Used this in the end ..
public void preSolve(Contact contact, Manifold oldManifold) {
if (contact.getFixtureA().getBody().getUserData() instanceof Spring){
float impulse = contact.getFixtureB().getBody().getMass() * impulseToApply;
contact.getFixtureB().getBody().applyLinearImpulse(
new Vec2(0, impulse),
contact.getFixtureB().getBody().getWorldCenter() );
}else if (contact.getFixtureB().getBody().getUserData() instanceof Spring){
float impulse = contact.getFixtureA().getBody().getMass() * impulseToApply;
contact.getFixtureA().getBody().applyLinearImpulse(
new Vec2(0, impulse),
contact.getFixtureA().getBody().getWorldCenter() );
}
}