The real challenge: a fixed date, a moving body
A half marathon build is a fixed progression toward a fixed day. Perimenopause is the opposite: cycles that shorten, lengthen, or skip, sleep that frays without warning, and energy that swings week to week. The friction between a rigid plan and an unpredictable body is exactly why so many women feel like they are failing a plan that never accounted for them. For why this happens, see why running feels harder during perimenopause.
How Phaes builds a half through the volatility
The plan flexes, the race date does not
Phaes still builds a real progression toward your date, with a long run that grows and quality work that sharpens you. The difference is that a rough, low-sleep, symptom-heavy week reshapes the days around it instead of forcing a key session you cannot execute. Hard work gets repositioned, not deleted, so you keep arriving at the start line trained.
Driven by your check-in, not a calendar
Because perimenopause cycles wander, a textbook 28-day periodization is wrong most months. Phaes works from your daily check-in (sleep, energy, soreness, symptoms) and your real cycle, so the plan tracks the body you have this week.
Strength stays in the build
Heavy strength does not get dropped when mileage climbs. It protects bone and muscle as estrogen swings and keeps you durable through the repetitive load of half marathon training, with day-level locking so it actually happens.
Recovery as the limiter
A load guard keeps the build conservative, and the plan spaces hard work around how you actually recover. The same recovery-first thinking carries through to the other side; see half marathon training during menopause for life once cycles stop.
Where it fits
This is the half-specific build for the perimenopause years, layered on the adaptive coaching in running through perimenopause. For the broader picture of training in this decade, see running over 40.