Exercise as it relates to Disease/Aerobic exercise method effects on glycemic control, physical fitness and micro/macro vascular function in elderly type 2 diabetic patients

This page is a critical appraisal of the article "Continuous vs interval training on glycemic control and macro- and microvascular reactivity in type 2 diabetic patients" by Mitranun et al (2012).

What is the background to this research?
Diabetes currently effects 1 in every 11 adults worldwide. By 2050, it is estimated there will be 2 billion people ≥60 years old. With the increase in life expectancy and the rise in type II diabetes across the globe, it is important to aid these groups in managing exercise requirements to improve their quality of life (QOL). The American Diabetes Association currently advocates for the use of continuous aerobic exercise as the safest approach to meet exercise requirements.

This study looks at the physiological effects of different exercise modalities in elderly type II diabetic patients. The article is a continuation from prior research investigating the positive effects of interval training on patients with coronary artery disease and patients with coronary artery bypass surgery. It aims to evaluate the use of interval training to manage the health and wellbeing of people with various cardiovascular conditions.

Where is the research from?
The study was carried out at the King Chulalongkorn memorial hospital (KCMH) in Bangkok, Thailand. Participants were recruited from the Diabetes club of the KCMH hospital.

Author Backgrounds
The study was supported by the Thailand government and the Chulalongkorn University. There were no noted biases or conflicts of interest.

What kind of research was this?
This study was carried out as a randomised control trial (RCT) within a relatively small sample group (45 adults, 16 males and 29 females). The use of an RCT typically allows for the most reliable data collection when assessing models of difference, however the small sample size does limit the statistical power of the data collected.

What did the research involve?
Once passing the selection criteria, participants were allocated randomly into one of three groups.


 * Sedentary control group (SED) (n=16)
 * Interval aerobic training group (INT) (n=15)
 * Continuous aerobic training group (CON) (n=15)

Participants were required to exercise 3 times per week at the prescribed intensities. Total oxygen consumptions and duration of exercise sessions were matched for INT and CON groups to isolate the effects of intensity. Exercise intensities were increased over 3 phases across the twelve weeks to match the increase in fitness built by participants. SED group remained sedentary for the 12 weeks.

Weeks 7-12
 undefined 

Measurements
All measurements were taken pre and post the 12-week program. Participants had blood samples taken day one at 7:00am after an 8 hour overnight fast. Post tests were taken under the same conditions (fasted, 7:00am) at the end of the 12 weeks. Health related physical fitness measures were measured 2 hours after breakfast. Vascular function was measured on day 2, then 48-72 hours after last exercise bout.

Subject Characteristics
Body mass index (BMI), body fat percentage, waist to hip ratio and resting heart rate all decreased with both INT and CON groups. Blood pressure only decreased with the INT group.

Physical Fitness
Leg extension strength increased with INT and CON groups however, knee flexion strength only increased in the INT group. Maximal oxygen consumption (VO2max) increased in both groups, with a larger magnitude of increase in the INT group.

Blood Biochemistry
Significant decreases in fasted glucose concentrations were seen in INT and CON groups. Significant decreases in haemoglobin A1c (a long term marker for glycemic control) levels were only achieved in the INT group. Both INT and CON groups displayed improved lipid profiles.

Vascular Reactivity
Flow mediated dilation reflecting the response of the vascular system increased in both INT and CON groups, with significantly larger increases in the INT group.

Researchers interpretation
A two way ANOVA analysis, followed by Tukey's multiple comparison, were used to determine significant differences in means ± standard error of the mean data.

When compared to their SED control group, both INT and CON groups displayed as effective methods to improve glycemic control, lipid profiles, aerobic strength, micro and macro-vascular reactivity in elderly patients with type II diabetes. These effects were significantly greater in the INT group, leading to the conclusion that while both training programs improve outcomes, interval training displayed larger effects and may be a safe and effective method of improving the vascular dysfunctions suffered by diabetics.

Limitations
The participant group was an old, sedentary group, on antihyperglycemic medications limiting the generalisability of the study. The Asian decent of the participant group was also noted as a factor that may limit generalisability. Analysis of the data may have been mis represented due to Tukey's multiple comparison test. The generous nature of the test is best applied to a large sample size to avoid statistical error of data. .

What conclusions can we take from this research?
Conclusions made by the researchers appear to be conservative considering the positive results stated. Both CON and INT are effective methods of improving glycemic control, physical fitness, and vascular function. However in this study, INT training was observed to improve these more than CON. The use of these methods in an older, diabetic population without injury or complication, further bolster a line of research into the effective use of interval training in health management.

Further studies including multiple meta-analysis, assessing interval training compared to continuous aerobic training across different populations, align with the findings found in this article.

Practical Advice

 * Interval training may be a safe and effective health intervention in management of certain health conditions.


 * Both interval and continuous aerobic training provide better health outcomes than sedentary behaviours.


 * Further research is needed on the mortality and morbidity of interval training in certain populations.


 * Always consider your patient/ clients requirements and limiting factors before exercise prescription is administered.

Further Information

 * Physical Activity/Exercise and Diabetes: A Position Statement of the American Diabetes Association. https://care.diabetesjournals.org/content/39/11/2065
 * Exercise and Sports Science Australia, Type II diabetes exercise prescription position statement. https://www.essa.org.au/wp-content/uploads/2015/10/ESSA_Diabetes-Position-Statement.pdf