Effects of High Intensity Interval or Continuous Moderate Training on Metabolic Thresholds: A Randomized Control Trial

Abstract

High intensity interval training (HIIT) has been suggested to promote superior metabolic and cardiovascular adaptations than classical moderate continuous training (MCT) in athletes or sedentary people. However, less is known about the effects of HIIT in metabolic thresholds like anaerobic (AT) or respiratory compensation point (RCP) in active women. Moreover, former studies have not compared exercise protocols with same training internal load (similar energy expenditure), which must be a main concern in order to compare HIIT and MCT. PURPOSE: It was our aim to compare changes in AT and RCP between HIIT and MCT exercise training protocols with the same energy expenditure. METHODS: Forty-one healthy women accepted to participate in the study (42.587.53 years; fat mass percent (%FM) 35.87.0%; maximum oxygen uptake (VO2max), 30.787.66 ml/kg/min). Thirty-two were previously active (>3 days/week restructured exercise), and they were randomized in HIIT (95% VO2max reserve, 172 min/week) or MCT (61% VO2max reserve, 279 min/week) groups, a control group (CG) of 9 women with similar age and body composition was selected from the university community. Both exercise-training protocols were designed to result in similar energy expenditure and were performed 2-3 times per week during 24 weeks. AT and RCP were measured using indirect calorimetry (Ultima CCM, MedGraphics, USA) during a ramp exercise test (delta 15 watts/min) on bike. Data from exercise test were used to prescribe training load. Repeated measured analyses were carried out in order to compare AT and RCP before and after 24 weeks of training between HIIT, MCT and CG groups. RESULTS: After 24-week of training exercise, both groups increased VO2 at AT (1067404 vs 1207351 ml/min and 947293 vs. 1128351 ml/min, HIIT and MCT respectively; P<0.05 for both) and RCP (1529434 vs 1730403 ml/min and 1599496 vs. 1815529 ml/min; HIIT and MCT respectively, P<0.01 for both). Post Hoc analysis showed that VO2 at AT and RCP were significantly different among training groups and CG, which did not modify any variable. CONCLUSIONS: Our results suggests that both HIIT and MCT promote similar improvements of VO2 at AT and RCP in previously active women, when similar energy expenditures are performed.