Your employer is responsible for your safety, so they are required to ensure that you are not lifting anything too heavy. If the load you were lifting was too heavy and that caused you to injure yourself, your employer could be liable.
This may lead you to wonder whether you can refuse to lift heavy objects at work.
If you have a valid reason for refusing to lift a heavy load – such as you haven’t been trained in manual handling or your employer hasn’t carried out a risk assessment – you should raise your concerns. There may be another way of getting the task done.