High intensity interval training protects the heart during increased metabolic demand in patients with type 2 diabetes: a randomised controlled trial.

Suryanegara J; Cassidy S; Ninkovic V; Popovic D; Grbovic M; Okwose N;
Trenell MI; MacGowan GG; Jakovljevic DG.

Acta Diabetologica. 56(3):321-329, 2019 Mar.

AIM: The present study assessed the effect of high intensity interval
training on cardiac function during prolonged submaximal exercise in
patients with type 2 diabetes.
METHODS: Twenty-six patients with type 2 diabetes were randomized to a 12
week of high intensity interval training (3 sessions/week) or standard
care control group. All patients underwent prolonged (i.e. 60 min)
submaximal cardiopulmonary exercise testing (at 50% of previously assess
maximal functional capacity) with non-invasive gas-exchange and
haemodynamic measurements including cardiac output and stroke volume
before and after the intervention.
RESULTS: At baseline (prior to intervention) there was no significant
difference between the intervention and control group in peak exercise
oxygen consumption (20.3 +/- 6.1 vs. 21.7 +/- 5.5 ml/kg/min, p = 0.21),
and peak exercise heart rate (156.3 +/- 15.0 vs. 153.8 +/- 12.5 beats/min,
p = 0.28). During follow-up assessment both groups utilized similar amount
of oxygen during prolonged submaximal exercise (15.0 +/- 2.4 vs. 15.2 +/-
2.2 ml/min/kg, p = 0.71). However, cardiac function i.e. cardiac output
during submaximal exercise decreased significantly by 21% in exercise
group (16.2 +/- 2.7-12.8 +/- 3.6 L/min, p = 0.03), but not in the control
group (15.7 +/- 4.9-16.3 +/- 4.1 L/min, p = 0.12). Reduction in exercise
cardiac output observed in the exercise group was due to a significant
decrease in stroke volume by 13% (p = 0.03) and heart rate by 9% (p =
CONCLUSION: Following high intensity interval training patients with type
2 diabetes demonstrate reduced cardiac output during prolonged submaximal
cardiopulmonary exercise testing. Ability of patients to maintain
prolonged increased metabolic demand but with reduced cardiac output
suggests cardiac protective role of high intensity interval training in
type 2 diabetes.