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The principle of specificity or SAID (specific adaptation to imposed demand) states the body will adapt to the type of demand placed on it. An example, weightlifters will adapt to lifting weights as runners will adapt to running. When applying SAID it’s important to use it appropriately, the body reacts differently to different stimuli.

There are two types of muscle fibers, Type 1 and Type 2. Type-1 are slow twitch, smaller in diameter, slower to produce max tension and slower to fatigue. They have the ability for long-term contraction aiding in stabilization, endurance and postural control. Type-2 are fast twitch, larger in size, quick to produce max tension, fatigue faster and produce force and power. Higher intensity training requires postural control.

The degree of adaptation is related to mechanical, neuromuscular and metabolic specificity.

  • Mechanical specificity: the weight and movement placed on the body. As an example lighter weights plus higher reps equals greater muscular endurance. Whereas higher weights plus lower reps equals greater muscular strength.
  • Neuromuscular specificity: speed of contraction and exercise performed. For improvements in this area exercises should be performed in a controlled unstable environment at slower speeds. Controlled environments plus heavier loads leads to higher levels of strength. While higher levels of velocity in a plyometric manner leads to higher levels of power.
  • Metabolic specificity: energy demand placed on the body. Endurance requires greater training times with minimal periods of rest. The aerobic pathways supply energy for this type of training. Strength training requires shorter training periods with higher intensity and longer rest between bouts. Anaerobic pathways supply energy for this type of training.