Glossary

Health & Fitness Glossary

Clear, science-backed definitions of the most important health and fitness concepts — so you can train smarter and live better.

A

Active RecoveryActive recovery is performing low-intensity exercise on rest days to promote blood flow, reduce muscle soreness, and accelerate the recovery process between harder training sessions.

B

Basal Metabolic Rate (BMR)BMR is the number of calories your body needs to perform essential life-sustaining functions at complete rest, such as breathing, circulation, and cell production.Body RecompositionBody recomposition is the process of simultaneously losing body fat and gaining muscle mass. It changes your body composition without necessarily changing your overall weight.

C

Calorie DeficitA calorie deficit occurs when you consume fewer calories than your body expends. It is the fundamental requirement for losing body fat, regardless of the specific diet you follow.

H

Heart Rate Variability (HRV)Heart rate variability is the variation in time between consecutive heartbeats. Higher HRV generally indicates better cardiovascular fitness and stress resilience.HIIT (High-Intensity Interval Training)HIIT is a training method that alternates short bursts of intense exercise with brief recovery periods. It is highly effective for improving cardiovascular fitness and burning calories in less time.

M

MacronutrientsMacronutrients are the three main nutrients your body needs in large amounts: protein, carbohydrates, and fat. Each plays a distinct role in energy production, tissue repair, and overall health.Metabolic RateMetabolic rate is the speed at which your body converts food and stored energy into usable energy. It determines how many calories you burn at rest and during activity.Muscle HypertrophyMuscle hypertrophy is the increase in muscle cell size that occurs in response to resistance training. It is the primary mechanism through which muscles grow larger and stronger.

P

Progressive OverloadProgressive overload is the gradual increase of stress placed on the body during exercise. It is the foundational principle behind gaining strength, muscle, and endurance.

R

Resting Heart RateResting heart rate (RHR) is the number of times your heart beats per minute while you are completely at rest. A lower RHR generally indicates better cardiovascular fitness.

S

Sleep DebtSleep debt is the cumulative difference between the amount of sleep you need and the amount you actually get. It accumulates over time and negatively impacts cognitive function, recovery, and health.

T

Total Daily Energy Expenditure (TDEE)TDEE is the total number of calories your body burns in a day, combining your basal metabolic rate, physical activity, and the thermic effect of food.

V

VO2 MaxVO2 max is the maximum rate of oxygen your body can utilize during intense exercise. It is widely regarded as the gold standard measure of cardiovascular fitness.

Z

Zone 2 TrainingZone 2 training is low-to-moderate intensity cardio performed at 60–70% of your maximum heart rate. It builds aerobic base, improves fat oxidation, and supports long-term cardiovascular health.