One of the many benefits of working with a trainer is the increased safety of having a spotter, an expert to help you with body alignment and someone to help guide you during your workouts. Even so, you want to be aware of the more common sports and workout injuries that occur so that you can be working proactively to avoid them from your end as well. Among the most common of these injuries are sprained ankles, knee pain, low back pain, and shoulder injuries. Work with your trainer to avoid alignment issues being causal in these injuries.
Remember, you're the one who laces up your shoes, so make sure they are appropriate for the task at hand. Ankle, knee and low back issues can arise from improper footwear. Next, make sure that you aren't letting your skeleton do the job, meaning, activate those muscles. Your skeleton can hold the weight for you, sure, but it puts pressure on joints rather than allowing the muscles to gain strength by doing the job.