The study purpose was to investigate the effect of functional training with the ascending AMRAP model and with the FOR TIME constant load model on increasing abdominal muscle strength and maximal oxygen consumption (VO2max) in adolescent males.
 Materials and methods. This study used the True-Experimental method with the research design of the Randomized Control Group Pretest-Posttest Design. A total of 21 adolescent males aged 18–21, body mass index (BMI) 18.5–24.9 kg/m2, normal blood pressure, normal resting heart rate, normal oxygen saturation (SpO2) participated in this study and were divided into three groups, namely CTRLG (n = 7; control group), FSTAG (n = 7; ascending AMRAP functional training group), and FSTFG (n = 7; FOR TIME constant load functional training group). Both the ascending AMRAPfunctional training and the FOR TIME constant load functional training interventions were carried out with a frequency of 3 times/week for 8 weeks. Statistical analysis used the one-way ANOVA test with the Statistical Package for Social Science (SPSS) software version 21.
 Results. The results showed that there was a significant difference in the mean delta (Δ) increase in abdominal muscle strength (p ≤ 0.05). The mean delta (Δ) increase in VO2max also showed a significant difference (p ≤ 0.05).
 Conclusions. Based on the results of the study, it was shown that the administration of functional training intervention with the ascending AMRAP model and functional training intervention with the FOR TIME constant load model which was carried out 3 times/week for 8 weeks increased abdominal muscle strength and maximal oxygen consumption levels.