Mountainside Fitness Chase Field At Mountainside Fitness, we take our reputation as being one of the leading gyms in downtown Phoenix, AZ very seriously. In each of our 18 health and fitness centers, our staff genuinely cares about the experience of our Members. Our downtown Phoenix location is designed for Members who work or live in the area and offers variety of amenities such as group fitness classes, cardio equipment with personal entertainment systems, full service locker rooms with free towel service and more. To see what our downtown Phoenix fitness center has to offer, check our amenities below. Our club memberships are created for individuals, couples and families with month to month or contract pricing options.