This phrase appears in a personal letter written by a male. He is discussing the difference between 2 different gyms he has been to. "Las pesas ya son historia. Aqui hay algun maquina de pesas tambien pero hacemos algun dia suelto." My translation so far is "The weights are already history. There are some weight machines here but ???". I am unclear as to whether this is a reference to loose weights in comparison to a machine or if the meaning is that he does the weights just when he feels like it.