As you all know, Holly Brooks is a fellow Birkie Ambassador. She is taking on the Marathon circuit, and I have no doubt she will do amazing things and make it look easy. Recently on Fasterskier, Brooks gave a rundown of a Marathon prep interval session she does. Click on the link for a more detailed overview, but in a sentence the workout consists of an easy warmup, a long period of threshold (L3, or sustainable) pace, and a cool down. Everyone does intervals in some form to prepare for big ski races, but what’s the purpose? For this week’s Birkie Countdown I’m going to take a look at why we do intensity training and what the physiological benefits are. Also note that I am not a scientist, nor do I claim to be. In fact I was a government major at Dartmouth. This is other people’s science, and just how I understood it–see the links at the bottom for the full articles!
Exact definitions of intensity training vary among scholarly articles. One article defines interval training as “repeated bouts of exercise lasting ~1 to 8 min and eliciting an oxygen demand equal to ~90 to 100 % of VO2max, separated by rest periods of 1 to 5 min” 1. In a further article, Seiler goes on to redefine intensity training using millimoles of lactate produced. High intensity training is any training where the millimoles of lactate produced is greater than 42.
The two most important “whens” of intensity training: Intensity training is beneficial when you are an experienced and established athlete with some base of training AND when it is done approximately 2 times per week. In Seiler’s literature review, he establishes the “80-20” low-intensity/high-intensity ratio. Further, periodization can be a beneficial for established endurance athletes. Periodization indicates a time with an altered ratio (less volume, but increased intensity), and may have minor benefits. Periodization is often associated with polarization, which represents a swing (for example a greater emphasis on high intensity training and a lesser volume of low intensity training). Overall, the literature seems to suggest that anything over the 80/20 ratio…for example 70/30 leads to “equivocal at best” results2
But what is the benefit of that 20%? The scholarly consensus stipulates that in experienced athletes the best way to increase peak oxygen uptake (VO2 max) is through high intensity training3. In the most basic sense, your VO2 max is how efficient you are at utilizing oxygen in your muscles. By performing interval sessions at a high level of intensity, an individual “trains” their body to become more efficient at pushing out lactic acid and increasing oxygen efficiency (upping the VO2 max number). Intervals are a practice in adaptation. The body is an amazing thing.
Brooks provided a great example of a high intensity session targeted at distance events. Here’s another suggestion, and a common workout for pre-race season and tune-ups. Warm-up for 20 minutes, with a 4 minute threshold block at the end. Then do a set of 4 by 4 minute intervals, with equal recovery and on time. These should be done at L4 (or at your VO2 max…really hard), and preferably going faster each set. Wrap up with a 20 minute cool down, and be sure to refuel after! I like 4 by 4s a lot, mostly because it is a short and sweet session that can leave you feeling fast, fit, but also completely exhausted.
For more detailed information on studies that look at interval training check these out…really interesting!