Gym Photoshoot Help Request
I've been shooting marketing and promotional pictures for the gym I work at.
I suggest using a prime lens because lighting is rarely ideal. I was using ISO-1600 with my kit lens, and around ISO-500 with my 35mm prime. You'll probably be using a wide aperture to take advantage of available light so be careful with your depth of field.
Using an external flash didn't work that great in the particular room I was using, and I suggest avoiding it if you're not an expert in flash photography.
Shoot in raw so you have more flexibility dealing with exposure and white balance issues in post-proccessing.
Try different approaches to the composition, mix up close-ups, scene shots, maybe even a slow-shutter speed to show motion when she's peddling the bike. Sounds like you know what you want though.