L5 rest intervals - Page 2

I know that the prevailing wisdom on these boards for VO2max workouts are sets of 5X5 intervals, but I was wondering how/why that number X duration was determined? I've searched, but haven't been able to find an answer. I ask b/c I've seemed to have good results doing 4X3 at about 113% FTP with 2 minutes rest or 4X4 at about 110% FTP with 3 minutes rest.

Steering things back to topic:

The workout that you described appears to be somewhat of a compromise between a VO2max workout and an SST/Threshold workout. As you noted, the goal of that particular protocol is to mimic a situation you are likely to encounter during competition rather than specifically stressing a particular physiological ability. It's impossible to say whether it's better than another workout, as its goal is slightly different.

Most folks use shorter rests during their VO2max workouts because they are resting at a much lower intensity. Resting at a higher intensity frankly means that you'll need a longer rest before you can get back up to the higher power again. The advantage to shorter rests is that the physiological processes drop less during the rest, and subsequently take less time to get back up near VO2max. Your workout uses longer rests, but ensures that the processes won't drop far by keeping the intensity higher between intervals. Folks using lower/shorter rests are probably doing 5-6 intervals, whereas you're doing 4, so they probably have more VO2max focus and you have some SST mixed in. So..... I wouldn't say one is better than the other, they're just aimed slightly differently.

I use a 4:3 work:rest ratio while shooting for 6 intervals at ~115%, also with good results.

I don't know if I'd call it prevailing wisdom. Longer rests mean that the intervals also need to be longer (ie, at least ~5 min) to ensure that the body sustains work near VO2max. Shorter rests mean that the intervals can be shorter while spending the same actual time near VO2max. Many folks do 5x5 (25 min of work), while others do 6x4 (24 min of work). Really, very little practical difference between the 2 routines.

That's ALL that really matters, my friend. You get an adaptation response with the duration and frequency you're using, for others it takes more duration at L5. Go with what you know.
People use that protocol (5x5) because they've probably read about a successful study on the net using same. I've read a number of studies successfully using a shorter protocol. No one-size-fits-all with this stuff...

My pet theory is that improvements in VO2max pertain to the frequency/degree with which you attain/approach maximal cardiac output. It's just a theory, though.

Energizer bunny style racing?

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