Theory 01/Space Medicine & Microgravity Physiology
Bone Loss Is a Remodelling Ratio
Microgravity bone loss is set by the ratio of mechanical loading to remodelling rate rather than by the absence of load, so brief high-strain loading can preserve bone that continuous low loading cannot.
01The mechanism
Bone remodels in response to strain. The signal is not the average load but the peak strain relative to the routine, and the remodelling rate sets how much of the deficit is repaired between bouts.
A short session of high strain creates a signal large enough to shift the balance, while prolonged low-level loading sits below the threshold at which remodelling changes direction.
02What this is not
Those treat bone loss as a consequence of weightlessness itself. This treats it as a deficit in signal-to-repair ratio, which predicts that the right loading can offset it.
03Predictions
- P1Bone density should track the loading ratio rather than total exercise time.
- P2Brief high-strain protocols should outperform longer low-strain ones.
04Refutation
Density tracking total load at controlled strain magnitude would remove the ratio.