. 2022 Jun 14;13:862793. doi: 10.3389/fphys.2022.862793

TABLE 2.

Mean (± standard deviation) muscle volume in mm³ from SR (N = 12) and SR + FRED (N = 12) at BDC2, HDT59, and R13.

Intervertebral Disc Level
Muscle	Group	Time	L1/L2	L2/L3	L3/L4	L4/L5	L5/S1
Lumbar multifidus	SR	BDC	1310 ± 397	2013 ± 513	3274 ± 819	4771 ± 838	4805 ± 613
		HDT59	1268 ± 387	1911 ± 474 ^a	3039 ± 754 ^a	4404 ± 783 ^a	4561 ± 615 ^a
		R13	1242 ± 428	1971 ± 527	3384 ± 954 ^b	4566 ± 854 ^a ^, ^b	4655 ± 617 ^a ^, ^b
	SR + FRED	BDC	1256 ± 355	1991 ± 487	3058 ± 698	4559 ± 862	4679 ± 700
		HDT59	1192 ± 329	1874 ± 492 ^a	2820 ± 689 ^a	4104 ± 864 ^b	4410 ± 702 ^a
		R13	1282 ± 327	1930 ± 545	3001 ± 954 ^b	4358 ± 894 ^a ^, ^b	4528 ± 602 ^a ^, ^b
Lumbar erector spinae	SR	BDC	8261 ± 1956	8337 ± 1839	7265 ± 1433	5324 ± 725	2177 ± 606
		HDT59	7298 ± 1768 ^a	7263 ± 1434 ^a	6470 ± 1220 ^a	5299 ± 743	2390 ± 721 ^a
		R13	7759 ± 1741^* ^, ^†	7827 ± 1504 ^a ^, ^b	6895 ± 1258 ^†	5118 ± 672	2124 ± 617
	SR + FRED	BDC	8559 ± 2246	8695 ± 2046	7601 ± 1712	5248 ± 928	2384 ± 674
		HDT59	7483 ± 2022 ^a	7832 ± 1917 ^a	6980 ± 1689 ^a	5202 ± 864	2621 ± 728 ^a
		R13	8249 ± 2191 ^a ^, ^b	8571 ± 2132 ^a ^, ^b	7595 ± 1814 ^b	5223 ± 943	2414 ± 765
Psoas major	SR	BDC	1963 ± 979	3619 ± 1405	4939 ± 1539	5879 ± 1616	5679 ± 1586
		HDT59	2104 ± 1120 ^a	3697 ± 1389	4931 ± 1562	5828 ± 1726	5709 ± 1658
		R13	2165 ± 959 ^a	3777 ± 1221	5014 ± 1379	5916 ± 1483	5665 ± 1420
	SR + FRED	BDC	2021 ± 1035	4358 ± 1491	5897 ± 1779	6799 ± 1797	6456 ± 1666
		HDT59	2143 ± 1078 ^a	4468 ± 1694	5971 ± 1793	6829 ± 1805	6418 ± 1663
		R13	2505 ± 1163 ^a	4589 ± 1466	6089 ± 1790	6993 ± 1820	6510 ± 1625
Quadratus lumborum	SR	BDC	1062 ± 401	1798 ± 755	2493 ± 813	—	—
		HDT59	1003 ± 380	1658 ± 702 ^a	2291 ± 777 ^a	—	—
		R13	990 ± 445	1720 ± 732	2392 ± 800 ^a ^, ^b	—	—
	SR + FRED	BDC	1125 ± 477	1919 ± 710	2733 ± 799	—	—
		HDT59	1015 ± 420	1660 ± 600 ^a	2383 ± 659 ^a	—	—
		R13	1111 ± 471	1716 ± 781	2561 ± 789 ^a ^, ^b	—	—

Pairwise comparisons (Bonferroni adjusted) relative to baseline (BDC) value (p < 0.05).

Pairwise comparisons (Bonferroni adjusted) relative to the end of head-down tilt (HDT59) bed rest value (p < 0.05).

SR, Standard Reconditioning; SR + FRED, Standard Reconditioning supplemented with Functional Re-adaptive Exercise Device; BDC, Baseline data collection; HDT, Head-down tilt; R, Recovery.