The Goldilocks Zone for Exercise: Not Too Little, Not Too Much

An emerging body of evidence indicates U-shaped or reverse J-shaped curves whereby low doses and moderate doses of PA significantly reduce long-term risks for both total mortality and CV mortality, however, at very high doses of chronic strenuous exercise much of the protection against early mortality and CV disease is lost. The optimal dose, or what we term ‘Goldilocks Zone,’ of PA may be: at least 150 minutes per week of moderate-intensity aerobic exercise or 75 minutes per week of vigorous-intensity aerobic activity, but not more than four to five cumulative hours per week of vigorous (heart-pounding, sweatproducing) exercise, especially for those over 45 years of age. It is also important to take at least one day per week off from vigorous exercise.


Thanks for posting. I gave it a quick skim. Interesting read. I’ll repeat my story again. Did a lot (for me) of high intensity from 2015-2019, I’d get on the bike and my HR would jump up almost immediately. Started to get concerned about a-fib, and also wondered why my resting heart rate wasn’t decreasing. Switched to mostly endurance riding (~6 hours/week( and RHR has dropped 12-14bpm and power curve went up. Wish someone would have convinced me sooner. I’m sold on lots of easy with a little fast/hard.


I’d like to see a more quantitative definition than heart pounding, sweat producing. I can sweat just walking but I’m guessing that’s not what they’re talking about. Do my Z2 rides count as vigorous? Or are we talking sweetspot and above?

Z2 is hardly heartpounding, isn‘t it?

I read some paragraphs if the study, the used wording is „strenuous endurance exercise“ - I‘m not sure where to put easy endurance.

Also: „There appears to be no concerns about an upper threshold for safety for leisure-time low-to-moderate intensity activities such as walking at a comfortable pace, housework, gardening, etc. After every 30 consecutive minutes spent sitting, stand up and move, ideally walking briskly for about five minutes.“


I have no idea. To a normal, off the couch person, I’m guessing it would be. Also, Z2 is absolutely sweat inducing for me. Like I said, I’d like to see a better definition of vigorous.

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Sorry, I edited my post, you were too fast. :slight_smile:

The above paragraph sounds like Z1/(lower?) Z2 to me.

@WindWarrior just curious, how many days per week do you ride on average and how many are Z2, sweet spot, threshold, and VO2?

I try to ride 5-6 days per week and did TR’s POL plans Jan - Mar. At the time these had 1 threshold, 1 VO2, and 1 long Z2 ride each week. I really enjoyed the plans and had a lot of flexibility to move the workouts around to accommodate a lot of work travel.

I’m finishing MV build this week, which has 2 VO2 days, 1 threshold, and 1 sweet spot. I’ve seen ftp gains over the last two blocks but it is definitely more physically fatiguing and there is much less flexibility to accommodate work travel, often requiring VO2 and threshold on back-to-back days.

I’m seriously considering dropping down to low volume (1 each VO2, threshold, and sweet spot / long Z2) and filling in 2-3 of the off days with Z2. Requires more planning on my end, though.

Anyway, curious about your plan high level. Thanks.

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I’m coming out of a 2 month allergy haze phase, so nothing is normal right now. But the plan often looks like this:

  • Mon 90-120 minutes with some intervals
  • Tue 90-150 minutes endurance
  • Wed 90-120 minutes with some intervals (or group ride from March thru October)
  • Thur core/hip work
  • Fri 90-120 minutes with some intervals
  • Sat 3-5 hour endurance ride (w/ or wo/ group), or 2.5 hours with some intervals
  • Sun core/hip work

The one constant is endurance work and raising overall capacity to do work. The intervals are rather short compared to what I did in TR. We also do mixed workouts, similar to what I heard Landry Bobo talk about on the April 25th HR vs Power Evoq pod. A little progression, but unlike what I remember of TR base/build/speciality or block focus, its playing the long game and not focusing on an event to drive a progression schedule across different durations in the power curve. Sure I have events but those become like mini sub-plots in my training.


@WindWarrior thanks!

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This came up in my Health feed a couple days ago. It’s Stronger by Science’s take on it:

also, FWIW, I’ve found the 2+ hour endurance rides to be quite potent. So I really try and do at least 2 hours as a minimum, twice a week.

Today somebody posted this on the forum: Construction and breakdown of mitochondria

And I downloaded and skimmed the PDF translation of that Dutch article. Regarding my “2 hour rule” there was this:

5. Booth F (1977). Effects of endurance exercise on cytochrome c turnover in skeletal muscle. Annals of the New York Academy of Science, 301, 431-439.
9. Fitts R et al. (1975). Skeletal muscle respiratory capacity, endurance, and glycogen utilization. The American Journal of Physiology, 228(4), 1029-1033.

I haven’t read those studies, and without any context that table summarizes that 60 minute “training units” resulted 40% increase in mitochondria content, versus 60% increase for 90 minute units, while 120 minutes resulted in 90% increase.

So that seemingly supports my 2 hour rule.

And FWIW #1 - in 2014 and 2015 when I was doing spin classes, I plateaued at 45 minute class so I started going earlier and bumped my sessions to 60 minutes and months later I pushed it even more and my rule became 5am arrival and 75-90 minutes total (I didn’t always make it at 5am).

And FWIW #2 - using TR I felt (feeling, not data) more benefit from doing an extended (repeated) TR Traditional Base with 2-3 hour workouts versus the short 60-90 minutes workouts.

I’ll go read those references at some point, and you can take my 2 hour rule for what its worth.


FWIW, the scientific literature indicates exactly the opposite, i.e., at least in rats the effects of training duration on muscle mitochondrial content plateau at 60-90 minutes:

You don’t really get much in the way of further increases with training up to 3.5 h/d (Howie Green’s research), or even electrically stimulating the muscle to contract 24 h/d (Dirk Pette’s work). Instead, these more extreme interventions seem to induce mechanisms to reduce ATP demand, rather than increase ATP supply.

With all that said, rats are not people, and can be forced to train more intensely day after day than most people would choose to. The high training volume of most elite endurance athletes therefore may simply reflect trading off intensity for duration (plus they are obviously incentivized to always do more, not less).


LOL, yeah I skimmed those last night and immediately thought “my legs are human.” Appreciate the reply. I’m good with doing things that appear to work, even if there is no science to back it up!

It could be that 2+ h rides benefit your performance for reasons other than an increase in muscle respiratory capacity.

Not directed at you, but I see a LOT of folks here drawing unwarranted conclusions re. mechanisms w/o fully understanding the physiology of exercise and the complexity of the human body.

For example, there is no evidence that “over-unders” are particular efficacious for improving lactate clearance. In fact, even Brooks’ own data show that increases in lactate clearance with training are far less important than reductions in lactate production (not that he would ever admit, of course…it a challenging dilemma, I tell you).


yes, its so much easier to focus on figuring out what works for me, and then doing them until they no longer work!

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And at the end of the day, that’s all you care about, right?

The vast majority of athletes are better off leaving the science to actual scientists (not wannabes, influencers, or coaches…no matter what their track record) and just getting on with the training.


Division of labour?

That’s crazy talk around these parts… :wink:

Where do they find bikes in frame sizes to fit the rats, though?