Reference
Glossary
27 terms. Each links to the lessons that teach it. Study them as flashcards →
1
1RM (one-repetition maximum)
The heaviest load that can be lifted once with correct technique.
Used to express training intensity as a percentage (%1RM). Can be tested directly or estimated from repetitions to failure; estimates lose accuracy above ~10 reps.
Example: 100 kg × 5 reps ≈ 117 kg estimated 1RM (Epley).
A
ATP (adenosine triphosphate)
The molecule whose breakdown directly powers muscle contraction and most cellular work.
Muscle stores only enough for seconds of maximal work, so it is continuously resynthesised by the phosphagen, glycolytic and oxidative systems.
Example: Myosin needs ATP to detach from actin.
Atrophy
A decrease in the size of a tissue or muscle, usually from disuse, illness or ageing.
Muscle atrophy can occur within days of immobilisation; resistance training can slow or reverse it.
Example: Thigh circumference falls after six weeks in a knee brace.
C
Cardiac output
Volume of blood pumped by the heart per minute (heart rate × stroke volume).
≈5 L/min at rest; can exceed 35 L/min in elite endurance athletes at maximum.
Example: 150 bpm × 110 mL = 16.5 L/min.
Concentric action
Muscle produces force while shortening.
Concentric force falls as shortening velocity increases (force–velocity relationship).
Example: Quadriceps while standing up from a squat.
D
Dynapenia
Age-associated loss of muscle strength and power, not explained by neurological or muscular disease.
Strength declines faster than muscle mass with ageing, so dynapenia and sarcopenia are related but distinct.
Example: Falling grip strength despite stable arm muscle size.
E
Eccentric action
Muscle produces force while lengthening.
Highest force and lowest metabolic cost of the three actions; unaccustomed eccentric work causes delayed-onset muscle soreness.
Example: Hamstrings during the Nordic hamstring exercise.
Energy availability
Dietary energy intake minus exercise energy expenditure, expressed per kg of fat-free mass.
It is the energy left for all other body functions. Chronically low energy availability underlies RED-S.
Example: An athlete eating 2,000 kcal, expending 800 kcal in training, with 50 kg FFM: (2000 − 800) / 50 = 24 kcal/kg FFM/day.
H
Hypertrophy
An increase in the size of a tissue; in training, usually growth of muscle fibres.
Driven mainly by mechanical tension, with weekly training volume showing a dose–response relationship.
Example: Increased quadriceps cross-sectional area after 12 weeks of squatting.
I
Isometric action
Muscle produces force without a visible change in length.
Strength gains are largest near the trained joint angle.
Example: Holding the bottom of a plank or a wall sit.
L
Lactate threshold
The exercise intensity at which blood lactate begins to rise above baseline (LT1), or rises disproportionately (LT2).
Many definitions exist and they are not interchangeable. A key determinant of endurance performance alongside VO₂ max and economy.
Example: A runner’s LT2 pace of 4:10 min/km.
M
MET (metabolic equivalent)
A unit of energy expenditure; 1 MET ≈ resting oxygen uptake ≈ 3.5 mL O₂·kg⁻¹·min⁻¹.
Activities are rated in METs (e.g., brisk walking ≈ 3–4 METs). A convention that varies between individuals.
Example: 10-MET fitness = VO₂ max of ~35 mL·kg⁻¹·min⁻¹.
Motor unit recruitment
Activation of additional motor units to increase muscle force.
Follows the size principle — small, low-threshold units first, large high-threshold units as force demand rises.
Example: Lifting a heavier box recruits more motor units.
N
Neuromuscular adaptation
Changes in the nervous system’s control of muscle with training — recruitment, firing rate, coordination.
Responsible for much of the strength gained in the first weeks of training.
Example: Leg press strength rising before visible muscle growth.
O
Osteopenia
Bone mineral density lower than normal but not low enough to be classified as osteoporosis.
Defined by DXA T-score between −1.0 and −2.5. Impact and resistance training can help maintain bone.
Example: A post-menopausal client with a T-score of −1.6.
P
Periodization
The planned, systematic variation of training over time to reach goals and manage fatigue.
Organised into macro-, meso- and microcycles; many models (linear, undulating, block).
Example: A 12-week plan moving from hypertrophy to strength to peaking.
Progressive overload
Gradually increasing training demands so the body continues to adapt.
Can be achieved by load, reps, sets, density, range of motion or complexity — not only by adding weight.
Example: Adding one rep per set each week until reaching the top of the rep range.
Proprioception
The sense of the position and movement of body parts, from receptors in muscles, tendons, joints and skin.
Often impaired after injury; balance and movement training aim to restore it.
Example: Knowing your knee angle with your eyes closed.
R
Rate of force development (RFD)
How quickly force rises at the start of a muscle action (change in force ÷ change in time).
Important in sprinting, jumping and injury-avoidance reactions where little time is available.
Example: Force-plate jump testing reports RFD in N·s⁻¹.
Relative energy deficiency in sport (RED-S)
A syndrome of impaired physiological function caused by low energy availability.
Affects metabolism, bone health, hormones, immunity and performance in all sexes. Requires multidisciplinary management.
Example: An endurance runner with recurring stress fractures and menstrual disruption.
RIR (repetitions in reserve)
How many more repetitions could have been performed at the end of a set.
Used to auto-regulate effort; most accurate close to failure.
Example: “3 sets of 8 at 2 RIR” — stop with about two reps left.
RPE (rating of perceived exertion)
A person’s rating of how hard exercise feels, on a standardised scale (Borg 6–20 or CR-10).
Valid for aerobic and resistance exercise; independent of heart-rate-lowering medication.
Example: RPE 12–13 on the 6–20 scale ≈ moderate intensity.
S
Sagittal plane
The plane dividing the body into left and right parts.
Flexion and extension occur in it, about a mediolateral axis.
Example: Squats, curls and walking strides.
Sarcomere
The basic contractile unit of striated muscle, between two Z-discs.
Shortens as actin slides over myosin; its length determines force via the length–tension relationship.
Example: Thousands of sarcomeres in series make up one myofibril.
Sarcopenia
Age-related loss of skeletal muscle mass and function (strength and/or physical performance).
Associated with falls, disability and mortality. Resistance training is the primary intervention.
Example: Low grip strength and slow gait speed in an 80-year-old.
Stretch-shortening cycle (SSC)
An eccentric action immediately followed by a concentric action, producing more force than concentric alone.
Uses stored elastic energy and reflex potentiation; the basis of plyometrics.
Example: A countermovement jump vs a squat jump.
V
VO₂ max
The highest rate at which the body can take up and use oxygen during intense whole-body exercise.
Usually limited by maximal cardiac output in healthy people; strongly associated with health outcomes.
Example: 45 mL·kg⁻¹·min⁻¹ in a recreationally active 30-year-old.