Paul J asked:
…would one of these tests be ‘better’ than the other depending on the type of training/racing you will be doing? In other words, if my weakness is VO2max power and higher, and I really want to focus on this area over the upcoming season (think Cyclocross next fall) would I be better served doing the 2×8 minute test rather than the 20 minute? I’m a bit better at a longer sustained effort than the shorter, higher intensity efforts and I’m pretty certain the 20 minute test would yield a better result than the 2×8. Also, if I’m focusing on VO2max work, would the 2×8 be a better measure of my improvement in that area? Lastly, if it does make sense to use one test over another depending on the type of training you’re doing, would it then make sense to use the 20 minute test earlier in the season when you’re doing more base/tempo/threshold work and then switch to the 8 minute when it’s all about high intensity?
Chad T replied:
Nope, not overanalyzing at all. In fact, you bring up some questions that I’m sure aren’t yours alone so I’d like to publish your email and my response on our blog if you don’t mind.
Our primary intent with assessment is to get a snapshot of your fitness that’s as close to accurate as possible, so I recommend using whichever test gives you the best representation of your current capabilities whether that’s a 60min TT, a 20-30min maximal lactate steady state (MLSS), or a set of 6-8min power at VO2max (pVO2max) efforts. Each test has its own pros and cons, and I’ll elaborate on each of them briefly.
The obvious downsides to my least preferred format, the 60min time trial is that few riders can muster the motivation to push at their limit for an hour (indoors especially), pacing for an effort that long is difficult to do without a fair amount of experience, and many riders simply don’t have the endurance, muscular or pyschological, to push hard for a full hour. Due to these factors and a couple others, this format is likely to yield average power lower than a rider’s true power at LT or FTP and therefore underestimate fitness.
The 20min format is the format I prefer to use for newer riders if only due to the fact that many less experienced or new riders simply don’t have a good feel for riding at 110-112% of FTP which is what’s necessary during the short, pVO2max efforts used in the 2×8 or 2×6 format. It’s also a good format to break into manageable 5-minute segments allowing riders to subtly tweak their effort every so often based on longer periods of muscular feedback. The downside is simply that it’s a relatively long effort and pacing is once again an issue for less experienced riders. Additionally, many riders play it safe during the longer formats and end up finishing with too much gas in the tank as evidenced by a 2 or 3-minute power surge at the end of an effort that would ideally be pretty even over the entire 20 minutes, and once again, their fitness will be underestimated.
Finally, my preferred format of 2x8min efforts a la Carmichael’s field test protocol yields the greatest amount of information by demonstrating power at VO2max (aerobic capacity), sustainable power (FTP) after a 10% reduction, and aerobic fitness when comparing the 2 efforts afterward. Additionally, riders can also observe improvements in FTP and arguably as important, improvements in power at peak aerobic uptake from assessment to assessment, information that can be of particular value to different sets of riders.
And this is where your concern over assessment specificity really rings true because improvement in peak VO2 power output isn’t nearly as important for an Ironman competitor or 40km time trialist as it is for a cyclocross racer or a criterium specialist. So I guess my recommendation would hinge upon what information you hope to glean from your assessments, and I’d steer you toward that format which best mimics the demands of your events, especially considering how assessment efforts are often workouts themselves so why not work out in a manner that suits your needs.
And it’s worth mentioning that whichever format you choose, perhaps even after a bit of format experimentation, that’s the format you should follow for the entire season, or at least until your most immediate training peak. Changing formats mid-training cycle could be risky in that a new format might not express the improvement you might have seen using your existing format, if for no other reason that you’re familiar with your existing format and therefore more likely to perform more closely to your actual level of fitness.