Final answer:
Interval training involves altering speed, distance, rest, and repetitions, which are key elements in designing an effective exercise routine to improve overall fitness, speed, and endurance.
Step-by-step explanation:
Interval training is a type of exercise that involves alternating periods of high-intensity work with periods of lower-intensity recovery or rest. In interval training, the factors manipulated can include various elements to target improvements in cardiovascular fitness, speed, and endurance. These factors are indeed speed, distance, rest, and repetitions, which are crucial aspects that trainers and athletes adjust to meet their specific training goals.
Speed refers to how fast the exercises within the interval are performed. Distance pertains to the length of the exercise interval. Rest is the duration of the low-intensity or recovery phase between high-intensity bouts. Repetitions signify the number of times the high-intensity and recovery intervals are repeated during a training session. Therefore, the correct answer to the question is E; All of the above. Manipulating these factors allows for a variety of workouts that can increase the intensity, increase the frequency, or alter the target of the exercise program depending on the individual's fitness goals.