Table 2.
Serum markers of bone and calcium metabolism before, during, and after 30 days of bed rest
| Pre-BR | BR 4 | BR 12 | BR 19 | BR 26 | Post-BR 0 | Post-BR 1 | Post-BR 2 | |
|---|---|---|---|---|---|---|---|---|
| Calcium (mmol/L) | ||||||||
| CON | 2.34 ± 0.10 | 2.33 ± 0.12 | 2.35 ± 0.08 | 2.37 ± 0.13 | 2.37 ± 0.14 | 2.40 ± 0.13 | 2.34 ± 0.14 | 2.32 ± 0.15* |
| EX | 2.33 ± 0.12 | 2.31 ± 0.13 | 2.27 ± 0.10 | 2.29 ± 0.12 | 2.35 ± 0.13 | 2.35 ± 0.15 | 2.31 ± 0.13 | 2.28 ± 0.15* |
| 25(OH)-vitamin D (nmol/L) | ||||||||
| CON | 68 ± 41 | 68 ± 39 | 64 ± 34 | 65 ± 29 | 66 ± 30 | 61 ± 22 | 59 ± 20 | 65 ± 25 |
| EX | 57 ± 34 | 58 ± 30 | 52 ± 27 | 55 ± 28 | 55 ± 27 | 63 ± 31 | 60 ± 31 | 57 ± 28 |
| 1,25(OH)2-vitamin D (pmol/L) | ||||||||
| CON | 126 ± 46 | 119 ± 53 | 134 ± 42 | 110 ± 35 | 101 ± 32 | 107 ± 16 | 101 ± 44 | 117 ± 36 |
| EX | 128 ± 41 | 94 ± 23 | 110 ± 34 | 119 ± 37 | 111 ± 37 | 114 ± 24 | 101 ± 29 | 111 ± 41 |
| Parathyroid hormone (pg/mL) | ||||||||
| CON | 20.8 ± 4.0 | 18.9 ± 3.7 | 17.0 ± 2.7 | 17.7 ± 5.2 | 16.6 ± 5.1 | 15.8 ± 4.4 | 18.4 ± 4.9 | 19.9 ± 6.3 |
| EX | 20.5 ± 6.0 | 22.9 ± 3.9 | 24.0 ± 8.2 | 19.3 ± 6.4 | 18.1 ± 2.9 | 19.1 ± 4.1 | 17.7 ± 2.8 | 20.2 ± 5.7 |
| BSAP (μg/L) | ||||||||
| CON | 18.7 ± 5.7 | 19.5 ± 5.3 | 18.5 ± 4.9 | 17.3 ± 4.0 | 17.8 ± 4.2 | 18.9 ± 3.6 | 18.2 ± 4.0 | 16.4 ± 2.9 |
| EX | 16.9 ± 3.1 | 15.7 ± 3.2 | 16.1 ± 3.1 | 15.1 ± 2.8 | 16.4 ± 3.4 | 15.2 ± 3.3 | 16.7 ± 2.9 | 16.1 ± 3.0 |
| Alkaline phosphatase (U/L) | ||||||||
| CON | 47 ± 14 | 47 ± 14 | 49 ± 14 | 47 ± 13 | 49 ± 12 | 47 ± 14 | 47 ± 14 | 45 ± 13 |
| EX | 47 ± 12 | 43 ± 10 | 40 ± 8 | 40 ± 8 | 42 ± 9 | 43 ± 12 | 43 ± 9 | 42 ± 10 |
| Osteocalcin (ng/mL)** | ||||||||
| CON | 12.4 ± 2.2 | 13.0 ± 3.1 | 12.9 ± 3.2 | 13.1 ± 2.7 | 14.2 ± 3.0 | 13.9 ± 3.6 | 11.5 ± 2.2 | 11.9 ± 2.6 |
| EX | 10.3 ± 3.3 | 10.4 ± 4.0 | 10.0 ± 3.3 | 12.4 ± 2.3 | 13.3 ± 2.4 | 12.3 ± 2.0 | 11.7 ± 1.4 | 11.1 ± 1.2 |
Subjects were identical twins assigned at random to sedentary bed rest (CON) or bed rest combined with lower body negative pressure treadmill exercise (EX). BR, bed rest. For each subject, Pre-BR represents an average of 3 consecutive-day data collections. Data are means ± SD for 7 subjects per group, except for osteocalcin, for which n = 5.
*
P < 0.001, different from Pre-BR.
**
There was a significant effect of time for osteocalcin, but the Bonferroni t-test revealed no significant difference between any BR value and the Pre-BR value.