Soul Cycle lovers and spin class devotees make dedicated and fun Pilates clients. Cycling plus Pilates during the week is my "go to" for Spring training.  With this powerful duo, you get an excellent combination of cardio, strength training, and most importantly, Pilates gives you the posture your body needs for riding on a bike.  The most efficient workout for your deep core muscles, hamstrings and glutes comes from positioning yourself on the bike in neutral "S" curve (see below). Starting from a neutral position will work your muscles harder and you won't have the joint soreness in the neck and shoulders that many daily spinners report. 

The video below shows how to find the "S" curve in the back.