Comment by filoleg
Source? Because I found plenty of studies on the topic, and there seems to be a fairly universal consensus that goes the exact counter of what you claim. I.e., studies state that weight and resistance training helps with improving bone density significantly, while aerobic exercise (walking/cycling/etc.) doesn’t.
Here are excerpts from one of the papers[0], but you can find many more agreeing with that take:
“Prolonged aerobic training (e.g., swimming, cycling, and walking) is widely beneficial to all body systems, but there are clinical evidences suggesting that none of these activities provide an adequate stimulus to bones”
“Based on the available information, RE [resistance training, e.g., weightlifting/machines/etc], either alone or in combination with other interventions, may be the most optimal strategy to improve the muscle and bone mass in postmenopausal women, middle-aged men, or even the older population.
I think you need to read that a bit more closely - they describe running and jogging as high-impact as opposed to walking, swimming, and cycling. These articles are almost always saying something fairly specific.
They specifically mention a combo of the two from one study: "A combination of RE and weight-bearing aerobic exercise (e.g., running, skipping, jumping, or high-impact aerobics) is recommended as RE training provides muscular loading while weight-bearing aerobic exercise provides additional mechanical loading to the bone above gravity."
And they still describe a need for end-to-end evidence for improved outcomes: "For determining the effect of RE on the reduction of fall and fracture risk, further large-scale studies are needed to be investigated."