About This ProjectExercise intensity has a huge effect on how endurance training, like running, effects health. While research has shown that two or more weeks of 30 sec sprint interval training (SIT) results in large blood sugar improvements, we are unsure how the length of rest after each sprint affects the health benefits of a single session of SIT. Our research compared the effect of short and long rests during SIT on inflammation and blood sugar responses.
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What is the context of this research?
There are several ways to improve blood sugar maintenance in the body without medication. Endurance exercise, like running and cycling, improves insulin sensitivity (Si) - how responsive your cells are to insulin. It has also been shown to reduce inflammation in the body by releasing chemicals (cytokines) like IL-6 and IL-10. More recently, however, two or more weeks of intense sprint interval training taking less than 20 min, three times each week has been shown to be as effective as endurance exercise.
Many research studies have shown that just one session of medium to high intensity endurance exercise decreases inflammation by increasing IL-6 and IL-10, which in turn improves blood sugar. Currently, however, no research has shown this effect for a single session of short duration maximal sprint exercise. For example, 6 min of maximal rowing has increased IL-6, as well as run sprint training. We do not know if this short term increase improves blood sugar. Furthermore, no researchers have studied if the amount of rest taken after each sprint also impacts inflammation or blood sugar. Exercise trainers and coaches understand that shorter rests can drastically impact cardiovascular demand and hormonal response during training, which could impact cytokine release during SIT.
Despite the current interest in sprint interval training, very few researchers have provided information on the immediate (i.e., 1 – 24 hrs) response to SIT. It was valuable to compare two sprint sessions burning a similar amount of calories, but using either 4 min of rest or just 10 sec of rest after each sprint. Therefore, the purpose of this study was to compare what are called Wingate sprints (4 min rest) with a Tabata sprint sessions (10 sec rest). Our initial data indicate that IL-6 and IL-10 inflammation markers do increase, but may make insulin sensitivity worse 24 hrs after SIT.
What is the significance of this project?
The concept that exercise is medicine has gained considerable support in the last decade. It is believed that metabolic (like diabetes) and cardiovascular diseases are driven by inflammatory processes in the body and that exercise is largely anti-inflammatory. It has also been shown that overweight and obese people who engage in regular exercise are at significantly reduced risk for disease than those normal weight but sedentary individuals.
There are many unanswered questions about how exercise intensity (how hard you work) and the total calories burned influence improved health. Specifically, is there a minimum number of calories we need to burn to improve health?
This project could fill in several gaps of information regarding how a single session of sprint exercise influences blood sugar and inflammation after exercise; we know it improves these after at least two weeks. This is important because we still do not understand the mechanisms (i.e., how) by which sprint interval training improves health. It appears that both prolonged endurance and brief sprint exercise have similar effects when performed over many days or weeks, but their short-term mechanisms may be considerably different. This study would be the first to suggest a distinct mechanism following a single session sprint training with short and long rest periods. Our initial analysis of data seems to support this assumption. However, further follow-up analyses are required.
What are the goals of the project?
This research was approved by Virginia Commonwealth University's (VCU) Review Board and is part of my final doctoral work. Data collection ended in February with 13 men and 2 women. I am seeking to rerun our cytokine data for this project. My initial results showed statistically significant increases in IL-10, as well as a consistent, non-significant increase in TNF-a (increases inflammation). I also saw a significant decrease in insulin sensitivity following sprint sessions using long rest periods, though short rests also showed a smaller decrease, suggesting that sprint training has a far different short-term impact than traditional sustained endurance training. IL-6 is believed to be a stimulus for IL-10, but our data could not find any change in IL-6.
Our major goal for this study is to re-analyze all our blood samples in June (2014) and gain a more complete picture of the acute impact SIT has on inflammation and metabolic function ($3500). This study would be the first to suggest a distinct mechanism following brief sprint training. Stretch Goals I would like to meet:
1. Our initial funding did not allow for the measurement of hormones. A secondary goal would be to test for cortisol, a major anti-inflammatory hormone released during exercise $1000
2. A final goal is to raise money to cover a small stipend for my work from May until June. $1000.
Exercise has a clear dose-response benefit for countless diseases; in general, the more you exercise, the more your health improves. Understanding how high-intensity, low caloric expenditure exercise fits into the exercise dose is critically important. I have already contributed a considerable of money to this project and I need your support to complete the work!
With your support, though, I can complete my entire analysis, present my findings at the upcoming American College of Sports Medicine's World Congress on the Role of Inflammation in Exercise, Health, and Disease (already accepted), and publish this information. I am asking you to help us complete the study and meet our stretch goals to cover the research costs for additional data collection through June.
Meet the Team
Team BioI am an exercise scientist at heart. I believe that exercise is one of the most powerful treatments anyone can use to improve health, reverse disease, and transform their lives. I have been blessed with immense support and an astounding clinical research staff at the VCU Medical Center. Without their help, I could not have conducted this research. This research will add a significant piece to the exercise puzzle.
Chris Harnish, MS, CSCS, HFS
As a former elite cyclist turned triathlete, I enjoy all things active and work to promote activity in my local community as a board remember of our local Road Runners club. I have been fortunate to work with spinal cord injured persons while at the VA medical center, which helped shape my current research philosophy. In my spare time, I produce the science based Exercise & Sports Performance Podcast (ESP Podcast @ i-Tunes) and blog at www.espanswers.com.
Additional InformationThis research received clinical nursing support from the Center for Clinical and Translational Research at Virginia Commonwealth University. My prior arm crank sprint training research in persons with spinal cord injury is currently in review for publication. I am committed to identifying and understanding what are optimal training strategies for individuals.
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