@ans From the study protocol (actual study not yet published) you can see the time periods that were supposed to be used. Personally I think it's plenty of time to show improvement. BTW, I also own a Marodyne and no longer use it after a year with no success. Maybe it's useful in some other ways but it looks doubtful for bone density at this point IMO.
"Methods: Postmenopausal women with low areal bone mineral density (aBMD) at the proximal femur and/or lumbar spine, with or without a history of fragility fracture, and either on or off osteoporosis medications will be recruited.

Eligible participants will be randomly allocated to one of four trial arms for 9 months: LIV, HiRIT, LIV + HiRIT, or control (low-intensity, home-based exercise).

Allocation will be block-randomized, stratified by use of
osteoporosis medications.

Testing will be performed at three time points: baseline (T0), post-intervention (T1; 9 months), and 1 year thereafter (T2; 21 months) to examine detraining effects.

The primary outcome measure will be total hip aBMD determined by dual-energy X-ray absorptiometry (DXA). Secondary outcomes will include aBMD at other regions, anthropometrics, and other indices of bone strength, body composition, physical function, kyphosis, muscle strength and power, balance, falls, and intervention compliance. Exploratory outcomes include bone turnover markers, pelvic floor health, quality of life, physical activity enjoyment, adverse events, and fracture. An economic evaluation will also be conducted "