Background: This study investigated the acute effects of two high-intensity interval training (HIIT) programs on physiological responses and internal workload. Methods: Ten national-level adolescent male rowers (age: 15.7 ± 0.2 years; maximal oxygen uptake (VO2max): 60.11 ± 1.91 mL∙kg−1∙min−1) performed two HIIT testing sessions: short (S-HIIT) and long (L-HIIT). In S-HIIT, the rowers performed 25 reps of 30 s at 100% power at VO2max (Pmax) interspersed with 30 s at P@20% Pmax; whereas in L-HIIT, the rowers executed 4 × 4 min at P@90% Pmax interspersed with 3 min of active recovery (P@30% Pmax). Results: The acute physiological responses and internal workload were evaluated. The significance level was set at p < 0.05. Oxygen uptake (VO2) (p < 0.05), time spent per session at ~90% VO2max (p < 0.01), total VO2 consumed (p < 0.01), total distance (p < 0.001), the rating of perceived exertion, blood lactate concentration and heart rate (always p < 0.0001) were significantly higher in L-HIIT than in S-HIIT. However, peak power output was significantly lower in L-HIIT compared to S-HIIT (p < 0.0001). Conclusion: In adolescent rowers, both HIIT tests stimulated aerobic and anaerobic systems. The L-HIIT test was associated with acute cardiorespiratory and metabolic responses, as well as higher perceptions of effort than the S-HIIT test. In adolescent rowers, HIIT emerges as an asset and could be introduced into a traditional in-season, moderate-intensity and endurance-based rowing program once a week.
Keywords: HIIT; RPE; adolescent; rowing; workload.