The ideal bodybuilding physique tends more towards mesomorph with broad shoulders, narrow hips with arms and legs of medium length. Two further inherited features have a role to play in determining muscle building potential, and these are muscle fiber density and neurological efficiency. Fiber density determines size potential of a muscle while neurological efficiency refers to relationship between nervous system and muscles. This is relevant because, in all out effort genetically blessed individuals have ability to activate up to 50% of fibers in a given muscle compared to average person's 30%. This allows greater scope for stimulating growth.

The fact that there is no easy way to measure fiber density or neurological efficiency is actually a blessing because incentive remains for all of us to train hard and strive for improvement. Only a tiny minority of people have genetic tools to become champions but rest of us can go a long way to fulfilling our own personal goals.

In this article we'll take a close look at bent-knee sit-up.

MUSCLES TARGETED: rectus abdominis

STARTING POSITION

Assume a supine position on floor. Flex knees to bring heels close to buttocks. Fold arms across chest.

UPWARD MOVEMENT

Flex neck to move chin to chest. Curl torso toward thighs until ONLY upper back is off mat.

DOWNWARD MOVEMENT

Allow torso to uncurl, then neck to extend back to starting position. Repeat or finish set.