# Effect of low-volume combined aerobic and resistance high-intensity interval training on vascular health in people with type 2 diabetes: a randomised controlled trial PMID: 38695912 Journal: European Journal of Applied Physiology Published: 2024 Sep Authors: Cox ER, Gajanand T, Keating SE, Hordern MD, Burton NW, Green DJ, Ramos JS, Ramos MV, Fassett RG, Cox SV, Coombes JS, Bailey TG ## Question Does low-volume combined aerobic and resistance high-intensity interval training improve vascular health after 8 weeks of supervised training and after 12 months including self-directed training in adults with type 2 diabetes, compared with combined moderate-intensity continuous training and waitlist control? ## Summary In low-active adults with type 2 diabetes, 8 weeks of supervised low-volume combined aerobic and resistance HIIT improved brachial artery flow-mediated dilation compared with waitlist control, but did not improve blood pressure indices, aortic reservoir pressure, or carotid-femoral pulse wave velocity compared with control. Over 12 months, both HIIT and moderate-intensity combined training improved some hemodynamic indices, while moderate-intensity training was superior for carotid-femoral pulse wave velocity. ## Population - Sixty-nine low-active adults with type 2 diabetes, mean age 59.5 years, BMI 33.5 kg/m2, and baseline HbA1c 8.5%, randomized to C-HIIT, C-MICT, or waitlist control. - Sample size: 69 - Age: Mean 59.5 +/- 8.8 years; eligible 18-80 years. - Sex: 27 female (39.1%) and 42 male (60.9%). - Fitness level: Low active; baseline VO2peak 24.1 +/- 5.8 mL/kg/min. - Health status: Type 2 diabetes with elevated cardiometabolic risk; excluded major exercise contraindications. ## Methodology - Randomized controlled trial with an 8-week supervised phase comparing C-HIIT, C-MICT, and waitlist control, followed by a 10-month self-directed phase comparing C-HIIT and C-MICT after waitlist participants were re-randomized. - 8 weeks supervised training plus 10 months self-directed training; vascular outcomes measured at baseline, 8 weeks, and 12 months. - University exercise training and vascular testing setting for supervised phase; self-directed home/community training for phase two with optional monthly supervised sessions. - Randomized and controlled study design. ## Protocol - C-HIIT. - Modality: Combined aerobic exercise plus high-intensity resistance intervals. - Work intervals: 4 min aerobic at 85-95% HRpeak, then 8 x 1 min resistance intervals at RPE >= 17. - Recovery: 1 min rest after the aerobic interval and 1 min rest between resistance intervals. - Sets or repetitions: 8 resistance exercises for 1 min each; at least 5 repetitions and aiming for 10-25 repetitions per bout. - Intensity: Aerobic 85-95% HRpeak; resistance RPE >= 17. - Session duration: 26 min. - Frequency: 3 sessions/week, non-consecutive days. - Program length: 8 weeks supervised plus 10 months self-directed. - Progression: Workload and repetitions monitored; self-directed phase attempted to replicate supervised program using available equipment/bodyweight. - C-MICT and waitlist control. - Modality: Combined moderate-intensity aerobic and resistance training; waitlist usual care. - Work intervals: C-MICT combination sessions: 22 min 30 s aerobic at 55-69% HRpeak plus 30 min resistance; aerobic-only sessions: 52 min 30 s at 55-69% HRpeak. - Recovery: C-MICT resistance sets separated by 1 min rest. - Sets or repetitions: Two sets of 10 repetitions for each resistance exercise in combination sessions. - Intensity: Aerobic 55-69% HRpeak; resistance RPE 11-13. - Session duration: 52.5 min. - Frequency: 4 sessions/week; two combined aerobic-resistance and two aerobic-only sessions. - Program length: 8 weeks supervised plus 10 months self-directed for exercise groups; waitlist usual care for 8 weeks before re-randomization. - Progression: Comparable to Exercise and Sports Science Australia recommendations for type 2 diabetes. ## Outcomes ### Relative flow-mediated dilation at 8 weeks Status: improved C-HIIT improved relative FMD compared with waitlist control. Mean difference 0.8% [95% CI 0.1, 1.4], p=0.025. ### Absolute flow-mediated dilation at 8 weeks Status: improved C-HIIT improved absolute FMD compared with waitlist control. Mean difference 0.004 mm [95% CI 0.002, 0.006], p=0.002. ### Hemodynamic indices, cfPWV, and ARP at 8 weeks Status: no clear change There were no significant between-group differences for hemodynamic indices, carotid-femoral pulse wave velocity, or aortic reservoir pressure after supervised training. Reported as no significant between-group differences in Table 2. ### 12-month hemodynamic indices Status: improved Across C-HIIT and C-MICT, brachial and central diastolic blood pressure, mean arterial pressure, reflection magnitude, and aortic reservoir pressure decreased over time. bDBP p=0.014; cDBP p=0.013; MAP p=0.047; reflection magnitude p=0.009; ARP p<0.001. ### 12-month carotid-femoral pulse wave velocity Status: mixed C-MICT was superior to C-HIIT for cfPWV change, driven by a C-HIIT increase and slight C-MICT decrease. Group x time p=0.018; C-HIIT +0.6 m/s, C-MICT -0.2 m/s. ### 12-month flow-mediated dilation Status: no clear change No differences in brachial artery FMD indices over time or between C-HIIT and C-MICT. Table 3 reports no significant time or group x time effects for FMD measures. ## Practical Insights - A 26-minute, three-times-weekly combined aerobic-resistance HIIT protocol can improve endothelial function over 8 supervised weeks in adults with type 2 diabetes. - Long-term self-directed HIIT adherence may be undermined by equipment access and time barriers even when the prescribed session is low volume. - For clinical or high-risk users, HR/RPE monitoring, screening, and professional supervision are central parts of the evidence context. - Low-volume HIIT should not be presented as clearly superior to guideline-based moderate combined training for all vascular outcomes. ## Limitations - Vascular outcomes were secondary outcomes and the study was powered for HbA1c. - The 8-week supervised phase may have been too short to detect some vascular changes. - Groups were not energy matched and had different external loads. - Self-directed C-HIIT adherence was poor in phase two. - No waitlist control group during phase two. - FMD analysis had reduced sample size because many images were excluded for quality or analysis limitations. ## Safety And Adherence - The article reports screening against ACSM absolute contraindications to exercise. - Aerobic mode was selected by an accredited exercise physiologist based on orthopedic limitations. - No adverse events were reported in the extracted article text for this manuscript. ## Original Sources - [PubMed](https://pubmed.ncbi.nlm.nih.gov/38695912/) (pubmed) - [DOI](https://doi.org/10.1007/s00421-024-05473-8) (doi) - [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11365856/) (full text) ## Agent Guidance Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.