Table 5. Comparison of muscle fiber characteristics between porcine skeletal muscles within the same pennate structural subtype

Traits Muscle fiber type Unipennate Bipennate Multipennate
DP LD (PE) p-value BB BF RF (PE) p-value SS SDF (PE) p-value
Cross-sectional area (μm2) I 2,062.2 1,937.1 (142.1) 2,668.5 3,039.5 2,302.3 (237.8) 3,150.2 3,329.0 (324.5)
IIA 1,653.9a 1,106.9b (146.9) ** 1,964.6 2,191.7 1,791.1 (198.3) 2,850.3 2,491.7 (229.8)
IIAX nd nd nd 1,801.7 1,285.7 1,970.9 (202.5) 2,846.6 2,488.6 (170.1)
IIX 1,959.5 1,801.5 (116.6) 2,625.4 2,898.2 2,517.5 (205.6) 3,518.5a 1,704.8b (638.0) *
IIXB 1,858.6 2,009.5 (109.0) 2,266.7 2,018.7 2,901.6 (262.0) 3,522.5a 2,190.0b (465.2) **
IIB 2,609.2 1,718.5 (361.6) 2,656.4 2,905.0 2,920.9 (157.4) 3,568.6a 2,354.8b (412.2) **
Mean 1,953.5 1,714.7 (124.0) 2,307.2 2,601.8 2,403.0 (161.9) 3,283.3a 2,480.1b (295.4) **
Relative fiber area (%) I 43.2a 4.2b (9.1) *** 16.7 28.1 14.8 (4.2) 23.9 29.3 (9.1)
IIA 33.0a 11.2b (5.4) *** 20.5 14.1 21.0 (2.7) 18.6 23.1 (3.6)
IIAX nd nd nd 3.6a 1.0b 0.9b (0.7) * 1.3 2.0 (1.3)
IIX 10.1b 26.4a (5.6) * 32.4a 17.6b 11.2b (5.1) ** 27.7 13.3 (9.3)
IIXB 8.1 15.9 (3.4) 16.0 7.1 18.6 (4.2) 11.7 14.0 (3.8)
IIB 5.7b 42.2a (9.1) *** 10.8 32.1 32.7 (6.4) 16.7 18.3 (9.6)
Fiber density (number/mm2) I 210.7a 21.9b (42.9) *** 56.5 92.0 63.6 (12.9) 73.8 80.8 (23.3)
IIA 200.7a 102.5b (26.8) ** 105.0a 65.9b 113.2a (12.4) * 66.0b 93.6a (13.5) *
IIAX nd nd nd 17.7 7.6 4.7 (3.6) 4.8 8.0 (4.9)
IIX 51.8b 152.0a (32.1) * 121.9a 65.9b 44.8b (18.6) * 77.4 58.7 (29.8)
IIXB 43.5 79.0 (17.6) 65.8 29.1 65.7 (14.3) 34.8 60.2 (15.0)
IIB 23.2b 242.8a (51.1) *** 36.9b 114.0a 112.3a (21.5) * 46.7 72.0 (33.2)
Total 529.8 598.2 (32.4) 403.8 374.6 407.8 (21.1) 303.4b 373.3a (30.8) *
Data are means and pooled SE (PE).
Significant differences (p<0.05) between muscle types within the same pennate structural subtype are indicated by different superscripts.
p<0.05,
p<0.01,
p<0.001.
DP, M. diaphragm; LD, M. longissimus dorsi; BB, M. biceps brachii; BF, M. biceps femoris; RF, M. rectus femoris; SS, M. subscapularis; SDF, M. superficialis digital flexor; nd, not detected.