Six opportunities to give it everything you got and recover enough to do it again,faster. The sled isn't very heavy so you should be able to get a good full 100m sprint with out stopping. You're legs won't give out, your arms won't get tired and your form won't break down. If you stop it's all on you ( the mental you not the physical you). So what are you going to do? Are you going to goo all out every time and see how fast you can go?