# High-Intensity Interval Training Is Equivalent to Moderate-Intensity Continuous Training for Short- and Medium-Term Outcomes of Glucose Control, Cardiometabolic Risk, and Microvascular Complication Markers in Men With Type 2 Diabetes PMID: 30210450 Journal: Frontiers in endocrinology Published: 2018-08-28 Authors: Wormgoor SG, Dalleck LC, Zinn C, Borotkanics R, Harris NK ## Question Whether 12 weeks of supervised HIIT plus resistance training is more effective than moderate-intensity continuous training plus resistance training for glucose control, cardiometabolic risk markers, microvascular complication markers, and 6-month durability in men with type 2 diabetes. ## Summary In middle-aged obese men with type 2 diabetes, a 12-week supervised program combining resistance training with either HIIT or moderate continuous cycling produced similar improvements in aerobic capacity, HbA1c, adiposity, and heart-rate variability. The HIIT program was clinically supervised, progressed over stages, used cycle ergometry plus resistance training, and required frequent monitoring and occasional protocol reductions for blood pressure, angina, overexertion, low blood glucose, and fatigue. ## Population - Middle-aged obese men with moderate-duration type 2 diabetes, multiple prescribed medications, and low baseline aerobic fitness. - Sample size: 23 - Age: MICT+RT 52.5 +/- 7.0 years; HIIT+RT 52.2 +/- 7.1 years. - Sex: Men only. - Fitness level: Unfit at baseline; VO2max about 20.4-22.7 mL/kg/min by group. - Health status: Type 2 diabetes for about 8-8.5 years, class II obesity, poor glucose control, common antihyperglycaemic, antihypertensive, statin, and beta-blocker use. ## Methodology - Randomized clinical exercise intervention with 12-week supervised training phase and 6-month follow-up. - 12-week intervention plus 6-month follow-up - Clinical exercise physiology Health and Wellness Clinic in Palmerston North, New Zealand. - Randomized and controlled study design. ## Protocol - HIIT+RT. - Modality: Cycle ergometer HIIT plus machine resistance training. - Work intervals: Intermediate: 3 x 3:30 min at 75% eWLmax; advanced alternated 12 x 1 min at 95% eWLmax and 8 x 30 s at 120% eWLmax. - Recovery: Intermediate: 3:30 min at 45% eWLmax; advanced: either 1 min at 40% eWLmax or 2:15 min at 30% eWLmax. - Sets or repetitions: Three intermediate HIIT bouts; advanced twelve 1-min bouts alternating by session with eight 30-s bouts; RT four compound exercises plus abdominal exercise. - Intensity: 75%, 95%, or 120% eWLmax depending on stage/session; target RPE about 16-18 for HIIT portions. - Session duration: Scheduled 1-hour combined session; advanced HIIT cardiovascular component 28 min, plus 5-min transition/stretch/BG check and RT. - Frequency: 3 sessions/week. - Program length: 12 weeks plus 6-month follow-up. - Progression: 3-week introductory MICT for both groups, 4-week intermediate HIIT, 5-week advanced HIIT/SIT alternating variations; workloads adjusted at weeks 4 and 8. - MICT+RT. - Modality: Cycle ergometer moderate-intensity continuous training plus same machine resistance training. - Work intervals: Continuous cycling; advanced stage 26 min at 55% eWLmax. - Sets or repetitions: Continuous cycling plus same resistance training as HIIT+RT. - Intensity: Introductory 50% eWLmax; intermediate and advanced 55% eWLmax with target RPE about 13-14. - Session duration: Scheduled 1-hour combined session; advanced MICT cardiovascular component 32 min including warmup/cooldown. - Frequency: 3 sessions/week. - Program length: 12 weeks plus 6-month follow-up. - Progression: 10 min MICT in introductory stage, 17:30 min in intermediate stage, 26 min at 55% eWLmax in advanced stage. ## Outcomes ### HbA1c Status: improved Both training modalities improved HbA1c after 12 weeks, with no significant group-by-time difference; improvement was not significantly sustained at 6 months. Post-12-week time effect beta -6.27 mmol/mol, P = 0.011; group*time interaction P = 0.955. ### VO2max Status: improved Both groups improved aerobic capacity by more than 3.9 mL/kg/min during intervention, and improvements were significantly maintained at 6 months. 12-week P < 0.001; 6-month P < 0.001; group*time interaction P = 0.224. ### Adiposity Status: improved Waist girth and subcutaneous adiposity were reduced in both groups and adiposity improvements were maintained at follow-up. Skinfolds P < 0.001 at 12 weeks and 6 months; waist girth P = 0.008 at 12 weeks and P = 0.001 at 6 months; no significant group*time interaction. ### Heart rate variability Status: improved HRV improved comparably during the supervised phase but was not sustained at 6 months. 12-week P = 0.021; 6-month P = 0.671; group*time interaction P = 0.539. ### Safety and tolerability Status: mixed No major acute adverse events occurred, but both groups required protocol respite; advanced HIIT respite occurred in 10.6% of sessions. Intermediate MICT 11.6% vs AIT 12.9%, P = 0.75; advanced MICT 15.8% vs HIIT 10.6%, P = 0.15. ## Practical Insights - In men with type 2 diabetes, HIIT+RT was not superior to MICT+RT for glycemic and cardiometabolic outcomes over 12 weeks. - Clinical HIIT protocols can require frequent in-session modification even when no major adverse events occur. - For high-risk populations, supervised screening and monitoring are core protocol components, not optional details. - Combining HIIT with RT makes outcomes relevant to multimodal exercise programming but limits attribution to HIIT alone. ## Limitations - Small sample of 23 men only. - Participants were heavily medicated and medication changes occurred during the 9-month study period. - All participants were screened and supervised, limiting generalization to unsupervised broader T2D populations. - No blinding was possible for participants, assisting exercise physiologists, or the lead researcher. - Advanced HIIT stimulus lasted only 5 weeks. - HIIT was combined with resistance training, so isolated HIIT effects cannot be cleanly separated. - Follow-up training adherence was self-reported and intentionally not objectively monitored. ## Safety And Adherence - No major acute adverse events were reported during the intervention. - Precautionary respite was used for elevated blood pressure, overexertion, moderate angina, hamstring strain/musculoskeletal discomfort, low blood glucose, post-exercise hypotension, and fatigue. - One participant with pre-existing atrial fibrillation was diagnosed with congestive heart failure and withdrew during follow-up. ## Original Sources - [PubMed](https://pubmed.ncbi.nlm.nih.gov/30210450/) (pubmed) - [DOI](https://doi.org/10.3389/fendo.2018.00475) (doi) - [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6120973/) (full text) ## Agent Guidance Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.