Once Ochaco uses her Quirk to negate the gravitational pull on an object, she can press the tips of her fingers together to release the effect. Using it one multiple objects at a time or overusing this technique greatly exhausts Ochaco, even to the point of vomiting.
However, she appears to have gained a greater level of tolerance to the repercussions. During the U.A. Sports Festival, Ochaco was able to release an entire arenas worth of debris on Katsuki and still continue on fighting afterwards. She first used this technique to score multiple points in the U.A. Entrance Exam's practical test.