Glossary: Carbohydrate periodisation, Yousuli Help

What carb periodisation is

Adjusting daily and per-workout carbohydrate intake to match the training session ahead and the adaptations you are targeting. The two extremes:

High carb for high intensity: top up glycogen before and during VO2, threshold, race-pace, or race-day work.
Low carb for low intensity: do some easy aerobic work in a lower-carb state to support fat oxidation adaptations.

Why "train low, race high"

A popular periodisation pattern. The idea:

Train low: some easy aerobic sessions done without pre-fueling and with limited in-session carbs trains the body's fat oxidation pathways. Slower in the moment, potentially useful for long-distance race fueling economy.
Race high: races are fully fueled. The trained fat adaptations remain useful, but you do not handicap your performance on race day.

What the Hub's fueling planner assumes

The fueling planner defaults to a fully-fueled approach (race high, high-intensity days fully fueled). It does not auto-prescribe low-carb sessions; that is a coaching decision communicated through notes or the workout plan.

What carb periodisation is NOT

Not the same as keto. Periodisation alternates; ketogenic diets keep carbs low permanently.
Not a magic shortcut. Most adaptations from periodisation are modest and require months of consistent application.
Not for everyone. Athletes with disordered-eating history, women in certain cycle phases, and athletes approaching A races should typically NOT train low.

Practical rules of thumb

Easy aerobic (Yousuli Zone 1-2): can be done low-carb occasionally.
Sweet spot, threshold, VO2 (Zone 3b through 6): full fuel.
Race-pace specificity sessions: race fueling, not low-carb experiments.
Long sessions (3+ hours): always carry race-day carbs. Even on otherwise low-carb days.

How to communicate

If a coach prescribes a session as "train low":

Write a CoachNote explaining the intent and the limits.
Mark it visible to the athlete.
Include the fall-back plan if the athlete feels truly bad mid-session (eat, do not push through to harm).

Glossary: Carbohydrate periodisation