Table 2.

Definition of muscle primary function, quantity and quality components to integrate functional or morphological muscle quality[12-21].

Muscle primary function parameters
Force	Influence that can change the movement of an object. It has magnitude and direction.
Moment (strength)	Rotational effect of the force generated by a muscle or a muscle group around a joint.
Muscle strength	Amount of force a muscle can produce with a single maximal effort.
Muscle power	Ability to exert maximum force in the shortest amount of time, such as accelerating, jumping, or throwing.
Muscle work	Force exerted by a muscle a muscle or group of muscles to perform a physical task.
Muscle contraction type	Two main forms of contraction can be described, when length of the muscle remains without change (isometric) and when length of the muscle changes with contraction (isotonic). Isotonic contraction can be concentric (shortening of muscle length) and eccentric (elongation of muscle length). Isokinetic fixed angular velocity
Muscle quantitative parameters
Volume	Tridimensional space of a muscle, considering length and shape (through magnetic resonance, ultrasound)
Thickness	Distance between superficial and deep aponeurosis of the muscle (through magnetic resonance, computarized tomography, ultrasound)
Cross sectional area	Anatomic: Bidimensional space of a transversal view of an image Physiologic: ratio of muscle volume between the length of its fibers (through magnetic resonance, computerized tomography, ultrasound
Lean mass	Fat-free and bone mineral–free component that includes muscle and other components such as skin, tendons, and connective tissues (through densitometry, bioimpedance, anthropometry or formulas)
Appendicular lean mass	Is the sum of lean soft tissue from both arms and legs (through densitometry, bioimpedance, anthropometry or formulas)
Skeletal muscle mass	Sum of total muscle mass from the whole body (through magnetic resonance, tomography, indirect by ultrasound and formulas) [20]
Appendicular skeletal muscle mass	Sum of muscle mass from arms and legs (magnetic resonance, computerized tomography)
Muscle qualitative parameters
Fascicle length	Length of the fascicular path between the insertion of the fascicle to the superficial and deep aponeurosis (magnetic resonance, ultrasound)
Stiffness	Change in force divided by the corresponding change in length, when the length change is imposed by an external agent or by a change in the external load in a muscle (myotonometry, ultrasound, magnetic resonance)
Muscle contraction	Muscle contraction correlated to cross sectional area at rest and maximal contraction (ultrasound)
Microcirculation	Capillary flow in skeletal muscle (ultrasound, magnetic resonance)
Pennation angle	Angle of insertion of the fascicles of muscle fibers in the deep aponeurosis (ultrasound)
Echogenicity	Brightness of the image acquired by ultrasound in gray scale caused by the reflection of soundwaves and is influenced by sound beam characteristics and tissue density (ultrasound)