Strength and Fatigue: Experiments and Modeling - Human Motion Simulation: Predictive Dynamics - page 127

FIGURE 6.1
Muscle modeling using curves of action ( Patrick, 2007 ).
torque measurements produced about a joint. Thus, all models of strength must
ultimately be validated against assessments of net joint torque. A muscle-level
model of a DHM is shown in Figure 6.1 and developed by the authors' team
( Patrick, 2007 ) where muscle lines and curves of action are depicted. This model
provides for muscle curves that wrap and slide.
If torque is calculated at the joint, which is at the heart of this topic, then mus-
cle forces can be calculated by resolving the torque into its various components
( Figure 6.2 ). And indeed there are several methods for accomplishing this calcula-
tion ( Patrick, 2007 ; Zatsiorsky, 2002).
6.2 Strength influences
Muscle strength definitions typically center on the capability to produce force, or
the maximal force-production of a muscle. Several factors can influence muscle
strength, including properties inherent to muscle contraction (i.e., at the cellular,
fiber, or single muscle level) and the mechanical arrangement of muscles within
the musculoskeletal system (i.e., considering individual and/or groups of muscles).