by Chad Kerksick PhD January 27, 2012 3 min read
The positive effect derived from high-intensity interval work continues to amaze me, and I have been a fan of intervals for a long time. Mainly because it appeased to my anaerobic sporting interests I developed from playing hoops and such. Easily the biggest problem with this research was that it wasn’t practical for many people who go to the gym for a workout. Many people can think they would go to the gym and sprint against resistance on a cycle for 30 seconds at a time, but I’m putting my money on the fact that people won’t. This is for much of the same reason why people don’t squat heavy either, because it’s downright hard and your body barks back at you.
A study was recently published by the same research group who has published a number of previous studies using this type of exercise, but this time they dialed back the intensity of the sprint bouts a little bit but made them twice as long. The result was a 60s sprint bout that had the research participants exercising at about 60 – 70% of the power needed to perform an ‘all out’ sprint. Without performing the workout myself, it seems like the workout would be similar to running repeat 300s or 400s on a track versus sprinting for 30 seconds. The awesome aspect was that similar improvements were found using this modified workout as what was found when sprinting was required. For example, the maximal capacity of exercise completed during a cycling time trial was significantly improved. In as few of words as possible this outcome means that the exercise program significantly improved fitness. In addition to measuring fitness improvements, the authors extracted muscle samples from the legs of the research participants before and after the training and found that key markers of exercise metabolism were significantly improved. This means that key molecules which are responsible for your muscle’s ability to exercise maximally were improved which helps to explain why fitness was improved. Finally, the authors measured to what extent mitochondria growth occurred and they found that the intense exercise program significantly improved the growth of mitochondria.
What are mitochondria? They are often referred to as the powerhouses of cells. Mitochondria are responsible for much of the energy production that occurs in our cells to fuel our bodies through life, but most particularly through intense and challenging exercise. Mitochondria are closely linked to fat burning, so it’s safe to speculate that an increase in mitochondrial growth and function would result in a situation where fat burning would also increase. It should be highlighted this specific aspect was not measured in this study, but it has been measured and found to be true in other studies employing high-intensity interval training.
What’s the take-home message? Intense bouts of interval exercise that are very challenging, but don’t require superhuman effort and mental vigilance can instigate favorable changes inside exercising muscles that can improve fitness, cell metabolism and likely go on to result in a situation where fat burning is improved as well. This being said, it’s likely the actual effort produced from the research participants in this challenging study will be much greater than what you are able to produce at first. However, consistent effort will improve your fitness and over time if you work hard at intervals the physical and mental benefits you will achieve will be worth it.