Exercise as it relates to Disease/Resistance training interventions for older type 2 diabetics

Article reviewed: Castaneda, C., Layne, J. E., Munoz-Orians, L., Gordon, P. L., Walsmith, J., Foldvari, M., ... & Nelson, M. E. (2002). A randomized controlled trial of resistance exercise training to improve glycemic control in older adults with type 2 diabetes. Diabetes care, 25(12), 2335-2341.

Background

This study implements a progressive resistance training (PRT) program for elderly type 2 diabetics to help improve glycemic and metabolic control.

Type 2 diabetes:

Type 2 diabetes (T2D) is a chronic progressive condition affecting blood glucose levels. It occurs due to insufficient pancreatic release of insulin, and a build-up of resistance. This results in inadequate control over blood glucose levels. T2D can be managed or improved through healthier lifestyle habits. Sufferers of the condition will also have to eventually start taking associated medications or have insulin shots to assist with long term management.

PRT:

PRT is a mode of exercise based on building muscular strength. It focusses on slowly advancing the amounts of weight lifted over a lengthy period. Decreased phases of intensity are incorporated amongst the progressions in an effort to minimise injury risks.

Where the research is from

This research was conducted at the Human Nutrition Centre on Aging, at Tufts University in Boston (U.S.A) during 2002. The results come from 62 (40 women, 22 men) elderly T2-diabetic Latino’s. They had all suffered with T2D for at least three years, and were an average age of 66.

Type of research

This research is a randomised controlled trial; the participants are randomly allocated into particular treatments being assessed. It examines certain physiological, metabolic and glycemic variables before, during and after a 16 week period. This is done as a means of assessing which of the variables will/won’t demonstrate improvements from the training program – therefore giving an indication of notions for management.

What the research involves

The study lasted 16 weeks and participants were split in half into the PRT group and controls. The exercisers trained for 45 minutes 3 times/week using 5 resistance machines. The machines targeted the chest, upper back and the upper/lower legs. The controls performed no exercise; instead they documented a weekly checklist on blood glucose levels, medical visits, hospitalisations and changes in medication. All participants were tested for strength at baseline, mid study and post study. Additionally participants were measured on several different glycecmic, metabolic and physiological variables at baseline and throughout the study

Basic Results

The main variables to improve were glycosylated haemoglobin levels, muscle glycogen and systolic blood pressure.

Variable	PRT	Controls
Plasma glycosylated haemoglobin concentration (%) (concentration of glucose in blood) Baseline: Final:	8.7 ± 0.3 7.6 ± 0.2	8.4 ± 0.3 8.3 ± 0.5
Muscle glycogen stores (mmol of glucose/kg of muscle) Baseline: Final:	60.3 ± 3.9 79.1 ± 5.0	61.4 ± 7.7 47.2 ± 6.7
Systolic Blood Pressure (mmHg) Baseline: Final:	145.2 ± 3.6 135.5 ± 3.3	142.7 ± 4.1 150.4 ± 3.9

The exercisers also had a mean gain of 1.2 kg of lean body mass and an average loss of 0.7 kg trunk fat. There was an average gain of 33% in whole body muscle strength, compared with the control group that had an approximate 15% loss. The exercisers also reported increased levels of spontaneous physical whilst at home – accounting for 3 times the weekly energy expenditure compared to baseline.

Interpretations of results

The results were broken into 7 outcome measures; the only outcomes which were statistically analysed were the glycemic, metabolic and physiological variables such as blood glucose, muscle glycogen, cholesterol, blood pressure, heart rate and body composition. They were said to be statistically significant if the 2-tailed p-value was <0.05 (inferring significant change had occurred from baseline-week 16). The variables which expressed significant change were blood glucose levels, muscle glycogen stores and systolic blood pressure.

Conclusions from research

The study demonstrated that PRT could be an effective modality for managing diabetes in high risk populations. Some factors strongly associated with the risk of T2D were shown to improve. These included systolic blood pressure, muscular strength, muscle glycogen, blood glucose, lean mass and abdominal adiposity. An analogous study had similar findings, expressing improvements to blood glucose levels, lean body mass and overall fat mass. Yet it prescribed a weight loss program alongside the RT, and this provided a greater improvement to glycemic control than just RT. The weight loss program seems more effective as it also incorporated a healthy eating plan and a high volume of aerobic exercise (Lifestyle adaptations). Suggestions from similar research propose that RT combined with aerobic training provided the greatest improvements to diabetes associated variables than doing them separately. When looking at these studies holistically, the take-home message seems to be that a combination of aerobic and resistance training in conjunction with healthier eating habits is the most effective modality for improving glycemic control. With that in mind, more research needs to be conducted on determining the safest, yet most effective exercise intensities/volumes for higher-risk patients.

Implications of the Research

Insulin resistance (IR) was not directly measured, yet similar researchers considered its link with diabetes associated issues, and what affects its risk of developing. Suggestions have been made that increased levels of abdominal adiposity and a loss of muscle mass are strongly associated with the development of IR. IR is also suggested to have a cause-effect relationship with hypertension – a metabolic issue associated with diabetes; these two issues are additive in negatively affecting blood pressure and also the delivery of glucose and insulin to skeletal muscle, which impairs glucose uptake. The PRT program was able to cause reductions in abdominal fat levels and increase lean muscle mass¹; this helped negate some of the insulin resistance risk factors, thus implying a protective factor. The metabolic risk factors associated with hypertension and IR are proposed to be more effectively managed with the addition of aerobic training, particularly for elderly diabetics. The research also inferred that RT stimulated more glucose uptake in skeletal muscle. This process seems to be a dual-effect with insulin, as RT is also suggested to increase insulin action within skeletal muscle. RT increases the amount of contraction-mediated mechanisms, which in-turn allows for more key proteins that are very important in the insulin signalling cascade - hence more insulin activity. These studies mainly implicate RT as being an effective modality for T2D management.