VO2max intervals: too much effort?

Originally Posted by yzfrr11

My FTP is around 300w in the off-season, which puts level 5 at 318-360w. It has been fairly easy for me to push 375-400w for 5min during my last interval out of 5.

Originally Posted by yzfrr11

Is this counterproductive if my goal is to target VO2max developement? Or does going anaerobic to this degree make it more difficult to recover, with little added benefit to VO2max?

Originally Posted by acoggan

What power do you maintain during the first four efforts?



I view the goal of level 5 intervals as being to repeatedly push your cardiac output*, and hence VO2, close to their maximum for several minutes at a time. To achieve this goal generally means exercising continuously at a power that also brings your heart rate close to maximum. If you are already working that hard during the first four efforts, then I don't think "kicking" harder during the last interval is likely to help your aerobic fitness significantly more than if you simply did the last effort at the same intensity. It may, though, help boost your anaerobic capacity a bit - but then the question becomes, do you want to be doing that right now, and if so, is this the best way to do it? (I'm not saying it isn't, just saying those are the questions you need to ask yourself.) OTOH, if your threshold is relatively low compared to your VO2max, then it might be that you're not working hard enough during the first four efforts, which then enables you to significantly crank up the power on the last one. If that's the case, then 1) your heart rate probably also isn't as high as expected during the first four efforts, but also 2) you might benefit focussing more on trying to raise your threshold power via longer efforts vs. trying to raise your VO2max.

In addition to looking at heart rate (which generally should be w/in 5-10 beats/min of maximum at the end of each interval), you can also look at your normalized power for the entire set of intervals (work + rest periods combined) - if this is significantly less than your functional threshold power, then that suggests that you may be dogging it a bit. Alternatively, you could simply try raising the power of the first four efforts to what you have been averaging for all five - if you can still significantly increase your power during the last interval, that again would suggest that you haven't been working as hard as you could/should.

*The reason that I emphasize cardiac output here is because I believe that, and not heart rate, is the probably determining factor in whether or not significant cardiac adaptations result due to such training. IOW, simply training at a high heart rate, e.g., as a result of thermal stress, exercise with a small muscle mass, cardiac and VO2 "drift", etc., probably isn't enough.