https://www.sciencedirect.com/science/article/abs/pii/S8756328221003963
As we exercise we put a force through our bones, this force causes the bone to respond by increasing its density and strength. This study looked at how many days a week we should exercise to improve our bones. They found that how often we exercise (exercise frequency) and how long we have been exercising for (program length) has the biggest impact on improving bone quality. They recommend that we should average 2 exercise sessions a week over the year at a minimum, and when you include holidays and days off you probably need to exercise 3 times a week to reach the 2 times a week average.