Pretty crappy product . the quality be very poor which be practically plastic . the only way to get it to work the way they advertise be to go so fast on it that you tire out before you see any result . in the long run it may become useful but you have to be in already great shape to reap any benefit from it . truth of the matter be that those who be already in shape rarely would utilize something like that . I would definitely think twice about buy this unit .