Exercise & Physical Training

Aerobic capacity is the most oxygen your body can take in and use to make ATP during long exercise. By the Fick principle (VO2 = Q × (a-v)O2), it depends on two things: how well…

Anabolic resistance is the age-related blunting of muscle protein synthesis (MPS) in response to protein and resistance exercise. In young adults, roughly 20 to 25 g of protein…

The anaerobic threshold (AT) is the exercise intensity above which your aerobic system cannot keep up with the energy demand, so lactate starts building faster than your body…

Blood flow restriction (BFR) training puts a pneumatic cuff or elastic wrap near the top of a limb. It partially blocks the blood leaving the limb (venous return) while still…

Bone mineral density (BMD) is the amount of mineral, mostly hydroxyapatite, packed into your bone, per unit area (g/cm²) or volume. It is most often measured at your lumbar spine…

Cardiac output (Q) is the volume of blood your heart pumps per minute. It equals heart rate (HR, beats per minute) times stroke volume (SV, mL per beat). At rest, Q is 4 to 6…

Cardiorespiratory fitness (CRF) is how well your heart, blood vessels, and lungs deliver oxygen to your muscles during sustained activity. It is most often measured as VO2max.…

The interference effect is the way endurance training can blunt your gains from resistance training, especially strength, power, and muscle growth (hypertrophy), when you do both…

Critical power (CP) is your aerobic 'ceiling'. It is the highest power output (or running speed, called critical velocity) you can sustain without fatiguing out. Just below CP,…

Daily step count is the total walking steps you rack up in 24 hours, measured by pedometers or wearables that detect vertical motion. It acts as a device-agnostic proxy for your…

Detraining is the partial or full reversal of training gains that happens when you cut back or stop exercising. How fast and how much you lose depends on your training history…

A DEXA scan (dual-energy X-ray absorptiometry) measures your body composition and bone density. It passes two X-ray beams at different energy levels through your body and…

Dynapenia is the age-related loss of muscle strength and power, separate from the loss of muscle mass. Clark and Manini coined the term in 2008. They wanted to distinguish…

Eccentric training emphasizes the lengthening phase of a muscle contraction. Think of the lowering part of a squat or a curl. Your muscles can produce more force when lengthening…

EPOC is the extra oxygen your body keeps taking in after exercise ends. Your body uses it to restore ATP and creatine phosphate, clear lactate, refill oxygen stores, and bring…

Grip strength is the maximal force you generate when you squeeze a device called a dynamometer. It is a cheap, simple proxy for your whole-body muscular function. In the…

Heart rate recovery (HRR) is how fast your heart rate drops after you stop hard exercise. It is measured in the first minute (HRR1) or the first two minutes (HRR2) after a peak…

HIIT (high-intensity interval training) alternates short bursts of near-maximal effort with periods of easy recovery. A session usually runs 10 to 30 minutes total. The hard…

Isometric training means contracting a muscle against an immovable resistance, with no joint movement. Think planks, wall sits, or holding a mid-range squat. It builds tendon…

Lactate threshold is used loosely for two points. LT1 (the aerobic threshold, around 2 mmol/L) is where your blood lactate first rises above baseline. LT2 is the highest…

Maximum heart rate (HRmax) is the highest beats per minute your heart reaches during all-out effort. It is mostly set by your age and genetics, not your fitness, and it declines…

The metabolic equivalent of task (MET) is a unit for the energy cost of an activity. It expresses that cost as a multiple of your resting metabolic rate. By definition, 1 MET is…

Mitochondrial density is how many mitochondria you have per unit of muscle. It also covers how much space they take up. Higher density means more capacity to burn fuel with…

Mitochondrial respiratory capacity is the top speed at which your mitochondria can push oxygen through their electron transport chain (ETC) to make energy, when fuel and ADP are…

Muscle protein synthesis (MPS) is how your muscle cells build new proteins from amino acids. It drives muscle maintenance, repair, and growth. It is controlled by mTORC1, a…

NEAT (non-exercise activity thermogenesis) is the energy you burn through all your daily movement outside of formal exercise. That means walking, standing, fidgeting, household…

The one-repetition maximum (1RM) is the heaviest load you can lift through a full range of motion, for one all-out rep with proper form. It is the gold-standard measure of your…

Plyometrics are explosive movements (jumps, hops, bounds, throws) that exploit the stretch-shortening cycle. In that cycle, a fast eccentric load primes a powerful concentric…

Progressive overload is the principle of gradually increasing your training demands, to keep driving adaptation. You can increase the load, the volume, the density, the range of…

Rate of force development (RFD) is the change in muscle force per unit of time (in N/s). It captures how fast you can express maximal force, which is a key part of power,…

Resting heart rate (RHR) is your heartbeats per minute at full rest. It is ideally measured lying down after several minutes of quiet rest, or right when you wake. It is swayed…

Reps in Reserve (RIR) is an autoregulation method for setting and grading how hard you train with weights. You estimate, at the end of a set, how many more reps you could have…

Sarcopenia is the age-related loss of your skeletal muscle mass, strength, and function. Several things drive it: anabolic resistance (muscle responds less to protein),…

Sarcopenic obesity is having two problems at once: low muscle mass or strength (sarcopenia) plus too much body fat. The combo is worse than either alone. Excess fat ramps up…

Satellite cells are the resident stem cells of your muscle. They lie dormant between the muscle-fiber membrane (the sarcolemma) and its outer sheath (the basal lamina), and you…

The sit-rise test measures your ability to lower yourself to the floor and stand back up, using as little support as possible. It is scored from zero to ten, with points deducted…

Strength training is structured exercise. You load your muscles against resistance. That can be free weights, machines, bands, or your own bodyweight. The load drives two things:…

Stroke volume is the amount of blood your left ventricle pumps out per heartbeat. At rest in healthy adults, that is about 60 to 100 ml. In elite endurance athletes at peak…

Tendon stiffness describes how much force a tendon transmits per unit of stretch (force divided by length change, usually in N/mm). A related property, Young's modulus, adjusts…

Your skeletal muscle has two broad fiber types: Type I (slow) and Type II (fast). They differ in their myosin type, metabolism, and contraction speed. Type I fibers are…

Visceral adipose tissue (VAT) is the metabolically active fat packed around your abdominal organs. It is different from the fat under your skin (subcutaneous fat). VAT is…

VO2max is the maximum rate at which you can use oxygen during intense exercise. It is usually expressed in mL/kg/min. By the Fick principle, it equals your oxygen delivery…

Zone 2 training is sustained aerobic exercise at or just below your first lactate threshold (LT1, around 1.5 to 2.0 mmol/L). That is often roughly 60 to 70% of your max heart…