Exercise as it relates to Disease/Impact of a long term exercise intervention on participants with type 2 diabetes

This is an analysis of the journal article Effect of regular exercise training on changes in HbA1c, BMI and VO2 max among patients with type 2 diabetes mellitus: an 8-year trial by Farzad Najafipour et al.

What is the background to this research?[edit | edit source]
Type 2 diabetes is a chronic disease that occurs when blood glucose levels are chronically too high. In the past 30 years, the incidence of type 2 diabetes has increased in countries all around the world, regardless of income level. Data from 2012 shows that 31.1 percent of the global population is physically inactive, and that inactivity levels rise as age increases. Obesity and inactivity are linked to insulin resistance, and so an exercise intervention was chosen to examine the effects of a long term program on the health of diabetes patients. This paper aims to asses how biological indicators of Hba1c, BMI and Vo2 max in patients presenting with type 2 diabetes respond to an eight year aerobic exercise trial. Though there are many studies showing the positive effects of an exercise intervention, most only track patients from 12 weeks up to 1 year, and thus the long term effects of sustained exercise is unclear. This study fills the gap in the research and follows patients on an eight year exercise journey.

Where is the research from?[edit | edit source]
Location

The Study was conducted in Iran, with the participants being chosen from from 'Endocrine and Metabolic Clinics, Tabriz University of Medical Sciences, Iran'.

Journal + Authors

The study was published in the BMJ Open Diabetes Research & Care which is an open access journal which publishes content related to diabetes mellitus type 1 and 2 and treatment.

Farzad Najafipour, Majid Mobasseri, Abbas Yavari and Akbar Aliasgarzadeh were the four contributors conducting the research over the eight year trial. They all work for the Tabriz University of Medical Sciences, and have an extensive track record within diabetes research with many papers published, including but not limited to:

- Prevalence and incidence of type 1 diabetes in the world: a systematic review and meta-analysis (cited by 228 papers)

- Insulin controls inflammation and metabolic endotoxemia in women with type 2 diabetes mellitus: a randomized-controlled clinical trial (cited by 168 papers)

What kind of research was this?[edit | edit source]
Researchers for this study conducted a quasi-experimental trial with pre-test post-test design.

What did the research involve?[edit | edit source]
The participants in the experimental group undertook three aerobic training sessions per week, lasting approximately 60 - 80 minutes at 50 - 80% of Vo2 max. The training largely consisted of treadmill, elliptical or bicycle ergometers for 40 - 50 minutes, with time either side for warm up and cool down. Vo2 max was assessed before and after trial using a submaximal one mile track walk. This will not give a completely reliable vo2 max score, however given that the mean age of the participants was over 57 years old and therefore having greater risk factors ascosiated with vigorous exercise, a submax test is a good approach.

Although this study was unique in its approach to evaluate patients over a long time period (>8 years), it failed to take into account any physical activity undertaken by patients in their own time, separate from the study. This includes; structured training sessions, commutes to work (walking/riding vs vehicle) and occupation. An experimental study by Balducci S et al , took into account activity/conditioning undertaken by participants outside of structured exercise required, with results showing that cardiovascular risk factors were significantly lowered in participants that did more conditioning as well as structured exercise.

The study did make the criteria for inclusion having a 'previous sedentary lifestyle', but was not specific on what qualified as sedentary. For example, total sitting time/ expending 1-1.5 met/s or not meeting total physical activity guidelines of 150minutes of moderate physical activity per week . This distinction matters for the participants in the control group, who were instructed to maintain their current lifestyle.

What were the basic results?[edit | edit source]
After the eight year trial, all three indicators - Hba1c, BMI and Vo2 max were all greatly improved in the experimental group. Hba1c markers showed a continual decrease in each follow up, with the experimental group's levels decreasing from 8.33% to 6.49% (diff of 1.84%).

The Vo2 max levels showed a post trial difference of 31.92 to 19.49 (+12.43) between the experimental and control groups respectively. This seems to be a big difference, however the pre vo2 max levels from either group were not shown, possibly indicating that the participants in the experimental group were already fitter than those in the control group. For this reason, Vo2 max findings may be over-emphasised.

What conclusions can we take from this research?[edit | edit source]
The results from this eight year trial show that type 2 diabetes mellitus does not have to be a progressive disease that requires increasing amounts of medication to control. The mean age of the participants was 57.2 at the start of the trial. After eight years many of those patients would be at or approaching retirement age, where people in general start to become more sedentary and have increased risk for cardiovascular diseases that can cause stroke, heart attack etc. Exercising at a minimum for 3 times per week or >150m/w can decrease risk factors for diabetes in older adults and improve overall cardiovascular fitness (Vo2max), essentially reversing markers of type 2 diabetes at any age.

The reduction in Hba1c levels in response to physical activity is consistent throughout the available research. One example includes

- Associations between physical fitness and HbA1c in type 2 diabetes mellitus, by J Larose et al ,

In regards to BMI, findings from other research are more contentious, with Krousel-Wood M et al showing a decrease in BMI and Boulé NG et al, showing no statistically significant difference post study. These varied findings are largely a result in the length of the studies undertaken, with short term studies (<1year) not long enough to produce meaningful weight loss.

The eight year trial being analysed focused solely on aerobic training. A trial by Sigal RJ et al showed that combined aerobic and resistance exercise is more effective at reducing Hba1c levels than either aerobic or resistance training alone.

Practical advice[edit | edit source]
Physical Activity Recommendations

This study aligns with specific recommendations from the 'World Health Organisations' stance on physical activity. This includes:

- 150 - 300 minutes of moderate-intensity aerobic physical activity

- Reducing the amount of time being sedentary (1-1.5 met's)

- 75–150 minutes of vigorous-intensity aerobic physical activity

Further information/resources[edit | edit source]
- World Health organisation - provides a basic overview of diabetes, its causes symptoms and treatments - https://www.who.int/health-topics/diabetes#tab=tab_3

- Epidemiology of Type 2 Diabetes – Global Burden of Disease and Forecasted Trends - this paper assesses the prevalence of type 2 diabetes globally and the burden it places on society - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7310804/