Yes, you can ride out of the saddle on a bike trainer. However, it is important to make sure that your bike trainer is compatible with your bike and cycling style before attempting this. Many trainers are designed for seated riding only and may not be able to handle the extra weight or force when standing up. Additionally, some trainers have adjustable resistance settings which must be adjusted properly in order to prevent damage from over-exertion. It is best to consult the manufacturer's instructions prior to attempting any type of out-of-the-saddle riding on a bike trainer.