I am always being asked about the correct positioning of the spine and pelvis, especially during pilates apparatus and yoga therapy classes. In a nutshell, we are all individual and will have different positioning of our body. The picture below shows a guide to where ‘form has followed function’. 
We all need what is called ‘tensegrity’, which is where we have some structural tension to hold us up and provide vital stability for the organs tissues and bones. But we also need pliability, flexibility and the ability to move with freedom. If we don’t have optimal axis of rotation in the joints, faulty firing patterns then begin to occur.
This then builds up poor engrams that will carry over to functional activities in life. This encourages degradation of the muscular skeletal system. Movements that begin and end with poor posture will foster muscle imbalance and shorten athletic occupational or recruitment patterns.

To prevent postural degeneration and help restore a normal lumber curve, individuals with a flat back or sway back posture should use a blood pressure cuff or towel when their lumber spine is supine (lying flat on back). The towel roll should be about the thickness and width of the palm of the hand when compressed.

A curve can also be implemented in axial loading (standing) by placing some rock tape on the lumbar area. the taping acts as a gentle reminder to pop a natural curve in. As previously mentioned one size does not fit all and is best to be assessed rather than guess, so the above is a guideline. Should you want more specific individual information do not hesitate to contact me.
Bibliography
Advanced Program Design – Paul Chek
Scientific Core Conditioning – Paul Chek
Nisha is a certified Chek practitioner and holistic lifestyle coach.Her journey started when a visiting Laban teacher introduced her to Pilates at Dance College during her first year. It's effects were forgotten but she then re discovered Pilates through Michael King eleven years later whilst running her dance school. Her background spans over 25 years with formal training in classical ballet, modern dance, tap, national choreography, stage production and theatre. Her formation includes Pilates, Thai bodywork, Yoga, GYROTONIC, GYROKINESIS, Garuda and anatomical studies. Her particular interest is fascia, and the connective lines and movement patterns that allow a full moving structure rather than the isolation of bones and muscles. Her fascination with questioning the traditions of modern medicine and fascination with searching for meaningful answers has taken her in many different directions and has offered her an abundance of opportunities gaining a wealth of knowledge. “I tried many movement modalities and extended my search after experiencing fascia, because of its simplicity in movement. Quickly, I noticed my own body changing as well as the bodies of my own clients. In the last 25 years of teaching I’ve developed a workout unique to Yoga Anatomy". Throughout her studies Nisha has done numerous dissections with Julian Baker and Cery Davies and has the opportunity to take lectures and courses from James de Silva, Robert Schleip, Joanne Avisons, Tom Myers, Matt Wallden, Emma Lane, Gary Carter, Paul Chek, Dan Hellman, Peter Blackaby plus many many more Nisha's teaching method promotes reflective self-discovery and provides the requirements to integrate a shift in consciousness for attaining individual goals. She maintains that an attitude of compassion, consistency and joyous humor are excellent components to growth and expanded potential. She welcomes all level of movers from the beginner to the seasoned athlete who have a desire to increase their skill potential, also teachers and students. Her specialties include assisting post rehabilitative individuals, injury prevention for dancers and athletes and advanced movement programs.