Fitness and health dictionary
Plain definitions of the words you meet in training, nutrition, sleep, gut health and AI coaching. Each entry links to the guides and calculators that use it.
Cardio and recovery
- Active recoveryActive recovery is light movement, such as walking, easy cycling or mobility work, on rest days or after hard sessions.
- Heart rate reserveHeart rate reserve is the difference between your maximum and resting heart rate.
- HRVHRV (heart rate variability) is the variation in time between heartbeats, a marker of how the nervous system is balancing stress and recovery.
- Polarised trainingPolarised training is an endurance approach with most sessions easy and a smaller share hard, and little in between.
- RecoveryRecovery is the process of returning to readiness after training, driven mostly by sleep, food and lighter days.
- Resting heart rateResting heart rate is your heart rate at complete rest, usually measured on waking.
- RMSSDRMSSD is the most common way to put heart rate variability into one number: the typical size of the change between one heartbeat interval and the next, in milliseconds.
- VO2 maxVO2 max is the maximum rate at which your body can use oxygen during hard exercise, in ml per kg per minute.
- Zone 2Zone 2 is steady, conversational aerobic exercise at roughly 60–70% of maximum heart rate.
Sleep and gut health
- BloatingBloating is a feeling of fullness or swelling in the abdomen, often with wind.
- Bowel movementA bowel movement is passing stool. Anywhere from about three a day to three a week is common.
- Bristol stool scaleThe Bristol stool scale is a seven-type chart of stool form, from separate hard lumps (type 1) to entirely liquid (type 7).
- Circadian rhythmThe circadian rhythm is the body's roughly 24-hour internal clock that times sleep, hormones and alertness.
- ConstipationConstipation means passing stool less often than usual or with difficulty, often hard and lumpy (Bristol types 1–2).
- Gut microbiomeThe gut microbiome is the community of bacteria and other microbes living in the digestive tract.
- Sleep cycleA sleep cycle is one pass through the stages of sleep, light, deep and REM, lasting roughly 90 minutes on average.
- Sleep debtSleep debt is the shortfall that builds up when you sleep less than you need over several nights.
Nutrition
- BMRBMR (basal metabolic rate) is the energy your body uses at complete rest to keep you alive.
- Calorie deficitA calorie deficit means eating less energy than you use, which leads to weight loss over time.
- EggetarianAn eggetarian diet is vegetarian with eggs: no meat or fish, but eggs and usually dairy.
- ElectrolytesElectrolytes are minerals such as sodium, potassium and magnesium that carry charge and help regulate fluid and muscle function.
- FibreFibre is the part of plant foods the body cannot fully digest, which supports digestion and gut bacteria.
- HydrationHydration is having enough body water for normal function, maintained by drinks and the water in food.
- Jain dietA Jain diet is a strict vegetarian diet that also avoids eggs and, for many, root vegetables such as onion, garlic and potato.
- MacronutrientsMacronutrients are the nutrients eaten in large amounts that provide energy: protein, carbohydrate and fat.
- ProteinProtein is the macronutrient that supplies amino acids for building and repairing muscle and other tissues.
- TDEETDEE (total daily energy expenditure) is the total energy you use in a day: resting metabolism plus activity and digesting food.
Training
- Bone mineral densityBone mineral density (BMD) is the amount of mineral in a given area of bone, measured with a DXA scan.
- CalisthenicsCalisthenics is strength training with your own bodyweight: push-ups, pull-ups, squats, dips and planks.
- Compound exerciseA compound exercise works several joints and muscle groups at once, such as a squat, deadlift, push-up or row.
- DeloadA deload is a planned lighter week or few days, with less volume or intensity, to let fatigue fall.
- DOMSDOMS (delayed-onset muscle soreness) is muscle soreness that peaks one to three days after unfamiliar or hard exercise.
- HypertrophyHypertrophy is the growth of muscle fibres in size, usually from resistance training and enough protein.
- HyroxHyrox is a standardised fitness race combining eight 1 km runs with eight functional workout stations.
- MobilityMobility is the ability to move a joint actively through its full range of motion with control.
- One-rep maxOne-rep max (1RM) is the heaviest load you can lift once with good form for a given exercise.
- PerimenopausePerimenopause is the transition before menopause, when periods change and symptoms such as hot flushes can start.
- Progressive overloadProgressive overload is gradually increasing the demand of training (reps, load, sets or difficulty) so the body keeps adapting.
- Prostate-specific antigenProstate-specific antigen (PSA) is a protein made by the prostate that can be measured in a blood test.
- RPERPE (rating of perceived exertion) is a 1–10 scale of how hard a set or session feels.
- Surya namaskarSurya namaskar (sun salutation) is a flowing sequence of yoga postures linked with the breath.
AI and tracking
- CadenceCadence is how often a session is expected, such as a run every three days or a swim every seven.
- Day scoreThe day score is a 0–100 summary of how a day went against your own targets across six pillars.
- MCPMCP (Model Context Protocol) is an open standard for connecting AI assistants to outside tools and data.
- MCP serverAn MCP server is a service that exposes tools and data to AI assistants through the Model Context Protocol.
- OAuthOAuth is a standard for granting an app limited access to your account without sharing your password.
- PillarA pillar is one of six areas the day score is built from: train, move, sleep, recover, fuel and mind.
- Rotation groupA rotation group is a set of sessions that take turns, such as a strength split of chest, back, legs and core.
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