A single bout of exercise can result in inflammatory responses, increased oxidative stress and upregulation of enzymatic antioxidant mechanisms. Although low-volume high-intensity interval training (HIIT) has become popular, its acute responses on the above mechanisms have not been adequately studied. The present study evaluated the effects of HIIT on hematological profile and redox status compared with those following traditional continuous aerobic exercise (CET). Twelve healthy young men participated in a randomized crossover design under HIIT and CET. In HIIT session, participants performed four 30-sec sprints on a cycle-ergometer with 4 min of recovery against a resistance of 0.375 kg/kg of body mass. CET consisted of 30-min cycling on a cycle-ergometer at 70% of their VO2max. Blood was drawn at baseline, immediately post, 24h, 48h and 72h post-exercise and was analyzed for complete blood count and redox status (thiobarbituric acid reactive substances, [TBARS]; protein carbonyls, [PC]; total antioxidant capacity, [TAC]; catalase and uric acid). White blood cells (WBC) increased after both exercise protocols immediately post-exercise (HIIT: 50% and CET: 31%, respectively). HIIT increased (+22%) PC post-exercise compared to baseline and CET (p 0.05) for TBARS and catalase following either exercise protocol. Low-volume HIIT is associated with a greater acute phase leukocyte count and redox response than low-volume CET, and this should be considered when an exercise training program is developed and complete blood count is performed for health purposes
