Heart Rate During Exercise in Type 2 Diabetes

Exercise training is a cornerstone for the prevention and treatment of metabolic disorders and associated cardiometabolic complications such as type 2 diabetes mellitus (T2D) and hypertension. Similar to the beneficial health effects after performing conventional continuous exercise modalities, high intensity interval training (HIIT) has been reported as an effective alternative exercise-modality to improve glucose homeostasis in both prediabetes subjects and individuals with T2D diagnosed. In this regard, although multiple HIIT-based interventions commonly report acute and long term benefits on body composition, cardiorespiratory fitness and insulin sensitivity in metabolically compromised subjects, little is known about the acute cardiovascular response (i.e., at heart rate level) during HIIT in subjects with different glucose control.

HIIT is described as performing brief periods of exercise at vigorous or maximal intensity, interspersed with inactive or low intensity recovery phases of variable duration. In order to characterize different HIIT-based protocols, exercise intensity is usually defined as relative percentages of individual maximal cardiorespiratory fitness (VO2max) or relative maximal power output values. Nevertheless, the need for specific technological equipment to assess these parameters usually limit the prescription and recommendations of HIIT in clinical settings and other public health contexts at massive level. Additionally, the use of self-perceived exertion scales and heart rate (HR) variations upon HIIT have been demonstrating to be accessible and feasible strategies to regulate exercise intensity during HIIT. For example, it was reported that HR and self-perceived exertion scores increased progressively in T2D subjects, parallel to the oxygen consumption rate throughout an acute HIIT session performed on cycle ergometer. Consequently, it is conceivable to hypothesize that determining HR variations during HIIT might optimize the recommendation of this training methodology in metabolically compromised subjects as those at risk or with T2D diagnosed. Therefore, the aim of the present study was To describe and compare the acute heart rate changes in response to an incremental maximal exercise test and a single HIIT session between normoglycaemic (NG), prediabetes (Pre-T2D) and type 2 diabetes mellitus (T2D) subjects.