Böcker et al. conclude that 60 days of bed rest without countermeasures models six-month spaceflight lower-limb bone loss, while equivalent muscle loss requires about 80 days

The bottom-line framing Böcker et al. give the bed-rest analog is a dose-equivalence, not a magnitude multiplier. From the paper's conclusion:

"This study also revealed that skeletal adaptations in the lower limb following a six-month mission could be effectively modeled by 60 days of bed rest without countermeasures, whereas muscle changes required approximately 80 days of bed rest for comparable effects."

This reframes the analog question away from "bed rest under-runs spaceflight bone loss by some fixed factor" — the framing carried by claim-head-down-bed-rest-is-the-standard-ground-analog-for-spaceflight-bone-loss and claim-bed-rest-under-runs-spaceflight-bone-loss-depends-on-readout — and toward "bed rest reaches comparable bone loss faster than it reaches comparable muscle loss." Bone and muscle are modeled at different bed-rest doses: ~60 days for the skeletal endpoint, ~80 for the muscular one. That timing gap is the dose-scale echo of the magnitude asymmetry in claim-matched-pqct-comparison-finds-bone-loss-comparable-while-muscle-loss-under-runs: muscle needs more bed-rest exposure to catch spaceflight because spaceflight muscle loss runs harder, while bone catches up sooner.

The conclusion is faithfully the authors' own, but its validity as a real-world equivalence rests on the same premise flagged in claim-bocker-matched-comparison-is-site-matched-not-duration-matched: that 60-day bed rest is a legitimate dose-stand-in for a six-month mission, a convention the paper attributes to Hargens & Vico 2016 and which this vault has not independently verified — question-verify-hargens-vico-2016-bed-rest-spaceflight-dose-equivalence. It partially addresses question-matched-head-to-head-bed-rest-vs-spaceflight-bone-comparison. Senior-author context: entity-jorn-rittweger.