What ballet movements and ballet positions will result in clean accurate split leaps? The first exercise at the ballet barre, demi and grand plie, your posture, the placement of your weight and the strength of your turnout, is the foundation of your ballet positions and ballet movements. Your split leaps, and even fancier allegro depends on it.
Starting with your primary level ballet classes, understanding and being able to execute correct posture as well as an accurate grand battment devant and derriere will eventually produce a good grand jete en avant, the well known ballet split leap.
A demi plie take off in a basic jump in first position without posture changing, or the turnout decreasing or the heel coming off the ground, is a secure take off. As you progress to more advanced jumps, this ballet technique will continue to support good positions and a good quality of balon, or easy bounce.
An effective brush of the foot on the floor,practiced hundreds of times in battment tendu, degage, and grand battment, will add power to your petit jete, and eventually your grand jete.
Being able to change from the upright back to a proper arabesque position (as in a grand battment derriere) will make for a good position in the air, and a good landing. Repetitive releves in arabesque at the barre will enable you to see if the position is being held well, and the demi plies are on balance and strong.
A chasse temps leve forward into arabesque is a good practice routine to also make sure the arabesque leg reaches its height at the height of the jump and can be held in the air. Much of the ballet I watch lacks a moment at the height of a releve or jump where everything freezes for a nano second, without stiffness or effort. In other words if someone wanted a snapshot, the position could be easily captured.
Brushing up into the devant position, releve, arms reaching their position at the same moment, holding the position , and then tombe forward, repetitively across the floor, helps too.
If all the basics are done with strength, it doesn't take too much to do a good ballet split leap, or grand jete. Positions that are not strong can be practiced at the barre in the usual exercises before the jumps will improve. The Body Series offers books and DVDs (try Effective Stretching The Ultimate Guide) with more about flexibility exercises for dancers.