Table 1.

Urinary markers of bone and calcium metabolism before, during, and after 30 days of bed rest

	Pre-BR	BR 5/6	BR 12/13	BR 19/20	BR 26/27	Post-BR
Calcium (mmol/d)
CON	3.95 ± 1.32	4.09 ± 1.31	5.38 ± 1.73*	5.76 ± 1.81*	6.64 ± 2.54*	5.22 ± 2.83
EX	3.90 ± 1.81	4.34 ± 1.87	4.67 ± 1.89*	4.41 ± 1.41*	5.46 ± 1.95*	3.67 ± 1.16
n-telopeptide (nmol/d)
CON	385 ± 112	424 ± 145	530 ± 190*	552 ± 152*	633 ± 178*	495 ± 115*
EX	337 ± 109	364 ± 108	503 ± 280*	533 ± 275*	498 ± 213*	506 ± 274*
Pyridinium crosslinks (nmol/d)
CON	198 ± 56	229 ± 55	269 ± 69*	312 ± 71*	364 ± 119*	374 ± 130*
EX	193 ± 70	199 ± 59	229 ± 54*	265 ± 86*	291 ± 95*	263 ± 94*
Deoxypyridinoline (nmol/d)
CON	50 ± 19	58 ± 22	75 ± 25	75 ± 26*	97 ± 28*	88 ± 27*
EX	50 ± 20	52 ± 21	55 ± 14	68 ± 21*	82 ± 29*	77 ± 45*
Helical peptide (μg/d)
CON	465 ± 183	595 ± 231	669 ± 232#	755 ± 354*	843 ± 339*#	749 ± 267*
EX	464 ± 300	426 ± 234	439 ± 162	508 ± 198*	507 ± 224*	481 ± 189*
Creatinine (mmol/d)
CON	1105 ± 208	1127 ± 235	1203 ± 279	1189 ± 242	1315 ± 276**	1294 ± 302**
EX	1113 ± 137	1177 ± 266	1336 ± 282	1286 ± 149	1403 ± 326**	1314 ± 286**
Phosphorus (mg/d)
CON	491 ± 124	661 ± 145*	686 ± 268	754 ± 206*	830 ± 358*	604 ± 207*
EX	494 ± 173	646 ± 115*	713 ± 267	688 ± 210*	819 ± 281*	585 ± 222*

Subjects were identical twins assigned at random to sedentary bed rest (CON) or bed rest combined with lower body negative pressure treadmill exercise (EX). Data are means ± SD for 7 subjects per group. BR, bed rest. For each subject, Pre-BR represents an average of 3 consecutive-day data collections. Data for all other time points are the average of two 24-h urine collections. Significant differences from Pre-BR are denoted as

^*P < 0.001,

^**P < 0.01.

^#Significant differences between CON and EX groups, P < 0.05.