Does it hurt?
During the workout, you might feel pain and fatigue. It's important for you to be able to distinguish between pushing yourself hard and when your body is asking you to stop.
For at least the first few sessions, you will likely be sore afterward. Usually after a few weeks, your soreness will likely decrease, unless you and your trainer add a new exercise.
What are the risk factors?
Exercise-related risk factors are one of the main reasons to get a personal trainer. One of the biggest risks of exercising is suffering from injuries based on poor form or from using the wrong weights.
A good personal trainer can decrease your likelihood of hurting yourself. One of your trainer's jobs is to watch your form carefully while you're exercising and correct any bad habits.
For example, knees and shoulders are typically the main two areas to be injured while exercising. If you're doing lunges, your trainer will make sure your knee isn't going too far forward.
What's the follow-up?
The number of sessions you have with your trainer will depend on your goals and financial means. If you have enough of an income to have regular sessions, you might go back weekly or every other week.
If you're training for a half marathon, then you might see your trainer up until the race and then take a break from personal training.
One of the benefits of having a trainer is that he or she will likely track your progress, allowing you to see how far you've come.
Source: Katie Howard,
of You & Improved Fitness; National Institute of Diabetes and Kidney Diseases;
The Mayo Clinic