Exercise as it relates to Disease/Adding resistance training to aerobic exercise for women with type 2 diabetes

Article reviewed: Effective Exercise Modality to Reduce Insulin Resistance in Women with Type 2 Diabetes

What is the background to this research?

What is Type 2 Diabetes?

According to Diabetes Australia Type 2 diabetes is "a progressive condition in which the body becomes resistant to the normal effects of insulin and/or gradually loses the capacity to produce enough insulin in the pancreas". The causes of this disease are still unclear but it is known that there are modifiable lifestyle risk factors as well as genetic risk factors.

What is the aim of this study?

This study has two objectives. The first aim is to evaluate whether a combined resistance and aerobic training program would improve insulin sensitivity compared to a program of aerobic training alone in postmenopausal women with type 2 diabetes. Secondly, this study aims to relate the improved insulin resistance with changes in abdominal adipose tissue (AT) and thigh muscle density.

Where is this research from?

This research was conducted in British Columbia, Canada in 2003 by Darcye J. Cuff, Graydon S. Meneilly, Alan Martin, Andrew Ignaszewski, Hugh D. Tildesley and Jiri J. Frohlich.

What kind of research was this?

This study involved a randomised control trial involving 28 obese postmenopausal women under three different 16-week treatments that they were randomly assigned to. The measured outcomes were used to determine which type of exercise intervention in most effective at decreasing insulin resistance and how abdominal AT and thigh muscle density relate to improved insulin sensitivity.

What did the research involve?

The research involved three groups under different training conditions: control, aerobic only (AeO) and aerobic and resistance training (Ae+RT). The control group did not participate in extra exercise, but all participants were encouraged to continue their regular diet and exercise regime outside of the study protocols. Diet was measured pre and post the 16 week intervention by a 3 day food diary completed by the participants. The outcomes measured pre and post treatment were glucose disposal (measured by hyperinsulinemic-euglycemic clamp) and computered tomography scans of abdominal AT and mid-thigh skeletal muscle.

What were the basic results?

Variables	Control Group	Ae+RT Group	AeO Group
Weight (kg)	2.1 ± 1.3	3.2 ± 1.5	1.5 ± 0.8
VO2peak (l/min)	-2.9 ± 3.4	10.2 ± 3.7	13.1 ± 6.5
Glycosylated Hemoglobin (%)	-0.43 ± 0.29	-1.4 ± 3.2	1.59 ± 1.74
Glucose infusion rate (mg.kg−1.min−1)	3.1 ± 12.2	77.1 ± 22.0	19.8 ± 12.9
Total Abdominal AT (L4-L5) (cm2)	2.1 ± 2.2	-6.7 ± 2.6	-2.8 ± 1.7
Subcutaneous AT (cm2)	3.2 ± 1.6	-4.7 ± 3.3	-2.0 ± 2.4
Visceral AT (cm2)	-0.15 ± 4.6	-10.5 ± 2.9	-4.1 ± 2.5
Mid-thigh skeletal muscle - Cross sectional area (cm2)	0.3 ± 0.7	2.8 ± 1.0	0.4 ± 0.9
Mid-thigh skeletal muscle - Low density muscle (cm2)	6.3 ± 2.0	-8.0 ± 4.9	2.8 ± 2.6
Mid-thigh skeletal muscle - Normal density muscle (cm2)	-2.0 ± 1.0	6.7 ± 1.3	1.3 ± 1.0

All values shown are relative. See original article for absolute values.

How did the researchers interpret these results?

The 5 variables that were measured were weight (kg), VO²peak (l/min), glycosylated haemoglobin (%), glucose infusion rate (mg.kg-1.min-1), total abdominal AT (broken into subcutaneous (cm²) and visceral (cm²)) and mid-thigh skeletal muscle (broken into cross-sectional area (cm²), low-density muscle (cm²) and normal-density muscle (cm²)). The results were to be considered significant it the 2-tailed p value (acquired through SPSS) was greater than 0.05 indicating significant change had occurred from results pre intervention to those following the 16 week programs.

What conclusions can be drawn from this research?

The measured outcomes that showed a significant change were glucose infusion rates increased significantly in the Ae+RT group which indicates increase in insulin sensitivity. Both exercise groups had a reduction in subcutaneous and visceral AT and increased muscle density at the mid-thigh, although the Ae+RT group showed a larger increase in muscle density than the AeO group. The results showed that both exercise groups lost weight in comparison to the control group but between the two groups there was no significant difference (P > 0.05). Improved glucose disposal was independently linked with changes to AT and muscle density as per the second aim of the study.

What are the implications of this research?

According to this study adding resistance training to an aerobic exercise regime will enhance glucose disposal in postmenopausal women with type 2 diabetes. This study directly measured glucose uptake rates and clearly showed that the implementation of the Ae+RT protocol had a significantly positive effect on the measured variable. This indicates that the implementation of this program is recommendable to postmenopausal women with type 2 diabetes as a method of reducing insulin resistance/increasing insulin sensitivity (which is the primary risk factor for type 2 diabetes). The improvement in glucose disposal/insulin sensitivity is significantly related to loss of abdominal subcutaneous and visceral AT and increase in mid-thigh muscle density. Considering high abdominal AT and low muscle density are risk factors for insulin resistance it is implied that by decreasing abdominal AT and increasing muscle density through a program involving both aerobic and resistance training, postmenopausal women with type 2 diabetes could help manage their illness themselves without medication.