Associations between exercise training characteristics and change in peak oxygen consumption in patients with chronic ischaemic heart disease and type 2 diabetes
Authors: Gass F , Mueller S , Dinges S M T , Fegers-Wustrow I , Weichenberger M , Treitschke J , Freigang F , Amelung V , Nebling T , Halle M 
Published: May 2023

Abstract

Funding Acknowledgements
Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Innovationsfonds des Gemeinsamen Bundesausschusses.

Introduction
Exercise interventions are well established in the treatment of chronic ischaemic heart disease (CIHD) and type 2 diabetes mellitus (T2DM). Yet, there remains a significant research gap when it comes to patients which suffer from both diseases.

Purpose
The aim of this study was to investigate the associations of training characteristics (average minutes of endurance training per week, average endurance training sessions per week and mean intensity) and change in peak V̇O2 following 6 months of a telemedicine supported exercise intervention in patients with CIHD and T2DM.

Methods
Among 251 intervention group patients of a randomised controlled trial that evaluated the effects of an individual home-based lifestyle intervention compared to usual care (N=502 patients), those who completed the 6-month follow-up (N=201) were included in this analysis. All patients received an individual exercise training plan via a smartphone application, which recorded training duration and heart rates (HR, utilizing a connected heart rate sensor, Polar H7, Polar, Finland). Patients also had the possibility to perform additional sessions without prescribed intensity zones. All recorded sessions were evaluated with a customized software and manually checked for plausibility. Intensities were calculated as the average % heart rate reserve (HRR) of all endurance exercise sessions. If HR measurements were classified as invalid/unreliable (e.g. very strong fluctuations), these sessions were excluded from the average HRR calculation but still included in the average minutes and sessions of endurance training per week. Associations between training characteristics and change in peak V̇O2 were evaluated via univariate regression analysis.

Results
Of the 201 patients (16% female, 68±8 years), 81 (40%) were classified as adherent to the exercise intervention (defined as having performed the prescribed training duration in ≥ 50% of the weeks and ≥ 66.7% of the recommended duration). On average, patients performed 78±94 minutes of endurance training per week across 3.26±3.13 sessions at an average of 51.6±18.2% HRR. Peak V̇O2 improved by a mean (SD) of 0.94±2.74 ml/kg/min. Change in peak V̇O2 was significantly associated with the average duration and number of sessions per week (p &lt; 0.01), but not with mean intensity (p = 0.10) (Fig. 1).

Conclusions
Mean changes in peak V̇O2 were low, likely due to low overall adherence. Accordingly, we found a significant positive association between the average minutes as well as the average sessions of endurance training per week and change in peak V̇O2, whereas change in peak V̇O2 was not significantly associated with mean exercise training intensity. Therefore, future telemedical exercise interventions need to find ways to improve adherence of patients towards the provided exercise recommendations.