Cardio
Also known as: Cardiovascular exercise
Cardio, short for cardiovascular exercise, is sustained or repeated physical activity that raises the demands on your heart, lungs, and circulation and develops cardiorespiratory fitness. Walking, running, cycling, rowing, swimming, and elliptical training can all be cardio when performed with enough duration and effort. The term overlaps with endurance training, although endurance can also refer more broadly to the ability to resist fatigue in a particular sport or task.
Cardio is an umbrella, not one fixed workout. It can be continuous or interval based, low impact or high impact, and easy or vigorous. HIIT alternates relatively hard work with recovery periods. LISS maintains a deliberately easy, steady effort. Zone 2 training targets a particular aerobic intensity, but the exact boundary depends on the zone system and the individual. A brisk walk may be meaningful cardio for one person and too easy to create the same training stimulus for another.
Regular aerobic activity can improve cardiorespiratory fitness and supports the health of the cardiovascular system. For adults aged 18–64, the WHO recommends 150–300 minutes of moderate aerobic activity or 75–150 minutes of vigorous activity per week, or an equivalent combination, alongside muscle-strengthening work on at least two days. These are population-level targets, not a rule that every person must reach immediately; the same guidance emphasizes that some activity is better than none and that volume and intensity can increase gradually.
Cardio also expends energy, but it is not a special fat-loss switch. Changes in body weight depend on overall energy intake and expenditure over time. Likewise, sweating more or choosing the machine that displays the largest calorie estimate does not prove that a session caused more body-fat loss; machine estimates can be imprecise.
Cardio does not automatically erase muscle or strength gains. In a meta-analysis of concurrent aerobic and strength training, combining both did not reduce average muscle-growth or maximal-strength gains, although explosive-strength gains could be attenuated, particularly when both modes occurred in the same session. The practical issue is usually the total dose and placement of demanding work. When lifting quality matters, use concurrent training principles: prioritize the key session, account for leg fatigue, and allow enough recovery.