The core principles of effective strength training include progressive overload, specificity, and recovery. Progressive overload involves gradually increasing the weight or resistance to encourage muscle growth. Specificity refers to designing workouts tailored to an individual's fitness goals, ensuring exercises target the desired muscle groups or skills. Additionally, incorporating adequate recovery time allows muscles to repair and grow stronger after workouts. Other key elements include maintaining proper form to prevent injuries, varying routines to challenge muscles, and integrating balanced nutrition to support training efforts and recovery.