VO2max intervals: too much effort?

[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. 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?

 

[acoggan]

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.

What power do you maintain during the first four efforts?

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?

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.

 

[yzfrr11]

I have been doing the intervals in ascending intensity: 330's, 340's, 350's, 360's, and then the last one 375-400w. I have been really trying to "smoke" the last one.

I assume that by "smoking the last one" I am developing anaerobic capacity rather than focusing on VO2max.

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.

 

[acoggan]

I have been doing the intervals in ascending intensity: 330's, 340's, 350's, 360's, and then the last one 375-400w. I have been really trying to "smoke" the last one.

I assume that by "smoking the last one" I am developing anaerobic capacity rather than focusing on VO2max.

That's what it sounds like to me. Now whether that's better or worse in the long run is difficult to say...but *if* your specific goal is to try to raise your VO2max, I'd suggest going a *bit* harder on the first four intervals (esp. the first), so that you don't have so much left in the tank at the end. If you can still complete five, 5 min efforts fairly easily, then either add another interval or raise the power even more. (FWIW, when I'm fit my functional threshold power is also 300 W, and I'll do 6 x 5 min at 340 W. However, it sounds as if your functional threshold power isn't as close to your VO2max as mine is, and/or you have a significantly higher anaerobic capacity, because my best 5 min power in recent years is only 370 W, and that's in competition when tapered.)