Many personal trainers dream of training athletes. At the YMCA, you're more likely to train people who are new to exercising. Mostly you will have people buying 5-10 sessions and looking for the tools and knowledge to be able to continue training once your sessions are up. If you're lucky, you will get repeat clients who continually buy the 20 session packages and meet with you regularly. Most people just want to feel confident in the facility, so learning proper technique and getting acquainted to the equipment with you by their side is huge.
You will show up 15 minutes early to fill out a time sheet, document the session, and prepare/write a workout. You'll warmup the client, guide them through a workout, and end the session usually with a cool down walk or stretch.