Most people will not be able to hold a back lever let alone do pull ups in the position without months of training. You can overcome this problem and still build strength with this great exercise by training with the progressions of the back lever until your strength increases.
The fastest way to progress is to train at your level but not beyond. Maintaining correct form is crucial, sacrifice it and you will be training the wrong muscles.
The first step of the front lever pullup is to get up to the bar until your arms are bent. Pull up in one smooth motion and stop when your eyes are level with the bar. Keep your arms bent and steady yourself in this position so that you can move into the lever phase of the exercise.
From the up stage of the pullup, you need to bring your body to a horizontal position. Raise your legs upward until your entire body is parallel to the floor. As you do so, push yourself away from the bar so that your hands are in a vertical line with your abdomen, instead of your chest or shoulders.
To complete the up phase of the lever pullup, raise yourself up to the bar while keeping yourself in the horizontal position. The upward movement should look and feel like an upright row or a reverse bench press. Try touching your torso to the bar, or go as high as you can, and then lower yourself back down to the lowered lever position.
After the first full rep you can either continue to do the pullups from the lever position or you can lower yourself down to a dead hang to repeat the lever pullup from its beginning position. Experiment with both options to see how they affect your workout.
This should not be attempted by people with weak backs.
Do not bend at the hips which is one of the more difficult parts of the lever.
