- PACE plans on iPhone and executes structured sessions on Apple Watch.
- WorkoutKit sends planned workouts; HealthKit returns completed training data.
- The watch is the execution layer — the training engine remains the decision layer.
The PACE approach: plan on iPhone, execute on Watch
Structured workouts can include warm-up, work blocks, recoveries, cool-down and target ranges for pace or heart rate. That structure matters because a quality session is defined by more than total distance.
Why structured workouts matter for half-marathon training
Threshold work, HM-specific blocks and interval sessions depend on duration, recovery and target intensity. Having those elements on the wrist reduces the need to improvise mid-session.
What happens when PACE changes the training?
If the plan is replanned, PACE reconciles the structured workout so the Watch should receive the current prescription instead of an obsolete one.
HealthKit and WorkoutKit do different jobs
WorkoutKit is used to send structured planned workouts to the Watch. HealthKit is used to import completed workouts and selected metrics such as distance, duration, heart rate and running speed.
The Watch executes; the engine decides.
PACE creates structured workouts with suitable pace, heart-rate or effort targets, synchronizes them through WorkoutKit and imports the completed session through HealthKit. The engine can then compare plan with reality and decide whether anything should change next.
How training method and Watch fit together
The performance lever is not the device itself. It is the training logic behind the workout: load distribution, intensity, progression, specificity and tapering. Apple Watch makes that logic easier to execute precisely.
Scientific context
Campos et al. (2022): Training-intensity distribution in middle- and long-distance runners.
Kaufmann et al. (2023): Thresholds for exercise intensity prescription.