The overload principle refers to resistance training. Overload occurs when a greater than normal physical demand is placed on a muscle. The amount of overload needed depends on the muscular fitness of each individual. Overload can be used to improve strength and endurance.

To gain strength, moderate to high loads (resistance or weight) are needed. When it comes to endurance training, the number of repetitions is more important. Muscles can be further loaded by decreasing the rest period between sets of exercises.

As the muscle adapts to the new load, more weight or more repetitions are added. Injury can occur from over training so caution must be used when progressing the program. If you're working out at a training club or facility, the staff should be trained in these concepts. They will be able to help you get set up on the right program.