Can I add weight training to XERO?

We recommend that you leave XERO untampered. Let XERO work the way it was designed to work. If you begin integrating the use of weights with XERO and gains are made, what do you attribute the progression to? At the very least, let your first run through of XERO be completely unaltered. You will be surprised just at how effective (and difficult) bodyweight training can be.