In case you were curious.

by Dr. Stephen Cheung, Ph.D.

In both 2005 and 2006, intriguing studies emerged that high intensity interval training can be equally effective as traditional endurance-based training in improving aerobic capacity. With the time for training getting short, let’s take a look at the latest studies and evidence…

Base Camp
The concept of base training is absolutely engrained within the sport of cycling. From the early eras of cycling through to today, base training for the pros involve thousands of kilometers of “long steady distance” ridden at low to moderate intensity. Indeed, one school of thought holds that you should absolutely avoid any effort beyond a low-intensity at the risk of jeopardizing weeks if not months of training.

The physiological and sport science theory behind this dominance of low/moderate endurance efforts during base training is sound when viewed from the surface. The training concept of specificity implies that the best way to train for cycling is to ride your bike, and that constant repetition of the cycling motion is what will enable optimal neuromuscular, cardiovascular, and metabolic adaptations of the critical cycling muscles and the body as a whole.

The metabolic pathways of the body would also suggest a strong justification for prolonged endurance base training. While linked, the anaerobic and aerobic pathways have a lot of fundamental differences. The anaerobic (glycolytic) pathway relies on carbohydrates only and does not require oxygen, taking place in the main cell body. In contrast, the aerobic pathway, while a continuation of the glycolytic pathway, takes place within the specialized mitochondria within cells, requires oxygen and can utilize fats and proteins also. Again within the concept of specificity, it is somewhat hard to imagine how stressing high intensity efforts may translate to optimal development of the aerobic metabolic pathways.

The Best of Both Worlds?
Yet as highlighted in previous Toolbox articles during both 2005 and 2006, scientists are finding that previous consensus may not really hold, and that the body is a lot more adaptable to training than previous assumed. In studies coming from Martin Gibala’s lab at McMaster University in Canada, Burgomaster et al. (2005) demonstrated that six sessions over 14 days, each consisting of 4-7 supramaximal intensity (Wingate) sprints of 30 s, was successful in improving the VO2peak of relatively untrained subjects and also time to exhaustion at a constant level of 80% max power output.

This initial study was followed up by Gibala et al. (2006), which directly compared this high intensity training regimen (2.5 h total training time) to a more traditional endurance-based (10.5 h of 60-65% VO2peak) training. It’s important to keep in mind that the difference in total work performed was huge, 630 versus 6500 kJ! This second study demonstrated that the two training programs provided similar performance improvements. Not only that, in both of these studies, the concentrations of key enzymes in the aerobic metabolic pathway increased with high intensity training, and at similar rates as with endurance training. The same similar improvement was also found in the level of muscle glycogen, another key determinant of aerobic endurance. These cellular and biochemical changes show that the aerobic performance changes are not simply flukes or artifacts of testing.

On the Road
The work from McMaster has important implications for cyclists. Especially with the decreased daylight and extreme cold in Northern Hemisphere regions during the off-season, it can be very difficult putting in the long bike time required for traditional aerobic base training. The prospect of prolonged steady efforts on the trainer is also anathema to many. Therefore, the judicious use of high-intensity workouts during the offseason will most likely NOT damage or ruin your fitness. Indeed, it may help to not only maintain but to increase your aerobic capacity in the process. See my article summarizing many studies on the benefits of high-intensity efforts during the offseason.

The key as always is moderation. I am certainly not advocating that your only training consists of high-intensity efforts. First off, the Wingate sprints are extremely tough and demanding, with a high risk of losing one’s cookies when done in the lab, especially back-to-back ones. The second is that we have a lot more research to do to truly understand the nature of adaptations to training. Scientifically, we also need more work in translating and adapting the actual lab-based training protocols into real-life training with athletes.

However, I feel that it is clear that aerobic adaptations can be achieved in more than one way, and that high intensity efforts can be incorporated even into training phases primarily emphasizing aerobic adaptations.

The Bigger Picture
Lots of work is required to further understand the crossover between high intensity efforts and aerobic adaptations. I’ve noted it before in my previous Toolbox articles on this topic, but the implications for these studies are potentially revolutionary for both sport science, physical activity recommendations, and also rehab medicine.

This was highlighted by a major symposium organized by Gibala at the annual conference of the Canadian Society for Exercise Physiology this past November. One of the previous hesitations about the practicality of such a training program is the clinical risk of such training for relatively sedentary populations. However, Darren Warburton in Vancouver has been spearheading the use of modified versions of high intensity training programs for cardiac rehab patients with success. Similar applications may be found for many rehab medicine situations, from post-spinal cord injury recovery to cancer rehab.

Reference
Burgomaster KA, Huges SC, Heigenhauser GJ, Bradwell SN, Gibala MJ. Six sessions of sprint interval training increases muscle oxidative potential and cycle endurance capacity in humans, J Appl Physiol 98:1985-90, 2005.

Gibala MJ, Little JP, van Essen M, Wilkin GP, Burgomaster KA, Safdar A, Raha S, Tarnopolsky MA. Short-term sprint interval versus traditional endurance training: similar initial adaptations in human skeletal muscle and exercise performance. J Physiol 575:901-911, 2006.