Training glossary: 40 data and endurance terms
A practical reference for understanding the language of training data. Definitions explain concepts, not individual training prescriptions. Models, devices and zone systems can use different conventions.
Jump to a term
- ATL — Acute Training Load
- Acute-to-Chronic Workload Ratio
- Cadence
- CTL — Chronic Training Load
- Cardiac drift
- Running economy
- Fartlek
- Maximum heart rate
- FTP — Functional Threshold Power
- HRV — Heart Rate Variability
- HYROX
- IF — Intensity Factor
- Mechanical impact
- Lactate
- Long run
- NP — Normalized Power
- Periodisation
- Polarised training
- Relative Effort
- RER — Respiratory Exchange Ratio
- RPE — Rating of Perceived Exertion
- Sled push
- Sled pull
- Suffer Score
- Tapering
- Talk test
- Tempo run
- TRIMP — Training Impulse
- TSB — Training Stress Balance
- TSS — Training Stress Score
- Aerobic threshold
- Second threshold
- VO2max
- Wall balls
- Zone 1
- Zone 2
- Zone 3
- Zone 4
- Zone 5
- Heart-rate zones
ATL — Acute Training Load
A short-term summary of recent training load. Read it alongside longer-term load and how you feel, rather than as a direct measurement of fatigue.
Acute-to-Chronic Workload Ratio
A comparison of recent and longer-term training load. The result depends on the calculation method; it should not be treated as a universal safe range or an injury prediction.
Cadence
The number of steps per minute in running, or pedal revolutions per minute in cycling. Check whether a device reports both feet or one side when comparing running values.
CTL — Chronic Training Load
A longer-term summary of training load. It is a model-based estimate, not a direct test of fitness.
Cardiac drift
A gradual change in heart rate during a prolonged effort even when pace or power remains similar. Conditions and session context matter when interpreting it.
Running economy
The energy or oxygen cost of running at a given speed.
Fartlek
A session that alternates faster and easier running, often using terrain or landmarks rather than a rigid interval structure.
Maximum heart rate
The highest heart rate an individual can reach during maximal effort. Age-based equations are estimates, not individual measurements.
FTP — Functional Threshold Power
A cycling power reference used to set training intensities and compare workouts. Estimates depend on the test and protocol used.
HRV — Heart Rate Variability
Variation in the time between heartbeats. Interpret trends under consistent measurement conditions rather than labelling one reading as recovered or fatigued.
HYROX
A fitness race combining running with eight workout stations. See the HYROX guide for the race format and event resources.
IF — Intensity Factor
A ratio comparing a cycling workout’s Normalized Power with the athlete’s FTP.
Mechanical impact
The physical loading associated with repeated impacts, such as foot strikes in running. It is not interchangeable with a cardiovascular training-load score.
Lactate
A substance produced and used during energy metabolism. Blood lactate measurements can help describe the response to increasing exercise intensity.
Long run
A longer endurance run within a training programme. Its duration and intensity depend on the athlete and the goal.
NP — Normalized Power
A calculated cycling metric intended to represent the demands of variable power output rather than simply averaging all watts.
Periodisation
Organising training into phases with different priorities, such as building endurance, specific preparation and recovery.
Polarised training
An intensity distribution emphasising easier training and a smaller amount of hard work. Percentages depend on how sessions or time are counted.
Relative Effort
A Strava metric used to summarise cardiovascular effort from available workout information.
RER — Respiratory Exchange Ratio
The ratio between carbon dioxide output and oxygen uptake, measured through respiratory gas analysis.
RPE — Rating of Perceived Exertion
A subjective rating of how hard exercise feels. Always state which scale is being used.
Sled push
Pushing a loaded sled along the floor. Competition loads and requirements depend on the event and division.
Sled pull
Pulling a loaded sled, often using a rope. Competition loads and requirements depend on the event and division.
Suffer Score
An older Strava effort-metric name that may appear in historical articles or activity records.
Tapering
Reducing training load before a target event while retaining suitable training stimulus. There is no single schedule for every athlete or race.
Talk test
Using the ease of speaking during exercise as a practical indication of effort. It is not an exact substitute for individually measured thresholds.
Tempo run
A sustained, purposeful running effort. The term is used differently across plans, so check the intended intensity.
TRIMP — Training Impulse
A family of training-load calculations combining exercise duration and an intensity measure, commonly heart rate.
TSB — Training Stress Balance
A model comparing longer-term and recent training load. It is not a guarantee of race readiness.
TSS — Training Stress Score
A training-load metric combining duration and relative intensity. Comparisons depend on accurate reference values and the calculation method.
Aerobic threshold
A term used for the transition from lower to more demanding aerobic exercise. Lactate and ventilatory testing use related but distinct markers.
Second threshold
A higher-intensity transition described through lactate or ventilation testing. Fixed percentages or blood lactate values do not identify it precisely for everyone.
VO2max
The maximum rate at which the body can take up and use oxygen during intense exercise. Device estimates are not the same as a laboratory measurement.
Wall balls
A movement combining a squat and a medicine-ball throw towards a target. Loads, target height and repetitions depend on the competition rules.
Zone 1
The lowest-intensity band in many five-zone training systems. The exact boundaries depend on the chosen model.
Zone 2
An easier aerobic training band in many five-zone systems. Its meaning is not identical across all zone models.
Zone 3
A middle-intensity band in many five-zone systems. Its training purpose depends on the programme and the chosen model.
Zone 4
A higher-intensity band, often associated with threshold work in five-zone models. Check the method used to define it.
Zone 5
The highest-intensity band in many five-zone systems. Heart rate, pace and power zones do not necessarily align during short efforts.
Heart-rate zones
Intensity bands based on a selected reference such as maximum heart rate, heart-rate reserve or a measured threshold. Different methods produce different boundaries.