistically significantly (t(19)=2.1, p=0.047). These findings are consistent with the theory that HIIT offers a more effective training stimulus for developing adolescent athletes' aerobic capacity and speed (Baquet et al., 2010; Rønnestad et al., 2015). Table 4 Paired t-tests (Pre vs Post within groups) Group Variable t p-value HIIT VO₂ 13.1 <0.001 HIIT Sprint -10.5 <0.001 Control VO₂ 2.1 0.047 Control Sprint -1.3 0.20 According to independent-samples t-tests on change scores (Table 5), the HIIT group outperformed the Control group in both 30m sprint performance (t(38)=-7.2, p<0.001) and VO₂ max (t(38)=8.5, p<0.001). HIIT training was significantly more successful than normal training at eliciting physiological changes, as indicated by these significant between-group differences. The results align with earlier research showing that HIIT improves both aerobic and anaerobic performance more than moderate-intensity continuous training in young people (Buchheit and Laursen, 2013; Racil et al., 2016). Table 5 Independent t-tests (Change Scores, HIIT vs Control) Variable t p-value VO₂ Change 8.5 <0.001 Sprint Change -7.2 <0.001 A two-way repeated measure ANOVA was conducted to further investigate the intervention’s effect, using Time (Pre vs. Post) as the within-subject factor and Group (HIIT vs. Control) as the between-subject factor (Table 6). There was a significant Group×Time interaction (F(1,76=4.30, p=0.042) and a significant main effect of Group (F(1,76)=4.23, p=0.043) and Time (F(1,76)=6.60, p=0.012) for VO₂ max. According to this, the HIIT group improved significantly more than the Control group, even though both groups saw changes throughout time. Additionally, there was a significant Group×Time interaction (F(1,76)=6.02, p=0.016) and a significant main effect of Group (F(1,76)=5.11, p=0.027) and Time (F(1,76)=7.45, p=0.008) for 30m sprint performance. These outcomes demonstrate that, in comparison to the Control condition, the HIIT intervention led to greater gains in sprint performance.
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