Fitness & Nutrition Glossary
Plain-English definitions of the most common training and nutrition terms — written for beginners, useful for anyone.
Activity
NEAT
Non-Exercise Activity Thermogenesis — calories burned by everyday movement (walking, fidgeting, posture). Often the largest controllable lever after training.
Nutrition
BMR
Basal Metabolic Rate — the calories your body burns at complete rest to maintain organ function.
Caloric deficit
Eating fewer calories than your body expends. The required condition for fat loss. Sustainable range: 10–25% below maintenance.
Energy balance
The relationship between calories in and calories out. Determines weight direction; macros and food quality determine composition.
Macronutrients
Protein, carbohydrate, and fat — the three nutrients that supply calories. Each plays a distinct role in body composition and performance.
Maintenance calories
The daily calorie intake at which bodyweight neither rises nor falls over a 2–4 week average.
Mifflin-St Jeor
The most accurate published equation for estimating BMR from height, weight, age, and sex. Used by the Macro and TDEE calculators here.
Protein
The macronutrient required for muscle repair and growth. Recommended intake for trainees: 1.6–2.4 g per kg of bodyweight per day.
Surplus
Eating more calories than maintenance. Required for maximum muscle growth — typically +150 to +300 kcal/day.
TDEE
Total Daily Energy Expenditure. Sum of BMR + activity + thermic effect of food. Practical maintenance estimate.
Programming
AMRAP
As Many Reps As Possible. A set taken to one or two reps shy of failure, or to true failure depending on the protocol.
Cut
A focused phase of fat loss, typically 8–16 weeks at a 15–25% calorie deficit.
Full-body split
A training structure where each session trains all major muscle groups, typically 3 days per week.
PPL split
Push / Pull / Legs — a 3- or 6-day training structure organising sessions by movement category.
Recomposition
The simultaneous loss of fat and gain of muscle. Most achievable in beginners, returnees, and trainees coming off long restriction cycles.
RIR
Reps In Reserve — the number of additional reps you could have completed with good form. Used to gauge effort without going to true failure.
RPE
Rate of Perceived Exertion (1–10). RPE 8 = 2 reps in reserve; RPE 10 = true failure.
Volume
Total work performed for a muscle in a week — usually counted as hard sets per muscle (10–20 is the practical range for most).
Recovery
Deload
A planned week of reduced training volume and intensity (around 60% of normal) used every 6–10 weeks to manage fatigue.
Strength
1RM
One-rep max. The maximum weight you can lift for a single repetition with good form. Used to set training percentages.
Supplements
BCAAs
Branched-Chain Amino Acids (leucine, isoleucine, valine). Already present in adequate amounts in any complete protein source — separate supplementation rarely adds value.
Creatine monohydrate
A naturally occurring compound that increases the body's phosphocreatine stores. Most-studied performance supplement; safely effective at 3–5 g/day.
Whey protein
Fast-digesting milk protein. Convenient way to hit daily protein targets. Isolate is lowest in lactose; concentrate is cheaper.
Training
Compound lift
An exercise that uses multiple joints and muscle groups (squat, deadlift, bench press, row, overhead press).
Concentric
The 'lifting' phase of a rep — the muscle is shortening (e.g. standing up from a squat).
Eccentric
The 'lowering' phase of a rep — the muscle is lengthening under load. Often the highest-stimulus portion of the lift.
Failure
The point at which another full-range rep is impossible despite maximal effort. Most working sets target 0–3 reps short of failure (RIR).
Hinge
A movement pattern that bends the body at the hips with minimal knee bend (e.g. Romanian deadlift). Builds posterior chain.
Hypertrophy
The growth of muscle tissue. Driven by sufficient mechanical tension, volume, and proximity to failure across consistent training.
Progressive overload
The principle that strength and muscle growth require gradually increasing training stimulus over time (load, reps, density, or quality).
Set
A group of consecutive reps performed without resting. A 'working set' is one taken close enough to failure to drive adaptation.
Time under tension
The total seconds a muscle is under load during a set. Eccentric tempo and pause work both increase it.