Latest Twitter post. Someone asks for data/link to database but he refused to share, and to be fair I dont blame him there if he has spent years compiling this stuff
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Thanks, just read the thread. A few tweets down someone posted their (non AC) test results, with declining but not zero fat utilisation even at faster pace. This is more like what Iād assume is correct 
Edit : in fairness we donāt know their VO2max or how close to top end this is
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That is what i was unsure of, i thought you always used a small amount of fat until you were using pure stored ATP. @explorerJC is the resident scientist so may have a bit more of an idea.
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Reading ACs responses I think he may be using a respiratory exchange ratio of 1.0 to mean ā100% carbohydratesā and also acknowledging that this may be an oversimplification
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Donāt know about āzeroā. But Iāve seen things before that some people can be so metabolically inflexible they have extremely low fat oxidation at very low relative intensities, ie very slow jog in good level runner to require planned walk training.
Whether that extends as far as saying the average person like AC implies Iām even less sure
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I am no physiologist, but understand that to be correctā¦
the predominant sourceā¦
Correctā¦
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Can we define negative consequences - or does that mean walking like youāve crapped yourself and unable to do stairs?
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He actually goes on at how everyone should be able to get up, run 7min kās (sub 5hr) for a marathon and walk away.
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Technically, in the main, thatās right though isnāt it. Thatās what weāre all designed to do. Weāre just extremely good at undoing Mother Natureās best efforts! 
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Not directly related, but just followed Alan and came across this nice graphic of heart rate zones/paces/effort/energy sources and various terminology. Pretty comprehensiveā¦(credit to @fluidathletics)
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I really like what he does, willing to put most of his learnings out there. Downside is he thinks everyone needs to ātrainā a lot and he doesnt accept discourse or challenges
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Personally I like the three zone model
easy, medium, hard.
Thatāll do
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Same, I rarely do medium, except when racing
Also with hard there is āParkrunā hard and āintervalsā hard - both are hard, but different distance.
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I remember reading some time ago that genetically we are well adapted to run around 30km, but not designed to run 40km+
Certainly for me, running a half marathon is very easy, so long as pace is zone2 no recovery time is required. Even an easy marathon feel hard and does require recovery time
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Nothing new, based on the two lactate thresholds but has limitations as there are a whole heap of different āhardsā above 2nd Threshold, all with varying physiological and psychological benefits
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Agree, for me, from a practical perspective, hard means as hard as I can go for that distance. So a hard parkrun is 3:45/km @ 170bpm while hard 400m intervals are 3:25/km @ 180bpm and a sprint may 2:50/km @ 190bpm
I have enough experience to know how much I can push, I really donāt look at my watch that much doing hard sessions - intervals I check the pace after each interval and make sure I hit the same on the next; if I get it right, the last interval is very, very painful, and normally a couple of seconds faster than the first
@Hammerer and @explorerJC may have some advice as I could be doing it wrong
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the last rep?
if the first rep is still a part of āwarming into the sessionā then yepā¦but it can change the session outcome if the last rep is significantly faster than the firstā¦
All respectable pacesā¦other than to novices, i am always perplexed as to why coaches prescribe 5k pace for 400m repsā¦
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thatās a reasonable generalisation based on evolutionary biologyā¦
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Yes last rep. One of my favourite sets is 400 fast, 200 easy * 5 then 800 easy then 400 fast 200 easy * 5 with the objective of going as fast as possible while still able to hold the same pace for each rep.
The only time I ever run 5k pace on a track is when the interval builds in pace with each rep.
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