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

This is an analysis of the journal article "A randomized controlled trial of resistance exercise training to improve glycemic control in older adults with type 2 diabetes" by Castaneda et al. 2002.

What is the background to this research?
Type 2 Diabetes (T2D) is a metabolic disease characterized by chronic hyperglycaemia resulting from the inability of the body to use insulin (insulin resistance) and or insufficient levels of insulin produced by the pancreas (insulin deficiency). T2D prevalence is increasing and accounts for 90-95% cases of diabetes. Risk factors associated with developing T2D include increasing age, obesity and lack of physical activity. Consequently, T2D increases premature mortality and cardiovascular disease and can lead to complications such as retinopathy, neuropathy, nephropathy and amputations.

Management of T2D has traditionally been achieved and published in literature through medication, dietary intervention and aerobic exercise. Recently resistance training has been investigated as a possible intervention for glycaemic control   and it has been considered as a beneficial intervention as it increases muscle mass. This increase in muscle mass is extremely important in older adults who suffer from age related sarcopenia (loss of muscle mass). Monitoring levels of glycosylated haemoglobin (HbA1c) within T2D patients is the gold standard marker of glycaemic control. Monitoring this reflects the long-term plasma glucose levels in the patient and small improvements significantly reduce the risk of diabetic related complications.

Where is the research from?
The research was conducted at the General Clinic Research Centre at the New England Medical Centre and the Jean Mayer U.S. Department of Agriculture Human Nutrition Research Centre on Aging (HNRCA) at Tufts University, Boston, Massachusetts. The article was reviewed and published later by Diabetes Care in December 2002.

What kind of research was this?
The research conducted was a 16-week randomized control trial based on 62 Latino older adults. The research had an aim of determining whether resistance exercise training can improve glycaemic control in T2D patients. Research shows that randomized control trials reduces bias and are considered to be the best source of evidence in intervention studies.

What did the research involve?
The study itself involved 62 community-dwelling Latino individuals, over the age of 55 years who have had T2D for at least 3 years’ duration. Pre-screening procedures were conducted to determine the eligibility of the participants including confirmation of diabetes diagnosis, physical examination, blood pressure, electrocardiogram and blood haematology. Subjects were excluded from the study if they were currently participating in resistance training, had had a myocardial infarctions within the past 6 months or any other unstable chronic condition.

The primary measure for the subjects glycaemic control was the HbA1c concentration followed by the muscle glycogen stores. The study also examined other glycaemic and metabolic variables such as plasma glucose, cholesterol and triglyceride levels. Body composition, physical activity, muscular strength and dietary intake were also examined. These outcomes were measured at baseline, mid-study and post-study intervals.

Eligible subjects were randomized to a control group or a high intensity, low volume progressive resistance training (PRT) group. The PRT subjects exercised at the HNRCA three times per week for of 45 minutes. The exercise program progressively increased in intensity with week 1-8 at 60-80% of baseline one repetition maximum (1RM) while weeks 10-14 at 70-80% of mid study 1RM. Furthermore, to prevent overuse injury, the exercise intensity during weeks 9 and 15 was lowered.

Basic results
The implementation of 16 weeks of PRT training resulted in:
 * Reduced HbA1c levels
 * Increased muscle glycogen stores
 * Reduced dosage of prescribed diabetes medication in 72% of subjects

Additionally the PRT subjects increased lean mass, reduced systolic blood pressure and decreased trunk fat mass.

The control group exhibited:
 * No changes in HbA1c levels
 * Reduced muscle glycogen stores
 * Increased dosage of prescribed diabetes in 42% of subjects

How did the researchers interpret the results?
The researches found the high intensity PRT intervention in T2D subjects resulted in significantly improved HbAIc levels, which enhances glycaemic control. They concluded that change in HbAIc suggests that PRT reduces hyperglycaemia by stimulating glucose uptake in skeletal muscle.

In addition, they observed improvements in abnormalities associated with metabolic syndrome. These improvements included a reduction in hypertension and abdominal adiposity.

Finally, the researches noticed a statistically significant positive correlation between a decrease in HbA1c levels with an increase in both lean tissue mass and muscle strength and a decrease in trunk fat among the PRT subjects. This is important as these three measures greatly reduce the chance of being diagnosed with T2D.

Conclusions
Results produced from the study demonstrate that appropriately prescribed and supervised PRT is practical and successful in Latino older adults with T2D and improves their glycaemic control. Furthermore, high intensity PRT results in a greater reduction in HbA1c compared to moderate intensity resistance training shown in previous studies, suggesting that it is more effective in glucose uptake in the body. Additionally participating in the PRT training three sessions a week is beneficial in increasing muscle mass and strength and improves glycaemic control in older adults.

Implications of this research?
Though these findings are preliminary, further research needs to be undertaken to determine the most appropriate PRT intervention for older adults with T2D. These include further examining training intensity and dietary intake intervention.

New literature has established the benefits of combined exercise (aerobic and resistance) in relation to glycaemic control in T2D. It was reported that the combined exercise group had greater glycaemic control than individual aerobic and resistance groups.

Furthermore adherence to exercise has been highly debated. It is believed that home-based resistance training may increase long-term adherence, as it is more flexible and convenient to the subject. Although adherence may increase, it was observed that improvements in glycaemic control were not maintained after supervised exercise is withdrawn. This might be problematic in a real world setting.