You may have grounds to rescind the contract for fraud, if they knowingly misrepresented the terms of the contract by not disclosing one page of it. You could also argue that you are not subject to any terms contained on the second page, since you did not consent or agree to them--you could not, if they were not before you. If the gym will not voluntarily accept that you are not bound by the agreement (or at least the terms on page 2), however, you could end up in litigation with them, so if it comes to that, you need to decide if it's potentially worth a lawsuit to escape those terms.