If you are going to use a harness we now only recommend one for adult Labradors. The Julius K9 Powerharness.
This is the original, robust model originally developed for professional use for emergency and police dogs. These harnesses are made from robust, scratch-proof, water-resistant polyester, making it the perfect harness for your active Labrador.
NB: No matter how well you fit a harness your dog may be able to wriggle out of it, DO NOT OVER TIGHTEN, regularly check it is fitted right and she hasn’t loosened it.