There are exact methods used by some trimmers that cause lameness, in the horse. Any invasion of supportive structures of the hoof will cause issues. Be aware of these actions.
Removing live sole and sole ridge
Over lowering of heels
beveling of the buttress and heel
Removing all bar support
incorrect balance of the hoof. Long toes stressing the lamina (also known as white line disease)
What does not lame a horse. Many times students start trimming and are fearful they will lame the horse. The trim is set up to protect the trimmer from making these mistakes.
Lowering walls, to remove stress on the lamina.
Backing the toe with the Apex Trim Method.
Correct beveling of the hoof.
Lowering heels that are too high.