Metrics glossary
Feature comparisons reflect each product's publicly documented features as of September 2026.
Product names are trademarks of their respective owners. Tempo is not affiliated with, endorsed by, or sponsored by any of them.
Tempo shows a lot of numbers. This page defines each one: what it measures, how Tempo derives it, and — where a value is a judgement rather than a measurement — what counts as a normal range. These are the definitions the in-app tooltips give, collected in one place so you can read them end to end instead of hunting for the information icon.
A note on naming before the list. Tempo calls the training-load family Load, Fitness, Fatigue and Form; the research literature and most other platforms call the same four quantities TSS, CTL, ATL and TSB. Both names appear throughout, because you will meet both.
Training load
These are not independent measurements. Load is the measured quantity; everything else in this section is an average of it, or arithmetic on those averages.
| In Tempo | Also called | What it is | Window |
|---|---|---|---|
| Load | TSS | one session's training stress | a single workout |
| Fitness | CTL | average daily Load | 42 days |
| Fatigue | ATL | average daily Load | 7 days |
| Strain | ACR, ACWR | Fatigue ÷ Fitness | today |
| Form | TSB | Fitness − Fatigue | today |
Load
Load quantifies how much stress a workout put on your body, combining how hard and how long you trained. For a ride with power it comes from normalized power against your FTP; for workouts without power, Tempo derives it from heart rate against your threshold heart rate instead.
A workout's Load badge classifies the session by comparing its Load with your Fitness on the day before the workout — the load your body was accustomed to going in. The higher that ratio, the bigger the day was relative to what you are adapted to. With Fitness below 20 there is no established baseline to compare against, so the badge falls back to absolute Load values instead of a ratio.
Fitness (CTL)
Fitness, or Chronic Training Load, is a rolling 42-day average of daily training stress. Higher means greater long-term fitness. It moves slowly by design: one big weekend barely shifts it, and a month off drags it down steadily. The ranges Tempo shows are relative rather than strict categories — a Fitness of 60 means something different for a first-year rider than for someone eight seasons in.
Fatigue (ATL)
Fatigue, or Acute Training Load, is a 7-day average of daily training stress. High Fatigue means recent training has been hard. Because the window is short, it rises and falls within days, which is exactly what makes it useful next to Fitness.
Form (TSB)
Form, or Training Stress Balance, is freshness against fatigue. Negative values mean you are carrying fatigue; positive values mean you are fresh. It is the number to look at before a race, and the one that tells you whether a bad week is fatigue or something else.
Tempo shows Form two ways, and the toggle matters:
- Abs is Fitness minus Fatigue using rounded values, in load points:
round(CTL) − round(ATL). - % expresses that same difference relative to your Fitness:
((round(CTL) − round(ATL)) ÷ max(round(CTL), 25)) × 100.
The percentage view scales the zones to your current fitness, so it is easier to compare against yourself as fitness changes. The trade-off is that when fitness is low it exaggerates Form and can push you into the extreme zones on an ordinary day — the floor of 25 in the denominator limits this while you are still ramping up, but prefer the absolute value unless you train a lot. The same day can land in a different zone depending on which view you have selected.
Strain (ACR)
Strain is the ratio of Fatigue to Fitness, known in the literature as the Acute:Chronic Workload Ratio (ACWR) or Acute:Chronic Ratio (ACR). It monitors how much recent load you are carrying relative to what you are adapted to. 0.8–1.3 is considered optimal; above 1.5 may increase the risk of injury or overtraining.
Two caveats. Some sources use "strain" to mean Foster strain, which is load multiplied by monotony — a different quantity from this one. And Tempo shows "Insufficient Data" rather than a number when your Fitness is below the minimum the ratio needs to be reliable, which is typically your first several weeks of training: a small denominator makes the ratio swing wildly on a single ride.
Ramp Rate
Ramp Rate is the change in Fitness across the last 7 days, expressed in CTL per week. Positive values mean training load is building, negative values mean it is coming down.
Building faster than your current fitness supports increases injury and illness risk, so the bands scale with Fitness rather than sitting at one number for everyone: Low Risk is 3 CTL/week or less below a Fitness of 45, 4 or less up to 70, and 5 or less above that. The bands above Low Risk step up with it — below a Fitness of 45 they are Moderate 4 to 6, High 7, and Extreme 8 and above, each moving up by one in the 45-to-70 range and by one again above 70. So a rider at 80 is still in Low Risk at 5 CTL per week, where a rider at 40 is already at Moderate.
Monotony
Monotony answers "how varied has your training been?" It is your average daily load over the last 7 days divided by the standard deviation of those daily loads. Lower is better, because a low number means you are mixing hard days, easy days and rest rather than riding the same moderate session every day.
Persistently high monotony above 2.0 is associated with increased illness and overtraining risk, particularly when total training load is also high (Foster, 1998). Tempo's status bands are: Low <1.5, Moderate 1.5-1.9, High 2.0-2.4, Very High >=2.5.
Monotony complements Strain: Strain asks how much recent load you are carrying relative to your fitness, and Monotony asks how evenly you spread it.
Readiness
Readiness blends Form, Strain, Sleep, HRV, Resting HR and recent training-load changes (Ramp Rate and the change in Form) into a single 0-100% score. Higher suggests you are well recovered; lower suggests prioritising recovery. Large deviations in HRV or resting heart rate from your own baseline pull the score down hard, which is deliberate — those are the two signals that most often precede illness.
Training Status
Training Status names your current phase — Building, Maintaining, Peaking and so on — from Ramp Rate and Form. The risk badge beside it indicates overreaching and overtraining risk from Strain and Form.
Power
FTP
Functional Threshold Power is the highest power you can sustain for approximately one hour. It is the anchor for training zones and for Load, so an FTP that is badly wrong makes every downstream number wrong with it. The badge classifies your FTP into a Coggan-inspired tier based on absolute watts.
Tempo scores each ride against the FTP that was in effect on the day you rode it, so reprocessing an old workout no longer rewrites its intensity with today's number. Your FTP history lists every change, newest first, whether you set the value yourself or accepted an estimate.
Estimated FTP
Estimated FTP is calculated from your power outputs and updated automatically as you complete workouts. Tempo estimates it two ways, at two different scopes.
Per workout, when a ride contains a strong sustained effort, Tempo projects from your best sustained effort in the 8 minute to 1 hour range using typical Critical Power curve percentages, since longer efforts map closer to FTP than shorter ones. Anchors shorter than 8 minutes are excluded so that strong anaerobic power does not inflate the estimate. This is intentionally conservative: a single ride cannot fit a true model, so treat it as a soft per-ride reading.
Your training FTP comes from the rolling-window Critical Power fit on the Performance page, described next.
Critical Power
Critical Power is the highest power you can sustain without progressively depleting your anaerobic reserves — the asymptote of your power-duration curve. Tempo fits it by least-squares regression of the Monod & Scherrer 2-parameter model on the canonical 3/5/8/10/12/15/20-minute best efforts in the selected window, or the Morton 3-parameter model when a maximal sprint is also available.
Morton 3P adds a time-delay term for a more personalised estimate, but requires a 5-second sprint anchor and returns nothing without one, which is why Monod & Scherrer 2P is the default: it is less sensitive to noise in any single anchor. When fewer than 3 of the canonical efforts are present, the fit falls back to whatever minute-resolution efforts your workouts contain in the 3-20 minute range. The contributing-efforts list on the card shows which workouts and durations actually drove the estimate.
W-prime
W-prime, written W′, is the finite work you can do above Critical Power, measured in kilojoules. Once you exceed Critical Power you spend it; when you drop below, it recharges. A larger W′ means a bigger matchbook for attacks and supra-threshold efforts. The same quantity appears on the Performance page as above-threshold energy.
The badge classifies your body-mass-normalised W′ in joules per kilogram using guidance bands from the Critical Power literature (Jones & Vanhatalo 2017): <150 developing, 150-250 recreational, 250-350 trained, 350-450 strong, 450+ elite. These are guidance ranges rather than a published standard. When a fitted W′ falls outside physiological bounds — usually because no true maximal 3 to 5 minute effort exists in the window — Tempo hides the value and the card says why.
Normalized Power
Normalized Power is a weighted average that estimates the physiological cost of an effort by weighting surges more heavily than coasting. A steady hour and a ragged hour at the same average power are not the same ride, and this is the number that says so.
Intensity
Intensity is the ratio of Normalized Power to FTP. 1.0 is an hour at threshold by definition; endurance rides sit far below it and short races can exceed it.
Power curve
Your power curve is your best power at every duration, from sprints to endurance. Toggle between watts and watts per kilogram, and click any point to jump to the workout it came from; the dashed line overlays a wider time range for comparison.
On a single workout, the same chart shows that ride's maximum average power at each duration. The highlighted 3-20 minute band is the range used for FTP estimation, because maximal efforts there best reflect threshold power.
The power profile chart is the same data grouped into Sprint, Attack and Climb durations, which is the view that shows where your strengths sit. Your rider profile classifies that curve across sprint, attack and sustained efforts.
Power zones
Power zones use the Joe Friel 7-zone system, as percentages of FTP. Each zone is a different training intensity. Sweet Spot is a commonly prescribed range that straddles the top of Tempo's zone 3 and the bottom of threshold rather than being a step of its own.
Power-to-weight
Power-to-weight, in watts per kilogram, is a decisive performance metric in cycling, and the one that predicts climbing. Tempo classifies it using the Allen & Coggan power-profile system. Note that the short-duration badges (5 seconds, 30 seconds, 1 minute) use sprint and anaerobic thresholds, which are several times higher than the FTP figure — a 5-second W/kg of 15 is not the same achievement as an FTP W/kg of 15.
Work
Work is the total mechanical work done during a ride, in kilojoules — one second at 300 watts is 300 joules. This is work at the cranks, not metabolic energy: cycling is only about 21-23% efficient, so the calories your body actually burned are roughly 4-5 times larger.
Work above FTP counts only the seconds where instantaneous power exceeded your FTP. It is sensitive both to how long you spent above threshold and to how far above it you rode.
Efficiency and pacing
These metrics compare two things you already have — usually power against heart rate, or the first half of a ride against the second — and they are most informative on steady, sub-threshold efforts. On an interval session or a race they mostly report the shape of the session.
Efficiency Factor
Efficiency Factor is Normalized Power divided by average heart rate. Higher means more normalized watts per heartbeat, which is the signature of improving aerobic fitness. It is most useful for tracking base training over weeks, and only valid for steady, sub-threshold efforts.
Power:HR ratio
The ratio of average power to average heart rate. The same idea as Efficiency Factor but using average rather than normalized power, so it is slightly blunter and slightly easier to reason about. Joe Friel describes this ratio as one of the better measures of fitness change — it works rather like miles per gallon for an engine.
Cardiac drift
Cardiac drift, also called aerobic decoupling or Pw:HR, measures how much your heart rate rises relative to power output over the course of a ride. Tempo compares the Efficiency Factor of the first half with the second half.
Under 3% indicates strong aerobic fitness and efficient pacing. 3-5% is normal for longer efforts. Above 5% suggests cardiovascular fatigue, dehydration or overheating — which is why it is worth reading next to Heat Load on a hot day.
Power fade
Power fade measures how much your power dropped from the first half of a workout to the second. Positive values mean power fell. Near 0% or negative — a negative split — indicates good pacing. Above 5% suggests fatigue, a poor pacing strategy, or under-fuelling.
Variability Index
Variability Index measures how smooth or how variable your power output was: Normalized Power divided by average power. A steady, even effort such as a time trial should have a VI of 1.05 or less. In a criterium it may be 1.2 or higher.
Heart-rate recovery
Heart-rate recovery is an adaptation of the clinical HRR60 protocol to continuous ride data. Tempo scans every 60-second window whose start is at near-peak effort — at or above threshold heart rate, or 85% of maximum — and whose end is above your resting heart rate, then takes the largest drop. It needs resting heart rate and either threshold or maximum heart rate set on your profile.
Higher is better, and rising over time indicates improving fitness and parasympathetic recovery. On the trend chart it is shown as the median across workouts in the window, which filters out day-to-day autonomic noise.
VO₂ max
VO₂ max is maximal oxygen uptake in millilitres per kilogram per minute, the standard measure of aerobic capacity. On the Performance page it is an athlete-level estimate taken from your connected health data and is not filtered by workout type.
Per workout, Tempo estimates it with the Sitko et al. (2022) 5-minute maximum power
method: VO₂ max = 16.6 + 8.87 × (W·kg⁻¹). That method was validated on trained cyclists
with a typical prediction error of ±3-4 mL·kg⁻¹·min⁻¹, so read changes of a point or two
as noise. A displayed value may be carried forward from an earlier day — from your most
recent qualifying 5-minute effort — until a newer one is logged.
Performance summary
The performance summary is your overall fitness trajectory over the last 90 days, taken from the trends in estimated FTP, estimated VO₂ max, 5 minute power, 20 minute power, Power:HR ratio, Efficiency Factor, cardiac drift, power fade and heart-rate recovery.
Wellness
Resting heart rate
Resting heart rate, in beats per minute, is your heart rate when completely at rest. Lower values typically indicate better cardiovascular fitness, and it feeds the calculation of your heart-rate training zones. What matters day to day is change rather than level: a jump above your own baseline is a common early signal of fatigue or illness.
HRV
Heart rate variability is the variation in time between heartbeats, and a proxy for
autonomic balance. Tempo shows it as an HRV Score calculated as ln(RMSSD) × 20, the
standard transformation used by most HRV apps, which produces an intuitive figure —
typically 50-100 for healthy adults — where higher indicates better recovery.
Normalized HRV
Normalized HRV adjusts your HRV for the heart rate it was measured at. Because a lower heart rate mechanically allows more variability, raw HRV can look high simply because your pulse was slow that morning. This compares your HRV with what would be expected given your heart rate, which is what isolates the meaningful changes.
Sleep
Sleep duration in hours. Sleep is where adaptation actually happens, and athletes typically need 7-9 hours a night. It is one of the inputs to Readiness.
Weight, body fat and hydration
Body weight is tracked in kilograms, and matters both for power-to-weight and as context for hydration and body composition changes.
Body fat percentage correlates with power-to-weight in cycling; athletes often range from 8-15%.
Hydration is total body water as a percentage of body weight. Tempo compares it with your recent baseline and with sex- and age-adjusted thresholds — roughly below 50% for men and below 45% for women, slightly lower with age. Read it alongside recent weight rather than on its own.
Body Mass Index is a height-and-weight measure of body fat. It is imperfect for athletes, who carry more muscle than the population it was derived from, but it is a useful guide to a healthy weight range; for adults, 18.5 to 24.9 is generally considered healthy.
Heart-rate zones
Heart-rate zones use the Andy Coggan 5-zone model, as percentages of your threshold and maximum heart rate.
Threshold heart rate is the highest heart rate you can hold steady without fatiguing, typically the average over a 20-30 minute time-trial-style effort. Tempo keeps separate cycling and running values, because they differ for most people, plus a general value used for strength, walking, hiking and other workouts — the general value also seeds the two sport-specific ones until you set them.
Maximum heart rate is the highest rate you can reach under exercise stress. It is often estimated as 220 minus age, but that formula has a wide error margin and a measured value is much better.
Fueling
BMR and TDEE
Basal Metabolic Rate is the energy your body needs at rest to maintain basic function. Tempo calculates it with the Mifflin-St Jeor equation, which is generally the most accurate for most people.
Estimated total daily energy expenditure is your non-exercise daily burn: BMR multiplied by an activity factor describing how active you are on an ordinary day, not counting workouts. Pick that factor from your job and lifestyle; most athletes choose 1.2 to 1.4, because Tempo adds workout calories on top rather than assuming them.
Calories burned, consumed and balance
Calories burned is your total daily burn: BMR plus non-exercise activity plus exercise calories from completed workouts and events. On the Energy page the tile carries a pill comparing burn so far with your baseline of BMR plus non-exercise activity: Baseline means little exercise yet, Elevated is 10%+ above baseline, High is 35%+ above.
Calories consumed is total dietary energy from logged intake, added manually or synced from the Tempo mobile app. Its pill grades intake against total burn: 95%+ well fueled, 80–95% slightly under, below 80% under-fueled.
Calorie balance is consumed minus total burned. This is not the same as energy availability, which subtracts only exercise calories and divides by fat-free mass.
Energy availability
Energy availability is the energy left to run your body once training has taken its share:
EA = (intake kcal − exercise kcal) ÷ fat-free mass in kg
Sustained low energy availability is linked to Relative Energy Deficiency in Sport (REDs), whose consequences include impaired bone health, endocrine disruption and suppressed immunity (Loucks 2004; Mountjoy 2014/2018/2023). It is the metric on this page with the clearest health stakes, which is why Tempo shows it as a 7-day average rather than a daily figure — one low day is a Tuesday, three low weeks is a problem.
| EA (kcal/kg fat-free mass/day) | Zone | Meaning |
|---|---|---|
| 40+ for men, 45+ for women | Optimal | The level recommended for hard training |
| 30 up to optimal | Moderate | Subclinical low EA; may impair recovery |
| Below 30 | Low | Clinical low energy availability and REDs risk |
The threshold below 30 applies to everyone; the optimal threshold differs by sex because the research behind the higher figure was derived in women (Melin et al. 2019). Where sex is unspecified Tempo uses the more conservative 45.
Carbohydrate targets
Your daily carbohydrate target is periodised against your training load: hard days target 8–10 g/kg, moderate 6–8, easy 3–5 (Burke 2018).
Mechanically, Tempo builds the number as a rest-day baseline plus the carbohydrate needed
to replace what the day's workout burned, so the total scales automatically with what you
actually did: total = base × weight + workout calories ÷ 4. The rest-day baseline is
typically 2–3.5 g/kg. At low intensity fat covers around 55% of fuel, so easy days come
out lower than a naive "calories ÷ 4" would suggest, and harder sessions shift the mix
toward carbohydrate.
Protein and fat targets
Protein targets 1.6–2.2 g/kg for endurance athletes and stays flat across training days — protein needs do not vary meaningfully by training phase (Schoenfeld & Aragon 2018; Phillips & Van Loon 2011; IOC consensus).
Fat targets 1.0–1.5 g/kg as a minimum, or 20–35% of total energy intake (ACSM and IOC guidance). It is the remainder macronutrient, set after carbohydrate and protein, and it is not periodised.
Session and recovery fueling
Next-session targets are pre-, in- and post-workout fueling figures in grams of carbohydrate, protein, fluid and sodium. The defaults follow Burke 2018 and Jeukendrup 2014, and become personalised once your sweat rate and tested carb tolerance are set.
For recovery, within 60–90 minutes of a hard session: replace glycogen at roughly 1.0–1.2 g/kg of carbohydrate per hour and trigger muscle protein synthesis with about 0.3–0.4 g/kg of leucine-rich protein (Schoenfeld & Aragon 2018; Alghannam 2018).
Sweat rate, sodium and carb tolerance
Sweat rate, in millilitres per hour, determines your hourly fluid replacement target. Tempo accepts 200–3000; run a sweat test to establish yours rather than guessing (McCubbin 2020).
Sweat sodium concentration, in milligrams per litre, pairs with sweat rate to compute hourly sodium needs. The accepted range is 200–2000, and individual variation here is larger than most riders expect.
Carb tolerance is the highest in-workout carbohydrate intake, in grams per hour, that you have comfortably tolerated. It caps the recommender, so Tempo never advises more than your gut has actually trained for (Jeukendrup 2014).
Heat
Heat Load
Heat Load measures the thermal stress you carried, adding up your heat strain across the whole session. The scale is anchored to the Heat Strain Index: one hour spent at the very top of the strain scale scores 100. In practice an hour of genuinely hard thermoregulation lands near 30, and a long day in the heat can pass 60.
Heat Load sits alongside Load rather than inside it. The same ride done in the heat and in the cold is the same training stress — your power and duration have not changed — but the recovery cost is very different. Folding heat into Load would blur that distinction and make your Fitness incomparable across seasons.
One caveat worth knowing: the Heat Load cutoffs are absolute, not personal. Load is classified against your own Fitness, but there is no equivalent heat-acclimation baseline yet, so an acclimated rider and an unacclimated one get the same band for the same ride. Read the bands as a description of the session, not of how well you coped with it.
Heat adaptation time
Heat adaptation time is time spent at High or Extremely High heat strain, meaning a strain index of 3.0 and above. That is the range that drives heat adaptation — a bigger plasma volume and an earlier, heavier sweat response — typically over one to two weeks of repeated exposure.
Rehydration guidance after a hot session replaces about one and a half times your estimated sweat loss, because fluid taken without sodium is largely passed rather than retained. When your profile has a measured sweat rate, the target is calculated from it and the session's duration.
Where heat data comes from
Heat metrics come from a CORE body temperature sensor, and they need a FIT file to reach Tempo. That means they appear for workouts synced from Garmin, Wahoo or Hammerhead, or uploaded directly. Strava's API does not carry core temperature or heat strain, so rides that arrive that way show no heat data even when you were wearing the sensor.
Ride detail
A few numbers on a workout page are worth a line each.
- Average power is the arithmetic mean across the whole ride, including coasting and recovery. Unlike Normalized Power it makes no allowance for surges.
- Maximum power is the highest instantaneous power recorded, usually a sprint.
- Average and maximum heart rate gauge overall cardiovascular effort, and the maximum is a useful check on whether your zone settings are right.
- Cadence is pedalling revolutions per minute; most cyclists sit around 80-100 rpm. Lower cadence at higher force loads the muscles more, higher cadence shifts the cost to the cardiovascular system.
- Left/right balance is the share of power from each leg. A perfectly balanced rider reads 50/50, and small imbalances up to about 52/48 are common and usually not a concern.
- Elevation is total gain, a rough proxy for how much climbing the ride contained.
- Calories are estimated from workout type, duration and weight. The meal-equivalent figure beside them assumes 600 calories per meal.
- Distance comes from GPS or sensor data.
Sources
The definitions above follow the published work each metric comes from. The main references are Coggan & Allen on training load and the power-duration profile, Foster (1998) on monotony and strain, Gabbett (2016) on acute-to-chronic workload ratios, Jones & Vanhatalo (2017) on Critical Power and W′, Sitko et al. (2022) on estimating VO₂ max from 5-minute power, and Burke (2018), Jeukendrup (2014), Loucks (2004) and Mountjoy et al. (2014, 2018, 2023) on fueling and energy availability. Each in-app tooltip links to the specific article behind its metric.
Where Tempo departs from a published standard — the W′ guidance bands, and the Heat Load scale — this page says so rather than presenting the choice as settled science.