PMID 35053064

Research
All papers

High-Intensity Interval Training Improves Cardiac Autonomic Function in Patients with Type 2 Diabetes: A Randomized Controlled Trial

Silva LRB, Gentil P, Seguro CS, de Oliveira JCM, Silva MS, Marques VA, Beltrame T, Rebelo ACS

Question

Do two HIIT formats improve heart-rate variability and heart-rate recovery more than moderate continuous training in adults with type 2 diabetes?

Summary

In adults with long-standing type 2 diabetes, 8 weeks of supervised HIIT improved cardiac autonomic markers more than moderate continuous training. The 30-second interval format showed the clearest improvements, but the trial was short and used clinical screening and monitoring.

Methodology

  • Adults with type 2 diabetes for at least 5 years.
  • 44 participants.
  • Aerobic exercise from CPET workload.
  • Work intervals: 30 seconds or 2 minutes.
  • Recovery: Passive recovery; 30 seconds for HIIT-30:30.
  • Intensity: 100% workload at VO2max.
  • Varied by protocol.
  • 2 sessions/week.
  • 8 weeks.
  • Randomized clinical trial
  • Heart-rate variability, Heart-rate recovery, and Resting heart rate were tracked.

Outcomes

HRV

HIIT-30:30 improved R-R interval, pNN50, SDNN, and 2UV% markers more consistently than MICT.

Reported interactions included R-Ri p=.015, SDNN p=.036, and 2UV% p=.029.

Improved

HR recovery

HIIT groups showed faster post-exercise heart-rate recovery kinetics than MICT.

offTAU/offTMR interactions reported; MICT was higher/slower than HIIT groups.

Improved

Resting HR

Resting HR decreased more in HIIT-30:30 than MICT.

Group x time HRrest p=.031; HIIT-30:30 greater reduction than MICT p=.038.

Improved

Insights

  • Short-interval 30:30 HIIT may be promising for autonomic function in screened T2D adults.
  • Clinical HIIT should include cardiac and glycemic safety workflows.
  • Equating distance does not make protocols equivalent in autonomic response.

Limitations

  • Short 8-week intervention.
  • No longer HRV monitoring 12 or 24 hours after sessions.
  • No nutritional control.
  • Higher-risk patients were excluded during CPET screening.
  • Attendance-based exclusions may bias toward adherent participants.

Safety

  • Exercise screening excluded participants with unstable angina, uncontrolled arrhythmias, low exercise capacity, or abnormal blood pressure response.
  • Session monitoring included blood pressure, heart rate, and glycemia.