Progressive overload requires placing an above-normal demand on the muscles during exercise. The amount of overload greatly depends on individual fitness levels. To produce muscular strength and endurance, the muscles must be overloaded on a fairly consistent basis. Overload can be achieved by increasing the repetitions, number of sets or resistance weight during exercise.
Specificity is the body's adaptions to training in order to acquire specific results. For instance, strength is produced by using more resistance during exercise and fewer repetitions. Endurance develops as a result of more repetitions accompanied by low-to-moderate resistance. Static exercises (isometric) and dynamic exercises (range-of-motion or isokinetic) are used to obtain specific results. Isometric exercises are performed without any visible movement in the angle of the joint. Dynamic exercises make use of free weights and weight machines.
To achieve optimal benefits from resistance training, you must include variation in the routine. Typically, this means that participants should rest between training sessions at least 48 hours to give muscles time to recuperate.