Table 2 Comparison of mean myofibers’ morphology across age groups

From: Automated image-analysis method for the quantification of fiber morphometry and fiber type population in human skeletal muscle

	Age group (years old)
Myofibers’ morphology	15–29	30–49	50–69	70–89
Number of fibers (by area)^±	2225.7 ± 330.4	2238.9 ± 190.5	2567.6 ± 252.3	2235.5 ± 262.1
Number of type I (%)	39.9 ± 5.7	46.7 ± 3.3	50.4 ± 4.4	50.1 ± 4.5
Number of type II (%)	60.1 ± 5.7	53.3 ± 3.3	49.6 ± 4.4	49.9 ± 4.5
CSA all fibers (μm²)	2362.3 ± 253.6^ab	2568.8 ± 146.3^b	2534.8 ± 193.7^ab	1868.6 ± 201.2^a
CSA type I (μm²)	2397.5 ± 263.1	2371.6 ± 151.8	2279.7 ± 201	2236.8 ± 208.8
CSA type II (μm²)	2359.5 ± 313^ab	2771.9 ± 180.5^b	2654.0 ± 239.1^b	1443.2 ± 248.4^a
Perimeter all fibers (μm)	205.7 ± 11.7^ab	214.1 ± 6.7^b	210.3 ± 8.9 ^ab	179.0 ± 9.3^a
Perimeter type I (μm)	205.0 ± 11.4	204.0 ± 6.5	199.4 ± 8.7	198.8 ± 9.0
Perimeter type II (μm)	207.2 ± 14.9^ab	224.2 ± 8.6^b	215.4 ± 11.4^b	160.4 ± 11.8^a
Major diameter all fibers (μm)	70.1 ± 3.8^ab	73.1 ± 2.2^b	71.8 ± 2.9^ab	61.0 ± 3.1^a
Major diameter type I (μm)	69.9 ± 3.7	69.8 ± 2.1	68.0 ± 2.8	66.8 ± 2.9
Major diameter type II (μm)	70.6 ± 4.9^ab	76.4 ± 2.8^b	73.5 ± 3.7^b	55.4 ± 3.9^a
Minor diameter all fibers (μm)	41.2 ± 2.1^b	43.1 ± 1.2^b	41.8 ± 1.6^b	33.3 ± 1.7^a
Minor diameter type I (μm)	42.6 ± 2.2	42.1 ± 1.3	41.0 ± 1.7	38.1 ± 1.8
Minor diameter type II (μm)	40.5 ± 2.6^b	44.1 ± 1.5^b	41.4 ± 2.0^b	28.6 ± 2.0^a

Morphology of total, type I, and type II myofibers of deltoid muscle samples evaluated using our macro run in Fiji-ImageJ. Analysis of covariance (two-way ANCOVA) results by age group are shown. Averages of each sample were used for all, type I, and II fiber analysis. Values are LSmeans ± SEM. For each parameter, means in the same row that have no superscript in common are significantly different from each other (Tukey-Kramer test, p < 0.05). CSA cross-sectional area. ±Normalized number of fibers/area (10 mm²)

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