QT2.0 Build/TH (L) Block Comments

QT2.0 Build/TH (L) Block Comments

The Build/TH - Lengthening block is used for a very specific type of physiological state, in a very specific situation.

This phase is typically applied when:

  • An athlete is in a strongly Aerobic physiological state

  • The “physiological attic” is already more like a crawlspace

  • Either a VO₂ Max block has already been used, or

  • We do not believe that pushing VO₂ Max will be effective or appropriate right now

In short: the roof is limiting the ceiling - but lifting the roof is either risky or unlikely to work.

So instead of forcing movement where it probably won’t happen, we shift the objective.

1. Muscle Fiber Utilization

Living at the threshold crossover longer

From a muscle fiber standpoint, this block lives almost entirely at the Type IIA O-G Crossover:

  • Between oxidative and glycolytic behavior

  • Just below threshold

  • At intensities that are sustainable, but only with training

The emphasis is not on recruiting new fibers or raising maximal output. Instead, it is on:

  • Increasing time-to-fatigue at sub-threshold intensities

  • Teaching Type IIA fibers to remain oxidative for longer durations

  • Improving resistance to metabolic drift over extended efforts

This is where threshold stops being something you can touch and becomes something you can hold.

2. The Athletic Architecture Model

When the roof won’t move, extend the ceiling

In the house model:

  • Ceiling = Critical Power / Critical Speed

  • Roof = Power or Speed at VO₂ Max

Normally, when the ceiling is constrained by the roof, we try to lift the roof. But there are cases where:

  • VO₂ Max work carries elevated injury risk

  • The athlete does not respond well to roof-lifting strategies

  • The expected return on VO₂ Max work is low

In those cases, continuing to chase higher Critical Power or Speed is unlikely to be productive.

So instead of trying to move the ceiling upward, we focus on making the ceiling usable for longer.

This block is about:

  • Accepting that peak values may not change much

  • Improving how long Critical Power or Critical Speed can be sustained

  • Turning a “short ceiling” into a longer, more livable one

The performance gain here comes from duration, not height.

3. Quality, Duration, and Fatigue Accumulation

Longer work requires smarter limits

In many ways, this block resembles a standard Build/TH block - but with an important difference:

  • Durations at or near threshold are longer

  • Interval structure is extended

  • Execution demands increase because fatigue is accumulating within sessions

Because of this:

  • Workout quality must still be protected

  • Fatigue accumulation is managed carefully

  • Recovery matters more than it did in Base/Durability

However:

  • The fatigue constraints are not as strict as in a VO₂ Max block

  • We can tolerate more accumulated fatigue than in roof-lifting phases

As a result:

  • CTL growth is typically similar to a standard Build/ TH block

  • Fitness becomes more durable rather than sharper

  • Progress shows up as repeatability and staying power, not spikes

The Big Picture

Build/TH (L) is a pragmatic training block.

When:

  • The roof won’t move

  • Or shouldn’t be forced

  • Or has already been addressed

We stop chasing higher numbers and start expanding how long your existing fitness can actually be expressed.

This is how performance improves when height is capped - but duration is not.

That’s the role of "threshold lengthening" in QT2.0.