Pilates teasers and quad pains?

[herya]

Is anybody out there who have experienced this and could help? When I'm doing Pilates teasers with straight legs my quads contract and hurt, almost to the point of cramp. I can do any kind of teaser with bent legs or any other Pilates abs exercise so it's not that my abs are weak. I thought that it's abs that make you do the teaser not quads and I try to engage my abs as much as possible but it's quads that hurt! Am I doing something wrong?