How does high-intensity interval training (HIIT) affect cardiovascular fitness?

High-intensity interval training (HIIT) is especially effective in improving cardiovascular fitness because it involves alternating short bursts of intense exercise with periods of lower-intensity recovery or rest. This pattern of exertion encourages the heart and lungs to become more efficient at delivering oxygen-rich blood to working muscles, leading to significant improvements in cardiovascular endurance over a relatively short duration of training.

Research has shown that HIIT can lead to greater adaptations in cardiovascular fitness markers, such as VO2 max, compared to traditional steady-state exercise. This is primarily due to the intense aerobic and anaerobic efforts that push the cardiovascular system beyond its usual limits, thus promoting improvements in heart function, vascular health, and overall stamina. Additionally, the shorter sessions typical of HIIT workouts make them appealing and manageable, allowing more individuals to engage in effective cardiovascular training regardless of their fitness level.

The other options do not accurately reflect the benefits or characteristics of HIIT. For instance, the idea that it has no impact on fitness or can only be performed by elite athletes overlooks the accessible nature and widespread effectiveness of this training method across various fitness levels.