Interval training (IT) is a method commonly used by coaches. The rest between stimuli is a variable that can be manipulated in IT. Rest time influences the specificity of workload. Considering that Blood Lactate (BLa) represents the balance of metabolic intracellular production-removal-oxidation, is very important to determine different levels of Lactate Steady-State (La SS) with variation in rest time, which are able to sustain La SS for longer periods, using IT workouts. PURPOSE: To analyze BLa during 90s of passive rest (pr) in steady-state moderate intensity IT (mIT). In previous work, we have shown that La SS was maintained for 60s of pr (Mazza et al., 2018), without significant differences (SD). METHODS: Eleven trained swimmers (19.4±3.8 y) performed a mIT (BLa 4 to 6 mMol/l). The bout was 10x100m freestyle with 90s pr. BLa and heart rate (HR) were measured at 10s, 50s and 80s at same time, during pr, every 2 reps. We applied Shapiro-Wilk test to analyze distribution’s data. We compared BLa-10s vs. BLa-50s vs. Bla-80s applying One-way ANOVA (p<0.05) in reps 2-4-6-8 and 10; also, we determine Pearson correlation coefficient (r) between BLa-10s, BLa-50s, Bla-80s vs. HR-10s, HR-50s, HR-80s, respectively. RESULTS: BLa data show normal distribution (p>0.05). The mean BLa max./min. values were 6.25/5.08 mMol/l, respectively, at 1.49±0.07 m/s. Statistical analyses are shown in the following table: & SD BLa-10s vs. BLa-50s; * SD BLa-50s vs. BLa-80s; # SD BLa-10s vs. BLa-80s. We found a low r between BLa and HR (r=0.25-0.30). CONCLUSION: This work shows that La SS in mIT depends of pr duration to generate sustained metabolic stress during whole exercise - rest workout. BLa-10s vs. BLa-50s does not register SD (except rep. 6). However, BLa-50s vs. BLa-80s are SD, showing a tendency to lower BLa level. La SS is maintained within BLa 4 to 6 mMol/l range with only 1.17 mMol/l differences between max./min. mean values. Also, we found that HR is not valid variable to control metabolic stress in mIT.