CONTRACTION-Stimulation of a muscle.
ISOTONIC CONTRACTION-A contraction with movement, either concentric of eccentric.
CONCENTRIC CONTRACTION-Shortening of the muscle. Positive weight training.
ECCENTRIC CONTRACTION-Lengthening of the muscle. Negative weight training.
ISOMETRIC CONTRACTION-A static contraction.
STATIC CONTRACTION-Contraction but no muscle or limb movement.

SPECIFICITY- The activity performed must be specific to the desired effect. An example, muscle strength training may not lead to flexibility; flexibility training may not help cardiovascular endurance. Also, each area of the body must be worked on specifically for strength, endurance, and flexibility. However, it is possible to design a program that improves more than one aspect at a time.

OVERLOAD In order to improvement in any area of fitness, the workload must be greater
than that to which the individual is accustomed.

REVERSIBILITY "If you don't use it you lose it." With no training, the effects of training will be lost. This is called atrophy.

PROGRESSION The overload should be gradual and moderate within minimum and maximum limits to prevent soreness and injury.

REGULARITY --- F.I.T. The activity must be performed on a regular and frequent basis with an adequit amount of intensity and time in order for improvement to occur.
Frequecy---Exercise must be performed at least 3 times a week for improvement to be seen.
Intensity-- You must continue to use the overload principle to see improvement. If exercise intensity is too low, no improvements will be made.
Time-- You need to exercise at least 30 minutes at a time for maximum benefits.