Exercise as it relates to Disease/High-intensity resistance training to improve cardiovascular health in individuals with type 2 diabetes

Source article: De Sousa RA, Azevedo LM, Improta-Caria A, Freitas DA, Leite HR, Pardono E. Type 2 diabetes individuals improve C-reactive protein levels after high-intensity weight lift training. Science & Sports. 2021 Jun 1;36(3):225-31.

Background
The prevalence of cardiovascular diseases (CVD) in individuals with type 2 diabetes (T2D) has been well documented over the years,. Lifestyle interventions such as healthy diet, physical exercise and reducing sedentary activities are often considered as the primary methods to lower CVD risks. In the past, traditional aerobic exercise and Moderate Intensity Continuous Training (MICT) are the preferred training modalities for CVD prevention. However, recent studies have suggested that the use of High Intensity Interval Training (HIIT) may reap superior benefits.

Up to this day, the focus of such studies has been on traditional HIIT protocols which are mainly characterised by bouts of explosive sprints, jumps, or circuit-based bodyweight works. Nevertheless, there is limited evidence on the efficacy of High Intensity Weightlifting (WLT) as an alternative training protocol to reduce CVD risks in T2D population.

Why it matters?
Since the effectiveness of physical exercise in countering CVD heavily depends on continuous adherence, motivation should be one of the main factors to consider in designing an exercise program. Therefore, a training modality is ideally chosen based on each individuals' preference to ensure higher motivation and adherence rate. As such, there is a need to explore other training types beside HIIT or traditional aerobic to provide more options for the population to choose from.

Therefore, through the use of a Randomized Control Trial (RCT), this study aims to explore the potential benefits that High Intensity Weightlifting might offer in relation to reducing CVD risk in T2D population. To assess any metabolic changes, the High Sensitivity C-Reactive Protein (Hs-CRP) test is used.

Where is the research from?
The study was published in 2021 as an original research paper in volume 36, issue 4 of Science & Sports, which is an open access peer-reviewed journal in the area of sports and exercise physiology. The experiment was conducted by researchers from 4 universities across Brazil, and was headed by Dr. Ricardo Augusto Leoni De Sousa, who has published 36 research papers and currently undertaking postdoctoral research in the Federal University of the Valleys of Jequitinhonha and Mucuri. The rest of the team consists of Ph.D students in relevant fields with 8 to 27 publications each, and can be considered experienced and reliable.

What kind of research was this?
The study is a randomized controlled trial with sample consisted of 40 males who were divided into 4 groups: Healthy Individuals (Control), Individuals with T2D (D), Healthy Individuals with training (HT) and T2D Individuals with training (DT). Control and D groups were not subjected to the high-intensity WLT protocol prescribed to the HT and DT groups. The test subjects are all aged between 45-65 years old and has not exercised regularly within the past 6 months. The control group did not have diabetes or any pathology. In the diabetic groups, the inclusion criteria require the participants to have a clinical diagnosis of T2D for a minimum of 6 months, having no major or micro complications, and are fully capable of performing regular physical activity.

Methods
Prior to the program’s commencement, a period of WLT habituation is prescribed to the HT and DT groups to reduce the risk of injury by stimulating muscular and neural adaptations in the participants. After 1 week, a One Maximum Repetition Test (1RM) is performed to test baseline strength and calculate the intensity of the training load. 2 days before the program begins, blood samples were collected by the median cubital vein (2 mL/individual) to assess the initial level of high sensitivity CRP.

The High-intensity WLT protocol is a 4-week exercise program consisted of 6 exercises performed in this specific order: Bench Press, Triceps Pulley, Rowing Machine, Barbell Curl, Lateral Raise with dumbbells, and Barbell Squat. The sessions are conducted 3 times weekly, with alternating days to allow rest and recovery. All exercise variations are performed for 3 sets of 8 repetitions each, with 80% of 1RM intensity. Each repetition is performed in a controlled motion, with emphasis on both the eccentric and concentric phase of the lift, which amounts to 2 seconds each. The resting time between sets was 1 minute to keep the elevated levels of heart rate.

On the final week, 48 hours after the last session of the program, any changes in strength were measured through the 1RM test. 2 days afterward, the hs-CRP test is again performed on each participant to assess any cardiometabolic changes.

Results
The research found that the DT group had a significant reduction in hs-CRP level after completing the program. However, the same effect was not observed in the HT group (fig.1). Moreover, the DT group also exhibited a greater progress in body mass and blood glucose when compared to the HT group.

Reflecting on the changes in hs-CRP levels, the author concluded that high intensity WLT is an effective training method to reduce the risk of CVD development in middle aged individuals with T2D. This supports the finding from another recent study in similar field, in which 4 weeks of moderate-intensity WLT is reported to yield significant reduction in tumor necrosis factor-alpha (TNF-α), another biomarker of inflammation. The combined data from both studies serves as powerful evidence of the protective effects that WLT may provide to counter the prevalence of CVD in T2D population.

Nevertheless, since these changes were not replicated in the healthy population, the benefits of high intensity WLT towards CVD prevention may be limited to individuals with T2D. The general population might reap more benefits via the traditional HIIT or MICT, which have been thoroughly studied over the years.

Conclusion
In this study, high intensity WLT has been proven to reduce the level of hs-CRP, a critical biomarker of inflammation which are commonly used to detect CVD risk even in seemingly healthy individual. Moreover, this result occurred only after a relatively brief intervention, indicating that WLT might have more untapped potential in the cardiometabolic context and should be examined further. Overall, high intensity WLT should be considered as an option in designing physical exercise intervention to reduce CVD risk, especially in middle-aged individuals with T2D.

Nevertheless, there are a few limitations to this experiment:

1.      Dietary intake is not taken into consideration during the experimentation.

It is evident that the choice of daily food plays a critical role in the cardiometabolic function of individuals with T2D. When this variable is not properly regulated in the experiment, it may pose a threat as a confounding factor to the validity of the results.

2.      The duration of the experiment might be too short to conclude if the intervention had any lasting impact on the hs-CRP level.

The hs-CRP test measures a slight, but prolonged elevation in the levels of plasma CRP to assess a chronic inflammation in the body. In common practice, these tests are to be taken 2 weeks apart, and the mean level is calculated to determine abnormality. However, in the experiment, the CRP levels were only measured 2 days before and after the training program. To conclude whether the program had any lasting changes in CRP level, there is a need to add another 2 weeks to the exercise intervention.

Practical advice
Weightlifting, when performed at high intensity, is a great tool for individuals with Type 2 Diabetes to improve their cardiovascular health. Moreover, it also provides benefits in terms of muscular strength and hypertrophy, blood glucose, and hypotensive effects. A general breakdown of the training protocol is:

1.      Volume: 3 days/week, consisting of 6 exercise variation/training day, which alternates between compound and isolation exercises.

2.      Sets, Repetitions, and intensity: 3 sets of 8 repetitions, 80% of 1 RM. Emphasis on proper form via controlled concentric and eccentric phases.

3.      Rest Period: 1 minute between sets

Further information/resources

 * CRP:    https://labtestsonline.org/tests/c-reactive-protein-crp
 * Hs-CRP:    https://labtestsonline.org/tests/high-sensitivity-c-reactive-protein-hs-crp
 * CRP    in CVD treatment: https://www.nature.com/articles/nature04672?free=2
 * Diabetes    & CVD: https://www.heartfoundation.org.au/heart-health-education/diabetes-and-heart-disease
 * Diabetes    & CVD: https://www.cdc.gov/diabetes/library/features/diabetes-and-heart.html
 * Resistance    Training & Blood Pressure: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4270306/