Training Glossary
A categorized glossary of endurance training metrics, including training load, CTL, ATL, TSB, PMC, FTP, CP, LTHR, VO2 Max, power, heart rate, and pace concepts used by Trainingload.ai.
Training Glossary
Last updated: 2026-05-23
This page is the Trainingload.ai glossary for endurance training metrics. It explains the terms used across training load, PMC, power, heart rate, pace, VO2 Max, and physiology docs, and links each term to a deeper reference page.
Training metrics are most useful when they work together. A single number rarely explains training status by itself: load metrics describe dose, heart rate describes internal response, power and pace describe external output, and physiology metrics explain the underlying capacity.
Quick definitions
| Term | Plain meaning | Use it for |
|---|---|---|
| Training load | The stress created by completed workouts over time. | Deciding whether to build, hold, or recover. |
| PMC | Performance Management Chart, combining modeled CTL, ATL, and TSB load history. | Comparing longer and recent load trends over time. |
| CTL | Chronic Training Load, a slower-moving longer-load trend. | Establishing longer-term load context. |
| ATL | Acute Training Load, a faster-moving recent-load trend. | Locating recent changes in training load. |
| TSB | Training Stress Balance, the current CTL minus current ATL. | Seeing how recent modeled load differs from longer modeled load. |
| TSS | Training Stress Score, a workout stress score based on duration and intensity. | Comparing load across workouts or weeks. |
| TRIMP | Training Impulse, a heart-rate-based load estimate. | Estimating internal load when power is unavailable. |
| FTP | Functional Threshold Power, a practical threshold-power anchor. | Setting power zones and workout targets. |
| CP | Critical Power, a modeled sustainable power boundary. | Understanding power-duration capacity and W′. |
| LTHR | Lactate Threshold Heart Rate, a practical threshold heart-rate anchor. | Setting heart-rate zones. |
| VO2 Max | Maximal oxygen uptake or an estimated aerobic-capacity reference. | Tracking aerobic capacity trends. |
How to use this glossary
Use this glossary as a map, not as a standalone verdict. If you are reviewing how load has changed, start with training load, PMC, CTL, ATL, and TSB, then inspect the activities and athlete context behind the model. If you are setting workout intensity, start with FTP, CP, LTHR, power zones, heart-rate zones, and pace zones. If you are reviewing longer-term performance response, add VO2 Max, effective VO2max, physiology metrics, workout quality, and subjective signals.
Training Load
PMC (Performance Management)
Power
Power
FTP (Functional Threshold Power)
CP (Critical Power)
NP (Normalized Power)
VI (Variability Index)
Power Zones
PDC (Power Duration Curve)
W′ (Anaerobic Work Capacity)
Heart Rate
Pace
Physiology
AeT (Aerobic Threshold)
AnT (Anaerobic Threshold)
LT (Lactate Threshold)
Aerobic Capacity
Anaerobic Capacity
VO2 Max
Endurance Workout DSL
Write and validate endurance workout steps, targets, repeats, and sport-specific zones in Trainingload.ai text/rules mode.
Power
What power is in endurance training, how cycling and running power are measured or estimated, and how Trainingload.ai uses power for zones, TSS, FTP, CP, NP, and VI.