Furthermore, sufficient protein is obviously required and movement (lifting heavy things) to trigger an increase in muscle mass and/or strength. High intensity training on the lower rep range benefits more strength, higher reps more hypertrophy.
Usually, when on a animal based diet, suffient protein should not be a problem. I target 1g to 1.5g per kg bodyweight, but more as a guideline than absolute. Always consume protein with fat as it has a higher anabolic effect. In nature animal protein always comes with fat but never with carbs and eating as close to nature as possible is optimal.