A-Z Fitness Topics

Low-intensity movement performed on rest days — such as walking, light cycling, or yoga — that promotes blood flow to muscles, reduces soreness, and accelerates repair without adding training stress.

Physical activity that relies on oxygen to produce energy, sustained over extended periods. Examples include running, cycling, and swimming. Improves cardiovascular efficiency and burns fat at lower intensities.

The building blocks of protein. There are 20 amino acids, 9 of which are essential (must come from food). They are critical for muscle protein synthesis, enzyme production, and neurotransmitter function.

The exercise intensity at which lactic acid accumulates in the blood faster than it can be cleared. Training at or near this threshold improves speed and endurance capacity.

Referring to metabolic processes that build or synthesize complex molecules from simpler ones — particularly the construction of muscle tissue from amino acids. The opposite of catabolic.

The reduction in muscle size and strength caused by inactivity, caloric restriction, illness, or aging. Prevented by resistance training and adequate protein intake.

The number of calories your body needs to maintain basic life functions at complete rest — breathing, circulation, and cell maintenance. Accounts for 60–75% of total daily energy expenditure.

The proportion of fat mass to lean mass (muscle, bone, organs, water) in the body. A more accurate measure of fitness than bodyweight or BMI alone.

The proportion of total body weight that is fat. Essential body fat is approximately 3–5% for men and 10–13% for women. Measured via DEXA, hydrostatic weighing, or skinfold calipers.

A screening tool calculated as weight (kg) divided by height squared (m²). Classifies weight status as underweight (<18.5), normal (18.5–24.9), overweight (25–29.9), or obese (≥30). Does not account for muscle mass.

A training phase focused on building muscle mass by consuming a caloric surplus (typically 200–500 calories above maintenance) while following a progressive resistance training program.

A unit of energy. In nutrition, "calories" refers to kilocalories (kcal). The body obtains calories from macronutrients: carbohydrates (4 kcal/g), protein (4 kcal/g), and fat (9 kcal/g).

A state in which you consume fewer calories than you expend. Required for fat loss. A deficit of ~3,500 kcal corresponds to roughly 0.45 kg (1 lb) of fat loss.

A macronutrient providing 4 kcal per gram. The body's preferred fuel source. Classified as simple (sugars) or complex (starches, fiber). Stored as glycogen in muscles and the liver.

The ability of the heart, lungs, and circulatory system to supply oxygen to working muscles during sustained physical activity. Measured by VO2 max.

A movement that engages multiple muscle groups and joints simultaneously. Examples: squat, deadlift, bench press, pull-up. More metabolically demanding than isolation exercises.

A stress hormone produced by the adrenal glands. Chronically elevated cortisol (from overtraining, poor sleep, or chronic stress) can impair muscle growth, increase fat storage (especially visceral), and suppress immunity.

One of the most researched and effective sports supplements. Increases phosphocreatine stores in muscles, allowing more ATP regeneration during high-intensity exercise. Proven to improve strength and power output.

A phase focused on reducing body fat while preserving muscle mass. Achieved through a caloric deficit combined with resistance training and adequate protein intake.

A fundamental compound lift that involves picking a loaded barbell from the floor. Trains the entire posterior chain — hamstrings, glutes, lower back, and traps — along with the core.

A planned period of reduced training volume or intensity, typically lasting one week, taken every 4–8 weeks. Allows the body to fully recover from accumulated fatigue and prevents overtraining.

Muscle soreness that peaks 24–72 hours after unfamiliar or intense exercise. Caused by microscopic muscle fiber tears and inflammation. A normal response to progressive training; not an indicator of workout quality.

The sum of food and beverages consumed by an individual. In fitness contexts, often refers to a structured eating plan designed to achieve a specific goal such as fat loss, muscle gain, or improved health markers.

The lowering or lengthening phase of a resistance exercise (e.g., lowering the barbell in a bench press). Eccentric loading causes more muscle damage and is key to hypertrophy.

The ability to sustain physical activity for prolonged periods. Cardiovascular endurance relates to aerobic capacity; muscular endurance relates to the ability of a muscle to perform repeated contractions.

The relationship between calories consumed and calories expended. A positive balance (surplus) leads to weight gain; a negative balance (deficit) leads to weight loss.

The elevated oxygen consumption and caloric burn that continues after intense exercise stops. Colloquially called "afterburn." More pronounced after HIIT than steady-state cardio.

The minimum amount of fat required for normal physiological functioning, including hormone production, organ protection, and vitamin absorption. Approximately 3–5% for men and 10–13% for women.

Type II muscle fibers that contract quickly and powerfully but fatigue faster. Used for sprinting, jumping, and heavy lifting. Respond well to hypertrophy training.

A macronutrient providing 9 kcal per gram. Essential for hormone production, fat-soluble vitamin absorption, and cell membrane integrity. Includes saturated, unsaturated, and trans fats.

The range of motion available in a joint or group of joints. Influenced by muscle length, tendon elasticity, and joint capsule structure. Improved through regular stretching.

A self-myofascial release technique using a foam roller to apply pressure to soft tissue. Helps break up adhesions, improve tissue quality, reduce perceived soreness, and increase range of motion.

The stored form of glucose in muscles (~400g) and the liver (~100g). The primary fuel source during moderate-to-high-intensity exercise. Replenished by consuming carbohydrates post-workout.

The three muscles of the buttocks: gluteus maximus (largest, primary hip extensor), gluteus medius (hip abduction and pelvic stability), and gluteus minimus. Critical for running, squatting, and hip hinge movements.

The number of times the heart beats per minute. Resting heart rate (60–100 bpm for adults) is a marker of cardiovascular fitness — elite athletes often have resting HRs of 40–60 bpm.

A training method alternating short bursts of intense effort with brief recovery periods. Effective for improving cardiovascular fitness, burning fat, and creating EPOC. Sessions typically last 15–30 minutes.

An increase in muscle cell size driven by resistance training and adequate protein intake. Myofibrillar hypertrophy increases muscle density (strength-focused); sarcoplasmic hypertrophy increases muscle fluid volume (size-focused).

A hormone released by the pancreas in response to elevated blood glucose. Facilitates glucose uptake into cells. After exercise, elevated insulin sensitivity enhances nutrient partitioning — making post-workout nutrition especially effective.

An exercise that targets a single muscle group and moves through one joint. Examples: bicep curl, leg extension, lateral raise. Used to address weak points after compound work.

A metabolic state where the body primarily burns fat for fuel, producing ketone bodies. Achieved by restricting carbohydrate intake to <50g per day, as in the ketogenic diet.

Total body weight minus fat mass. Includes muscle, bone, organs, and water. Higher LBM is associated with improved metabolic rate, strength, and longevity.

An essential branched-chain amino acid (BCAA) that acts as a primary trigger for muscle protein synthesis by activating the mTOR pathway. Found in high quantities in animal proteins, whey, and eggs.

Cardiovascular exercise performed at a constant, moderate pace (60–65% max HR) for 30–60 minutes. Burns fat efficiently and is easier to recover from than HIIT. Examples: brisk walking, light cycling.

The highest heart rate achievable during maximal exertion. Commonly estimated as 220 minus age. Used to calculate training zones.

The three main nutrient categories providing energy: carbohydrates (4 kcal/g), protein (4 kcal/g), and fat (9 kcal/g). Tracking macros allows precise control over body composition.

All chemical processes in the body that convert food into energy. Basal metabolic rate (BMR) is the largest component. Influenced by age, sex, muscle mass, hormones, and thyroid function.

Vitamins and minerals required in small amounts for normal bodily function. Unlike macronutrients, they don't provide energy but are essential for enzyme function, immunity, bone health, and energy metabolism.

The ability to move a joint through its full range of motion under active muscular control. Distinct from flexibility (passive range). Improved through dynamic stretching, joint circles, and movement-based training.

The process by which the body builds new muscle protein from amino acids. Stimulated by resistance training and dietary protein intake (particularly leucine). The key driver of muscle hypertrophy.

Performing only the eccentric (lowering) phase of an exercise with a weight heavier than you could normally lift. Used to build strength in the eccentric portion and overcome strength plateaus.

The difference between nitrogen intake (from dietary protein) and nitrogen excretion. Positive nitrogen balance indicates net protein synthesis (muscle building); negative balance indicates net protein breakdown.

The maximum weight you can lift for a single repetition of an exercise with proper form. Used to calculate training percentages across strength and hypertrophy programs.

A condition resulting from excessive training volume without adequate recovery. Symptoms include performance decline, persistent fatigue, mood disturbances, and increased injury risk. Treated with rest and nutrition.

The systematic variation of training variables (volume, intensity, frequency) over time to maximize long-term progress and prevent overtraining. Includes linear, undulating, and block periodization models.

The fundamental principle of strength training: gradually increasing the demands placed on the musculoskeletal system over time. Achieved by adding weight, reps, sets, or reducing rest time.

A macronutrient providing 4 kcal per gram, composed of amino acids. Essential for muscle repair, enzyme production, immune function, and satiety. General recommendation: 1.6–2.2 g/kg bodyweight for active individuals.

The number of calories burned at rest to maintain basic body functions. Slightly higher than BMR because RMR is measured after a shorter fasting period. Used interchangeably with BMR in most fitness contexts.

One complete execution of an exercise movement — for example, lowering and raising the bar one time in a bench press. Typically combined with a target number of sets (e.g., 3 sets of 10 reps).

A subjective scale (1–10) used to rate exercise intensity. In strength training, RPE 10 = absolute maximum effort; RPE 8 = 2 reps left in the tank. Widely used in powerlifting programming.

A group of consecutive repetitions performed without rest. Common set-rep schemes: 3×10 for hypertrophy, 5×5 for strength, 3×15–20 for endurance.

Type I muscle fibers that contract slowly but are highly fatigue-resistant. Predominant in endurance athletes. Used during low-intensity, long-duration activities like marathon running.

A foundational compound lower body exercise that involves bending the knees and hips to lower the body and then standing back up. Primarily targets quads, glutes, and hamstrings.

Performing two exercises back-to-back with minimal rest. Agonist supersets target the same muscle; antagonist supersets target opposing muscles (e.g., bicep curl followed by tricep extension).

The total number of calories you burn each day, accounting for your BMR, physical activity, and the thermic effect of food. The baseline from which caloric goals (deficit or surplus) are calculated.

The energy cost of digesting, absorbing, and metabolizing food. Protein has the highest TEF (20–30%), followed by carbohydrates (5–10%) and fat (0–3%). Accounts for ~10% of total daily energy expenditure.

The primary anabolic sex hormone in men (also present in lower amounts in women). Promotes muscle protein synthesis, bone density, and fat metabolism. Stimulated by heavy compound training, adequate sleep, and healthy fat intake.

The total amount of work performed in training, calculated as sets × reps × weight. The primary driver of hypertrophy. Research suggests 10–20 working sets per muscle group per week for optimal growth.

The maximum rate at which the body can consume oxygen during maximal exercise. The gold standard measure of aerobic fitness. Trainable through high-intensity interval training and long-distance endurance work.

Fat stored around the internal organs within the abdominal cavity. Metabolically active and associated with increased cardiovascular disease, type 2 diabetes, and inflammation risk. Reduced by caloric deficit and exercise.

A preparatory phase before exercise that gradually increases heart rate, blood flow to muscles, and tissue temperature. Reduces injury risk and improves performance. Typically 5–10 minutes of light cardio and dynamic stretching.

Water is essential for every physiological process — thermoregulation, nutrient transport, joint lubrication, and cellular function. General recommendation: 35 ml/kg bodyweight, plus additional amounts for sweat loss.

A fast-digesting, complete protein derived from milk during cheese production. Rich in leucine and BCAAs. Highly effective for stimulating muscle protein synthesis post-workout.

Cardio performed at 60–70% of maximum heart rate — a pace where you can hold a conversation. Optimal for building aerobic base, mitochondrial density, and fat oxidation capacity. Also known as "base training."