Does Rittweger et al. 2010's cortical bone loss during 56-day bed rest accrue linearly, or front-load and decelerate?

space-medicineaerospace-physiologybone-densitybed-rest-analogverification

Böcker et al. 2026 cite Rittweger et al. 2010 (Bone 46:137–147, the Berlin BedRest / BBR study, Böcker's reference 22) for the claim that bed-rest bone loss "follows a linear pattern." Böcker's own dose-equivalence conclusion — that 60 days of bed rest models six months of spaceflight bone loss (claim-bocker-concludes-60-days-bed-rest-models-six-month-spaceflight-bone-loss) — instead requires the opposite kinetic: bed-rest bone loss front-loading in the first 60 days and decelerating thereafter, a hypothesis Böcker's Discussion names explicitly and flags as unproven (claim-bocker-bone-dose-equivalence-rests-on-unconfirmed-front-loading-hypothesis).

Ref 22 has already been read in full primary text by this vault, but for a different question: claim-rittweger-2010-bed-rest-tibial-loss-almost-entirely-cortical establishes the compartment split (bed-rest loss is almost exclusively cortical, not trabecular) from that same paper. That note does not report whether the cortical loss it documents accrued at a constant rate across the 56 days or was itself front-loaded — the temporal shape of the curve, not its tissue compartment.

What would answer it

• Re-read Rittweger et al. 2010 (Bone 46:137–147, DLR institutional repository, https://elib.dlr.de/63898/1/2010_P.088_Rittweger_BBR_Main.pdf, sha256 8176b1c2ea71457cf011618a5dd4c75f3685676976668760ff92d9698d72c6ed) for any intermediate-timepoint pQCT measurement of the control arm's cortical tibial loss during the 56-day bed-rest period (not just baseline-vs-day-55). If the study only measured bone density at the start and end of bed rest, it cannot itself settle linear-vs-front-loaded and the question routes one layer further back, to whichever source Rittweger's own "linear pattern" characterization rests on.
• If a within-bed-rest time course exists, confirm whether it shows loss distributed evenly across the 56 days or concentrated early.

Resolving this would either confirm or undercut the kinetic assumption behind Böcker's bone dose-equivalence conclusion, and discharge the [unverified-mechanism] flag on claim-bocker-bone-dose-equivalence-rests-on-unconfirmed-front-loading-hypothesis.

Progress

• 2026-10-31 (promotion of 10-inbox/raw/2026-10-27-does-rittweger-et-al-2010s-cortical-bone-loss.md, headless). Rittweger et al. 2010 re-read in full primary text for the time-course question. Partial answer — leaving OPEN; the quantitative resolution this question wants is not obtainable from this paper. Three findings:
  1. The study's hedged premise is ruled out: it did measure within the bed-rest phase, at five pQCT timepoints (days BR.2/17/31/45/55), not only baseline-vs-end — claim-rittweger-2010-bed-rest-time-course-measured-but-not-published-numerically.
  2. But those five measurements were never tabulated — Table 5 reports only baseline, R+14, and R+360. The intra-bed-rest curve exists only as Figs. 2 and 4 (pixels, not digits), so no fitted rate / linearity statistic is available from the paper's text. The [unverified-quant] gap therefore cannot be closed by re-reading this PDF.
  3. The direction the prose supports is against front-loading, not toward it: delayed epiphyseal cortical onset (day BR.17) and a diaphysis described as "continuously decrease[ing]" — claim-rittweger-2010-bed-rest-cortical-loss-prose-points-away-from-front-loading. This is qualitative, not a fitted curve, and does not establish strict linearity either.
  • What now routes one layer further back: digitizing Figs. 2/4 for the numeric time course, or reading the LTBR predecessor (Rittweger et al. 2005, Bone 36:1019–29, ref. 16 in the 2010 paper — which the 2010 Discussion says predicted the 90-day losses from the 56-day ones "with an R2 value of 0.98," a different cross-duration-linearity claim worth checking directly). The [unverified-mechanism] flag on the Böcker note stays; this advance strengthens the vault's reading of it without discharging it.