M-mode – A mode in ultrasound imaging that displays motion of structures such as the heart in one dimension.

Macronutrient – Nutrients required in large amounts (carbohydrates, proteins, fats) for energy and growth.

Magnetic resonance imaging (MRI) – A scanning technique using magnetic fields to image soft tissues like muscles.

Magnitude – The size or extent of a physical quantity, such as force or displacement.

Maintenance training – Training designed to preserve current fitness levels rather than improve them.

Manual muscle testing – A method to assess muscle strength using resistance from a tester.

MANOVA – A statistical test comparing multiple dependent variables across different groups.

Marathon – A long-distance running event covering 42.195 kilometres, testing endurance.

Margaria–Kalamen test – A power test involving timed sprint up stairs.

Mass – The amount of matter in an object, a fundamental property in biomechanics.

Mass–moment of inertia – A measure of an object’s resistance to angular acceleration, depending on mass distribution.

Mass-specific oxygen uptake – Oxygen consumption expressed per unit of body mass (e.g., mL/kg/min).

Maximal aerobic speed – The lowest speed at which VO₂ max occurs during an incremental test.

Maximal heart rate – The highest heart rate an individual can achieve during maximum effort.

Maximal lactate steady state – The intensity at which lactate entry and removal are balanced during exercise.

Maximal strength – The greatest force a muscle or muscle group can produce in a single contraction.

Maximal voluntary contraction (MVC) – The highest level of force that can be voluntarily produced by a muscle.

Mechanotransduction – The conversion of mechanical stimulus into cellular response in muscles and bones.

Mechanical efficiency – The ratio of work output to energy input during movement.

Mechanical loading – The application of mechanical force to muscles or bones during activity.

Mechanoreceptor – A sensory receptor that responds to mechanical deformation, such as pressure or stretch.

Medial – A directional term meaning toward the midline of the body.

Median – In statistics, the middle value of a data set when ordered.

Meditation – A mental practice often used to manage stress and enhance focus in sport.

Mental rehearsal – Imagining a performance in detail to improve actual execution under pressure.

Mental toughness – The psychological edge that helps athletes persist and perform under stress.

Metabolic cart – A device used to measure gas exchange for assessing aerobic fitness.

Metabolic cost – The energy required to perform a given action or exercise.

Metabolic equivalent (MET) – A unit estimating the amount of energy used during physical activity relative to resting metabolism.

Metabolism – All chemical processes in the body that convert nutrients into energy.

Metaphysis – The growth region between the shaft and end of a long bone.

Metastasis – Spread of a disease such as cancer cells from one area of the body to another.

Method error – The variation in test results due to inconsistency in measurement procedures.

Microcycle – A short training cycle, usually one week, used in periodisation.

Micronutrient – Nutrients needed in small amounts (vitamins, minerals) essential for body function.

Middle-distance – Running events between 800 m and 3000 m, combining speed and endurance.

Migration (sporting) – Movement of athletes between countries or teams, often for competition or development.

Mindfulness – A mental state of focus and awareness used to reduce stress and improve performance.

Minor axis – A short axis through an object or body; used when analysing movement.

Mission statement – A statement that defines a team’s or organisation’s purpose and values.

Mitral valve – The valve between the left atrium and left ventricle of the heart.

Modality – The type or mode of data collection or training, such as visual feedback or resistance training.

Modal strength – The typical strength level of a muscle measured during regular movement.

Modalities (training) – Different methods of training such as aerobic, strength, or plyometric.

Mode – The most frequently occurring value in a data set.

Model – An idealised representation of a process used for teaching or analysis, such as the Fitts and POSSSUM model.

Moment – The turning effect produced by a force around an axis.

Moment arm – The perpendicular distance from the axis to the line of force; influences torque.

Moment of force – Another term for torque, the product of force and moment arm.

Momentum – The product of mass and velocity; remains constant if no force acts.

Monotony – A measure of how repetitive training is; low variety may lead to boredom or injury.

Motivation – The drive that initiates and directs behaviour toward goals.

Motor control – The process by which the nervous system activates and coordinates muscles for movement.

Motor development – The process of changes in movement ability across the lifespan.

Motor learning – Permanent improvement in movement performance through practice.

Motor programme – A stored movement sequence that is executed as a whole unit.

Motor unit – A motor neuron and all muscle fibres it controls.

Motor unit recruitment – The selection and activation of motor units to produce force.

MRI spectroscopy – A variation of MRI used to assess chemical composition in tissues like muscle or liver.

Multicollinearity – A statistical issue when two or more predictor variables in a model are highly correlated.

Muscle biopsy – Removal of tissue samples from muscle for analysis such as fibre typing.

Muscle cell hypertrophy – Increase in the size of individual muscle fibres.

Muscle cross-sectional area – A measure of muscle size often linked to strength.

Muscle endurance – The ability of muscles to sustain repeated contractions over time.

Muscle fibre – A long, cylindrical cell forming part of muscle tissue; includes Type I and II fibres.

Muscle fibre type distribution – The proportion of slow and fast twitch fibres in a muscle.

Muscle fatigue – The decline in ability of a muscle to generate force over time.

Muscle memory – Improved neuromuscular efficiency due to repeated practice.

Muscle spindle – A receptor in muscle that detects stretch and contributes to the stretch reflex.

Muscle stiffness – Resistance of muscle tissue to stretch or deformation, influencing movement efficiency.

Muscle tension – The force generated within a muscle during contraction.

Muscle tone – The continuous, passive partial contraction of muscles at rest.

Muscle traction – Force applied via tendon to bone during muscle contraction.

Muscle viscosity – A property of muscle related to resistance and fluidity during movement.

Musculoskeletal – Relating to muscles and the skeleton as functional units.

Mutualism – In sports ecosystems, the beneficial relationship between athlete and support staff.

MVIC – Maximum voluntary isometric contraction; the greatest force produced without movement.

Myalgia – Muscle pain commonly experienced after intense or unfamiliar exercise.

Myasthenia gravis – An autoimmune disorder causing fatigue and weakness in muscles.

Myelin sheath – The insulating covering around nerve fibres that speeds conduction.

Myocyte – A muscle cell involved in contraction and force production.

Myoglobin – An oxygen-binding protein in muscle that supports aerobic metabolism.

Myotendinous junction – The area where muscle fibres join tendon tissue.

Myotomy – A surgical procedure to cut muscle fibres for medical treatment.

Myosin – A motor protein that interacts with actin for muscle contraction.

Myosin ATPase – An enzyme in myosin heads that breaks down ATP to release energy for contraction.

Myotube – An immature muscle cell formed during muscle repair and development.

Myotubular myopathy – A genetic condition affecting muscle structure and function.

Myotendinous unit – The functional coupling of muscle fibres and tendon during force production.

Myosin-heavy chain – The protein component determining muscle contraction speed and type.

Myofascial – Referring to muscle and surrounding connective tissue (fascia), often targeted in therapy.

Myofibril – A repeating unit of sarcomeres within muscle cells responsible for contraction.

Myoglobin concentration – Amount of myoglobin present in muscle, influencing aerobic performance.

Myoglobinuria – Presence of myoglobin in urine after severe muscle damage or exertion.

Myocardial infarction – Medical term for a heart attack, due to blocked coronary blood supply.

Myocardial oxygen consumption – The amount of oxygen used by heart muscle during function.

Myocyte hyperplasia – Increase in the number of muscle cells, a debated concept in adult humans.

Myoplasty – Surgical repair of muscle tissue often after injury.

Myocyte apoptosis – Programmed cell death in muscle tissue, related to atrophy or regeneration.

Myostatin – A protein that inhibits muscle growth; genetic suppression leads to increased muscle mass.

Mystery pinch test – A clinical assessment for deep tissue measurement, rarely used in sports.

Myofilament – The individual filaments of actin or myosin within sarcomeres.

Myofunctional therapy – Exercises to improve muscle function, often for neck or jaw.

Myogenic – Originating within muscle tissue, such as growth or response to overload.

Myofiber – Another term for muscle fibre.

Myopathic conditions – Diseases that impact muscle tissue and function.

Myosin light chain – Component of myosin that regulates contraction mechanics.

Myokine – A signalling molecule released by muscle during exercise, influencing metabolism.

Myology – The study of muscle structure, function, and disorders.

Myotonometry – Measurement of muscle mechanical properties like stiffness and tone.

Myoneural – Relating to the interface between nerve and muscle, such as neuromuscular junction.

Myoneural junction – The connection site where a motor neuron communicates with a muscle fibre.

Myotome – A group of muscles innervated by the same spinal nerve.