VO2 Max Intervals

Now that I'm in the thick of my preparation for the upcoming US Ski Mountaineering National Championships, I've been giving a lot of thought to the various training intensities I need to visit during the training week. Visitors to this site have read plenty about my opinions regarding this stuff. One aspect of conditioning I've not formally covered is the topic of what most physiologists call VO2 max intervals.

Breaking up the training week or weeks, we need to address recovery, steady state, tempo, sub-threshold, threshold and maximal efforts. Throw in the odd weight training/lactate tolerance workout and you have a full program. Clearly, as I've maintained previously, the 7-day training week is not enough time to hit them all. Training periodization with micro and macro cycles is how we deal with this and makes the application of these various stressors more effective. Volumes have been written on the ways to organize the training year so I'll avoid reinventing the wheel here.

Right now, with the race looming in about a month, I'm focusing on building up my skiing volume so I can make through the race while simultaneously attempting to increase my work capacity so I can keep up with as many fast guys as possible. Now, this schedule is not ideal. Most coaches would rather me build my base first with mostly low and medium intensity efforts and leave the high-end work for later. But with a key event early in the season this just isn't possible. 

One solution would be to simply build base right up to the event and simply race at a lower intensity, results be damned. I'd then shoot for a top performance (for me) later in the season. I could do that….but I'm not going to. The Jackson event is local for me and stands to be one of the coolest events in North America. I want to be as good as I can be for it so these are the cards I'm going to play. And I don't think this is entirely unreasonable. It's not like I'm coming off the couch and into skimo training. From a cardiovascular standpoint, I've lots of base fitness to build from. One could argue that I lack the skiing-specific fitness upon which to build high intensity fitness this early. Probably true. On the other hand, my early forays into these maximum effort intervals have felt good. I think I'm ready.

Before I jump into the practical science behind these efforts I want to make one thing clear. These hurt! This is about the most unpleasant thing an endurance athlete can do in training. The effort is maximal and must be sustained longer than you really want to go. But (to conjure Yoda here) go you must and longer than you want it must be. As you'll read below, the effort and duration is needed to elicit the adaptations we're after. But because these are so hard and, thus, physiologically stressful, they must be used sparingly. I do the long ones only once a week. When fit you could probably get away with twice a week but certainly no more than that. You should shoot for 15 to 30 minutes of work duration with full recovery between. Athletes should build the total work time as the weeks pass.

Once you gain the stomach for these efforts, race pace (which is slower) becomes more reasonable. Basically, my attitude has been that if I can tolerate these five to six minute bastards I can handle anything! I've also noticed that my first effort of the session is really awful. The second and third are much better. This either reflects better pacing or some metabolic shift that makes them more tolerable. I think it's the latter. At my next session I'm going to experiment with five one-minute efforts to start with in an attempt to up-regulate my system prior to jumping into the longer pieces. I predict that this will make the transition a little more tolerable.

Now, for the science. Instead of re-writing this whole piece I'm simply going to cut and paste an exchange I had with Matthew at Restwise regarding this topic. I think it makes my point(s) perfectly.  

I think the first step is to look at the overall goal of VO2 max intervals. I am going to call upon Dr. Sue Dobson's (former head exercise physiologist for the US Ski Team) explanation and general assessment of why we do VO2 max intervals. She states that the aim is to stimulate a steady state at a maximal load. The idea is to maximize time at the appropriate load. Max stroke volume is the key to max VO2.  Max stroke volume cannot be challenged at less than max load, so time must be spent at maximum to improve max stroke volume and max VO2. It's important to look at the overall perspective of what's happening to the body when we do such intervals. Technical and neuromuscular adaptations happen simultaneously as well. Keep a strong sense of perceived effort to assist with improving pace and technical form. Monitoring your heart rate can be an asset or a liability depending on how you use this information. It's critical to focus attention on your pace and perceived exertion and utilize the heart rate monitor to provide valuable feedback. The heart rate monitor should not dictate your training, however.

It generally takes the heart rate about 1.5 to 3 minutes to stabilize. It's possible to build up to a max heart rate quicker, but excessively high lactate accumulation will occur. This is counter-productive. Therefore the general length for max VO2 intervals is between 3 and 6 minutes in length. This develops a balance between allowing the body to ramp up to achieve maximum stroke volume and not too long that you need to slow the pace to lower than a max stroke volume pace.  

This heart rate lag is also witnessed when training effort is decreased after the interval. The ramp-up of the heart rate during intervals is individual. The ramp-down of the heart rate after exercise is dependent on the individual and the individual's present fitness. A high level of fitness will allow for a more rapid recovery rate. Other variables can affect this - for example altitude and hydration. Altitude, for example, will require more recovery time between intervals.

I encourage you to keep an eye on pace and effort of each interval. The goal is to maintain the same distance each interval or possibly go further each interval. Focus on strategies that will improve your pace, yet maintain the same intensity (heart rate or lactate). For example, modify technique or cadence. Your heart in combination with the pace can provide valuable feedback as to whether the modifications improved your performance. Also watch your heart rate recovery rate between intervals. Are you fully recovering? Remember there are numerous reasons why this is changing. A decrease in recovery rate may mean an improvement in performance or the simple fact that less lactate was produced in the last interval. Less lactate could mean better biomechanics or more consistent pacing. An increase in heart rate may display inconsistent pacing or dehydration to name just a couple of possibilities.

Remember that heart rate monitoring is a means to monitor, but certainly not the "ends." There are numerous debates questioning whether muscle fatigue dictates heart rate or heart rate dictates muscle fatigue. The debates between the traditional studies by AV Hill on monitoring VO2 versus the more contemporary studies by Dr Tim Noakes on the Central Governor Theory (brain and nervous system) are on-going. The reality is that both complement one another and ONLY looking at heart rate for your training will likely stifle performance more than enhance it. However, using heart rate as a tool and keeping heart rate in context to the numerous parameters that can affect performance can enhance performance.

In short, do intervals that are 3-6 minutes in duration with complete recovery.  The pace should be such that your first interval is as fast as your last.

I think this last point is pretty simple. Being able to finish strong will be a matter of proper pacing and not over-shooting your fitness and recovery at any given session. In other words, don't do too many of these repeats too soon and get your pacing right. Remember, if you go too slow (don't kid yourself here) in an attempt at ensuring you make the splits, you'll not achieve the greatest benefit as you would going all out. It may take exploding a time or two to get it right.

For me, the key is to not sprint out of the blocks. As Dr. Dobson points out, this may drive up heart rate quickly but the acid load will also soar and it may make you unable to finish the interval. I find that starting out just a hair harder than race pace seems easy at first but after 3 minutes the monkey is definitely on my back but I finish without fading. I'm still watching every second pass but it's manageable, just barely. Have fun with these. - Brian