Talk:Physiological cross-sectional area

Original source in the literature.

I found new sources. Here's the complete list (including the source kindly provided above by Mokele), sorted by year of publication:

• Alexander, R. McN. and Vernon, A. (1975). The dimension of knee and ankle muscles and the forces they exert, Journal of Human Movement Studies, 1:115–123.
• R.D. Sacks & R.R. Roy (1982). Architechture of The Hind Limb Muscles of Cats: Functional Significance. Journal of Morphology, 185-195.
• Narici MV, Landoni L, Minetti AE (1992). Assessment of human knee extensor muscles stress from in vivo physiological cross-sectional area and strength measurements. European Journal of Applied Physiology & Occupational Physiology. 65(5):438-444.
• Maganaris CN, Baltzopoulos V, Sargeant AJ (1998). In vivo measurements of the triceps surae complex architecture in man: implications for muscle function. J Physiol., 512:603-614.
• Maganaris, C.N., Baltzopoulos V. (2000). In vivo mechanics of maximum isometric muscle contraction in man: Implications for modelling-based estimates of muscle specific tension. In Herzog W. (Ed). Skeletal muscle mechanics: from mechanisms to function. Wiley & Sons Ltd, p.267-288.

So, Alexander is the original source. All these authors use the original formula, except for Sacks and Roy (which is not the original source).

Notice that there's a book in which Zatsiorsky uses the formula by Sacks and Roy (PCSA2), but gives it the original interpretation, which is incompatible with it. This same mistake was made by Wikipedia's editors in Pennate muscle, before I corrected the article.

− Paolo.dL (talk) 18:43, 11 September 2010 (UTC)

I believe the cosine term comes from Gans & Bock, 1965, where they use the term "physiological cross section" to refer to the projection of the force produced by fibers onto the line of action of the muscle. The term may precede them, but Gans & Bock formalizes the conceptual framework and mathematical formalism that all of those guys use for 2-D/planar approximations of muscle. I haven't seen that particular Alexander paper, but you'll find Gans & Bock cited by all of the Roy/Edgerton papers.

Cosine also appears in Spector et al 1980, where they show that the cosine term is required to match force production to architectural estimates. They put cosine in the denominator.

Powell, et al 1984 show that the cosine-containing form accurately predicts whole muscle force for eight muscles, but cosine is in the numerator.

Spector, Sacks and Powell are all out of the Edgerton group at UCLA; those papers came out within 4 years of each other. The research community has settled on the PCSA2 form (cosine in the numerator) because we're interested in the muscle force output. Other forms (eg, Spector) result from confusion or approximation. In practice the cosine is not important. Pennation angles are generally less than 20 degrees, so cosine is greater than 0.94, and the precision with which one can characterize the fiber angulation of a whole muscle by a single number introduces much more than 6% variability.

PCSA, in either sense, has no physical equivalent, and characterizing it as the illustrations are slightly misleading because they assume there is an anatomical section that goes through all of the muscle fibers.

• Gans, C., Bock, W.J., 1965. The functional significance of muscle architecture--a theoretical analysis. Ergebnisse der Anatomie und Entwicklungsgeschichte 38, 115-42.
• Powell, P.L., Roy, R.R., Kanim, P., Bello, M.A., Edgerton, V.R., 1984. Predictability of skeletal muscle tension from architectural determinations in guinea pig hindlimbs. Journal of Applied Physiology 57, 1715-21.
• Spector, S.A., Gardiner, P.F., Zernicke, R.F., Roy, R.R., Edgerton, V.R., 1980. Muscle architecture and force-velocity characteristics of cat soleus and medial gastrocnemius: implications for motor control. Journal of Neurophysiology 44, 951-60.

Figures 1B and 1C not compatible with PCSA definitions

Figure 1 Pennate muscle fiber arrangements

Fig. 365 from the book Gray Anatomy

As explained in Talk:Pennate muscle, pictures 1B and 1C are currently compatible with none of the two definitions of PCSA (while 1A is compatible with the original definition by Alexander).

The picture from Gray Anatomy is not compatible for a different reason: for muscles B and C, the lines shown for PCS = physiological cross-section, are not orthogonal to the fiber directions, and longer than the actual PCSA. − Paolo.dL (talk) 19:47, 11 September 2010 (UTC)

Requested move

The following discussion is an archived discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. No further edits should be made to this section.

The result of the move request was: page moved. Vegaswikian (talk) 02:18, 19 October 2011 (UTC)

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Physiological cross sectional area → Physiological cross-sectional area –

Cross-section is hyphenated in the major dictionaries. Will match the formatting of related article titles. WP:HYPHEN Tony (talk) 09:41, 12 October 2011 (UTC)

• Support better punctuation and supported by peer reviewed literature. +mt 08:53, 13 October 2011 (UTC)
• Support Paolo.dL (talk) 20:25, 13 October 2011 (UTC)

The above discussion is preserved as an archive of a requested move. Please do not modify it. Subsequent comments should be made in a new section on this talk page. No further edits should be made to this section.

Improve the "Estimating muscle force from PCSA" section

The explanation in that section is logically inconsistent with the definition of the PCSA provided.

The definition of PCSA is given as ${\text{PCSA}}={{\text{muscle volume}} \over {\text{fiber length}}}={{\text{muscle mass}} \over {\rho \cdot {\text{fiber length}}}}$

It is reasoned that increases in volume or mass cannot directly be associated with increases in PCSA since they might be due to change in fiber length. However, the provided definition scales the volume or mass with the fiber length. Therefore this argument seems to be inconsistent with the definition of the PCSA.

Since I myself have just learned of the PCSA I dare not edit this article and trust that someone who knows better will improve it. — Preceding unsigned comment added by 217.251.138.110 (talk) 11:33, 19 July 2014 (UTC)

Could you re-state your objection? I'm not quite sure what you're confused about. HCA (talk) 19:53, 27 July 2014 (UTC)