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, usually combining CTL, ATL, and TSB. | Seeing fitness, fatigue, and form together. |
| CTL | Chronic Training Load, a longer-term load trend. | Checking whether training is building sustainably. |
| ATL | Acute Training Load, a short-term fatigue/load trend. | Spotting recent stress pressure before key workouts. |
| TSB | Training Stress Balance, a freshness/form estimate from CTL and ATL. | Timing hard workouts, recovery, and taper decisions. |
| 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 trying to answer “Should I push or recover?”, start with training load, PMC, CTL, ATL, and TSB. If you are setting workout intensity, start with FTP, CP, LTHR, power zones, heart-rate zones, and pace zones. If you are reviewing long-term fitness response, add VO2 Max, effective VO2max, and physiology metrics.
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
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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.