[{"data":1,"prerenderedAt":706},["ShallowReactive",2],{"lexique-en-fibers":3,"lexique-all-en":346,"lexique-trans-en-fibers":700},{"id":4,"title":5,"body":6,"description":336,"extension":337,"lang":338,"letter":339,"meta":340,"navigation":341,"path":342,"ref":12,"seo":343,"stem":344,"__hash__":345},"lexique/lexique/en/fibers.md","Fibers",{"type":7,"value":8,"toc":325},"minimark",[9,13,18,34,37,40,43,48,51,85,87,91,189,195,197,201,233,235,239,245,270,272,276,280,291,295,309,311,315],[10,11,5],"h1",{"id":12},"fibers",[14,15,17],"h4",{"id":16},"definition","Definition",[19,20,21,25,26,29,30,33],"p",{},[22,23,24],"strong",{},"Muscle fibers"," are ",[22,27,28],{},"the cells that make up skeletal muscle",". Each fiber is a long multinucleated cell that contracts to produce movement. A single muscle contains thousands to millions of fibers, grouped into bundles called ",[22,31,32],{},"fascicles",".",[35,36],"blockquote",{},[19,38,39],{},"💡 An adult human has between 200 and 400 billion muscle fibers, and the count is largely set at birth.",[41,42],"hr",{},[44,45,47],"h3",{"id":46},"fiber-structure","Fiber structure",[19,49,50],{},"From outside to inside:",[52,53,54,61,67,73,79],"ul",{},[55,56,57,60],"li",{},[22,58,59],{},"Sarcolemma",": outer membrane of the fiber",[55,62,63,66],{},[22,64,65],{},"Sarcoplasm",": cytoplasm containing nutrients",[55,68,69,72],{},[22,70,71],{},"Myofibrils",": the contracting threads",[55,74,75,78],{},[22,76,77],{},"Sarcomeres",": contractile units (actin + myosin)",[55,80,81,84],{},[22,82,83],{},"Mitochondria",": cellular powerhouses",[41,86],{},[44,88,90],{"id":89},"the-2-main-types-of-fibers","The 2 main types of fibers",[92,93,94,110],"table",{},[95,96,97],"thead",{},[98,99,100,104,107],"tr",{},[101,102,103],"th",{},"Characteristic",[101,105,106],{},"Type I (slow)",[101,108,109],{},"Type II (fast)",[111,112,113,125,136,147,157,168,179],"tbody",{},[98,114,115,119,122],{},[116,117,118],"td",{},"Contraction speed",[116,120,121],{},"Slow",[116,123,124],{},"Fast",[98,126,127,130,133],{},[116,128,129],{},"Force",[116,131,132],{},"Low",[116,134,135],{},"High",[98,137,138,141,144],{},[116,139,140],{},"Endurance",[116,142,143],{},"Excellent",[116,145,146],{},"Poor",[98,148,149,151,154],{},[116,150,83],{},[116,152,153],{},"Many",[116,155,156],{},"Few",[98,158,159,162,165],{},[116,160,161],{},"Energy system",[116,163,164],{},"Aerobic",[116,166,167],{},"Anaerobic",[98,169,170,173,176],{},[116,171,172],{},"Color",[116,174,175],{},"Red",[116,177,178],{},"White",[98,180,181,184,187],{},[116,182,183],{},"Hypertrophy potential",[116,185,186],{},"Limited",[116,188,135],{},[19,190,191,192,33],{},"Most muscles contain a mix of both types. The exact proportion is largely ",[22,193,194],{},"genetic",[41,196],{},[44,198,200],{"id":199},"fiber-proportion-by-activity","Fiber proportion by activity",[52,202,203,209,215,221,227],{},[55,204,205,208],{},[22,206,207],{},"Marathon runner",": 70-90% type I (endurance)",[55,210,211,214],{},[22,212,213],{},"100m sprinter",": 70-90% type II (explosive)",[55,216,217,220],{},[22,218,219],{},"General population",": 50/50 in most muscles",[55,222,223,226],{},[22,224,225],{},"Soleus"," (calf, postural muscle): up to 80% type I",[55,228,229,232],{},[22,230,231],{},"Triceps",": predominantly type II",[41,234],{},[44,236,238],{"id":237},"can-you-change-your-fiber-type","Can you change your fiber type?",[19,240,241,242,33],{},"Partial answer: ",[22,243,244],{},"YES, partially",[52,246,247,254,260,267],{},[55,248,249,250,253],{},"✅ ",[22,251,252],{},"Type IIb fibers"," can shift to type IIa (more endurance) with cardio training",[55,255,249,256,259],{},[22,257,258],{},"Type IIa fibers"," can shift back to IIb with explosive training",[55,261,262,263,266],{},"❌ ",[22,264,265],{},"Pure type I and pure type II"," conversion is highly limited",[55,268,269],{},"⚠️ Genetics largely sets your starting profile",[41,271],{},[44,273,275],{"id":274},"how-to-develop-both-types","How to develop both types",[14,277,279],{"id":278},"for-type-i-slow-endurance","For type I (slow / endurance)",[52,281,282,285,288],{},[55,283,284],{},"High reps (15-30+)",[55,286,287],{},"Short rest (30-60 sec)",[55,289,290],{},"Endurance cardio",[14,292,294],{"id":293},"for-type-ii-fast-explosive","For type II (fast / explosive)",[52,296,297,300,303,306],{},[55,298,299],{},"Heavy reps (1-8)",[55,301,302],{},"Long rest (3-5 min)",[55,304,305],{},"Plyometrics, sprints",[55,307,308],{},"Maximum movement speed",[41,310],{},[44,312,314],{"id":313},"key-takeaways","Key takeaways",[19,316,317,318,321,322,33],{},"Muscle fibers determine ",[22,319,320],{},"your physical potential",". Type I dominate in endurance, type II in explosive efforts. Genetics sets your base profile, but smart training optimizes everything you've got. ",[22,323,324],{},"Train both types to be a complete athlete",{"title":326,"searchDepth":327,"depth":327,"links":328},"",2,[329,331,332,333,334,335],{"id":46,"depth":330,"text":47},3,{"id":89,"depth":330,"text":90},{"id":199,"depth":330,"text":200},{"id":237,"depth":330,"text":238},{"id":274,"depth":330,"text":275},{"id":313,"depth":330,"text":314},"Muscle fibers are the cells that make up muscle. Two main types — Type I (slow) and Type II (fast) — define your physical potential.","md","en","F",{},true,"/lexique/en/fibers",{"title":5,"description":336},"lexique/en/fibers","457zUKFdoz2AkW8kmhWuHrGtN5yUxYWHY-8rOLSrPf4",[347,351,355,359,363,367,371,375,379,383,387,391,395,399,403,407,411,415,419,423,427,431,435,439,443,447,451,455,459,463,467,468,472,476,480,484,488,492,496,500,504,508,512,516,520,524,528,532,536,540,544,548,552,556,560,564,568,572,576,580,584,588,592,596,600,604,608,612,616,620,624,628,632,636,640,644,648,652,656,660,664,668,672,676,680,684,688,692,696],{"title":348,"description":349,"slug":350},"AMRAP - As Many Reps/Rounds As Possible","AMRAP is a high-intensity training format: do as many reps or rounds as possible in a fixed time. CrossFit favorite.","amrap-as-many-reps-rounds-as-possible",{"title":352,"description":353,"slug":354},"ATP (Adenosine Triphosphate)","ATP is the universal energy currency of the body. Every muscle contraction, every cellular function depends on it.","atp-adenosine-triphosphate",{"title":356,"description":357,"slug":358},"Abduction","Discover what abduction is in bodybuilding, this movement which moves a limb away from the central axis of the body to develop the stabilizing muscles.","abduction",{"title":360,"description":361,"slug":362},"Active recovery","Active recovery uses light activity to speed muscle recovery. Find out how to effectively integrate it into your routine.","active-recovery",{"title":364,"description":365,"slug":366},"Adduction","Adduction is a movement that brings a body part toward the body's midline. Opposite of abduction.","adduction",{"title":368,"description":369,"slug":370},"Aerobic System","The aerobic system produces energy with oxygen, fueling long-duration efforts. It's the foundation of endurance and recovery.","aerobic-system",{"title":372,"description":373,"slug":374},"Anabolic window","The anabolic window is the post-workout period considered ideal for nutrition. The reality: it's much longer than thought.","anabolic-window",{"title":376,"description":377,"slug":378},"Anaerobic System","The anaerobic system produces energy without oxygen — for explosive, intense efforts. Limited but powerful, it fuels strength and sprints.","anaerobic-system",{"title":380,"description":381,"slug":382},"BCAA","BCAAs are 3 essential branched-chain amino acids: leucine, isoleucine, valine. Discover their real usefulness, timing, and whether you actually need them.","bcaa",{"title":384,"description":385,"slug":386},"BMI","BMI (Body Mass Index) is a quick health screening tool, but it doesn't account for body composition. Limited but useful.","bmi-body-mass-index",{"title":388,"description":389,"slug":390},"BMR","BMR (Basal Metabolic Rate) is your resting metabolism — the calories burned just to stay alive. Learn how to calculate and optimize it for your fitness goals.","bmr",{"title":392,"description":393,"slug":394},"Body fat percentage","Body fat percentage measures the share of fat in your total body mass. A key indicator of body composition.","body-fat-percentage",{"title":396,"description":397,"slug":398},"Body recomposition","Body recomposition is gaining muscle and losing fat at the same time. Possible but slow — discover the conditions for success.","body-recomposition",{"title":400,"description":401,"slug":402},"Bodyweight","Bodyweight training uses your own body as resistance. No equipment, anywhere, scalable to any level.","bodyweight",{"title":404,"description":405,"slug":406},"Calorie Maintenance","Caloric maintenance is the calorie level keeping your weight stable. Foundation of any nutritional plan.","calorie-maintenance",{"title":408,"description":409,"slug":410},"Calorie Surplus","A caloric surplus means consuming more calories than you burn. Mandatory mechanism for serious muscle building.","calorie-surplus",{"title":412,"description":413,"slug":414},"Calorie deficit","A caloric deficit means consuming fewer calories than you burn. It's the only proven mechanism for fat loss. Learn how to set yours up properly.","calorie-deficit",{"title":416,"description":417,"slug":418},"Calories","Calories measure the energy provided by food. Understanding your caloric needs is the foundation of every fitness goal.","calories",{"title":420,"description":421,"slug":422},"Carbohydrates","Carbohydrates are the main source of energy for intense training. Discover your needs, the different types and their role in performance.","carbohydrates",{"title":424,"description":425,"slug":426},"Circuit training","Circuit training chains several exercises with little rest. Ideal for burning calories and improving cardiovascular fitness while keeping muscle.","circuit-training",{"title":428,"description":429,"slug":430},"Concentric (Phase)","The concentric phase is the lifting movement, where the muscle shortens under load. It's the active phase that produces force.","concentric-phase",{"title":432,"description":433,"slug":434},"Creatine","Creatine is the most studied supplement in sports nutrition, proven to boost strength, power and muscle mass. Learn dosage, timing and real benefits.","creatine",{"title":436,"description":437,"slug":438},"Cutting","A cutting phase is a period of caloric deficit aimed at losing fat while preserving muscle. Discover how to do it without losing your hard-earned gains.","dried",{"title":440,"description":441,"slug":442},"DOMS (Delayed Onset Muscle Soreness)","DOMS is the muscle soreness that appears 24-72h after exercise. Discover its causes, how to manage it, and what it really means for your progress.","doms-delayed-onset-muscle-soreness",{"title":444,"description":445,"slug":446},"Deload","Deload is an active recovery week where you intentionally reduce volume and intensity to allow your body to fully recover and come back stronger.","deload",{"title":448,"description":449,"slug":450},"Dropset","A dropset extends a set by reducing the load when failure hits. Powerful intensification method for hypertrophy.","dropset",{"title":452,"description":453,"slug":454},"EMOM - Every Minute On the Minute","EMOM (Every Minute On the Minute) is a training format where you start a set at the top of each minute and rest until the next.","emom-every-minute-on-the-minute",{"title":456,"description":457,"slug":458},"Eccentric (Phase)","The eccentric phase is the lowering movement, where the muscle lengthens under tension. It's the most damaging phase and the key driver of hypertrophy.","eccentric-phase",{"title":460,"description":461,"slug":462},"Extension","Extension is the anatomical movement that increases the angle between two body segments. Opposite of flexion.","extension",{"title":464,"description":465,"slug":466},"Fat mass","Fat mass is the total weight of fat tissue. Essential for survival, but excess harms health and aesthetics.","fat-mass",{"title":5,"description":336,"slug":12},{"title":469,"description":470,"slug":471},"Flexion","Flexion is the anatomical movement that decreases the angle between two body segments. Opposite of extension.","flexion",{"title":473,"description":474,"slug":475},"Foam rolling","Foam rolling is a myofascial self-massage technique to release muscle tension. Find out how to use it effectively to improve recovery and mobility.","foam-rolling",{"title":477,"description":478,"slug":479},"For Time","For Time is a training format where you complete a fixed amount of work as fast as possible. Race against the clock.","for-time",{"title":481,"description":482,"slug":483},"Full Body","A full body program trains all major muscle groups in each session, 2-4 times per week. Ideal for beginners and strength training.","full-body",{"title":485,"description":486,"slug":487},"Hypertrophy","Muscle hypertrophy is the increase in muscle fiber size. It's the primary mechanism behind muscle growth from resistance training.","hypertrophy",{"title":489,"description":490,"slug":491},"Hypertrophy Training","Hypertrophy training aims to maximize muscle growth using moderate loads (65-85% 1RM) with 8-15 repetitions per set.","hypertrophy-training",{"title":493,"description":494,"slug":495},"Intra-workout","Intra-workout refers to nutrition consumed during training to maintain energy, hydration and performance on long sessions.","intra-workout",{"title":497,"description":498,"slug":499},"Isometric","Isometric contraction is when the muscle produces tension without changing length. No visible movement, intense work.","isometric-contraction",{"title":501,"description":502,"slug":503},"Lean mass","Lean mass is everything in your body except fat: muscles, bones, organs, water. A real performance indicator.","lean-mass",{"title":505,"description":506,"slug":507},"Lipids (Fats)","Lipids are essential for hormone production and vitamin absorption. Discover your needs, the right sources and their role in bodybuilding.","lipids-fats",{"title":509,"description":510,"slug":511},"Macrocycle","A macrocycle is the global organization of your training over 3-12 months. The highest level of periodization, your annual game plan.","macrocycle",{"title":513,"description":514,"slug":515},"Macronutrients (Macros)","Macronutrients are the 3 main types of nutrients: proteins, carbohydrates and lipids. Their balance is crucial for performance and body composition.","macronutrients-macros",{"title":517,"description":518,"slug":519},"Maintenance","Maintenance is the calorie level at which your weight remains stable. The neutral baseline for any nutritional strategy.","maintenance",{"title":521,"description":522,"slug":523},"Mass gain","Mass gain (or bulk) is a controlled caloric surplus phase aimed at building muscle. Discover how to do it without gaining excess fat.","mass-gain",{"title":525,"description":526,"slug":527},"Meal timing","Meal timing is the strategic distribution of your meals around training and through the day to optimize performance and recovery.","meal-timing",{"title":529,"description":530,"slug":531},"Mesocycle","A mesocycle is a 4-8 week training block with a specific objective (hypertrophy, strength, peak, deload). The cornerstone of periodization.","mesocycle",{"title":533,"description":534,"slug":535},"Microcycle","A microcycle is the smallest planning unit in bodybuilding: generally 1 week of training. This is your weekly routine.","microcycle",{"title":537,"description":538,"slug":539},"Mobility","Mobility is the ability to actively control range of motion. Find out how to improve your mobility to optimize your performance.","mobility",{"title":541,"description":542,"slug":543},"Muscle mass","Muscle mass is the total weight of muscles in the body. Key indicator of strength, metabolism, and longevity.","muscle-mass",{"title":545,"description":546,"slug":547},"Muscular Endurance Training","Muscular endurance training develops the ability to sustain prolonged effort. Light loads, high reps, short rests.","muscular-endurance-training",{"title":549,"description":550,"slug":551},"Muscular endurance","Muscular endurance is a muscle's capacity to sustain repeated or prolonged contractions without excessive fatigue. Foundation of many sports.","muscular-endurance",{"title":553,"description":554,"slug":555},"Muscular strength","Muscular strength is the maximum force a muscle (or group) can produce. The fundamental physical quality of any athlete.","muscular-strength",{"title":557,"description":558,"slug":559},"NEAT","NEAT is the energy you burn through all your daily activities outside of training. The most underestimated lever of your body composition.","neat",{"title":561,"description":562,"slug":563},"PR - Personal Record","A PR (Personal Record) is your best performance ever on a movement. The fundamental progress marker.","pr-personal-record",{"title":565,"description":566,"slug":567},"Passive recovery","Passive recovery links on complete rest to allow the body to regenerate. Find out when and how to use it effectively.","passive-recovery",{"title":569,"description":570,"slug":571},"Periodization","Periodization is the cyclical organization of training into distinct phases to optimize progression, prevent plateaus, and avoid injuries.","periodization",{"title":573,"description":574,"slug":575},"Plateau","A plateau is a period of stagnation despite consistent training. Identifying the cause is the key to breaking it.","plateau",{"title":577,"description":578,"slug":579},"Post-workout","The post-workout is the nutrition right after training to optimize recovery and growth. Protein, carbs, hydration.","post-workout",{"title":581,"description":582,"slug":583},"Pre-workout","The pre-workout is the meal or supplement taken before training to optimize performance. Energy, focus, and pump.","pre-workout",{"title":585,"description":586,"slug":587},"Progressive overload","Progressive overload is the foundational principle of training: gradually increasing the demand on your muscles to keep gaining strength and size.","progressive-overload",{"title":589,"description":590,"slug":591},"Protein","Protein is the essential macronutrient for building and repairing muscle. Discover your needs, the best sources and the optimal timing.","protein",{"title":593,"description":594,"slug":595},"Protein powder","Protein powders are concentrated protein supplements. Practical for hitting daily protein needs.","protein-powder",{"title":597,"description":598,"slug":599},"Push/Pull/Legs (PPL)","The Push/Pull/Legs program divides the workout into 3 types of sessions: push (chests/shoulders/triceps), pull (back/biceps) and legs. Optimal for all levels with frequency 2x/week per muscle.","push-pull-legs-ppl",{"title":601,"description":602,"slug":603},"RIR","RIR (Reps in Reserve) measures how many reps you have left before failure. Modern, intuitive tool to manage intensity.","rir-reps-in-reserve",{"title":605,"description":606,"slug":607},"RPE","RPE (Rate of Perceived Exertion) is a 1-10 scale to measure subjective effort. Essential tool for managing intensity.","rpe-rate-of-perceived-exertion",{"title":609,"description":610,"slug":611},"Range of motion (ROM)","Range of motion (ROM) is the amplitude through which a joint or muscle can move during an exercise. Crucial for hypertrophy and joint health.","range-of-motion-rom",{"title":613,"description":614,"slug":615},"Repetitions (Reps)","A rep is one complete execution of an exercise. The rep range determines whether you primarily develop strength, hypertrophy, or muscular endurance.","repetitions-reps",{"title":617,"description":618,"slug":619},"Rest","Rest between sets is critical and depends on the goal. Strength: 3-5 min. Hypertrophy: 1-3 min. Endurance: 30-60 sec.","rest",{"title":621,"description":622,"slug":623},"Rest-Pause","Rest-pause is an intensification method using ultra-short pauses to extend a set. Powerful tool for hypertrophy.","rest-pause",{"title":625,"description":626,"slug":627},"Sarcomere","The sarcomere is the basic contractile unit of muscle. Composed of actin and myosin, it produces all your movements.","sarcomere",{"title":629,"description":630,"slug":631},"Series (Sets)","A series (or set) is a group of consecutive reps without rest. The basic unit of training programming.","series-sets",{"title":633,"description":634,"slug":635},"Sleep","Sleep is the most underrated training variable. It's during sleep that recovery, muscle building, and hormonal regulation happen.","sleep",{"title":637,"description":638,"slug":639},"Split (Split program)","A split workout involves dividing muscle groups over different days. The classic split trains each muscle once a week for 5-6 days.","split-split-program",{"title":641,"description":642,"slug":643},"Strength Training","Strength training aims to develop maximal strength using heavy loads (80-95% of 1RM) with few repetitions (1-6 reps).","strength-training",{"title":645,"description":646,"slug":647},"Stretching","Stretching improves flexibility and range of motion. Learn about the different types and how to effectively incorporate them into your routine.","stretching",{"title":649,"description":650,"slug":651},"Superset","A superset chains two exercises with no rest between them. Time-efficient method that boosts intensity and density.","superset",{"title":653,"description":654,"slug":655},"TDEE","TDEE (Total Daily Energy Expenditure) represents your total daily energy expenditure. Find out how to calculate it precisely to optimize your results.","tdee",{"title":657,"description":658,"slug":659},"TUT - Time Under Tension","TUT (Time Under Tension) measures the total time the muscle is under load during a set. Key variable for hypertrophy.","tut-time-under-tension",{"title":661,"description":662,"slug":663},"Tabata","Tabata is a 4-minute HIIT protocol: 20 seconds max effort, 10 seconds rest, 8 rounds. Maximum efficiency in minimum time.","tabata",{"title":665,"description":666,"slug":667},"Tempo - Execution speed","Tempo is the controlled speed of each phase of a movement. Powerful tool to maximize stimulus and control.","tempo-execution-speed",{"title":669,"description":670,"slug":671},"Training density","Training density measures the amount of work done per unit of time. Increase it to boost intensity and metabolic stress.","training-density",{"title":673,"description":674,"slug":675},"Training frequency","Training frequency defines how many times per week you work a muscle. Discover the optimal frequency to progress.","training-frequency",{"title":677,"description":678,"slug":679},"Training intensity","Bodybuilding intensity measures the difficulty of the effort. Find out how to calculate it with % of 1RM, RPE, and RIR.","training-intensity",{"title":681,"description":682,"slug":683},"Training volume","Training volume represents the total amount of work performed. Discover the optimal volumes per muscle per week to progress.","training-volume",{"title":685,"description":686,"slug":687},"Type I muscle fibers","Type I fibers (slow-twitch) are endurance-oriented muscle fibers. Resistant to fatigue, they sustain prolonged efforts.","muscle-fibers-type-i",{"title":689,"description":690,"slug":691},"Type II muscle fibers","Type II fibers (fast-twitch) are powerful muscle fibers optimized for explosive efforts. Essential for strength and power.","type-ii-muscle-fibers",{"title":693,"description":694,"slug":695},"Upper/Lower","The Upper/Lower program divides training into upper body and lower body sessions over 4 days per week. Perfect balance between frequency (2x/week) and volume for all levels.","upper-lower",{"title":697,"description":698,"slug":699},"VO2 max","VO2 max is the maximum amount of oxygen your body can use during intense exercise. It's the gold standard of cardiovascular fitness.","vo2-max",{"de":701,"en":12,"es":702,"fr":703,"it":704,"pt":705},"muskelfasern","fibras","fibres","fibre","fibras-musculares",1784214982038]