Physical Activity: A Plain-Language Reference Glossary

Aerobic Exercise

Physical activity that relies primarily on oxygen to produce energy, typically sustained over longer periods at moderate intensity. Common examples include walking, cycling, and swimming. The word 'aerobic' means 'with oxygen.'

Anaerobic Exercise

High-intensity activity that outpaces the body's ability to supply oxygen, relying instead on stored energy within muscles. Sprinting and heavy resistance training are common examples. Anaerobic efforts are typically short in duration.

VO2 Max

The maximum rate at which the body can consume oxygen during intense exercise, often used as a marker of cardiorespiratory fitness. A higher VO2 max generally indicates a more efficient cardiovascular system, though it varies with age, genetics, and training history.

Lactate Threshold

The exercise intensity at which lactic acid accumulates in the bloodstream faster than the body can clear it. Training at or near this threshold is a common strategy in endurance sports to improve sustained performance.

Hypertrophy

The increase in muscle size resulting from resistance training. Hypertrophy occurs when muscle fibers experience stress and repair with slightly more mass. It is distinct from gains in muscular strength, though the two often accompany each other.

Progressive Overload

The principle of gradually increasing the demands placed on the body during exercise over time — through added weight, volume, frequency, or reduced rest. It is widely considered essential for continued fitness adaptation.

HIIT (High-Intensity Interval Training)

A training format alternating short bursts of high-effort exercise with recovery periods. HIIT is used across both cardiovascular and strength-based workouts and is valued for time efficiency, though it is not appropriate for all fitness levels.

Resting Heart Rate

The number of times the heart beats per minute while the body is at rest. It is commonly measured first thing in the morning and is used as a general indicator of cardiovascular health; lower resting rates often correlate with higher aerobic fitness.

RPE (Rate of Perceived Exertion)

A self-assessed scale — commonly ranging from 1 (minimal effort) to 10 (maximum effort) — used to describe how hard exercise feels. RPE helps individuals calibrate intensity without objective monitoring tools.

Muscular Endurance

The ability of a muscle or group of muscles to sustain repeated contractions over time without fatiguing. It differs from muscular strength, which refers to the maximum force a muscle can exert in a single effort.

Recovery

The period following exercise during which the body repairs tissue, restores energy stores, and adapts to the training stimulus. Adequate recovery — including sleep, nutrition, and rest days — is considered as important as the workout itself.

Functional Movement

Exercise patterns that mimic everyday movements — such as squatting, pushing, pulling, and rotating — to improve strength and mobility for daily activities. Functional training is often contrasted with isolated machine-based exercise.