Cardiac autonomic modulation in type 1 diabetes during exercise-heat stress

Acta Diabetol. 2020 Aug;57(8):959-963. doi: 10.1007/s00592-020-01505-9. Epub 2020 Mar 6.


Aims: Cardiac autonomic modulation, as assessed by heart rate variability (HRV), is independently attenuated by both type 1 diabetes (T1D) and exercise-heat stress, although their combined effects remain unclear. We therefore assessed HRV during exercise-heat stress in young individuals (18-37 years) with (n = 14) and without type 1 diabetes (n = 14).

Methods: Participants completed 30-min seated rest and three, 30-min bouts of semi-recumbent cycling at light, moderate, and vigorous metabolic heat productions (200, 250, 300 W/m2, respectively), each followed by 30-min recovery. Body core temperature (Tcore) and electrocardiogram were recorded throughout and analyzed during the final 5-min of rest and each exercise period.

Results: Relative to baseline, Tcore was increased in both groups, albeit to a greater extent in type 1 diabetes during vigorous exercise (T1D, 1.1 ± 0.3 °C; control, 0.8 ± 0.3 °C; P < 0.05). Overall HRV (as reflected by entropy) was attenuated throughout exercise relative to baseline in both groups, with the magnitude of the reduction greater in type 1 diabetes during vigorous exercise (T1D, - 108%; control, - 70%; P < 0.05).

Conclusions: Given the negative correlations between decreased HRV and cardiac risk, our novel observations indicate that vigorous exercise in hot environments may pose a health concern for individuals with type 1 diabetes.

Keywords: Diabetes mellitus; Exercise-heat stress; Heart rate variability; Sympatho-vagal balance; Vagal tone.

Publication types

  • Clinical Trial

MeSH terms

  • Adolescent
  • Adult
  • Autonomic Nervous System / physiopathology*
  • Blood Glucose / metabolism
  • Body Temperature / physiology
  • Diabetes Mellitus, Type 1 / blood
  • Diabetes Mellitus, Type 1 / physiopathology*
  • Exercise / physiology*
  • Female
  • Heart / physiology*
  • Heart Rate / physiology
  • Heat-Shock Response / physiology*
  • Humans
  • Male
  • Rest
  • Young Adult


  • Blood Glucose