Workout effort
Duration and intensity shape each session.
Heart-rate intensity changes the contribution of a workout, so not every hour of exercise is treated as the same load.
Workout load
See how each session changes the load you are carrying.
Metric estimates workout load from session duration and heart-rate intensity, then compares fast-changing recent load with a slower long-term baseline. The result is an explainable strain view for pacing a training week. It is a training-context tool, not an injury predictor or a replacement for how you feel.
- Heart-rate-weighted session effort
- Acute and chronic load
- Session-to-month drilldown
The useful answer
A hard week makes more sense when the sessions remain visible.
Metric uses a TRIMP-style approach: duration contributes load, and harder heart-rate work is weighted more aggressively. Recent sessions influence short-term load quickly while the longer baseline changes at a slower pace.
That structure helps you see whether today is an isolated hard effort, part of a stable block, or a rapid increase. It does not know every stressor or guarantee what will happen next.
Inside Metric
Designed to keep the context attached.
Every summary should lead back to the signal, date range, or source that shaped it.
Two speeds
Recent work moves faster than your baseline.
Short-term load responds quickly to new sessions; the longer baseline decays and grows more gradually.
Drill down
Move from strain to the workout list.
Review the route, zones, pace, distance, and history behind a load change instead of stopping at a single score.
How it works
Three steps from data to a better question.
Import consistent workouts
Allow Metric to read workouts and usable heart-rate data from Apple Health.
Review the session load
Check whether duration, heart-rate collection, and workout details match what you completed.
Watch the rate of change
Use the short-versus-long view with your own plan, recovery, and subjective effort.
What to know first
Useful, with clear limits.
- Workouts with missing or poor heart-rate samples may not represent intensity well.
- Load does not capture technique, pain, illness, life stress, terrain, nutrition, or every source of fatigue.
- Research thresholds from one sport or population should not be treated as universal injury rules.
A good fit if
- You record workouts with heart-rate data and want a training-block view.
- You want the sessions behind a strain number to remain inspectable.
- You are increasing or changing training and want to see the rate of change.
Probably not for you if
- You need a return-to-play decision or injury-risk calculation.
- Your training rarely produces usable workout or heart-rate samples.
- You want a score to replace a coach, clinician, or your own symptoms.
Common questions
The short version.
How does Metric calculate workout load?
Metric weights workout duration by heart-rate intensity, then uses different decay rates to compare recent load with a slower long-term baseline.
Is workout load the same as calories?
No. Calories and training load answer different questions. Metric’s load estimate focuses on duration and cardiovascular intensity.
Can workout load predict injury?
No. It can describe a training pattern, but injury is affected by many factors that a load model cannot observe or predict for an individual.
Sources and context
Read the primary material.
Official platform documentation and original research are linked for context, not used to overstate what one app view can conclude.
Apple Support
Monitor your heart rate with Apple Watch
Apple describes how Watch measures heart rate and HRV, along with fit, sampling, and reliability considerations.
Journal of Athletic Training / PubMed
Workload and noncontact musculoskeletal injury in collegiate swimmers
A prospective cohort study of one athlete population. It is useful context for load monitoring, not a universal injury rule or individual prediction.
Apple Developer
HealthKit framework overview
Apple explains HealthKit as a user-controlled repository for health and fitness data from iPhone, Apple Watch, apps, and compatible devices.
Metric for iPhone
Make your health history easier to use.
Connect only the categories you choose. Start with the dashboard, then go deeper when a trend earns your attention.
Download on theApp Store