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. Author manuscript; available in PMC: 2011 May 1.

Published in final edited form as: Exp Gerontol. 2010 Mar 11;45(5):389–393. doi: 10.1016/j.exger.2010.03.007

Table 4.

Myofiber profiles in young, and aged plantaris, and soleus muscles

	Plantaris		Soleus
Cross-sectional area (μm²)	Young (N=10)	Aged (N=10)	Young (N=10)	Aged (N=10)
Fiber types combined	2218 ± 119	2018 ± 93	2159 ± 101	2243 ± 127
Type I fibers	1359 ± 117	1292 ± 46	2218 ± 110	2286 ± 126
Type IIA fibers	2632 ± 173	2369 ± 112	1939 ± 111	2164 ± 193
^*Type IIX/B fibers	1304 ± 160	1250 ± 86	1667 ± 135	1796 ± 195
Fiber type composition (%)
Type I fibers	16.5 ± 1.3	22.3 ± 1.8	85.2 ± 2.1	86.0 ± 1.1
Type IIA fibers	67.8 ± 6.1	66.6 ± 2.3	10.6 ± 2.2	9.1 ± 1.2
^*Type IIX/B fibers	15.7 ± 5.5	11.1 ± 1.5	4.2 ± 0.7	4.9 ± 0.8

Values are means ± SE.

^*

Type IIB myofibers are not expressed in the soleus muscle of rats (Delp and Duan, 1996).