As long as you can cope with the additional stress then that’s fine.
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Uh, yes, there is.
I have a related question. I have been doing an hour of Z2 on my “off” days. How effective is this going to be compared to doing an hour of Z2 after my TR interval workouts?
It’s not good to have generated lactates on Z2 rides because than your body uses them as fuel also and not just fats
Can you elaborate on that then?
I’m really sorry to say that I haven’t been able to put this into practice yet. All talk and no action so far.
The primary adaptation to endurance training is an increase in total mitochondrial volume. There are, however, also subtle changes in the characteristics of the mitochondria, such that they become more like those of the heart (a mitochondrion is not a mitochondrion is not a mitochondrion). The effects of training intensity on these secondary changes in mitochondrial “quality” are still uncertain. In terms of the overall volume, however, training intensity clearly plays an important role (as does duration).
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Many thanks! 
Haven’t done quite what you describe. Do fairly regularly throw in some epic Z2 weekends. As luck would have it my parents, my sister and my in-laws all live 80-120 miles away in different directions but which all have nice cycling roads to get to. Quite often if we’re visiting for the weekend I take Friday afternoon off work to cycle down there, do an easy recovery ride on Saturday, then ride home again Sunday afternoon. So something like 10-14 hours of Z2 across 3 days. Have always found those weekends really beneficial and not too disruptive. Have to make Monday a rest or very easy day, but if I’ve stuck to true Z2 and refueled properly during and after the rides I’m usually fine training normally by Tuesday.
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The Time-Crunched Cyclist covers the science behind this, and the simplistic way to say this is that various studies have shown sprint interval training results in similar adaptations as traditional endurance training.
If you don’t have the book, here is similar info from a blog post on the website of the authors of The Time-Crunched Cyclist
“Researchers like Burgomaster, Gibala, and other have shown that these same short, high-intensity intervals improve oxidation of fat and carbohydrate by mitochondria to a similar degree as traditional, lower-intensity endurance training, but in a fraction of the training time.”
Source: Busting the Myth of Winter Aerobic Base Training - CTS
One of the goals of z2 training is to improve aerobic energy production, and you can get many of the same results by doing sprint interval training. Or as you put it, mix the best of both worlds!
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I assumed he was alluding to David Bishop’s work.
Dunno, that name doesn’t ring a bell so I defer to you. My tendency is to focus on the fundamental principles (e.g. pairing of endurance and short sprints during certain portions of base) and less on the specific research, authors. etc.
The problem with that approach is that now you are at the mercy of how others interpret (or misinterpret or overinterpret) the data.
I don’t know if this helps, but I have always (since starting TR in April) skipped the Wednesday 30-60 minute Z1 “recovery ride” and instead I have done a 2 hr Z2 ride with some engineering buddies (for them it is a tough ride, so it works out for all of us) and it has never affected my ability to do my Thursday HIIT workout. For the last month, I have incorporated a 10 minute Z2 interval after my warmup, with 5 min rest before my HIIT intervals and added 10-20 min Z2 at the end. My fitness has increased this month amazingly…and friends are asking me what the heck I’ve been doing…so it works really well for me. A few months ago, I did a full week of nothing but Z2 in between blocks, and I told my friend that my legs had never felt better. Do it!
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Because there is only one correct interpretation? Focusing on fundamental principles allows for individualization, because not everyone responds the same way to training.
“(e.g. pairing of endurance and short sprints during certain portions of base)”
isn’t a fundamental principle. You only think it is because somebody else told somebody else who told you that it was. See the problem?
That was my conclusion. I accept PayPal.
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Probably you know this already but wanted to add this study as it seems not to be mentioned in the trainright article:
https://physoc.onlinelibrary.wiley.com/doi/full/10.14814/phy2.12864
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You really should read some of David Bishop’s work. One of the points he makes is changes in signaling factors like PGC1a aren’t necessarily predictive of changes in muscle mitochondrial content.
ETA: Here you go.
Thank you, haven’t seen that one!
interesting and I get the gist, but a hard read for someone without exercise physiology background.