Accurately prescribing supramaximal interval training facilitates targeting desired physiological adaptations. This study compared the homogeneity of adaptations in cardiorespiratory parameters to supramaximal [i.e., intensities beyond maximal aerobic speed (MAS)] interval interventions prescribed using anaerobic speed reserve (ASR), the speed attained at the end of 30-15 Intermittent Fitness Test (V_IFT), and MAS. Using repeated-measures factorial design, and during the off-season phase of the athletes’ yearly training cycle, thirty national-level soccer players (age = 19 ± 1.6 years; body mass = 78.9 ± 1.6 kg; height = 179 ± 4.7 cm; Body fat = 11 ± 0.9%) were randomized to interventions consisting of 2 sets of 6, 7, 8, 7, 8, and 9-min intervals (from 1^st to 6^th week), including 15 s running at ∆%20ASR (MAS + 0.2 × ASR), 120%MAS, or 95%V_IFT followed by 15 s passive recovery. All ASR, V_IFT, and MAS programs sufficiently stimulated adaptive mechanisms, improving relative maximal oxygen uptake [V̇O_2max (p < 0.05; ES = 1.6, 1.2, and 1.1, respectively)], absolute V̇O_2max (p < 0.05; ES = 1.5, 1.1, and 0.7), ventilation [V̇_E (p < 0.05; ES = 1.6, 1.1, and 1.1)], O₂ pulse [V̇O₂/HR (p < 0.05; ES = 1.4, 1.1, and 0.6)], first and second ventilatory threshold [VT₁ (p < 0.05; ES = 0.7, 0.8, and 0.7) and VT₂ (p < 0.05; ES = 1.1, 1.1, and 0.8)], cardiac output [Q̇_max (p = 1.5, 1.0, and 0.7)], and stroke volume [SV_max (p < 0.05; ES = 0.9, 0.7, and 0.5)]. Although there was no between-group difference for the change in the abovementioned variables over time, supramaximal interval training prescribed using ASR and V_IFT resulted in a lower coefficient of variation [CV (inter-individual variability)] in physiological adaptations compared to exercise intensity determined as a proportion of MAS. Expressing the intensity of supramaximal interval programs according to the athlete’s ASR and V_IFT would assist in accurately prescribing interventions and facilitate imposing mechanical and related physiological stimulus according to the athletes’ physiological ceiling. Such an approach leads to identical stimulation across athletes with differing profiles and potentially facilitates more homogenized adaptations.

• Expressing the intensity of supramaximal HIIT according to the athlete’s ASR and VIFT resulted in accurately prescribing interventions and normalizes mechanical stimulus according to the athletes’ physiological ceiling.

• Such individualization ensures the creation of more identical physiological demands across athletes with different profiles and facilitates the same degrees of physiological adaptations.

• Irrespective of the homogeneity of the adaptations to these HIIT interventions, all three methods sufficiently stimulated adaptive mechanisms and improved cardiorespiratory fitness in well-trained soccer players.