# The effects of three different low-volume aerobic training protocols on cardiometabolic parameters of type 2 diabetes patients: A randomized clinical trial PMID: 36755928 Journal: Frontiers in endocrinology Published: 2023-01-23 Authors: Gentil P, Silva LRBE, Antunes DE, Carneiro LB, de Lira CAB, Batista G, de Oliveira JCM, Cardoso JS, Souza DC, Rebelo ACS ## Question Do different low-volume aerobic training protocols, including short-interval HIIT, long-interval HIIT, and moderate continuous training, produce different cardiometabolic adaptations in adults with type 2 diabetes? ## Summary This randomized clinical trial compared two low-volume treadmill HIIT formats with low-volume moderate continuous training in adults with type 2 diabetes. Both HIIT protocols used only 10 minutes of high-intensity work per session, twice weekly for 8 weeks, and improved VO2max more than the moderate continuous protocol. The longer 2-minute interval protocol also significantly reduced HbA1c, triglycerides, and systolic blood pressure within group, while several other cardiometabolic markers did not significantly change. ## Population - Adults with type 2 diabetes, age 40 years or older, not participating in other training programs; moderate/high cardiovascular-risk conditions and several cardiopulmonary/orthopedic exclusions applied. Fifty-two were randomized and 44 were included in final analysis. - Sample size: 44 - Age: MICT 54.6 +/- 8.9 years; L-HIIT 57.3 +/- 8.9 years; S-HIIT 55.7 +/- 7.4 years - Sex: Final analysis: 22 males and 22 females; by group, MICT 9 male/5 female, L-HIIT 6 male/9 female, S-HIIT 7 male/8 female - Fitness level: Adults with T2DM not in another physical training program; excluded if exercise capacity below 6 METS after CPET - Health status: Type 2 diabetes; BMI approximately 28.5-29.4 kg/m2 by group mean; many participants used diabetes, antihypertensive, and lipid medications ## Methodology - Parallel randomized clinical trial with three exercise groups: long-interval HIIT, short-interval HIIT, and moderate-intensity continuous training. - 8 weeks - Hospital/laboratory setting at the Hospital of the Federal University of Goias; morning testing under controlled temperature and humidity - Randomized and controlled study design. ## Protocol - Low-volume treadmill HIIT protocols. - Modality: Motorized treadmill walking/running. - Work intervals: S-HIIT: 30 seconds; L-HIIT: 2 minutes. - Recovery: S-HIIT: 30 seconds passive; L-HIIT: 2 minutes passive. - Sets or repetitions: S-HIIT: 20 bouts; L-HIIT: 5 bouts. - Intensity: 100% vVO2max during HIIT work bouts; warmup/cooldown at 50% vVO2max. - Session duration: Approximately 24 minutes including warmup and cooldown. - Frequency: 2 sessions/week. - Program length: 8 weeks. - Progression: No explicit progression schedule; intensity individualized and adjusted using perceived exertion. - Low-volume MICT. - Modality: Motorized treadmill walking/running. - Work intervals: 14 minutes continuous. - Sets or repetitions: 1 continuous bout. - Intensity: 70% vVO2max; warmup/cooldown at 50% vVO2max. - Session duration: 18 minutes including 2-minute warmup, 14-minute continuous exercise, and 2-minute cooldown. - Frequency: 2 sessions/week. - Program length: 8 weeks. - Progression: No explicit progression schedule reported. ## Outcomes ### VO2max Status: improved VO2max improved significantly in both HIIT groups and improved more than MICT, with no meaningful difference between L-HIIT and S-HIIT. L-HIIT MD +3.2 +/- 1.7 ml/kg/min, p<0.001; S-HIIT MD +3.4 +/- 1.7 ml/kg/min, p<0.001; L-HIIT vs MICT p=0.04, S-HIIT vs MICT p=0.01, L-HIIT vs S-HIIT p=0.9. ### HbA1c Status: mixed HbA1c significantly decreased only in the L-HIIT group, while S-HIIT and MICT did not reach significance. L-HIIT MD -1.8 +/- 1.8%, p<0.01; S-HIIT MD -0.92 +/- 2.0%, p=0.09; MICT MD -0.59 +/- 1.7%, p=0.2. ### Triglycerides Status: mixed Triglycerides significantly decreased only in the L-HIIT group; S-HIIT trended down but was not statistically significant, and MICT did not improve. L-HIIT MD -23.80 +/- 39.6 mg/dL, p=0.04; S-HIIT MD -23.19 +/- 49.0 mg/dL, p=0.09; MICT MD +5.36 +/- 31.9 mg/dL, p=0.5. ### Resting systolic blood pressure Status: mixed Resting SBP significantly decreased only in the L-HIIT group. L-HIIT MD -12.07 +/- 15.3 mmHg, p<0.01; S-HIIT MD -7.33 +/- 17.1 mmHg, p=0.1; MICT MD +4.43 +/- 13.1 mmHg, p=0.2. L-HIIT reduced SBP more than MICT, p=0.018, d=1.56. ### Other cardiometabolic markers Status: no clear change Fasting glycemia, total cholesterol, HDL, LDL, resting HR, and resting DBP did not significantly change in any group. Reported p>0.05 for all groups. ## Practical Insights - A low-volume treadmill HIIT dose of 10 minutes hard work per session, 2 times per week for 8 weeks, can improve VO2max in adults with T2DM under screened, monitored conditions. - Short 30-second intervals and longer 2-minute intervals both improved VO2max, but the stronger HbA1c, triglyceride, and SBP signal came from the 2-minute interval protocol. - For app guidance, metabolic claims should be scoped tightly: this trial supports cardiorespiratory improvement more consistently than broad metabolic-marker improvement. - Clinical users with T2DM need screening/supervision language, especially because CPET excluded several safety-risk participants before training. ## Limitations - No non-exercise control group, so exercise effects cannot be separated from all non-exercise conditions. - No dietary control beyond instructions to keep usual diet habits. - Small final group sizes and no a priori sample-size definition. - Clinical T2DM sample limits direct general-population translation. - Intervention was supervised and intensity was based on CPET-derived vVO2max. ## Safety And Adherence - No intervention adverse-event count was reported. - CPET screening excluded participants with low exercise capacity, uncontrolled arrhythmias during exertion, unstable angina, and abnormal SBP response. - Authors highlight that longer HIIT intervals may create greater cardiovascular stress in T2DM patients, requiring cost-benefit judgment. ## Original Sources - [PubMed](https://pubmed.ncbi.nlm.nih.gov/36755928/) (pubmed) - [DOI](https://doi.org/10.3389/fendo.2023.985404) (doi) - [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9900112/) (full text) ## Agent Guidance Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.