Magness, Canova, they do not really use LT during specific phase. Magness cites that is shifts your body to rely more heavily on glycogen than it should at that point of training.
As someone who is well versed in many training methods, what is your thought?
Where does Magness cite that?
LT is a moving target (exact pace depends on the day, the weather, the training environment, and your fitness within the training cycle).
"Specific Marathon Training" like Canova would say is about "extension." So we are looking at fusing together longer efforts (very close to Marathon goal pace or slightly faster) between slower Long Run efforts of 32-36km (fat burning stimulus) and shorter Reps (even alactic Hill Sprints) to even 1km and 800m repeats at 5km/10km pace.
Early on in a training cycle while building aerobic base we are looking to climb to high volume mileage at lower intensity generally (mainly to avoid injury, but also to develop the capacity for some lactate clearance). We should also have some fat burning ability from that. We are looking to still strengthen the leg muscles with hills (maybe even hill sprints) and shorter, faster work (light Fartleks and even 5km-10km pace training track intervals) to develop some aerobic power, but mainly to develop better Running Economy/form and a FT muscle fiber stimulus.
During the bulk of marathon training ("Specific") you are looking at maybe not pure Lactate Threshold (about half marathon pace exactly for an elite), but maybe something right between Full Marathon and Half Marathon pace for very high volume, workouts.
At Hansons it just happened to be "10 seconds per mile faster than marathon pace" for 3-mile repeats. With Canova it might be "105-102%" of MP.
Now if we do that with alternating surges during a 22-mile Long Run (i.e. 4 x 3-miles/5km) in the middle of a steady effort, with a 1-mile "float" between hard efforts we may be right at Marathon Pace (the goal is to be slightly faster though) and as we develop leg fatigue and lower glycogen stores late in the workout we are also working on some lactate clearance as well because we are in that HR/intensity zone. We limit some carbohydrate intake during some long run workouts to induce fat burning capacity.
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Ah I see.
The OP did not put that in context.
What Magness talks about is the periodization of LT targeted workouts (as well as the periodization of workouts/aerobic base building slower than MP AND workouts faster than LT).
Like what I said above in "pre-comp" general conditioning phase you need to work the full spectrum with speed. Long Runs and high mileage at lower intensity AS WELL as short high-end aerobic fartlek and Hill Reps and even 800-1km repeats.
Then as things "come together" in specific training you are mostly right around MP pace on a lot of workouts (i.e. slightly faster than MP...but maybe not as fast as LT).
The goal of marathon training is to get MP closer to LT pace. But you need to set the bar for "goal MP" by developing some LT specific speed and clearance first abilities first. That is what he talks about with the order/progression of workouts in regards to LT and MP. I can't say we really followed that order at Hansons though. A "10-mile cut-down run" from 5:50 to 4:50 pace certainly crosses the Threshold and MP at some point though (at least for me it did).
Remember the limiting factors in the marathon aren't lactate clearance (like it is a limiting factor in half marathon and below events). The limiting factors are sheer muscle fatigue and glycogen depletion. So you need specific, biomechanic muscular strength/endurance to not breakdown and you need some fat burning capacity (i.e. "glycogen sparing) to not bonk super hard in the last 10km.
Nobody is racing the marathon at their LT pace/intensity, but if one can get their LT pace down to a faster pace range AND THEN close the gap between LT and MP, they are also probably doing what Canova would call "extension" in the specific phase.
BTW I'm also heavily influenced by Pfitzinger's work (i.e. "Advanced Marathoning").