Is the principle of minimization of secondary moments validated during various fingertip force production conditions?
Human Movement Science. 2008-06-01; 27(3): 396-407
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1. Hum Mov Sci. 2008 Jun;27(3):396-407. doi: 10.1016/j.humov.2008.02.019. Epub 2008
Is the principle of minimization of secondary moments validated during various
fingertip force production conditions?
Vigouroux L(1), Ferry M, Colloud F, Paclet F, Cahouet V, Quaine F.
(1)Movement and Perception Laboratory, CNRS UMR 6152, Faculté des Science du
Sport, University of the Mediterranean, Case postale 910, 163, avenue de Luminy,
F-13288 Marseille Cedex 09, France.
During the application of fingertip forces with simultaneous flexion of the four
fingers, namely index, middle, ring, and little fingers, a stable force sharing
among fingers is adopted. Several studies have hypothesized that this stable
force sharing is established to minimize unnecessary rotational moments
(different from the main flexion moments). This principle labeled “minimization
of secondary moments” is presented in the literature as a principle used by the
central nervous system to solve musculoskeletal redundancy. However, this
principle has only been tested with one solicited degree of freedom and in one
finger posture. Our study tests this principle with various degrees of freedom
solicited as secondary moments and in two different finger postures. Participants
(n=6) were asked to apply a downward vertical force using their four fingers with
the forearm placed in two different configurations: a “horizontal” condition
(involving flexion/extension and pronation/supination at the wrist joint) and a
“vertical” condition (involving flexion/extension and radial/ulnar deviation at
the wrist joint). Additionally, two finger postures were tested in each forearm
configuration: in the first, the distal inter-phalangeal joints (DIP) were
extended and the proximal inter-phalangeal joints (PIP) highly flexed. In the
second finger posture, both DIP and PIP joints were flexed. The resultant
four-finger force and the relative involvement of each finger in the resultant
four-finger force (force sharing) were analyzed. Results showed that the finger
postures did not influence the finger force sharing, showing that the
minimization of the secondary moment principle was stable among the finger joint
angle configurations. Nonetheless, the relative involvement of each finger was
dependent on the secondary degree of freedom solicited (pronation/supination vs.
radial/ulnar). The modifications of the finger force sharing between the
“horizontal” and “vertical” conditions were in accordance with the principle of
minimization of the secondary moments.
PMID: 18400321 [Indexed for MEDLINE]