Tuesday, May 21, 2013

Intervals: Why Do We Use Them?

By Stephen McGregor, PhD, PCG Master Coach


When I was a wee lad, I played soccer in high school. My coach at the time was a conditioning freak and used to make us run intervals. A lot. We did Indian runs or suicides or half-mile intervals, etc. We ran as hard as we could until we thought we were going to puke. Between drills my teammates and I cursed the coach and asked ourselves, “Why are we doing these?” We never really got a satisfactory answer, so we just kept on doing what we were told.

Later I became interested in cycling, and when I learned about the training for this sport, to my horror I found that many coaches recommended intervals in cycling, as well. Again I asked myself, “Why are we doing these?”

Most coaches prescribe intervals, and many athletes perform intervals, but it’s often not clear why. In particular, the athlete may not be aware of the intended objective of the interval training and may just be “doing what I’m told.” Is the goal of performing intervals simply to make the athlete tougher and more resilient? Are they simply being done to mimic the high-intensity repeated efforts of racing, or are there specific physiological adaptations sought after by using intervals in training? Is there more to performing intervals than just being able to go “as hard as you can” for two, five, or ten minutes? Are some intervals better than others (i.e., is there a reason to perform two-minute intervals over ten-minute intervals)?

This may seem like a lot of questions, but they should be addressed before a coach or an athlete embarks on a period of interval training. By addressing the ultimate objective of the interval training approach, the athlete may be more likely to give everything required in the efforts. Further, consideration of the intervals being used and how they relate to racing objectives may help eliminate potentially irrelevant training approaches.

Exercise physiology tells us there are three primary principles of training: specificity, overload, and reversibility. Intervals can be used to address the first principle by mimicking the demands of a particular event. This may be the most common reason most athletes perform intervals. For example, if an athlete is training for the pursuit on the track and it’s anticipated that the event will require a five-minute all-out effort, in preparation the athlete may perform five-min intervals. In this case, though, the training is being used for a very tangible purpose. The athlete can clearly see that he’ll need to go as hard as he can for five minutes, so therefore he will train as hard as he can for five minutes.

The second principle, overload, can also be addressed through the use of intervals. If an athlete needs to perform sustainable efforts of ten minutes within the context of her event, she can perform efforts in a progressive overload fashion that builds from five, six, seven, and up to ten minutes or more in duration. Using intervals, progressive overload of duration (or even power if using power meter) can be applied in a very specific manner.

Finally, the third principle can be addressed by not performing intervals. To paraphrase one of my graduate professors, use it or lose it, baby!

Another less tangible way to use intervals is to not necessarily address specific effort durations of an upcoming event, but within the larger context of the overall training program target specific physiological adaptations that will result in improved performance at a later date. In this, I mean that certain intervals can be used to specifically target adaptations resulting in improved VO2max, whereas others may be more likely to elicit adaptations to the lactate threshold. Moreover, certain intervals are effective at raising one’s anaerobic capacity or neuromuscular fitness. As we all should be aware, the long-term goals of most competitive cyclists should be to raise their VO2max, LT power, and, for some disciplines, anaerobic capacity and neuromuscular fitness. Once these objectives have been attained, the specific needs of a given event may be targeted.

It is not simply the duration of a given interval that results in such adaptations, but also the manner in which the interval is performed at a given intensity. In other words, an interval may not need to be performed “as hard as you can” to target the desired adaptation. It may be better to perform at a given percentage of VO2max for a given duration (neither of which may be maximal), which induces an overload that’s not unduly stressful. Also, depending on how an interval is performed for a given duration—say, three minutes—the adaptation may be more anaerobic or aerobic, and vice versa; not all three-minute intervals are created equal.

Therefore, knowledge of the physiological responses of various interval approaches will provide coaches and athletes with information to most effectively use intervals to target not only specific needs of a given event, but also the physiological adaptations that will ultimately result in improvement as a cyclist. Athletes should not be asking themselves, “Why am I doing these?” but rather stating emphatically, “I am using these intervals to improve my _________.”

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