Exercise as it relates to Disease/Effects of exercise intervention on myocardial function in type 2 diabetes

An analysis of the journal article Effects of exercise intervention on myocardial function in type 2 diabetes, written by M D Horden et al. (2009)

What is the background to this research?
Type 2 Diabetes Mellitus (T2DM) is a chronic condition that affects blood glucose levels. It occurs when there is a build-up resistance, and insufficient pancreatic release of insulin. This results in inadequate regulation over blood glucose. T2DM can be managed with a healthier lifestyle. People suffering from the condition eventually will have to take associated medications, or have insulin injections to help with long term management.

Myocardial function is a broad term that is used to describe the health and function of the myocardium, it entails healthy function of diastolic and systolic tissue velocity, and myocardial strain rate. Myocardial dysfunction is a heterogeneous condition that affects the contractility of the ventricle, which can lead to heart failure.

Where is this research from?
The study was conducted by researchers from School of Medicine, School of Human Movement studies, and Diamantina Institute, (all) University of Queensland, Brisbane, Australia. Correspondence was to Professor Thomas H Marwick from University of Queensland School of Medicine. Supported in part by a Clinical Centre of Research Excellence Award from the National Health and Medical Research Council, Canberra, Australia. Funding from NHMRC, THM, JBP, CCRE, and GE Medical Imaging.

What kind of research is this?
The research of Hordern et al. was a randomised control trial consisting of an exercise intervention. The intervention comprised of individualised exercise training with the addition of some general dietary management. The randomised control trial is a level two research method stated by the National Health and Medical Research Council, it is the appropriate design for clinical trials. The secondary results from this study provide evidence to the relationship between physical activity and myocardial function in T2DM sufferers.

What did the research involve?
The research of Hordern et al. involved patients with T2DM from hospital clinics. The community was eligible for inclusion if they were between the ages of 18–75 years, were not pregnant, and without a co-morbidity or cardiovascular disease. Patients totalling 248, undertook screening for occult coronary artery disease under exercise echocardiography, which reduced the number of patients by 25. Patients were randomly allocated into two groups, one being usual care, totalling 112 patients, and the other being an exercise intervention, totalling 111 patients. Complete follow up data resulted in 176 available patients; with 88 intervention patients and 88 usual care patients. Intervention patients underwent a 4-week exercise gym-based training program which was supervised by an accredited exercise physiologist (AEP), followed by telephone-counselled home-based exercise training. This aimed to achieve at least 150 minutes of moderate to vigorous exercise, measured at 12–13 on Borg 20-point scale, with an individualized blend of aerobic and resistance training, along with two 1-hour supervised exercise sessions and were asked to perform extra 30 minutes of exercise at home each week. During the telephone-led home stage intervention, telephone contact was each week for 3 months, fortnightly for 3 months, and each month for the remainder of the 1-year study. Hordern et al. were searching for changes to both primary and secondary outcomes. The primary outcome was myocardial function, which entailed systolic and diastolic tissue velocity, and myocardial strain and strain rate. The secondary outcomes included waist circumference, fat mass, blood glucose, insulin sensitivity, VO2 MAX, and HbA1c (glycated haemoglobin).

What were the basic results?
Most important to note in this study, the 1-year exercise intervention group as a whole failed to show improve myocardial function in all patients. The results of this study showed three significant differences between the intervention and control groups. These were...
 * Patients who had the greatest increases in both moderate and vigorous activity significantly improved diastolic function, HbA1C and cardio-respiratory fitness.
 * Significant improvements in waist circumference, body fat, glycaemic control, insulin sensitivity, and functional capacity.
 * Intervention patients had greater increase in moderate or vigorous activity showed significant improvements HbA1C and diastolic blood pressure.

How did the researchers interpret the results?
Interpretation of the study by Hordern et al. found that the prescription of moderate to vigorous gym-based and telephone-counselled home-exercise training intervention did not decrease the prevalence of myocardial dysfunction of the whole group. This finding correlated with results from other research papers. Hordern et al. believed even though there were little difference in myocardial function between the overall groups in the primary analysis, the collaboration between groups and variations in activity levels in hypothesizing myocardial change has significant suggestions for exercise prescription references for patients with T2DM. Meaning that as a whole the groups did not show a decrease in myocardial dysfunction, however the patients with the greatest increase in moderate and vigorous activity did show myocardial benefit.

What conclusions should be taken away from this research?
This study has concluded that there is an association between moderate to vigorous activity and a decrease in myocardial dysfunction in T2DM patients. They believe the efficacy and effectiveness of the intervention is dependent on the compliancy rates of participants. It was expected that 50% of the patients would drop out or fail to train adequately, many studies have similar notions and exclude individuals who do not meet minimum requirements. The most significant benefits Hordern et al. concluded from moderate and vigorous physical activity not a decrease in myocardial dysfunction, however it was an improvement in several myocardial, metabolic, and cardiovascular functions. All of which make it much more likely for patients to improve their myocardial function. Therefore, a greater exercise prescription, attained through greater amounts of exercise and/or higher intensities than the research guidelines, may be required to reverse myocardial dysfunction.

Practical advice
This study has shown that for T2DM patients, the current exercise recommendations may be insufficient in reversing myocardial dysfunction. The prescribed exercise dosage for patients was 150 minutes of aerobic and resistance exercise at a 12-13 RPE each week. A blend of aerobic and resistance exercise for at least 150 minutes at minimum 12-13 RPE each week will grant benefits to myocardial function in T2DM sufferers. Further advice should be sought from a medical practitioner before administering any exercise plan.

Other readings
https://www.diabetesaustralia.com.au/ http://www.ncbi.nlm.nih.gov/books/NBK53885/pdf/Bookshelf_NBK53885.pdf http://care.diabetesjournals.org/content/diacare/29/6/1433.full.pdf http://www.nejm.org/doi/pdf/10.1056/NEJM200105033441801
 * Diabetes Australia:
 * Management of Type 2 Diabetes:
 * Exercise and Type 2 Diabetes:
 * The prevention of Type 2 Diabetes through Lifestyle Changes: