Fitness Glossary

The ultimate reference dictionary for translating gym jargon, dietary terms, and supplement and training concepts.

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Term of the Day

AMRAP

As Many Reps As Possible

A workout protocol where you perform an exercise for as many repetitions as you can within a specified timeframe or until failure.

Training

180 of 180 terms

Accommodating Resistance: Adding bands or chains to a barbell so the load increases through the range where you are mechanically strongest. It keeps tension high near lockout, where a plain barbell often feels easy.
Active Recovery: Low-intensity movement such as walking or easy cycling done on rest days or between sets to promote blood flow. It aims to aid recovery without adding meaningful training stress.
Adaptogen: A class of plant compounds, such as ashwagandha and rhodiola, proposed to help the body cope with stress. Evidence is mixed and effects tend to be modest rather than dramatic.
Adenosine: A molecule that accumulates in the brain during waking hours and builds sleep pressure. Caffeine works largely by blocking its receptors, which is why it delays tiredness.
AMRAP: As Many Reps As Possible; A workout protocol where you perform an exercise for as many repetitions as you can within a specified timeframe or until failure.
Anabolic Resistance: A blunted muscle protein synthesis response to a given dose of protein, common with aging and inactivity. It is why older adults are generally advised to eat more protein per meal, not less.
Anabolic vs Catabolic: Anabolic processes build tissue such as muscle, while catabolic processes break tissue down for energy. Training and nutrition shift the balance between the two.
Anabolic Window: The idea that there is a narrow post-workout period in which protein and carbs must be eaten to maximize gains. Research suggests this window is much wider than once believed, with total daily intake mattering more.
APRE: Autoregulatory Progressive Resistance Exercise; A training method where the load for later sets is adjusted based on how many reps you managed on an earlier set. It builds daily autoregulation directly into a structured progression.
ATP: Adenosine Triphosphate; The primary molecule that stores and transfers energy within cells, fueling intense muscle contractions.
Autophagy: The cellular process of breaking down and recycling damaged components. Research suggests it can be upregulated by fasting and exercise as part of normal cellular maintenance.
Autoregulation: Adjusting the weight, reps, or sets of a session based on how you actually feel that day rather than following a fixed number. RPE and RIR are the usual tools for doing it.
BCAAs: Branched-Chain Amino Acids; Essential amino acids (leucine, isoleucine, and valine) involved in muscle protein synthesis. Largely redundant as a standalone supplement if you already eat enough total protein, since complete protein sources already supply them.
Beta-Alanine: An amino acid that raises muscle carnosine levels, helping buffer acid during high-intensity efforts. Research associates it with small performance gains in exercise lasting roughly one to four minutes.
Bioavailability: The proportion of a nutrient or supplement that is actually absorbed and available for the body to use, rather than passed through unused.
Blood Flow Restriction: BFR; Training with a cuff that partially limits blood flow to a working limb, allowing muscle growth with much lighter loads. It is often used in rehab when heavy lifting is not tolerable.
BMR: Basal Metabolic Rate; The number of calories your body burns at rest just to keep basic life functions (breathing, circulation) running.
Body Recomposition: Losing fat and gaining muscle at the same time rather than in separate bulk and cut phases. It is most achievable for beginners, those returning from a layoff, and people with higher body fat.
Bone Mineral Density: BMD; A measure of the amount of minerals, mainly calcium, packed into bone. It is used as an indicator of bone strength, often assessed with a DEXA scan.
Botanicals: Plant extracts or herb-derived ingredients used therapeutically to promote health, reduce inflammation, or boost performance.
Caffeine Tolerance: The reduced effect of caffeine that develops with regular use as the body adapts. Cycling caffeine or taking periodic low-dose breaks is a common strategy to restore its ergogenic punch.
Calisthenics: A form of strength training that uses the resistance of your own body weight rather than external weights.
Caloric Deficit: Consuming fewer calories than you burn. A sustained deficit is the fundamental requirement for fat loss.
Caloric Surplus: Consuming more calories than you burn. A modest surplus supports muscle gain when paired with resistance training.
Carb Cycling: Alternating higher- and lower-carbohydrate days, often aligning higher intake with harder training days. It is used to support performance on key sessions while keeping overall intake in check.
Carb Loading: Deliberately eating extra carbohydrate in the days before a long endurance event to maximize muscle and liver glycogen stores. The aim is to delay fatigue during prolonged efforts like a marathon.
Casein Protein: The slow-digesting protein fraction of milk. It gels in the stomach and releases amino acids gradually, which is why it is often taken before bed.
Chronotype: Your natural tendency toward being a morning person or a night owl, driven by your internal circadian clock. Aligning training and sleep timing with your chronotype may support performance and adherence.
Circadian Rhythm: The roughly 24-hour internal clock that governs sleep, hormone release, and body temperature. Keeping consistent light exposure and sleep timing is associated with better recovery and metabolic health.
Citrulline: An amino acid, often taken as citrulline malate, that raises nitric oxide and may modestly improve blood flow and reduce fatigue. It is a common pre-workout ingredient linked to better training pumps.
Cluster Set: A set broken into small groups of reps with brief intra-set rests of roughly 10 to 30 seconds, allowing heavier loads or more quality reps than a straight set.
Collagen: The most abundant structural protein in the body, vital for maintaining skin elasticity, joint health, and connective tissue integrity.
Complete Protein: A protein source that supplies all nine essential amino acids in adequate amounts, such as meat, eggs, dairy, and soy.
Compound Movement: An exercise that works multiple joints and muscle groups at once, such as squats, deadlifts, and bench press. Efficient for building overall strength and mass.
Concentric: The shortening phase of a muscle contraction, such as pressing the bar up in a bench press.
Cortisol: A hormone released in response to stress and exercise. Normal in acute amounts; chronically elevated levels are associated with poorer recovery and sleep.
Creatine: An organic acid naturally occurring in the body that helps supply energy to muscle and nerve cells, widely used to boost athletic performance and cognitive health.
Creatine Loading: Taking roughly 20 grams of creatine daily, split into four doses, for 5 to 7 days to saturate muscle stores quickly, then dropping to 3 to 5 grams daily. Skipping the load and taking 3 to 5 grams from the start reaches the same saturation in about three to four weeks.
Creatine Non-Responder: Someone who gains little muscle creatine from supplementing, typically because their baseline stores are already near saturation. People with lower starting stores, such as vegetarians, tend to respond most.
CYP1A2: Cytochrome P450 1A2; The liver enzyme responsible for most caffeine breakdown. Common variants in its gene split people into faster and slower metabolizers, which helps explain why the same coffee wrecks one person's sleep and not another's.
Deload: A planned reduction in training volume or intensity (typically for a week) to allow recovery and reduce accumulated fatigue before pushing again.
DEXA: Dual-Energy X-ray Absorptiometry; A scan that uses low-dose X-rays to measure bone mineral density and estimate body fat and lean mass. It is considered one of the more accurate widely available body-composition tools.
Diet Break: A planned pause from a calorie deficit, typically one to two weeks at maintenance calories, used to ease diet fatigue and support long-term adherence. Unlike a refeed, it lasts longer than a single day.
Dietary Fiber: The indigestible part of plant foods that adds bulk, supports digestion and satiety, and helps steady the rise in blood sugar after meals.
DOMS: Delayed Onset Muscle Soreness; The muscle pain and stiffness that typically begins 12 to 24 hours after a new or intense workout.
DOTS: A scoring formula that adjusts a powerlifting total for bodyweight so lifters of different sizes can be compared. It replaced the Wilks formula in federations such as USAPL and USPA for best-lifter awards.
Double Progression: A progression method where you first add reps within a target range at a fixed weight, then add weight once you hit the top of the range and start again at the bottom.
Drop Set: Performing a set to near failure, then immediately reducing the weight and continuing for more reps to extend a set past normal fatigue.
e1RM: Estimated One-Rep Max; A one-rep max predicted from a submaximal set using the weight and reps performed, rather than tested directly. It lets you track strength without repeatedly lifting to a true maximum.
Eccentric: The lengthening phase of a muscle contraction, such as lowering the bar in a bench press. Eccentric loading is strongly associated with muscle damage and growth.
Electrolytes: Minerals such as sodium, potassium, and magnesium that carry an electrical charge and support hydration, nerve signaling, and muscle contraction. Lost through sweat.
EMOM: Every Minute On the Minute; A type of interval workout where you perform a specific task at the start of every minute for a set amount of time.
EPOC: Excess Post-exercise Oxygen Consumption; The elevated calorie burn that continues after intense exercise as the body returns to baseline. Often called the "afterburn" effect.
Ergogenic Aid: Any substance or method used to enhance performance, recovery, or work capacity, such as caffeine or creatine. The term simply means 'work-producing' and does not imply a supplement is effective.
Essential Amino Acids: EAAs; The nine amino acids the body cannot produce on its own and must obtain from food. They are required for building and repairing muscle.
Failure (Muscular): The point in a set where you can no longer complete another full rep with good form. Training to failure builds muscle but adds fatigue and recovery cost, so most programs deliberately stop one to three reps short.
Fartlek: A Swedish term meaning 'speed play,' describing unstructured runs that mix faster surges with easier recovery jogging by feel rather than a fixed plan. It blends aerobic and higher-intensity work in one session.
Fat Oxidation: The process of breaking down fatty acids to produce energy, which dominates fuel use at lower exercise intensities. The intensity where it peaks is sometimes called Fatmax.
FFMI: Fat-Free Mass Index; A height-adjusted measure of lean body mass used to gauge muscularity independent of height. Drug-free lifters rarely exceed an FFMI of about 25, which makes it a rough natural-potential benchmark.
Ghrelin: Often called the 'hunger hormone,' it is released largely by the stomach and rises before meals to stimulate appetite. Short sleep and dieting can push it higher, increasing the drive to eat.
Gluconeogenesis: The process by which the body makes glucose from non-carbohydrate sources such as amino acids and glycerol, mainly in the liver. It keeps blood sugar stable during fasting or low-carb intake.
Glycemic Index: GI; A ranking of how quickly a carbohydrate-containing food raises blood sugar. Higher-GI foods digest faster; lower-GI foods provide steadier energy.
Glycemic Load: GL; A measure that combines a food's glycemic index with the amount of carbohydrate actually in a serving. It gives a more practical picture of blood-sugar impact than glycemic index alone.
Glycogen: The stored form of carbohydrate in muscle and liver. It is a primary fuel for higher-intensity exercise; depleting it is associated with reduced performance and "hitting the wall."
Glymphatic System: The brain's waste-clearance network, which flushes metabolic byproducts out of brain tissue. Research suggests it is substantially more active during sleep than while awake.
Golgi Tendon Organ: GTO; A sensor located where muscle meets tendon that detects tension and can trigger a protective relaxation when force gets very high. It is one of the reflexes involved in flexibility techniques.
Grip Strength: The force you can generate squeezing a dynamometer, used as a quick proxy for whole-body strength. Lower grip strength is associated with worse health outcomes in older adults, though it is a marker rather than a cause.
Gut Microbiome: The community of trillions of microbes living in the digestive tract. Research suggests it plays a role in digestion, immune function, and overall health.
Heart Rate Reserve: HRR; Your maximum heart rate minus your resting heart rate. Cardio zones based on a percentage of this reserve, known as the Karvonen method, account for individual fitness better than percentages of max heart rate alone.
Heavy Slow Resistance: HSR; A tendon rehab protocol using heavy loads lifted with a deliberate tempo, roughly 3 seconds up and 3 seconds down. Studied progressions run about 12 weeks, moving from 15RM loads down to 6RM loads three times per week.
HIIT: High-Intensity Interval Training; A cardiovascular exercise strategy alternating short periods of intense anaerobic exercise with less intense recovery periods.
HMB: Beta-hydroxy beta-methylbutyrate; A substance produced when the body breaks down leucine. It is used to prevent muscle breakdown and increase muscle mass.
Hormetic Stress: A mild, acute biological stressor (like cold plunging or saunas) that triggers beneficial adaptive responses and improves overall resilience.
HRV: Heart Rate Variability; The measure of the variation in time between each heartbeat. A key indicator of nervous system readiness and physical recovery.
Hypertrophy: The increase and growth of muscle cells. Hypertrophy training focuses on building muscle size rather than pure strength.
Hyponatremia: A condition that occurs when the level of sodium in your blood is abnormally low, often caused by over-hydrating with plain water and flushing out electrolytes.
IIFYM: If It Fits Your Macros; A flexible dieting approach where you can eat whatever you want, provided you stay within your daily macronutrient targets.
Insulin Sensitivity: How responsive your cells are to insulin. Higher sensitivity helps the body manage blood sugar; regular exercise is associated with improving it.
Insulin-like Growth Factor 1: IGF-1; A hormone produced mainly in the liver that mediates many of growth hormone's effects and supports tissue growth and repair. It plays a role in how muscle adapts to training.
Interference Effect: The tendency for heavy endurance training to blunt strength and muscle gains when combined with lifting. Separating the two sessions and managing endurance volume are common ways to limit it.
IPF GL Points: International Powerlifting Federation Goodlift Points; The bodyweight-adjusted scoring system used at IPF-sanctioned meets since May 2020, replacing the older IPF formula. It is scaled so that roughly 100 points represents a world-class performance.
Isolation Movement: An exercise that targets a single muscle through one joint, such as a bicep curl or leg extension. Useful for bringing up lagging areas.
Isometric: A contraction where the muscle produces force without changing length, such as holding a plank or pushing against an immovable bar.
Junk Volume: Extra sets that add fatigue without driving further progress — for example, sets taken far from failure or piled on beyond what you can recover from. Adding volume helps only up to a point.
Ketosis: A metabolic state in which the body relies heavily on fat for fuel and produces ketones, typically brought on by very low carbohydrate intake.
Lactate Threshold: The exercise intensity at which lactate begins to accumulate in the blood faster than it can be cleared, often experienced as a sharp rise in effort.
Lengthened Partials: Performing only the bottom, stretched portion of a rep's range once full reps become too hard. Emerging research suggests training a muscle in its lengthened position can be a potent driver of growth.
Leptin: A hormone released by fat cells that signals energy sufficiency to the brain and helps suppress appetite. Levels fall during dieting, which is part of why hunger tends to rise as you lose weight.
Leucine: The amino acid most responsible for triggering muscle protein synthesis. Whey, eggs, and dairy are particularly rich sources.
Leucine Threshold: The idea that a meal needs roughly 2 to 3 grams of leucine, about 25 to 30 grams of quality protein, to maximally trigger muscle protein synthesis. It is a useful planning rule, though the evidence behind a hard cutoff is mixed.
LISS: Low-Intensity Steady State; A form of cardiovascular exercise where you maintain a consistent, low-to-moderate heart rate for an extended period of time.
Macrocycle: The longest training cycle, often a full season or year, made up of multiple mesocycles working toward a peak event or long-term goal.
Macros: Macronutrients; The three primary components of food that provide energy: Proteins, Carbohydrates, and Fats.
Maintenance Calories: The number of calories that keeps your body weight stable. It sits between a deficit and a surplus and roughly equals your TDEE.
Mechanical Tension: The force a muscle generates against a load, widely considered the primary driver of hypertrophy. It is greatest with challenging weights and reps taken close to failure.
Medium-Chain Triglycerides: MCT; A type of fat with shorter chains that is absorbed and used for energy more quickly than most dietary fats, often sourced from coconut oil. It is popular in ketogenic and endurance nutrition.
Mesocycle: A training block of several weeks (often 3–6) focused on a specific goal, sitting between the weekly microcycle and the season-long macrocycle.
Metabolic Adaptation: The tendency for the body to reduce energy expenditure during prolonged dieting, sometimes called adaptive thermogenesis, which can slow fat loss over time.
Metabolic Stress: The buildup of metabolites like lactate and hydrogen ions during higher-rep sets, often felt as the 'burn' and pump. It is thought to contribute to muscle growth alongside mechanical tension.
Microcycle: The shortest planned unit of training, typically a single week. Several microcycles stack into a mesocycle.
Micronutrient: Vitamins and minerals the body needs in small amounts to function, as distinct from the macronutrients (protein, carbs, and fat) needed in larger quantities.
Mind-Muscle Connection: Consciously focusing on contracting the target muscle during a lift. Research suggests it can increase activation of that muscle, especially on isolation work.
Mitochondria: The energy-producing structures inside cells that generate ATP. Aerobic training is associated with increasing their number and efficiency.
Mobility: The active range of motion of a joint. It is how far you can move a joint using only your own muscular strength and neurological control.
Motor Unit: A single motor neuron together with all the muscle fibers it controls. When the neuron fires, every fiber in that unit contracts.
mTOR: mechanistic Target of Rapamycin; A cellular signaling pathway that helps regulate protein synthesis and cell growth. It is activated by resistance training, protein intake, and leucine.
Muscle Fiber Types: Broadly, slow-twitch (Type I) fibers suited to endurance and fatigue resistance, and fast-twitch (Type II) fibers suited to power and maximal strength.
Muscle Memory: The tendency to regain lost muscle faster than it was first built. Research suggests trained muscle retains added nuclei that persist through detraining, easing the return to prior size.
Muscle Protein Synthesis: MPS; The process by which the body builds new muscle protein. Resistance training and adequate protein intake both elevate MPS, driving net muscle gain over time.
Myofibrillar Hypertrophy: Growth driven by adding contractile proteins (actin and myosin) to the muscle fiber. It is the form of growth most closely tied to producing force.
Myokine: A signaling molecule released by contracting muscle that communicates with other tissues such as fat, bone, and the brain. Their discovery reframed muscle as an organ that actively secretes beneficial compounds.
NEAT: Non-Exercise Activity Thermogenesis; The calories burned from all the movement you do that is not sleeping, eating, or intentional exercise (e.g., walking, fidgeting).
Neural Adaptation: Early strength gains that come from the nervous system learning to recruit and coordinate muscle more effectively, before much muscle size is added. It explains why beginners get stronger fast without visibly bigger muscles.
Nitrogen Balance: The difference between the nitrogen you take in from protein and the nitrogen you excrete. A positive balance generally reflects net muscle-building conditions.
Omega-3 Fatty Acids: A family of essential fats, notably EPA and DHA from fish, involved in cell membranes and inflammation regulation. Research associates adequate intake with cardiovascular and joint health.
One-Rep Max (1RM): The absolute maximum amount of weight you can lift for a single, clean repetition of a given exercise.
Osteopenia: Lower-than-normal bone mineral density that has not reached the threshold defined as osteoporosis. Resistance training and adequate calcium and vitamin D are commonly recommended for bone health.
Overreaching: A short-term overload that temporarily dips performance but leads to a rebound after rest. Unlike overtraining, it is planned and resolves within days to a couple of weeks.
Overtraining: A state of prolonged fatigue and declining performance that results from training beyond what the body can recover from. Adequate rest and deloads help prevent it.
Peptides: Short chains of amino acids that act as building blocks for proteins like collagen and elastin, often used to promote skin health, muscle growth, or recovery.
Periodization: The systematic planning of training in cycles that vary volume and intensity over time. It is used to keep progressing while managing fatigue and reducing plateaus.
Phosphocreatine: PCr; A high-energy compound stored in muscle that rapidly regenerates ATP during all-out effort. It is the main fuel for roughly the first 10 seconds of maximal work, and creatine supplementation raises these stores.
Plyometrics: Jumping and bounding exercises that use the stretch-shortening cycle, where a rapid lengthening is immediately followed by a powerful shortening. Used to develop explosive power.
PNF Stretching: Proprioceptive Neuromuscular Facilitation; A flexibility technique that alternates stretching a muscle with brief contractions against resistance to reach a greater range. It is often cited as one of the more effective ways to increase passive flexibility.
PR: Personal Record; Your best-ever performance on a lift or event — for example the most weight lifted for a given rep count, or a fastest time.
Pre-Exhaustion: Fatiguing a target muscle with an isolation exercise before a compound lift, such as leg extensions before squats. The goal is to make the target muscle the limiting factor rather than smaller assisting muscles.
Prebiotics: Types of dietary fiber that feed the beneficial bacteria already living in your gut, found in foods like onions, garlic, and oats. They act as fuel for the microbiome rather than adding microbes directly.
Probiotics: Live beneficial bacteria consumed through fermented foods or supplements that can add to the community of microbes in the gut. Effects are strain-specific, so benefits vary by product.
Progressive Overload: The gradual increase of stress placed upon the body during exercise training (e.g., adding weight, reps, or sets) to drive continuous improvement.
Quadriceps: The four-headed muscle group at the front of the thigh (the rectus femoris and three vastus muscles) that straightens the knee. The primary movers in squats, leg presses, lunges, and extensions.
Range of Motion: ROM; The full distance a joint can move through during an exercise. Training through a complete ROM is generally associated with better strength and muscle development.
Rate of Force Development: RFD; How quickly you can produce force, rather than how much force you can eventually produce. It matters most in explosive actions like sprinting and jumping, which allow only a fraction of a second to generate force.
Refeed: A planned short-term increase in calories, usually from carbohydrates, during a diet to replenish glycogen and support long-term adherence.
REM Sleep: Rapid Eye Movement Sleep; The sleep stage marked by vivid dreaming and heightened brain activity, important for memory consolidation and mood. It makes up a larger share of sleep in the later hours of the night.
Resistant Starch: A form of starch that resists digestion in the small intestine and ferments in the colon, acting much like fiber. It is found in cooked-and-cooled potatoes and rice, green bananas, and legumes.
Rest-Pause: A technique that extends a set by taking very short rests (roughly 10–20 seconds) between clusters of reps at a heavy load, allowing more total reps.
Resting Heart Rate: RHR; The number of times your heart beats per minute while fully at rest. A lower resting heart rate often reflects better cardiovascular fitness.
Reverse Diet: Gradually increasing calories after a period of dieting, aiming to limit fat regain while daily energy expenditure recovers.
Rhabdomyolysis: A serious condition in which severely damaged muscle releases its contents into the bloodstream, sometimes after extreme or unaccustomed exercise. Warning signs include dark urine, swelling, and intense soreness that warrant prompt medical attention.
RIR: Reps In Reserve; How many more reps you could have completed before failure. Training with 1–3 RIR is widely used to drive growth while managing fatigue.
RPE: Rate of Perceived Exertion; A 1–10 scale for how hard a set felt. An RPE of 8 means you had roughly 2 reps left in the tank — a common way to autoregulate training intensity day to day.
Sarcomere: The smallest contractile unit of a muscle fiber, where the proteins actin and myosin slide past each other to generate force. Muscles shorten because millions of sarcomeres contract in series.
Sarcopenia: The age-related loss of muscle mass and strength. Resistance training and adequate protein are the most consistently recommended countermeasures.
Sarcoplasmic Hypertrophy: Growth from an expansion of the fluid and non-contractile contents inside the muscle fiber. It adds size with less contribution to strength, and how much it can be trained independently is still debated.
SARMs: Selective Androgen Receptor Modulators; A class of therapeutic compounds that have similar properties to anabolic steroids but with reduced androgenic properties. Often sold in the grey market.
Satellite Cell: A muscle stem cell that sits dormant beside the fiber until training or damage activates it. Once active, it can fuse with the fiber and donate a nucleus, supporting repair and growth.
Satiety: The feeling of fullness and satisfaction after eating that reduces the drive to keep eating. Protein and fiber tend to be especially satiating.
Size Principle: The pattern in which the body recruits smaller, fatigue-resistant motor units first and larger, more powerful ones only as force demands rise. It is why heavy loads or reps near failure are needed to reach the highest-threshold fibers.
Sleep Debt: The cumulative shortfall between the sleep you need and the sleep you actually get. Research associates chronic sleep debt with impaired recovery, reduced muscle protein synthesis, and greater fat retention.
Sleep Hygiene: The set of habits and environmental factors that support consistent, quality sleep, such as a dark cool room, regular timing, and limiting late caffeine and screens. Better sleep hygiene is associated with improved recovery.
Sleep Latency: The time it takes to fall asleep after getting into bed. Very short latency can signal sleep deprivation, while a consistently long one may point to poor sleep hygiene or stress.
Slow-Wave Sleep: The deepest stage of non-REM sleep, when growth hormone release and physical recovery peak. Also called deep sleep, it is concentrated in the first half of the night.
Sticking Point: The hardest portion of a lift's range of motion, where a rep is most likely to stall, such as mid-way up in a bench press. Targeted accessory work and pauses are common ways to address it.
Stretch-Mediated Hypertrophy: The idea that loading a muscle in its lengthened position drives extra growth. Research suggests exercises that challenge the stretched position may have an advantage over those loading only the shortened one.
Stretch-Shortening Cycle: SSC; The rapid muscle lengthening immediately followed by a shortening that stores and releases elastic energy, as in a countermovement jump. It underpins plyometric training and explosive movement.
Subcutaneous Fat: The jiggly fat that lies directly beneath the skin. It is generally less harmful metabolically than visceral fat.
Superset: Performing two exercises back-to-back with little or no rest in between, used to save time or increase training density.
Tabata: A specific interval format of eight rounds of 20 seconds all-out effort and 10 seconds rest, totaling four minutes. It is one of the most intense and well-known high-intensity interval protocols.
TDEE: Total Daily Energy Expenditure; The total number of calories you burn in a given day, accounting for BMR, exercise, and daily movement.
TEF: Thermic Effect of Food; The amount of energy your body uses to digest, absorb, and metabolize the food you eat. Protein has the highest TEF.
Tempo: The speed of each phase of a rep, often written as four digits (eccentric-pause-concentric-pause), e.g. 3-1-1-0. Slower tempos increase time under tension.
Tendon Stiffness: How much a tendon resists stretching under load. Heavy, slow loading is associated with increasing it, which helps transmit muscular force more efficiently.
Testosterone: The primary androgen hormone, present in both sexes but higher in men, that supports muscle growth, bone density, and recovery. Levels are influenced by sleep, body composition, and training.
Time Under Tension: TUT; The total duration a muscle is under load during a set. Manipulating TUT (via tempo or pauses) is one variable used to drive hypertrophy.
Training Frequency: How often you train a given muscle group or movement per week. Spreading weekly volume across more sessions is a common way to accumulate quality work.
Training Split: How you divide your workouts across muscle groups or movements over a week, such as push/pull/legs, upper/lower, or a full-body split.
Training to Failure: Continuing a set until you can no longer complete a repetition with good form. Effective for growth but costly in fatigue, so it is usually used selectively.
Unilateral Training: Exercises performed one limb at a time, such as single-leg squats or single-arm rows. Useful for exposing and correcting side-to-side imbalances.
Valsalva Maneuver: Taking a deep breath and bracing against a closed airway to stiffen the torso during a heavy lift. It boosts core stability and intra-abdominal pressure, which is why lifters hold their breath at the bottom of a max squat or deadlift.
Velocity-Based Training: VBT; Using a device to measure how fast the bar moves and adjusting load or stopping a set once speed drops by a set percentage. It provides an objective, day-to-day gauge of readiness and fatigue.
Visceral Fat: A type of body fat that is stored within the abdominal cavity, wrapping around internal organs. High levels are linked to metabolic disease.
VO2 Max: The maximum rate at which your body can use oxygen during intense exercise. It is a widely used marker of cardiorespiratory fitness.
VO2 Reserve: VO2R; The difference between your VO2 max and your resting oxygen uptake. Prescribing cardio as a percentage of this reserve is generally more accurate than using a raw percentage of VO2 max.
Volume: The total amount of work performed in a training session or over a week, typically calculated as Sets × Reps × Weight.
Warm-Up Set: A lighter preparatory set performed before your working sets to prime the muscles and joints and rehearse the movement pattern.
Whey Protein: A fast-digesting complete protein derived from milk. It is rich in leucine and a popular choice around workouts for supporting muscle protein synthesis.
Wilks Score: A mathematical formula used to compare the absolute strength of lifters across different body weight categories and genders.
Xylitol: A sugar alcohol used as a low-calorie sweetener with a far smaller blood-sugar impact than sugar. Large amounts can cause bloating or a laxative effect, and it is toxic to dogs.
Yohimbine: A compound from yohimbe bark marketed as a fat-loss aid; by blocking alpha-2 receptors it may slightly raise fat mobilization during fasted exercise. Human evidence is limited and it can spike heart rate and anxiety.
Zone 2 Cardio: Aerobic exercise performed at 60-70% of your maximum heart rate. It is highly effective for building an aerobic base and cellular endurance.

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