Does Hargens & Vico 2016 actually establish that 60–90 days of strict bed rest is the dose-equivalent of ~6 months of spaceflight?

Böcker et al. (2026) compare 60-day head-down bed rest against 6-month spaceflight and find bone loss comparable despite the roughly threefold duration gap (claim-matched-pqct-comparison-finds-bone-loss-comparable-while-muscle-loss-under-runs). They justify comparing two arms of such different exposure by citing the convention that 60–90 days of strict bed rest is the duration-equivalent of ~6 months of orbital flight — attributed to Hargens AR & Vico L (2016), "Long-duration bed rest as an analog to microgravity," J Appl Physiol 120:891–903.

This dose-equivalence premise is load-bearing twice over: it is what licenses the "not duration-matched" comparison in claim-bocker-matched-comparison-is-site-matched-not-duration-matched, and it is the assumption underneath the authors' "60 days models six-month bone loss" conclusion in claim-bocker-concludes-60-days-bed-rest-models-six-month-spaceflight-bone-loss. As encountered so far it rests one citation layer back from Böcker et al. — the 2016 paper was not read directly at capture, only cited inside the 2026 study.

What would answer it

• Read Hargens & Vico 2016 (J Appl Physiol 120:891–903, DOI 10.1152/japplphysiol.00935.2015) directly and locate the specific passage that sets the 60–90-day-bed-rest ≈ ~6-month-spaceflight equivalence. Confirm (a) whether the equivalence is asserted for bone specifically or for the musculoskeletal system broadly, and (b) what evidence base it rests on — is it an empirical dose-response fit, or a rule-of-thumb convention?
• If the 2016 review itself only cites the equivalence to earlier work, chase it one more layer to the primary dose-response data.

Resolving this would either firm up or undercut the "bed rest reaches comparable bone loss faster" reframing the Böcker conclusion introduces. Until then, both dependent notes stay seedling.