Training data, in plain language.

Heart rate variability (HRV)

The variation in time between heartbeats. At rest in the morning it mainly reflects parasympathetic (recovery) activity, which is why it is used to judge how an athlete is coping with training.

See also: RMSSD and LnRMSSD

RMSSD and LnRMSSDRoot mean square of successive differences

The standard HRV measure in endurance training. LnRMSSD is its natural log, which makes day-to-day changes easier to compare. Endurance Signals uses morning LnRMSSD.

See also: Heart rate variability (HRV)

7-day baselineRolling average

The average of the last seven morning readings. Decisions use this trend, not a single day, because daily HRV is noisy.

See also: Normal range (SWC)

Normal range (SWC)Smallest worthwhile change

The band an athlete's HRV usually sits in, built from their own previous 60 days (a robust mean plus or minus 1.5 standard deviations). A 7-day baseline inside the band is normal variation; outside it is a meaningful change. Day-to-day shifts smaller than half a standard deviation, the smallest worthwhile change, are treated as noise. Athletes are never compared with each other.

See also: 7-day baseline

Coefficient of variation (CoV)

How much HRV moves from day to day within a week. A rising CoV can mean the athlete is struggling to absorb training, even when the average looks normal.

See also: Normal range (SWC)

Resting heart rate (RHR)

Morning heart rate before getting up. Read alongside HRV: falling HRV with rising RHR is a stronger warning than either alone.

See also: Heart rate variability (HRV)

HRV driverVolume-driven, intensity-driven

Whether an athlete's HRV is pushed down more by training volume or by intensity. Endurance Signals learns this from each athlete's history and plans stimulus and recovery weeks around it.

See also: Build:recovery ratio

Build:recovery ratioe.g. 3:1, 2:1

How many loading weeks come before a recovery week. Athletes who take longer to recover get a shorter build.

See also: HRV driver

Readiness

A plain-language summary of whether today suits hard training, drawn from HRV, resting heart rate and the morning check-in.

See also: Daily check-in

Daily check-in

A short morning questionnaire on sleep, soreness, illness, pain and mood. Fixed rules raise flags for the athlete's named check-in coach. A missing or partial check-in is never treated as all clear.

See also: Unresolved concern

Unresolved concern

A flagged issue, such as ongoing pain, that stays open until a coach resolves it with a note. It is kept separate from today's flags so an old issue is not mistaken for today's condition.

See also: Daily check-in

Training Stress Score (TSS)

A single number for the load of one session, combining duration and intensity relative to threshold. One hour at threshold is about 100.

See also: Fitness, fatigue and form (CTL, ATL, TSB)

Fitness, fatigue and form (CTL, ATL, TSB)Performance management chart

CTL (fitness) is a roughly six-week weighted average of daily load, ATL (fatigue) roughly one week, and TSB (form) is fitness minus fatigue. Useful for trends, not as a predictor of injury.

See also: Training Stress Score (TSS)

Efficiency factor (EF)Zone-restricted

Output per heartbeat: power or pace divided by heart rate. Endurance Signals measures it only in steady zone 2 to 3 work, because hard efforts break the link between heart rate and output.

See also: Durability

Aerobic decouplingPa:HR, Pw:HR

How much heart rate drifts upward against power or pace over a steady session. Low decoupling suggests good aerobic fitness for that duration.

See also: Durability

Durability

How well an athlete holds output and efficiency late in long or fatiguing sessions. A key limiter in long-course triathlon.

See also: Efficiency factor (EF)

VO2maxMaximal oxygen uptake

The highest rate the body can use oxygen. The ceiling of aerobic energy production.

See also: VLamax

VLamaxMaximal lactate production rate

The highest rate of glycolytic energy production. High VLamax supports sprints and surges but burns more carbohydrate at a given pace; low VLamax favours fat use and long steady efforts. Estimated from 20-second and 5-minute peak power (or the run-speed equivalents), body mass and body fat.

See also: VO2max

LT1 and LT2First and second lactate thresholds

LT1 is the top of truly easy, mostly fat-fuelled work. LT2 is the highest intensity that can be held for a long time before lactate accumulates. Training zones are anchored to them.

See also: Training zones

Training zones

Intensity bands for heart rate, power and pace, anchored to each athlete's thresholds rather than to age formulas.

See also: LT1 and LT2

Club plan

The training block a club coach writes once for a group. Athletes can follow it, adjust it, or not.

See also: Adjust for me

Adjust for me

Fits the club plan to one athlete's week, using their schedule, HRV, goals and commitments. Club sessions and race weeks are protected.

See also: Club plan

Longer explanations: HRV-guided training · Metabolic profiling without a lab