# phase.fitness for Intervals.icu users

> Intervals.icu already holds your fitness, fatigue and zones. What it does not write is the block. phase.fitness plans the phases, pushes each session to your Intervals.icu calendar with the structure intact, and reads the load back.

phase.fitness · The app you already use · Updated 15 October 2026 · HTML version: https://www.phase.fitness/for/intervals-icu-users

## The short answer

phase.fitness connects to Intervals.icu two-way for endurance: planned cardio sessions are pushed to your calendar as structured workouts with intervals and heart-rate or power zones, and from Intervals.icu they reach Apple Watch, Suunto, COROS, Garmin and the rest. Completed sessions come back with the full metrics, along with HRV, resting heart rate and CTL/ATL, which is also how Apple Health data reaches phase.fitness. Strength sessions are counted in your Intervals.icu load but not written there — they go to Hevy, Liftosaur or a Garmin watch. When a phase ends, the AI reads the sessions and the load and writes the next block.

## How do I get structured workouts into Intervals.icu automatically?

Let phase.fitness write them: every planned cardio session is pushed to your Intervals.icu calendar as a structured workout with intervals and heart-rate or power zones intact, and from there it reaches the devices Intervals.icu supports. Completed sessions come back with full metrics, HRV and load, and the next block is written from them.

## Does strength training count in Intervals.icu load?

It does with phase.fitness: gym sessions go to Hevy, Liftosaur or a Garmin watch, and they are counted in your Intervals.icu load, so the fatigue they cause sits next to the rides and the runs. Intervals.icu does not receive the strength sessions themselves, and the calisthenics runs in the phase.fitness player.

## Your week, honestly

- **The calendar is empty until you fill it.** Intervals.icu shows fitness and fatigue beautifully; the sessions that move them are typed in by hand or copied from a plan that does not know your numbers.
- **The plan does not know the load.** CTL, ATL and ramp rate are right there, and the plan for next month was written without them.
- **Strength is invisible to endurance apps.** The gym happens, adds fatigue, and never shows up in the picture.

## What phase.fitness does about it

- **Structured workouts on your calendar** — Every planned cardio session is written to Intervals.icu with intervals and zones intact, and from there to the watch you use. (https://www.phase.fitness/integrations)
- **Load comes back** — Completed sessions return with the full metrics, plus HRV, resting heart rate, CTL/ATL and ramp rate — and it is the route for Apple Health data too.
- **Strength counted in the load** — Gym sessions go to Hevy, Liftosaur or a Garmin watch and are counted in your Intervals.icu load, so the fatigue picture includes them.
- **Blocks from the endurance documents** — Base, build, peak and taper on a polarized distribution, with the volume ramp set by your level and the next block read from what came back. (https://www.phase.fitness/ai-periodization)

## Programs to start from

- [Cycling training plan built on power zones and real strength](https://www.phase.fitness/training-programs/cycling-training-plan) — phase.fitness plans road and gravel cycling as base, build and peak blocks with a recovery week every 3–4, keeps the low intensity genuinely low, and adds squat and hinge strength at 3–5 sets of 4–6 — two sessions in base, one in build, none or one in the peak.
- [Half marathon training plan that keeps you strong](https://www.phase.fitness/training-programs/half-marathon-training-plan) — phase.fitness plans a half marathon as three phases and a taper: the long run gets the clean slot every week, tempo work at goal pace arrives in the build, and the lifting is heavy and short so it never eats the run that matters.
- [Triathlon training plan: three sports and one strength day](https://www.phase.fitness/training-programs/triathlon-training-plan) — phase.fitness plans a triathlon week as an ordering problem: three sports, a recovery budget that does not grow because there are three, and one or two strength days that stay heavy and short instead of becoming a fourth sport.
- [Rowing training program: erg, base and strength](https://www.phase.fitness/training-programs/rowing-training-program) — phase.fitness plans rowing the way the rowing document prescribes: a base with 85% of the time in zones 1–2, a build that adds threshold and VO2max sessions while cutting volume 10–15%, a peak at race intensities, and two strength sessions a week built around pulling.

## The apps you already use

Intervals.icu receives cardio and counts strength; it does not receive strength sessions themselves, and calisthenics runs in the phase.fitness player.

- **Intervals.icu** — Cardio sessions go out with intervals and zones intact; completed sessions, HRV and load come back.
- **Hevy** — Strength routines are written to Hevy; logged workouts return to phase.fitness. Cardio and calisthenics do not travel here.

## The evidence

Read more in the knowledge base:

- [HRV as a training-readiness marker](https://www.phase.fitness/learn/posts/hrv-training-readiness-marker)
- [Zone 2 training and mitochondrial adaptations](https://www.phase.fitness/learn/posts/zone-2-training-mitochondrial-adaptations)
- [Fatigue management in periodized programs](https://www.phase.fitness/learn/posts/fatigue-management-periodized-programs)

## Frequently asked questions

### Does phase.fitness push workouts to Intervals.icu?

Yes. Planned cardio sessions are written to your Intervals.icu calendar as structured workouts with intervals and zones, and completed ones come back with the full metrics.

### Can I use Apple Watch?

Through Intervals.icu, yes: the planned session reaches the watch from your Intervals.icu calendar, and Apple Health data reaches phase.fitness the same way.

### Does phase.fitness read my CTL and ATL?

Yes. Fitness, fatigue and ramp rate come into phase.fitness with the sessions, along with HRV and resting heart rate, and are part of what the AI reads when a phase ends.

## The only app that plans strength, cardio and calisthenics together

For an endurance athlete on Intervals.icu the calisthenics day is the trunk and scapular strength the sport erodes — holds and hanging work — run in the phase.fitness player and counted in the same phase.

Right now, phase.fitness is the only training app that writes strength, cardio and calisthenics into one periodized program — same calendar, same phases, same recovery budget.

You choose the mix. A calisthenics-only plan, a cardio-only block, strength plus cardio, or all three: the phases, the end-of-phase analysis and the sync work the same way with one modality or three.

**Why calisthenics is in the plan.** Bodyweight skill work is strength training in a different shape. Straight-arm work, levers and handstands build scapular control, tendon capacity and relative strength that barbell and machine work leave untouched, and they transfer because they are closed-chain, whole-body patterns. Treated as a modality rather than a warm-up, they get sets, holds and progressions like a squat does.

No exercise catalogue on the market contains a tuck front lever, so those sessions run in the phase.fitness built-in player; strength goes to Hevy, Liftosaur or a Garmin watch, cardio to Garmin and Intervals.icu.

Build your first program: https://www.phase.fitness/signup