Which training method involves varying intensity with no rest in between?

Fartlek training, originating from Swedish meaning "speed play," is a unique form of training that integrates continuous training with interval training principles. It allows athletes to vary their speed and intensity throughout a workout without rest intervals. This method is particularly valuable for improving both aerobic and anaerobic fitness, as it encourages adaptations by challenging the body in different ways.

During a Fartlek session, an individual might alternate between fast and slow running or change pace based on the environment or terrain, such as sprinting to a distant tree and then jogging to recover. This unpredictability and emphasis on effort rather than set intervals provide a dynamic training experience that enhances endurance and speed while keeping the exercise engaging.

Other training methods, such as interval training, typically involve structured rest periods between bouts of high-intensity effort. Strength training focuses on building muscle through resistance exercises and doesn't inherently incorporate the concept of varying intensity during a continuous workout. Cardio training generally refers to activities that improve cardiovascular endurance but may not emphasize the varied intensity aspect characteristic of Fartlek training. Each of these other methods serves different training goals that are distinct from the concept of varying intensity without rest.