One of my favorite types of training is interval training. Interval training is when you mix high intensity work with low intensity work. This method is hardly a secret technique anymore but is often overlooked as another great tool for the toolbox.
During high intensity effort, our bodies use energy stored in our muscles. During these short bursts of activity lactic acid is produced. This lactic acid in turn creates a burning sensation in our muscles letting our bodies know we are reaching failure. During this period our muscles are also getting starved of oxygen. When we switch to low intensity tasks our heart and lungs work together to recover oxygen and remove excess lactic acid from our muscles. Our bodies adapt from the stress of the intense interval portion by building new capillaries and in turn improving oxygen delivery. This improves our muscle’s tolerance to the upsurge of lactate and also strengthens our cardiovascular system resulting in improved performance.
In the study Two weeks of high-intensity aerobic interval training increases the capacity for fat oxidation during exercise in women, published in the Journal of Applied Physiology, Dr. Jason Talanian found that after just two weeks of interval training, 75% of participants doubled their endurance before getting exhausted. Further, that bursts of high intensity exercise not only improve cardiovascular fitness but also the body’s ability to burn fat faster. The amount of fat burned in an hour of continuous moderate cycling increased by 36% and cardiovascular fitness increased by 13%. Although this study was conducted with women the study provides precedent to suggest that aerobic and mitochondrial enzyme adaptation in well-trained individuals would be similar across both sexes.
Further studies such as Mark Rakobowchuk’s Sprint interval and traditional endurance training induce similar improvements in peripheral arterial stiffness and flow-mediated dilation in healthy humans suggest that short bursts of high intensity sprints can improve the function and structure of our blood vessels, in particular arteries that deliver blood to our muscles and heart. The research compared individuals who completed interval training using 30-second “all-out” sprints three days a week to a group who completed between 40 and 60 minutes of moderate-intensity cycling five days a week. The results showed that six weeks of intense sprint interval exercise training improved the structure and function of arteries in a comparable manner to that of extended endurance training, making interval training a “time-efficient strategy to elicit improvements in peripheral vascular structure”.
For runners with limited time to train (like myself), interval training isn’t just an economical way to increase your aerobic threshold …but running speed as well. Intuitively, we can train at higher speeds for shorter distances so interval training gives us the opportunity to test speeds outside of our comfort zone. However, because we are training in and out of anaerobic and aerobic conditions, one should also approach this type of training with caution and make sure that they are in a condition to put this type of stress on their body. Serious interval training is not for anyone that remotely thinks they might have biological system deficiencies …but in healthy individuals it can be a great way to maximize results in a minimum amount of time.