How long should a sprint interval be

According to Stacy Sims, a sprint interval should be 30 seconds or less at maximum effort (9 or 10 on the perceived exertion scale) to fully engage your energy and nervous system 1. After such intense activity, it's important to allow for a substantial recovery period—typically 2 to 3 minutes—to regenerate ATP and recover sufficiently for another maximal effort 1. This recovery period ensures that you maintain high intensity and quality throughout your sprint training.