LONDON, England (CNN) -- So you want to get fit? What is the first thing you should concentrate on? Should it be how fast or far you can run or should you work on your flexibility? It can be alarming how much work there is to do when you first embark on a fitness program, so where should you start?
Rapper LL Cool J is lucky he doesn't have a desk job and can work on his abs.
CNN spoke to London based personal trainer Marisol Toroparedes who believes developing core strength is crucial to the start any fitness regime. "The first step should be building core strength. If you have a weak core you will put yourself in harm's way."
Says Toroparedes, "Core strength is all about posture. It's the way you stand -- it's keeping your shoulders back. It's standing tall and pulling the belly button into the spine and the lower back."
It's important to develop strength in your core (or trunk) as the muscles around this area protect your spine and help prevent back injury. Core training focuses on muscular areas of the abdominals including obliques (your sides), upper and lower back (deltoids, rhomboids), hips (gluteals, hip flexors, psoas), outer and inner thighs (abductors and adductors), hamstrings, even some pectorals and triceps work.
Poor core strength is an occupational hazard should you work in an office. "Your body is not designed to sit eight or nine hours a day," says Toroparedes. If you are stuck in an office job she advises taking regular screen breaks, stretching and sitting with "your tummy tight, shoulders, back and knees slightly soft."
"Posture and fitness are very closely related. If you have bad posture any exercise you do can put you in danger. You'll also get more out of your workouts if you improve your posture and core strength."
Before starting a fitness regime Toroparedes advises that you get a professional check-up to make sure you are in alignment as "everything starts with good posture."
To strengthen the core Toroparedes advises exercising on a Swiss Ball as "exercising on unstable surfaces can help develop strength" or doing pilates. When building up core strength at the gym, you should not hesitate to ask gym staff to help suggest exercises.
While downloading different exercises from the Internet can help, Toroparedes believes that nothing beats individual assistance when starting off a fitness program.
Experts also advise that when starting pilates to increase core strength you attend classes with small numbers, so you can get more attention and help on holding the posture. E-mail to a friend