Some people might perceive training as a threat, and the manner in which the training is carried out needs to be prepared with some care. Many participants may be anxious about opening up in discussions as they feel they might say the "wrong" thing and be open to criticism. It is therefore important to create a comfortable working and training environment.
Perhaps it is appropriate to welcome each trainee individually when they arrive. Also, it is important that the trainers mix (language barriers permitting) with the participants during break time in a more informal setting. The use of name badges helps people identify their fellow participants.
Try to maintain a supportive climate - be sensitive to possible signs of anxiety and be ready to provide encouragement and reassurances when necessary. And remember, non-verbal as well as verbal communication will provide useful feedback to the trainers.
Keep the sessions short and provide break times. However, you also need to make sure there is enough time for discussion and time to respond to questions to help ensure that training is proceeding at the pace needed by the trainees, and not that desired by the trainers.