This is the description of the three phases of the PMM:
• adaptation and filling-up phase
• contraction and emptying phase
• filling-up phase
1. Adaptation phase
During this phase, the muscle increases its blood mass to a threshold point which will trigger the contraction phase.
This trigger point is sensitive to changes in the pressure (particularly during palpation), and in the position of the tested limb (lifting or lowering the arm to test a brachial biceps)
This phase can last more than 10 seconds depending on how long the muscle takes to fill up and adapt to the surrounding tensions before reaching the ad hoc trigger point. During this phase, the muscle swells along all three planes of space.
2. Contraction phase
This is when the blood is pumped out of the muscle. The muscle contracts: it shortens, its volume and the circumference of its fleshy part decrease. This phase lasts about 3 seconds. The shortening of the muscle's fleshy part indicates muscle contraction. Note that, paradoxically, the diameter of the muscle also shortens.
3. Filling-up phase
Back to the filling-up phase but without the adaptation phase, providing the external vectors do not vary. This phase lasts about three seconds.
The first and third phases are really only one but we have divided it in two so as to be more precise.
