What type of training allows varying intensity levels during continuous sessions?

Fartlek training is a method of training that incorporates varying intensity levels during continuous exercise. The term "Fartlek" comes from Swedish, meaning "speed play," and it allows runners and other athletes to blend different speeds and intensities within a continuous workout. This could involve alternating between sprinting and jogging or incorporating different terrains and challenges to keep the body adapting and responding to diverse stressors.

The essence of Fartlek training lies in its flexibility, allowing athletes to choose when they want to increase their intensity or recover, which can be particularly beneficial for improving endurance and speed. It differs from interval training, which focuses on set periods of high-intensity effort followed by specific rest intervals, and steady-state training, which maintains a consistent level of intensity throughout the session. Circuit training typically involves a series of exercises performed in rotation with minimal rest but does not focus specifically on varying intensity levels continuously throughout the session.