ADP
Adenosine diphosphate.
Energy is released through ATP hydrolysis, which cells can use. Mitochondria produce ATP from nutrients (glucose, fats) through cellular respiration.

AMPK
Adenosine Monophosphate–activated Protein Kinase.
An energy-sensor protein in muscle cells that detects when additional energy is needed.

Aerobic Threshold
The intensity at which your body primarily uses oxygen for energy; the foundation of endurance training.

Anaerobic Threshold
The point at which your muscles begin to accumulate lactate; important for determining training zones and endurance capacity.

Anaerobic Glycolysis
Subsystem of the anaerobic energy system. Produces energy from glycogen without the use of oxygen and generates lactate in the process. Suited for high-intensity efforts of short duration (≈10 s to 2 min), such as short climbs, intense intervals, and high-power sprints.

Amino Acids
The building blocks of proteins; some (such as BCAAs) can provide energy during exercise and support recovery.

ATL (Acute Training Load):
Training load over a short period; reflects recent training stress.

ATP
Adenosine triphosphate. The fuel of a (muscle) cell. Cells use ATP as a direct energy source to carry out various processes, such as muscle contractions during exercise, active transport of substances in and out of the cell, and the synthesis of proteins and other molecules. When ATP releases energy (ATP hydrolysis), a phosphate group is removed, forming ADP.

ATP–PC
Phosphagen System.
Subsystem of the anaerobic energy system. Provides immediate energy from phosphocreatine stored in the muscles. Operates without oxygen and without lactate production. Suited for very short, maximal efforts (0–10 s), such as sprint starts and explosive accelerations.

Atrophy
Loss of muscle mass and strength due to inactivity, illness, or aging.

BCAAs
Branched-Chain Amino Acids.
Essential amino acids (leucine, isoleucine, valine) that can help reduce muscle breakdown and support recovery during endurance training.

Blood Glucose
Blood Sugar Level
The level of glucose in your blood; crucial for energy supply during endurance exercise.

BMI
Body Mass Index
An indicator of body weight relative to height. It provides a rough estimate of a healthy weight, but should be interpreted cautiously, as fitter or more muscular individuals often receive a misleading score.

Block Periodization
A multi-week training phase with a single primary focus, aimed at developing specific adaptations in muscles, energy systems, and endurance.

Caffeine
Stimulates the central nervous system, enhances alertness, reduces fatigue, and can improve endurance and high-intensity performance.

Calorie
A unit of energy that indicates how much energy the body can obtain from food or expend during exercise. Used to quantify energy intake and output in sports and nutrition.

CaMK
Calcium/Calmodulin-dependent Protein Kinase.
A protein sensor in muscle cells that responds to changes in calcium levels during muscle contractions. Active during high-intensity efforts such as sprints or intervals, driving adaptations related to power, speed, and explosiveness.

Chasse Patate
A chasing effort where a rider tries to bridge to the front group but makes no real progress; often demanding but ultimately ineffective.

CTL (Chronic Training Load):
Average training load over a longer period; reflects overall training volume and intensity.

Clavicle
The collarbone, connecting the sternum to the shoulder blade; contributes to shoulder stability and arm movement.

Contraction Types
Forms of muscle contraction: isometric; tension without a change in length.
Concentric; muscle shortens, e.g., lifting a weight.
Eccentric; muscle lengthens, e.g., lowering a weight.

Costae
The ribs, which protect the thoracic organs and support breathing and trunk stability.

Creatine
A supplement that increases the amount of creatine stored in muscles, boosting phosphocreatine (PC) levels. Most relevant for short, explosive efforts, with limited effect for pure endurance athletes, but can also support interval training and strength-focused work.

Dextrose
Another name for glucose. When glucose is used industrially as a sweetener or energy source in food and medical applications, it is referred to as dextrose.

DOMS
Delayed Onset Muscle Soreness
Muscle soreness occurring 24–72 hours after exercise.

Drafting
Riding behind another cyclist to conserve energy.

Electrolytes
Minerals such as sodium and potassium that are important for fluid balance and muscle function.

Erector Spinae
Muscles running along the spine; responsible for extending the back, maintaining posture, and stabilizing the torso during cycling and strength training.

Ergometer
A device used to measure performance in a controlled environment.

Fascia
Connective tissue that wraps, supports, and links muscles, organs, and other structures.

Fartlek
Swedish for “speed play.” An unstructured interval session alternating short periods of hard or fast effort with easy recovery. Fartlek develops both physical qualities—speed, power, and endurance—and mental skills, such as perceived exertion (RPE) and adapting to changes in terrain and condition.

Femur
The thigh bone, the largest bone in the body; connects the hip to the knee and bears the body’s weight during cycling and running.

Fibula
The smaller lower-leg bone next to the tibia; supports ankle and lower-leg stability.

Functional Overreach
A temporary increase in training load that causes short-term fatigue and performance decline, but with adequate recovery leads to supercompensation and performance improvement.

FTP (Functional Threshold Power)
The highest power output that can be sustained for approximately one hour.

Fructose
A simple sugar (monosaccharide) naturally found in fruit, vegetables, and honey. It raises blood glucose more slowly than glucose because it stimulates insulin less directly, but excessive consumption can still be harmful to health.

Galactose
A simple sugar (monosaccharide) primarily found in milk and dairy products. It is converted into glucose in the liver for energy.

Gel
A concentrated source of carbohydrates in liquid or paste form, designed to quickly replenish energy during exercise.

Glucose
A directly available sugar used by the body as fuel, sourced from food or glycogen breakdown.

Gluteus Maximus
The large buttock muscle, involved in hip extension, power, and stability during cycling and running.

Glycogen
The storage form of glucose in muscles and liver. During exercise, glycogen is broken down into glucose to provide energy.

GI
Glycemic Index.
A measure of how quickly a carbohydrate raises blood sugar; important for nutrition strategies in endurance sports.

Grimpeur
A climber—a rider who excels on long, steep climbs; usually light in weight with less power on flat terrain.

Half-Wheeler
Riders positioned just beside or slightly behind another rider; they benefit partially from wind protection but not optimally.

Hamstrings
The muscles at the back of the thighs, involved in knee flexion and stabilization during pedaling.

Heat Adaptation
Physiological process where the body adjusts to high temperatures, e.g., by increasing sweat production and improving blood flow efficiency.

Hemoglobin
A protein in red blood cells that transports oxygen from the lungs to tissues and carries carbon dioxide back to the lungs.

HRV
Heart Rate Variability
The variation in time between heartbeats; an indicator of recovery status and autonomic nervous system balance.

Humerus
The upper arm bone, connecting the shoulder to the elbow; important for force transmission and arm stability during cycling and strength training.

Hyperglycemia
High Blood Sugar
Excessively high blood glucose; can occur after consuming too many fast-digesting carbohydrates or in diabetes. Short-term relevance for exercise is limited, but it can affect energy metabolism.

Hypoglycemia
Low Blood Sugar
Excessively low blood glucose; can cause fatigue, dizziness, shaking, or fainting during exercise.

Hypertrophy
Muscle growth as a result of training.

IF (Intensity Factor):
Measures workout intensity relative to an athlete’s threshold.

Iron
A mineral essential for the production of hemoglobin and myoglobin, proteins that transport oxygen in blood and muscles. Deficiency can cause fatigue and is more common in female athletes or those with low energy intake.

Insulin
A hormone that transports glucose from the blood into muscles and liver; important for energy storage and recovery.

Intensity
How hard a workout or effort is; often expressed as a percentage of maximal heart rate, power, or RPE (Rate of Perceived Exertion).

Interval Duration
The length of the work period in interval training.

Interval Rest
Recovery time between interval efforts; affects training load and effectiveness.

Ketosis
A metabolic state in which the body uses fat as its primary fuel instead of carbohydrates, leading to increased ketone levels in the blood. Can occur through carbohydrate restriction, fasting, or prolonged exercise. Performance benefits are limited and depend on the individual and context.

Ketone Esters
Synthetic ketones taken as a supplement to provide extra energy during exercise. Their effect on performance is variable and highly dependent on timing, dosage, and the individual. Most recreational or amateur athletes do not need them; training, nutrition, and recovery have a far greater impact.

Lactaat
Een stof die tijdens intensieve inspanning in de spieren ontstaat uit glucose (anaerobe glycolyse). Het kan tijdelijk ophopen, maar wordt later weer gebruikt als energiebron of omgezet in glucose (glucose → pyruvaat → lactaat).

Latissimus dorsi
Grote rugspier die schouder en rug stabiliseert; helpt bij krachtoverdracht van armen naar romp en benen.

Lead-out
Voorbereidende actie van teamgenoten om een sprinter te positioneren voor de eindsprint.

LT1 (Lactate Threshold 1)
Het eerste punt waarop lactaat in het bloed begint te stijgen boven rustniveau.

LT2 (Lactate Threshold 2)
Het punt waarop lactaat snel opstapelt, ook wel de anaerobe drempel genoemd.

Macronutriënten
Voedingsstoffen: koolhydraten, eiwitten, vetten; essentieel voor energie en herstel.

Magnesium
Een mineraal dat essentieel is voor spierfunctie, energieproductie, zenuwgeleiding en het behoud van sterke botten. Tekort kan leiden tot vermoeidheid of verminderde prestaties; het voorkomen van spierkrampen is echter niet wetenschappelijk bewezen.

Maltodextrine
Snel opneembare koolhydraat voor directe energie tijdens langdurige inspanning.

MaxHR
Maximum Hartslag
De hoogste hartslag die iemand tijdens maximale inspanning kan bereiken. Wordt gebruikt om trainingszones te bepalen en intensiteit te monitoren.

Melkzuur
Een vaak verkeerd gebruikt woord voor lactaat. Het lichaam maakt geen melkzuur aan tijdens inspanning, maar lactaat, een stof die helpt bij het afvoeren en bufferen van afvalstoffen. Zie: lactaat.

Mitochondriën
Zijn de energiecentrales van de (spier)cel. Ze zetten voedingsstoffen, zoals glucose en vetten, om in energie in de vorm van ATP, dat je spieren en organen gebruiken om te werken. Hoe meer mitochondriën een cel heeft, hoe efficiënter hij energie kan produceren. Ze spelen ook een rol bij herstel, celdood en stofwisseling.

MLSS
Maximal Lactate Steady State
Het hoogste vermogen waarbij lactaatproductie en -afbraak in balans zijn, waardoor de lactaatconcentratie stabiel blijft. MLSS ligt net onder LT2 en geeft het maximale tempo dat langdurig duurzaam kan worden volgehouden.

Multifidus
Kleine diepe rugspieren langs de wervelkolom; ondersteunen wervelstabiliteit en controle tijdens beweging.

Myoglobine
Een eiwit in spiercellen dat zuurstof opslaat en beschikbaar maakt voor de spier tijdens inspanning, vooral bij korte, intensieve belasting.

Non-functional overreaching
De belasting is te hoog of het herstel onvoldoende; dit leidt tot langere prestatieachteruitgang en verhoogd risico op overtraining.

NP
Normalized Power
Effectieve trainingsbelasting bij variabele intensiteit; realistischer dan gemiddeld vermogen, maar kan bij korte pieken iets hoger schatten dan werkelijke belasting.

Obliquus externus
Buitenste schuine buikspier
Aan de zijkant van de romp; helpt bij rotatie en zijwaartse buiging van de romp, ondersteunt stabiliteit tijdens fietsen en krachttraining.

Obliquus internus
Binnenste schuine buikspier. Ligt onder de buitenste schuine buikspier; ondersteunt rotatie, zijwaartse buiging en stabiliteit.

Overtraining
Langdurige overbelasting zonder voldoende herstel; leidt tot prestatieverlies, vermoeidheid en verhoogd blessurerisico.

Patella
The kneecap; protects the knee joint and increases the leverage of the quadriceps when extending the knee.

Pectoralis Major
The large chest muscle at the front of the body; responsible for moving the arm forward, inward, and rotating the shoulder. Plays a role in power transmission during cycling, strength training, and pushing movements.

Pectoralis Minor
Located beneath the pectoralis major; helps move the shoulder blade forward and downward and supports breathing during intense effort.

PGC-1α
Peroxisome proliferator-activated receptor gamma coactivator 1-alpha.
A protein in cells that acts as a co-activator for genes controlling energy production and mitochondria.

Plasma
The liquid part of blood, transporting cells, nutrients, hormones, waste, and electrolytes. Plays a key role in hydration, temperature regulation, and transport of substances throughout the body.

Power
The energy an athlete produces per unit of time, measured in watts; used to quantify effort and performance.

Progressive Overload
Gradually increasing training load to stimulate adaptation and improve performance.

Proteins
Whey / Casein.
Support muscle repair and growth after training. Whey is fast-digesting and ideal immediately post-workout; casein digests more slowly, providing sustained amino acid release (e.g., before sleep).

Pull
A period when a rider leads the peloton to set the pace or shield others; requires significant energy and provides wind protection for following riders.

Puncheur
A rider strong on short, steep climbs and explosive efforts; less effective on long climbs or time trials.

Pyruvate
A product of glucose breakdown used for energy production when oxygen is sufficient; under low oxygen, it is temporarily converted into lactate.

Quadriceps
The four-headed muscle group at the front of the thighs; responsible for extending the knee joint and generating power during cycling, jumping, and other activities.

Radius and Ulna
Forearm bones responsible for movement and stability of the forearm and hand; contribute to steering control and force transmission.

Rectus Abdominis
Front of the abdomen/torso; responsible for bending the torso and providing stability during movement.

Rouleur
An all-rounder rider; proficient across various terrains, capable of climbing, time-trialing, and riding long distances.

RPE
Rate of Perceived Exertion
A scale used by athletes to subjectively rate the intensity of a training session or effort, usually from 1 (very light) to 10 (maximum effort).

Scapula
Shoulder blade; connects the arm to the torso and provides stability for shoulder movements.

Soleus
Lower leg, beneath the gastrocnemius; helps extend the ankle and plays a major role in endurance and stability.

Somatotype
Body type (ecto-, meso-, endomorph); useful for training and nutrition; most people are a mix of two types.

Spine
Comprised of cervical (neck), thoracic (mid-back), and lumbar (lower back) vertebrae; protects the spinal cord and supports posture and stability.

Steady State
General; constant effort where heart rate and energy expenditure remain stable.

Stephen Seiler:
American exercise physiologist and professor, known for research on training intensity and polarized training.

Sternocleidomastoideus
Side of the neck; responsible for turning and bending the head and assists breathing during exercise.

Sternum
Front of the chest; connects the ribs, protects the heart and lungs, and supports respiration.

Sweet Spot Training
General; training at moderately high intensity just below the lactate threshold, also called Tempo.

Threshold
The point at which effort becomes intense enough that lactate accumulates rapidly in the muscles.

Tibia
Front of the lower leg; the larger shinbone that bears weight and contributes to force transmission during cycling and running.

Trapezius
Neck and upper back; stabilizes shoulders and upper back, and assists in power transmission and posture on the bike.

Transversus Abdominis
Deepest abdominal muscle; acts as a natural “corset” for the torso and stabilizes the spine and pelvis.

Trevor Connor:
Canadian endurance coach and scientist, co-founder/CEO of Fast Talk Labs and Fast Talk podcast, expert in endurance training and nutrition.

TSB (Training Stress Balance):
Difference between CTL and ATL; indicates recovery status and fatigue.

TSS (Training Stress Score)
A relative measure of training load based on duration and intensity, useful for planning and recovery.

Vitamin D
Important for bone health, muscle function, and the immune system; many athletes are deficient, especially during winter months.

VO₂max
Maximum amount of oxygen your muscles can use per minute during exercise; partly determines endurance. Measures how efficiently your lungs, heart, and muscles work together to convert oxygen into energy.

Watt / Wattage
Power output a cyclist produces, measured with a powermeter on the crank, pedals, or an ergometer.

Watt/kg
Power output divided by body weight, expressed in watts per kilogram; used to compare performance fairly.

Wheel Sucker
A rider who drafts behind others to save energy without taking turns at the front.

XCM (Cross-Country Marathon)
Mountain biking discipline over long distances (usually 60–120 km) on varied terrain, focused on endurance and strategy rather than short technical laps.

XCO (Cross-Country Olympic)
Mountain biking discipline on a technical course with hills, obstacles, and varying surfaces, raced over multiple laps.

Yin Yoga
Rustige yogastijl waarbij houdingen lang worden vastgehouden (3–5 minuten of langer) om bindweefsel, flexibiliteit en ontspanning te bevorderen, nuttig voor herstel bij duursporters.

Zone
Training in specific heart rate or power zones to achieve different training goals (e.g., fat burning, lactate threshold, maximum effort).