A winter base block: what it looks like, Yousuli Help

The principle

A winter base block is the period when no A race anchors the plan. The job is to maintain or grow the aerobic engine, fix limiters, and arrive at the new season build phase ready to absorb intensity.

The Hub does not auto-detect "winter base"; it is a coaching decision communicated through the macrocycle and the race calendar.

What the macrocycle should look like

A typical winter base block:

Duration: 8 to 16 weeks (varies by hemisphere and next A race).
Volume: 70 to 90 percent of in-season peak. Steady week-over-week.
Intensity distribution: heavily Z1 to Z3a. Almost no Z5 to Z7. Some sub-threshold (Z3b sweet spot) work preserved.
Long sessions: maintained at moderate distance, not pushed to race-specific length.
Recovery weeks: every 3 to 4 weeks.

See Macrocycle plan basics for the model.

What to do this winter

Fix one or two limiters

The off-season is the time to do this. Examples:

Swim technique: a focused 8-week swim block can move CSS by 5 to 15 seconds per 100 m for many age-groupers. Use a Technical Swim Assessment (see Technical Swim Assessment) as a starting point.
Run economy: drills, form work, gait analysis. See Technical Run Assessment.
Bike position: a fit session if anything has drifted, plus a CdA test (see CdA Field Test).
Strength: a structured 8 to 12 week block. Maintain in-season.

Maintain aerobic base

3 to 5 sessions per discipline per week.
One mid-week sweet spot or threshold session per discipline.
One long session per discipline per week.

Address body composition slowly if relevant

Winter is when small composition changes can happen safely because the training stimulus is lower. See Glossary: race weight for the caveats; do not aggressively cut.

What to NOT do in winter

Maintain race-specificity year-round. It is not sustainable. Athletes who hold race intensity for 12 months show up to summer racing flat.
Skip intensity entirely. Some Z3 to Z4 work prevents detraining and supports limiter work.
Skip long sessions. Even at lower volume, the long session preserves aerobic adaptations.

What to test

Use winter for diagnostic tests, not race-readiness tests:

Metabolic test (see Metabolic Test) to set the season's targets.
Body composition if relevant.
Sweat rate as a baseline.
CSS, CP, run threshold at the start of winter and again before the spring build to track baseline.

How the season view shows winter base

If your next A race is more than 20 weeks out, the season view shows mostly "Base" phase weeks. See Athlete season view.

Some athletes add tune-up races (C priority) in late winter as fitness markers, which add small phase tags.

Common winter mistakes

Stopping completely. A full off-season is appropriate for some athletes but not most. Two to four weeks of unstructured movement after a race season is enough; beyond that, build the new base.
Going too slow. "All Z1 all winter" produces poor fitness. Include some Z2 to Z3 work.
Following someone else's winter plan. A pro winter base block (25 to 30 hours per week) is not a template for an age-grouper.

A winter base block: what it looks like